Auxiliary drive system for combines

In a crop harvester having main drive wheels and auxiliary drive wheels, a drive system comprising:

• a hydrostatic drive including a pump and a variable displacement motor cooperatively arranged to drive the main drive wheels;
• auxiliary drive means operable from said hydrostatic drive for driving said auxiliary drive wheels;
• and
• control means for deactuating said auxiliary drive means in response to sensing a forward climb angle of the crop harvester less than a predetermined angle.

In a combine particularly adapted to operate on hilly terrain and having a pair of forward main drive wheels and a pair of steerable rear drive wheels, a drive system comprising:

• a hydrostatic drive including a pump and a variable displacement motor cooperatively arranged to drive the main drive wheels;
• auxiliary drive means operable from said hydrostatic drive for driving said rear drive wheels;
• means for actuating said auxiliary drive means in response to sensing fluid pressure in said hydrostatic driven having risen to a predetermined pressure under the influence of an increased degree of slope being traversed or other increase of the load on the combine;
• and
• means for reducing the displacement of said variable motor in response to actuating said auxiliary drive means thereby providing additional fluid for said auxiliary drive means and minimizing combine speed change.

In a combine particularly adapted to operate on hilly terrain and having a pair of forward main drive wheels and a pair of steerable rear drive wheels, a drive system comprising:

• a hydrostatic drive including a pump and a variable displacement motor cooperatively arranged to drive said main drive wheels;
• a pair of auxiliary hydraulic motors for driving said rear steerable wheels;
• means operative to selectively drive said auxiliary motors from said hydrostatic drive;
• a control system for automatically actuating and deactuating said auxiliary hydraulic motors, said control system including means for actuating said auxiliary hydraulic motors in response to sensing a predetermined pressure in said hydrostatic drive and means for deactuating said auxiliary hydraulic motors in response to sensing a predetermined minimum forward climb angle of said combine, whereby said rear wheels may be automatically driven as the combine climbs a hill and automatically disengaged as the combine approaches level ground.

In a vehicle having main drive wheels and auxiliary drive wheels, a drive system comprising:

• a hydrostatic drive including a pump and a variable displacement motor cooperatively arranged to drive the main drive wheels;
• auxiliary drive means operable from said hydrostatic drive for driving said auxiliary drive wheels;
• and
• control means for reducing the displacement of said variable motor in response to actuation of said auxiliary drive means to thus provide additional fluid to said auxiliary drive means and minimize vehicle speed change as the auxiliary drive means is actuated.

In a vehicle having main drive wheels and auxiliary drive wheels, a drive system comprising:

• a hydrostatic drive including a pump and a variable displacement motor cooperatively arranged to drive the main drive wheels;
• auxiliary drive means operable from said hydrostatic drive for driving said auxiliary drive wheels;
• and
• control means for deactuating said auxiliary drive means in response to sensing a forward climb angle of the vehicle less than a predetermined angle.

In a vehicle having main drive wheels and auxiliary drive wheels, a drive system comprising:

• a hydrostatic drive including a pump and a variable displacement motor cooperatively arranged to drive the main drive wheels;
• auxiliary drive means operable from said hydrostatic drive for driving said auxiliary drive wheels;
• means for actuating said auxiliary drive means in response to sensing a predetermined fluid pressure in said hydrostatic drive;
• and
• means for reducing the displacement of said variable motor in response to actuating said auxiliary drive means thereby providing additional fluid for said auxiliary drive means and minimizing vehicle speed change.

In a vehicle having a pair of forward main drive wheels and a pair of rear steerable wheels, a drive system comprising:

• a hydrostatic drive including a pump and a variable displacement motor cooperatively arranged to drive said main drive wheels;
• a pair of auxiliary hydraulic motors for driving said rear steerable wheels;
• valve means operative to selectively drive said auxiliary motors from said hydrostatic drive;
• a control system for automatically actuating and deactuating said auxiliary hydraulic motors, said control system including means for actuating said auxiliary hydraulic motors in response to sensing a predetermined pressure in said hydrostatic drive and means for deactuating said auxiliary hydraulic motors in response to sensing a predetermined minimum forward climb angle to said vehicle, whereby said rear wheels may be automatically driven as the vehicle climbs a hill and automatically disengaged as the vehicle approaches level ground.

In a vehicle having main drive wheels and auxiliary drive wheels, a drive system comprising:

• a reversable hydrostatic drive including a reversable pump and a variable displacement motor cooperatively arranged to drive the main drive wheels selectively in forward and reverse drive;
• auxiliary drive means operable from said hydrostatic drive for driving said auxiliary drive wheels;
• control means for reducing the displacement of said variable motor in response to actuation of said auxiliary drive means to thus provide additional fluid to said auxiliary drive means and minimize vehicle speed change as the auxiliary drive means is actuated;
• and
• means for maintaining full displacement of said variable motor when the hydrostatic drive is in reverse drive.