GB2126671A

GB2126671A - Truck gearshift linkage

Info

Publication number: GB2126671A
Application number: GB08225748A
Authority: GB
Inventors: Peter Eames
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1982-09-09
Filing date: 1982-09-09
Publication date: 1984-03-28
Also published as: GB2126671B

Abstract

A gearshift linkage for a truck with resiliently suspended cab. A support arm (39) is pivoted at one end to the cab about the cab tilt axis (46) and restrained at the other end by a tie bar (42) connected to the gearbox. The support arm (39) provides a pivot anchor for a swivel arm (26) used as a relay lever between the gear lever (16) and an operating rod (28). <IMAGE>

Description

SPECIFICATION Truck gearshift linkage This invention relates to gearshift linkages particularly though not exclusively for heavy road vehicles.

Heavy road vehicles frequently have a gearbox mounted at some distance from the vehicle drivers position. This is especially true for socalled forward control trucks where the cab is mounted over the engine. A long linkage is needed to connect the gearbox to the drivers gear lever.

Hitherto cabs have commonly been fixed to the vehicle chassis so that the gear linkage may be mounted partially on the cab and partially on the gearbox, the linkage only needing a small amount of flexibility to compensate for the resilient mountings of the gearbox in the chassis. Such mountings are usually very stiff and consequently the required flexibility is small.

In recent times vehicle cabs have been resiliently suspended on the chassis to give increased driver comfort by reducing the vibration transmitted from the road and driveline. With this arrangement the gearlever must be fixed relative to the chassis because of the relatively large movement possible between the cab and the chassis. This is undesirable since the gear lever is not kept in a constant position with respect to the driver.

A further problem presented by forward control trucks is the widespread adaption of tilting cabs to allow access to the vehicle engine for maintanence. Any gearlever linkage adopted must allow for such cab tilting without fouling or derangement.

One solution is to utilise a sheathed cable linkage between a cab mounted gear lever and the vehicle gearbox. This is not ideal since flexible sheathed cables give an imprecise feel, the inner cables can stretch and they are subject to high internal frictional forces. Furthermore such a system also requires a large number of ball joints to transmit movement of the gearlever faithfully to the gearbox.

The present invention proposes a rod linkage to overcome the aforementioned disadvantages.

According to the present invention there is provided a gearshift linkage in a vehicle having a gearbox mounted on the vehicle chassis and a driver controlled gearlever mounted in a cab resiliently suspended on the chassis wherein the linkage comprises a support arm pivoted to the vehicle cab, a guide rod connected at one end to the support arm and at the other end to said chassis, a swivel arm pivoted to said support arm, a first rod connected at one end to the gearlever and at the other end to said swivel arm, a second rod connected at one end to said swivel arm and at the other end to the actuating mechanism of said gearbox and a radius rod connected at one end to said second arm and at the other end to said chassis.

Where the cab is tiltable about a transverse axis of the chassis the support arm may be advantageously pivoted about that axis.

Other features of the invention are disclosed in the following description of a preferred embodiment shown by way of example in the accompanying drawing in which: Fig. 1 is a somewhat ghosted view of a forward control truck and showing a prior art gearshift linkage between gearlever and gearbox: and Fig. 2 is a somewhat diagrammatic illustration of a gear linkage according to the invention.

With reference to Fig. 1 there is shown a typical heavy truck 11 having a gearbox 1 2 mounted in the chassis 13 behind a fixed cab 14.

A single gearshift rod 1 5 is mounted on the cab floor and on the gearbox to transmit angular and linear movement of the gearlever 16 to the gearbox selector rods. If the truck were fitted with a tilting cab the gearshift rod would be mounted on the chassis adjacent the cab floor with either a detachable gear lever or large floor aperture to allow cab tilt.

With reference to Fig. 2 there is shown a gearshift linkage suitable for a vehicle having a resiliently suspended cab. The linkage includes ball joints, which allow articulation in all directions and pin joints which allow only angular movement about the axis of the pin.

The gear lever 16 is mounted by a ball joint 21 to a bracket 22 secured to the floor of the cab. A rod 23 is secured at one end by pin joint 24 to the gearlever 1 6 and at the other end by pin joint 25 to one end of a swivel arm 26. The other end of the swivel arm 26 is connected by a pin joint 27 to one end of an operating rod 28. The rod 28 is supported adjacent the gearbox by a radius arm 29 secured at one end by a ball joint 31 to a bracket 32 fixed on the rod 28 and at the other end by a ball joint 33 mounted on a bracket 34 secured to the vehicle chassis.

A ball joint 35 connects the end of the rod 28 to a lever 36 having a pivot arm 37 for entry into the gearbox. The arm 37 transmits both angular and axial movement of the gearlever to the gearbox as shown.

The swivel arm 26 is supported by a ball joint 38 connected to a support arm 39 which is mounted at one end on the cab floor by a pin joint 40 and bracket 41. A guide rod 42 is connected at one end to the other end of the arm 38 by a ball joint 43 and at the other end by a ball joint 44 to a bracket 45 secured to the vehicle chassis. All the pin joints of the linkage have their axes substantially parallel and horizontal with respect to the vehicle.

The guide rod 42 holds the support arm 39 in the correct spatial relationship to the gearbox for all degrees of freedom of the cab with respect to the chassis.

The system described is only one of a number of alternative solutions, for example in one alternative the ball joint 38 is a pin joint and the pin joints 25 and 27 are ball joints, an additional vertical link must be provided to impart rotary movement to the operating rod 28. Such a solution has the same effective result as that shown in Fig. 2.

Where the vehicle is provided with a tilt cab the axis 46 of the swivel arm 26 and support arm 39 are advantageously arranged on the tilt axis of the cab. This arrangement allows free tilting of the cab without disconnection or derangement of the linkage. Where the cab is fixed there is no necessity for the axis 46 or the corresponding axis 47 to be common for the arms 26 and 39.

Whilst the brackets 34 and 45 are described as connected to the vehicle chassis in an alternative embodiment they could be connected to the gearbox casing, thus compensating for movement between gearbox and chassis where this unit is resiliently mounted. The linkage has the additional benefit that forces applied to operating rod 28 are cancelled out by the reactive force on the guide rod 42 thus avoiding lost motion effects due to resilient bush movement.

Claims

1. A gearshift linkage in a vehicle having a gearbox mounted on the vehicle chassis and a driver controlled gearlever mounted in a cab resiliently suspended on the chassis wherein the linkage comprises a support arm pivoted to the vehicle cab, a guide rod connected at one end to the support arm and at the other end to said chassis, a swivel arm pivoted to said support arm, a first rod connected at one end to the gearlever and at the other end to said swivel arm, a second rod connected at one end to said swivel arm and at the other end to the actuating mechanism of said gearbox and a radius rod connected at one end to said second arm and at the other end to said chassis.

2. A linkage according to Claim 1, wherein said cab is tiltable about a transverse axis of the chassis, said support arm being pivoted on said axis.

3. A linkage according to Claim 2, wherein said first rod is pivoted to the swivel arm on said transverse axis.

4. A gearshift linkage of a vehicle having a gearbox mounted on the vehicle chassis and a driver controlled gearlever mounted in a cab resiliently supported on the chassis substantially as described herein with reference to the accompanying drawings.