Agricultural system with a square baler controlled via a continuously variable transmission
An agricultural system includes a baler with a plunger and a sensor for sensing a plunger-related value; a vehicle including a power source operable to convey power to the plunger; and a CVT arranged to drive the plunger. In order to balance a fluctuating load of the plunger over the working cycle, an electronic control unit (ECU) is coupled to the sensor and to the CVT and is configured to receive the signal from the sensor and to cause the CVT to modify a gear ratio of the CVT based on the signal from the sensor and on a mathematical model defining a CVT gear ratio variation profile derived from an expected load applied by crop on the plunger over its operating cycle.
1. An agricultural system comprising:
a baler comprising:
a plunger operable to process a value of crop material and having an operating cycle; and
a sensor for sensing a plunger-related value indicating a progression of the operating cycle and configured to output a signal;
a vehicle comprising a power source operable to convey power to the plunger;
a continuously variable transmission (CVT) arranged to drive the plunger and driven by the power source; and
an electronic control unit coupled to the sensor and to the CVT and configured to:
receive the signal from the sensor; and
cause the CVT to modify a gear ratio of the CVT based on the signal from the sensor and on a mathematical model defining a CVT gear ratio variation profile derived from an expected load applied by the crop on the plunger over the operating cycle, the expected load comprising an increase when the plunger presses the crop and a decrease when the plunger retracts, so as to result in a change in the CVT gear ratio to such an extent as to compensate for a peak of the expected load,
wherein the electronic control unit is further configured to:
receive a time history of the expected load during a calibration phase, and
adjust the CVT gear ratio variation profile.
2. The system according to claim 1 , wherein CVT gear ratio variation profile has a starting point and the electronic control unit re-starts the variation profile from the starting point for each operating cycle.
3. The system according to claim 1 , wherein the gear ratio variation profile is unchanged when a speed of the vehicle is constant.
4. The system according to claim 1 , wherein the electronic control unit and the sensor are coupled via an ISOBUS on-board communication network.
5. The system according to claim 1 , wherein the sensor measures a position of the plunger.
6. The system according to claim 1 , wherein the power source is an internal combustion (IC) engine having a nominal power and the baler has a maximum peak power, the maximum peak power being higher than the nominal power.
7. The system according to claim 1 , wherein the electronic control unit stores a library of CVT gear ratio variation profiles, and wherein the agricultural system further comprises a user-interface configured for receiving a selection of a preferred profile.
8. The system according to claim 1 , wherein an output shaft of the CVT is connected to the plunger via a flywheel.
9. The system according to claim 1 , wherein the CVT is a planetary gear.
10. A vehicle comprising:
a power source operable to convey power to a plunger of a baler having an operating cycle;
a continuously variable transmission (CVT) arranged to drive the plunger and receive power by the power source; and
an electronic control unit coupled to the CVT and configured to:
be coupled to a sensor of the baler;
receive a signal from the sensor indicating a plunger-related value about a progression of the operating cycle; and
cause the CVT to modify a gear ratio of the CVT based on the signal from the sensor and on a mathematical model defining CVT gear ratio variation profile from an expected load applied by crop on the plunger over the operating cycle, the expected load comprising an increase when the plunger presses the crop and a decrease when the plunger retracts, so as to result in a change in the CVT gear ratio of such an extent as to compensate for a peak of the expected load,
wherein the electronic control unit is further configured to:
receive a time history of the expected load during a calibration phase, and
adjust the CVT gear ratio variation profile.
11. The vehicle according to claim 10 , wherein the vehicle is a tractor.