Gear change control mechanism for a vehicle

Abstract: A vehicle is described having a steering column 14, a gearbox 20 forming part of the vehicle drive train and having a selection lever 18 and a gear change mechanism 16 mounted on the steering column 14 for remotely operating the selection lever 18 of the gearbox 20. The gear change mechanism 16 comprises a collar 22 mounted for rotation about the axis of the steering column 14, a first bevel gear 40 fast in rotation with the collar 22, a second bevel gear 42 meshing with the first bevel gear 40 and mounted for rotation about a fixed axis that extends generally radially from the steering column 14, a crank arm 44 connected for rotation with the second bevel gear 42, and a flexible cable 23 connecting the crank arm 44 to the selection lever 18 of the gearbox 20, the cable 23 enabling the end of the selection lever 18 to be pulled and pushed by rotation of the collar 22 about the steering column 14.

Description: The present invention relates to a vehicle having a control mechanism for effecting a gear change and is particularly applicable to a mechanism for controlling a forward/reverse shuttle in an agricultural vehicle. Agricultural vehicles commonly have a lever for selecting the direction of travel which is different from the lever for selecting the gear ratio. Having such a separate forward/reverse shuttle lever is convenient during low speed steering manoeuvres, such as turning around a tractor towing a plough. In some vehicles, the shuttle can be operated without separately needing to operate a clutch during the gear changes. Currently more sophisticated agricultural vehicles with electronically controlled transmissions, have an electrical or electronic forward/reverse shuttle control lever mounted on the steering column. On the other hand, vehicles with mechanically controlled transmissions currently have a mechanical lever located either on the left or right side of the tractor, depending upon the model of the vehicle. The present invention seeks to provide a vehicle having a control mechanism for a mechanical gear box, especially a forward/reverse shuttle, that can be mounted on the steering column, so that a common position for the control mechanism may be adopted for vehicles having mechanically and electronically controlled gear boxes. There is provided a vehicle having a steering column, a gearbox forming part of the vehicle drive train and having a selection lever and a gear change mechanism mounted on the steering column for remotely operating the selection lever of the gearbox. Such a vehicle is described, for example, in US 2349297A, which shows the features of the preamble of claim 1. According to the present invention, the gear change mechanism comprises a collar mounted for rotation about the axis of the steering column, a bevel gear fast in rotation with the collar, a second bevel gear meshing with the first bevel gear and mounted for rotation about a fixed axis that extends generally radially from the steering column, a crank arm connected for rotation with the second bevel gear and a flexible cable connecting the crank arm to the selection lever of the gearbox, the cable enabling the end of the selection lever to be pulled and pushed by rotation of the collar about the steering column. Preferably, the collar is rotatable by a control lever that extends generally radially from the steering column and is mounted on the collar for pivotal movement in a plane containing the axis of the steering column and the radially inner end of the control lever extends through the collar into a shaped stationary groove that constrains the angular displacement of the collar about the axis of the steering column and the angular displacement of the control lever relative to the collar. As earlier mentioned, the invention is especially intended for the forward/reverse shuttle of an agricultural vehicle. Such a gearbox has a selection lever with three positions corresponding to forward, neutral and reverse. In such a case, it is desirable not to be able to overshoot the central neutral position and thereby switch directly between forward and reverse accidentally. In one embodiment of the invention, the stationary groove may be Z shaped so that a gate is defined in the neutral position that has to be crossed by moving the end of the control lever parallel to the steering column before it can be used to rotate the collar about the steering column from the forward position to the reverse position. In an alternative embodiment of the invention, the stationary groove may be T shaped and the control lever may be spring biased in its central position towards a locked position in which it cannot rotate the collar, so that neither forward nor reverse may be selected. The groove needs to be stationary in relation to the steering column and to this end it may either be formed in the steering column or it may be formed in a ring surrounding the steering column that is itself suitably anchored to the body of the motor vehicle. It is not necessary for the first and second bevel gears to be full gears as they are only rotated through a small angle and it would suffice for them to be toothed sectors or quadrants. The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of a control mechanism mounted on a steering column and connected to the selection lever of a remotely located gear box by means of a cable; Figure 2 is a schematic perspective view showing the steering column mounted control mechanism to an enlarged scale and showing the control lever in two different positions; and Figure 3 is a schematic section through the steering control mounted control mechanism. Figure 1 shows a steering wheel 10 of an agricultural vehicle, mounted on a steering shaft 12 that is rotatably supported within a steering column 14. As is clearer from the section of Figure 3, the steering shaft 12 is rotatably supported in the stationary steering column 14 by journal bearings 26. The vehicle also has a shuttle gear box 20 that is remotely operated by a control mechanism, generally designated 16. The control mechanism 16 is mounted on the steering column 14 and acts on a selection lever 18 of the gear box 20 by way of a push and pull Bowden cable 23 that comprises an inner cable and a stationary outer sheath. The control mechanism 16, which is shown in more detail in Figures 2 and 3, comprises a collar 22 mounted for rotation around a sleeve 24 that is secured to the steering column 14. A control lever 28 is pivotably mounted by means of a pin 30 on the collar 22. The inner end of the lever 28 has a projection 32 that fits in a slot in the sleeve 24. The collar 22 is fast in rotation with a first bevel gear 40 that meshes with a second bevel gear 42. The second bevel gear 42 can rotate about an axis that is fixed in relation to the steering column 14 and is fast in rotation with a crank arm 44. The free end of the crank arm 44 is connected to one end of the inner cable of the Bowden cable 23, the other end of the inner cable being connected in a similar manner to the selection lever 18 of the shuttle gear box 20. In operation, the collar 22 is manually rotated about the axis of the steering column by means of the control lever 28. Rotation of the collar 22 causes the meshing bevel gears 40 and 42 to turn and this results in the crank arm 44 pulling and pushing the end of the inner cable of the Bowden cable 23. The movement of the inner cable relative to he outer sheath results in the selection lever 18 being pulled and pushed to select the appropriate drive gear. In addition to being rotatable about the axis of the steering column 14, the control lever 28 can also be pivoted about the pin 30 relative to the collar 22 in the direction represented by the double arrow 46 in Figure 1. The purpose of this movement as will now be explained is to provide a central neutral position in which neither forward nor reverse gear is engaged. The groove in the sleeve 24 can be Z shaped, that it to say it may comprise two circumferentially offset tangential runs connected to one another by a central axially extending run. The central run defines a neutral gate. The engagement of the projection 32 of the lever 28 in this groove constrains the movements of the lever 28 and the collar 22. If the free end of the control lever 28 is pulled towards the steering wheel 10 while the collar 22 is in a neutral position, then it can be turned in only one direction about the axis of the steering wheel, to select for example forward gear. To select reverse, the control lever 28 must first be turned in the opposite direction and this movement ceases when the control 28 lever reaches the neutral gate. At this point, the free end of the control lever 28 must be moved away from the steering wheel 10 to traverse the neutral gate before it can be rotated further about the steering column axis to rotate the collar 22 into the reverse position. In this way, it is possible to ensure that the control lever 28 cannot accidentally engage a drive gear while it is being returned into the neutral position. If desired, a spring may be provided between the collar 22 and the control lever 28 to bias the control lever into a central position so that it must intentionally be pulled towards or pushed away from the steering wheel 10 before a drive gear can be selected. It is not essential for the groove in the sleeve 24 to be Z shaped and it may for example be T shaped. In this case, the upright of the T will correspond to neutral and a spring may be used to urge the control lever 28 so that its projection 32 is automatically biased towards the base of the upright of the T shaped groove. To engage a gear, the control lever 28 must be urged in the opposite direction to the spring bias before it can be turned in either direction about the axis of the steering column to select the appropriate drive gear. It will be clear that the bevel gears 40, 42 will not be required to turn through a full revolution and for this reason, they need not be full gears but may be formed as toothed sectors or quadrants. It is possible to prevent accidental operation of the control lever 28 by adding an interlock between the clutch and the shuttle control. If such an interlock is added, the clutch would need to be operated before forward or reverse could be selected. Such an interlock could for example take the form of a spring biased locking element acting on any of the components that rotate with the collar 22 and retracted from its locking position, against its spring bias, by means of a cable that is connected to the clutch operating lever or pedal.

Claims: A vehicle having a steering column (14), a gearbox (20) forming part of the vehicle drive train and having a selection lever (18) and a gear change mechanism (16) mounted on the steering column (14) for remotely operating the selection lever (18) of the gearbox (20), and characterized in that the gear change mechanism (16) comprises : a collar (22) mounted for rotation about the axis of the steering column (14); a first bevel gear (40) fast in rotation with the collar (22); a second bevel gear (42) meshing with the first bevel gear (40) and mounted for rotation about a fixed axis that extends generally radially from the steering column (14); a crank arm (44) connected for rotation with the second bevel gear (42); and a flexible cable (23) connecting the crank arm (44) to the selection lever (18) of the gearbox (20); the cable (23) enabling the end of the selection lever (18) to be pulled and pushed by rotation of the collar (22) about the steering column (14). A vehicle according to claim 1, characterized in that the collar (22) is rotatable by a control lever (28) that extends generally radially from the steering column (14) and is mounted on the collar (22) for pivotal movement in a plane containing the axis of the steering column (14). A vehicle according to claim 2, characterized in that the radially inner end (32) of the control lever (28) extends through the collar (22) into a shaped stationary groove of a sleeve (24) secured to the steering column (14) and constrains the angular displacement of the collar (22) about the axis of the steering column (14) and the angular displacement of the control lever (28) relative to the collar (22). A vehicle according to any of the preceding claims, characterized in that the vehicle is an agricultural vehicle and the gear box (20) is a forward/reverse shuttle. A vehicle according to claim 4, when appended to claim 3, characterized in that the stationary groove is Z shaped and defines a gate in the neutral position that has to be crossed by moving the end of the control lever (28) parallel to the steering column (14) before it can rotate the collar (22) about the steering column (14) from the forward position to the reverse position. A vehicle according to claim 4, when appended to claim 3, characterized in that the stationary groove is T shaped and the control lever (28) is spring biased in its central position towards a locked position in which the collar (22) cannot be rotated in either direction, so that neither forward nor reverse may be selected. A vehicle according to any of the preceding claims, characterized in that an interlock is provided between the gear change mechanism (16) and a clutch operating lever to permit rotation of the collar (22) only when the clutch has been disengaged.

Inventors: MOWATT JEFFREY W, MOWATT, JEFFREY W.
Applicants: CNH UK LTD, CNH U.K. LIMITED
Application year: 2000
Main classification: F16H61
IPC codes: F16H61, B60K20