Safety device in the control of a motor vehicle automatic transmission

Abstract: A safety device in the control of a motor vehicle automatic transmission, wherein the gear selector lever (17) is provided with a mechanical locking device (16) which is operated by a cable (12) connected to the brake pedal (11) and locks the lever (17) in predetermined positions, from which it can be released only by pressing the brake pedal (11).

Description: This invention relates to a safety device in the control of a motor vehicle automatic transmission. More particularly, the invention relates to a safety device which prevents the reverse gear or forward gears being accidentally engaged when the gear selector lever is in its neutral or park position. Safety devices in the control of automatic transmissions are known which use an electrical contact operable by the brake pedal and connected to an electromagnetic actuator by an electric cable. The electromagnetic actuator is provided with a locking element which engages in appropriate seats provided in the gear selector lever. These safety devices, which necessarily have to be connected to the vehicle electrical system, are consequently affected by the partial or total faults which the electrical system can develop, and moreover because of the nature of the electromagnetic actuator they are rather noisy when they engage. The US-A-4 096 930 discloses a mechanically-actuated gear shift selector brake interlock mechanism, for motor vehicles having automatic trasmissions, wherein a gear shift lever lock selectively inhibits movement of the gear shift selector lever to a drive position until an operator actuates the brake pedal. An object of the present invention is to provide a completely mechanical safety device for the selector lever of an automatic transmission which provides good reliability and is also constructionally simple and of low cost. A further object of the present invention is to provide a device which is entirely housed within the vehicle passenger compartment independently of the position of the gearbox, which can for example be either in the engine compartment or under the vehicle body. These objects are attained according to a safety device as claimed in claim 1. The technical characteristics and further advantages of the present invention will be more apparent from the non-limiting description thereof given hereinafter with reference to the accompanying drawings in which: Figure 1 is a partially plan view of a device according to the present invention; Figure 2 is a perspective view of an enlarged detail of Figure 1; and Figure 3 is a perspective view of an enlarged detail of Figure 1 with the components shown in a different operating position. In the figures the reference numeral 10 indicates overall a device according to the present invention which, in a preferred embodiment, is totally housed in the interior of the passenger compartment of a motor vehicle (not shown). The reference numeral 11 indicates a brake pedal to which there is connected a cable 12 which by way of a guide 13 extends to a rigid element 14. The cable 12 terminates with a spring 15 fixed to a locking device 16 for the selector lever 17 of a motor vehicle automatic transmission (not shown). The lever 17, pivoted to the rigid element 14, is engaged with a flange 18 also fixed to the element 14 and provided with selectors 19 positioned longitudinally. The lever 17 is also provided with a pawl 20 for engaging said selectors 19. To the sides of the rigid element 14 in positions corresponding with the lever 17 there are fixed plates 21, one of which carries the locking device 16 by means of a support 22. The locking device consists of a cylinder 23 rigid with the support 22 and provided with a piston 24 elastically slidable within its interior. The piston 24 extends to the outside of the cylinder by way of a pin-shaped end 25 and also by way of its other end, which carries a seat 26 for housing a rotatable arm 27 pivoted on the support 22 and connected to the cable 12. The pin-shaped end 25 is therefore slidingly engageable with a first hole 28 provided through the plate 21 and either with a second hole 29 provided through the lever 17 or with a side 30 of this latter. From the sectional view of the cylinder 23 (Figure 1) it can be seen that the piston 24 is urged towards the hole 28 and towards the hole 29 or side 30 by the action of a spring 31. The safety device of the present invention is therefore totally mechanical and is operable by pressing the brake pedal 11, which pulls the cable 12, to thus move the rotatable arm 27. This latter, being essentially T-shaped and being connected to the seat 26 of the piston 24, causes the piston to slide within the cylinder 23 against the opposing thrust action of the spring 31. As can be seen from Figure 2, when the lever 17 is in the park position, ie with the pawl 20 engaged in the first of the selectors 19, the pin 25 of the locking device 16 is in contact with the side 30 of the lever 17. To release the lever 17 it is necessary only to push the brake pedal to move the pin 25 and thus release the lever, which can then be moved into one of the gear engagement positions or into neutral. A further safety aspect of the present invention is that it also provides locking when the lever 17 is in the neutral position. In this position, shown in Figure 3, the hole 29 in the lever 17 corresponds with the hole 28 in the plate 21, so enabling the pin 25 to penetrate and lock the lever, to thus prevent a forward or reverse gear being engaged without firstly pressing the brake pedal.

Claims: A safety device (10) in the control of an automatic transmission for a motor vehicle provided with a brake pedal (11) and a lever (17) in mobile engagement with a flange (18) provided with longitudinally aligned selectors (19), said lever (17) operating an automatic transmission and being pivoted to a rigid element (14), whereby said flange (18) is fixed to the element (14) and said lever (17) is provided with a pawl (20) for engaging said selectors (19), characterised in that to the side of said rigid element (14) there is provided a plate (21) on which by means of a support (22) there is fixed a device (16) for locking the positions of said lever (17), said device (16) being operable by a cable (12) connected to said brake pedal (11), there being also provided a first through hole (28) in said plate (21) and a second hole (29) in said lever (17), said device (16) comprising a pin shaped end (25) of a piston (24) which is slidingly engageable with said first hole (28) and said second hole (29). A safety device (10) as claimed in claim 1, characterised in that said device (16) for locking the positions of said lever (17) consists of a cylinder (23) rigid with said support (22) and provided with an elastically slidable piston (24), said piston (24) extending to the outside of said cylinder (23) by way of a pin-shaped end (25), and also by way of its other end which carries a seat (26) for housing a rotatable arm (27) pivoted on said support (22) and connected to said cable (12) which is connected to the brake pedal (11), said pin-shaped end (25) being engageable with said first hole (28), and with said second hole (29) or with a side (30) of said lever (17). A safety device (10) as claimed in claim 2, characterised in that said piston (24) is elastically slidable within said cylinder (23) by means of a spring (31) with which it is engaged. A safety device (10) as claimed in claim 2, characterised in that said cable (12) is connected to said rotatable arm (27) by way of a spring (31). A safety device (10) as claimed in claim 2, characterised in that said rotatable arm (27), pivoted to said support (22), is essentially of T-shape.

Inventors: MALARA NICOLA, MALARA, NICOLA
Applicants: FIAT AUTO SPA, FIAT AUTO S.P.A.
Application year: 1990
Main classification: F16H61
IPC codes: F16H59, F16H61