A system for driving the control shaft of a motorcar mechanical gearbox

Abstract: In a system for driving the control shaft (2) of a motorcar mechanical gearbox, flexible push-pull cables (5, 7) associated to transmission members are used for transmitting control movements from the gear lever to the control shaft (2) so as to translate and rotate said shaft along and about its axis, in order to select and engage the single gears. The flexible cable (5) for translating the control shaft (2) and having the function of selecting or engaging the desired gear, according to the internal system of the gearbox, is directly connected to the said shaft in a coaxial manner.

Description: The present invention refers to a driving system for the control shaft of a motorcar mechanical gearbox; more particularly, the invention relates to a system of the above kind utilising flexible push-pull cables for driving said shaft by means of the gear lever. A driving system according to the preamble of claim 1 is known from document GB 538 110 A. With present systems, the flexible cables are generally arranged perpendicular to the control shaft. Therefore, either translation of the shaft along its axis and rotation of the shaft for accomplishing gear selection and engagement motions, respectively, are attained through transmission members. Besides involving high manufacturing and assembly costs, said transmission members have the drawback of reducing efficiency of the whole control system and that of increasing clearance, whereby the gear shifting manoeuvre becomes less immediate and precise. A second drawback with such known systems lies in that the rate of vibration transmitted to the inside of the passenger's cabin is increased, which reduces comfort. It is an object of the present invention to provide a driving system for the gearbox control shaft capable of overcoming the above discussed drawbacks. To this end, the present invention provides a system for driving the control shaft of a motorcar mechanical gearbox as claimed in claim 1. In a preferred embodiment of the present invention, the junction between the end portion of the flexible cable to the end portion of the gearbox control shaft is attained by means of a snap connection. For a better understanding of the present invention, reference is made to the following detailed description of an exemplary embodiment considered in combination with the accompanying drawings, in which: FIG. 1 is a partial schematical view of the driving system in accordance with the present invention; FIGS. 2 and 3 are a front and partially sectional view, respectively, of a detail of FIG. 1 to an enlarged scale; and FIG. 4 is a cross sectional view taken along line II-II of FIG. 2. With reference to the drawings, numeral 1 designates a gearbox case, schematically illustrated in phantom line, in which there is inserted the gearbox control shaft 2. Control shaft 2 serves to select and engage the single gears as selected by the driver moving the gear lever (not shown). As known, gear selection is accomplished by translating the control shaft 2 along its axis in one of the two directions indicated by arrows H, while engagement of the selected gear is attained by rotating the shaft about its axis in one of the two directions of rotation indicated by arrows F. In FIG. 1 there are shown two flexible cables 5 and 7 for controlling gear selection and engagement, respectively. The end portions of cables 5 and 7 not being illustrated are connected to the transmission members of the gear lever. The cable 7 for engaging the selected gear has its other end connected to a transmission member 12 through an articulated joint 11. The transmission member 12 is adapted, in a manner known per se, to rotate the shaft 2 when actuated through said cable 7. The sheathing 13 of cable 7 is provided with a contrasting point 15 normally fixed to the gear box 1. The cable 7 reaches the shaft 2 along a direction perpendicular to the axis of said shaft. The cable 5 for actuating a translation gear selection motion reaches the shaft 2 in a substantially coaxial position, and is connected thereto at its end portion 17 by means of a snap-fit connection, shown in further detail in FIGS. 2 to 4. The sheathing 21 of cable 5 uses a reverse U shaped bracket 23 secured to the gear box 1 as a contrasting point. However, it should be noticed that, as a function of the construction of the inner controls of the gearbox, the translation movement of shaft 2, that in this example provides gear selection, may otherwise be used for the gear engagement operation. The snap-fit connection 19 at the outer end 25 of driving cable 2 consists of a guard 27, preferably made of metal and provided with side splines 29 in which a clip 31 is inserted. The guard 27 is secured in known manner to the end portion 17 of cable 5, whilst the clip 31, positioned within the spline 29, is adapted to snap-fit into a groove 33 formed in the end portion 25 so as to transmit the rotational motion of cable 5 to shaft 2. The above arrangement avoid to have to provide a further transmission member on the gear box, which would cause the above discussed inconveniences.

Claims: A system for driving the control shaft (2) of a motorcar mechanical gearbox, of the kind utilising two flexible push-pull cables (5, 7) associated to transmission members for transmitting control movements from the gear lever to said control shaft (2) so as to translate and rotate said shaft along and about its axis, in order to select and engage the single gears, characterised in that the flexible cable (5) for translating said control shaft (2) having the function of selecting or engaging the desired gear, according to the internal system of the gearbox, is directly connected to said shaft in a coaxial manner. A system as claimed in claim 1, characterised in that the junction between the end portion (17) of the flexible cable (5) to the end portion (25) of the gearbox control shaft (2) is attained by means of a snap connection (19). A system as claimed in claim 2, characterised in that said snap connection (19) consists of a guard (27), preferably made of metal, and provided with side splines (29) in which a clip (31) is inserted, said clip being adapted to snap-fit into a groove (33) formed in said end portion (25) of said shaft (2).

Inventors: DE FRANCESCO GAETANO, GIOLITTI ELIO, LO CONTE FULVIO, DE FRANCESCO, GAETANO, GIOLITTI, ELIO, LO CONTE, FULVIO
Applicants: FIAT AUTO SPA, FIAT AUTO S.P.A.
Application year: 1997
Main classification: F16H59
IPC codes: F16H61