Process for weighing the harvested crop stored in a tank on a harvesting machine

1. A process for weighing a harvested crop stored in at least one tank supported by a frame of a harvesting machine, the frame being mounted on a wheel set by a lifting device which is operable to move the frame upwardly and downwardly upon control of a hydraulic system of the harvesting machine, the process comprising an acquisition procedure wherein, upon controlling the hydraulic system for lowering and raising the frame on a displacement course, the process including the steps of:

halting a displacement of the wheel set before performing the acquisition procedure;

determining at least one height position of the frame on said displacement course;

measuring a lowering pressure and a raising pressure in the hydraulic system at said position;

calculating, from said measured pressures, a balancing pressure for said frame;

wherein:

said acquisition procedure is performed before unloading the stored crop in order to calculate a loaded balancing pressure and after said unloading in order to calculate an empty balancing pressure; and

the weight of the stored crop is calculated from a pressure variation between said loaded balancing pressure and said empty balancing pressure.

2. The process according to claim 1 , wherein the lifting device comprises hydraulic cylinders which are mounted between the frame and the wheel set for activation by the hydraulic system, the lowering and raising pressures being measured in or at least one of said hydraulic cylinders.

3. The process according to claim 2 , wherein the lowering and raising pressures are measured in each of said hydraulic cylinders, the acquisition procedure providing for averaging said lowering and said raising pressures for calculating the balancing pressure from said averages.

4. The process according to claim 2 , wherein the hydraulic cylinders are activated on the same displacement course by the hydraulic system.

5. The process according to claim 2 , wherein the acquisition procedure provides for measuring the displacement course of at least one of said hydraulic cylinders to determine the height position of the frame.

6. The process according to claim 2 , wherein each said hydraulic cylinder comprises a barrel wherein a rod slides on a displacement course, the acquisition procedure providing for measuring lowering and/or raising pressures (Pbarrel) at the barrel side and lowering and/or raising pressures (Prod) at the rod side, and for calculating the lowering and/or raising pressures (Pcyl) in each said hydraulic cylinder by the following formula:

Pcyl=P−α*Prod

wherein a is a predetermined coefficient determined from a calibration of the hydraulic system.

7. The process according to claim 1 , wherein the acquisition procedure provides for determining a pressure measurement course defined by two height positions of the frame on the displacement course, the lowering and the raising pressures being calculated from the pressures measured during displacement of the frame between said two height positions.

8. The process according to claim 7 , wherein the determined height positions are respectively a low-height position corresponding to approximately 25% of the maximum displacement reachable by the frame and a high-height position corresponding to approximately 60% of said maximum displacement.

9. The process according to claim 1 , wherein the acquisition procedure provides for calculating the balancing pressures from an average of the measured pressures.

10. The process according to claim 1 , wherein the acquisition procedure provides for controlling the hydraulic system so that pressures generated by parasitic frictions during respectively lowering and raising displacements are substantially equal.

11. The process according to claim 10 , wherein the hydraulic system is controlled to obtain the same upward and downward displacement speed of the frame.

12. The process according to claim 1 , wherein the acquisition procedure provides for controlling the hydraulic system for successively lowering and raising the frame.

13. The process according to claim 1 , wherein the wheel set comprises at least one rear wheel that is mounted in rotation on the frame by a rear lever arm, the acquisition procedure providing for measuring an angular position of said rear lever arm to determine the height position of the frame.

14. The process according to claim 1 , wherein the preliminary step provides for controlling the hydraulic system for blocking rear wheels of the wheel set and for liberating front wheels of said wheel set, so as to limit the occurrence of parasitic pressures resulting from forces on said front wheels in said hydraulic system during the acquisition procedures.

15. A harvesting machine, comprising:

a wheel set on which a frame supporting at least one crop storage tank is mounted by a lifting device operable by a hydraulic system, said machine being characterized in that it further comprises a controller operable to control the hydraulic system for performing a process for weighing the harvested crop stored in said tank before the unloading of said crop, the process comprising an acquisition procedure wherein, upon controlling the hydraulic system for lowering and raising the frame on a displacement course, the process including the steps of:

halting a displacement of the wheel set before performing the acquisition procedure;

determining at least one height position of the frame on said displacement course;

measuring a lowering pressure and a raising pressure in the hydraulic system at said position;

calculating, from said measured pressures, a balancing pressure for said frame;

wherein:

said acquisition procedure is performed before unloading the stored crop in order to calculate a loaded balancing pressure and after said unloading in order to calculate an empty balancing pressure; and

the weight of the stored crop is calculated from a pressure variation between said loaded balancing pressure and said empty balancing pressure.