Transmission controllers

Abstract

A transmission controller for a multi-ratio tractor transmission is disclosed, the controller comprising a control dial ( 40 ) which is rotatable in one direction from a central position ( 43 ) into a field working zone ( 42 ) of movement and in the other direction into a road working zone ( 44 ) of movement to set the engine speed at which the transmission ( 11, 12 ) changes up in ratio when working in the field and on the road respectively.

1 . A transmission controller for a multi-ratio tractor transmission operable in an automated mode comprising a control member moveable in a field working zone of movement, and a roadworking zone of movement to set the engine speed at which the transmission changes up in ratio when working in the field and on the road respectively.  
   
   
       2 . A controller according to  claim 1  in which the control member is moveable in a first direction from a central position into the field working zone and in a second direction from the control position into the road working zone.  
   
   
       3 . A controller according to  claim 2  in which, with the control member in its central position, the associated transmission is set to operate in a manual mode in which ratio changes must be commanded by the operator.  
   
   
       4 . A controller according to  claim 1  for use in the control of a transmission having a series arrangement of a speed changing gearbox and a range changing gearbox in which either side of the central position two “speed matching” zones are provided for manual selection of the operative ratio for field and road use respectively, the control member when in a respective “speed matching” zone indicating to an overall transmission control system that, when a range change occurs, the ratio of the speed changing gearbox is also to be adjusted to ensure that the ratio provided by the overall transmission is the next overall ratio in the transmission.  
   
   
       5 . A controller according to  claim 4  in which as the control member is moved still further away from the central position in both the field and road zones it enters an automatic operation zone in which the position of the control member adjusts the speed at which the transmission changes up when operating automatically.  
   
   
       6 . A controller according to  claim 5  in which the position of the control member in the automatic operation zones also determine the speed at which the transmission changes down when operating automatically, the up and down changing speeds being linked by a predetermined relationship.  
   
   
       7 . A controller according to  claim 1  in which when the control member is operating in its field working zone the transmission can only operate automatically within its speed change gearbox.  
   
   
       8 . A controller according to  claim 2  in which the control member comprises a dial with a datum indicator rotatable in one direction from its central position into the field working zone and in the opposite direction into the road working zone.