Control of a continuously variable transmission
AssigneeCNH Industrial America LLC
InventorsRiccardo Morselli, Massimo Baroni, Francesco Roli
Life of this patent
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Abstract
A method is described for operating a vehicle fitted with a continuously variable transmission (CVT) and having a lever for varying the transmission ratio of the CVT to permit the vehicle operator to vary the vehicle wheel speed. In the invention, the transmission ratio of the CVT is limited to a value dependent upon at least one of the prevailing engine speed and the rate of change of the engine speed.
Claims8
A method of operating an agricultural vehicle fitted with a CVT and having a lever for varying a transmission ratio of the CVT within a range to permit an agricultural vehicle operator to vary vehicle wheel speed without causing an engine to stall, including the steps of:
- receiving a signal in a ratio computation unit indicative of a position of the lever, the position of the lever indicative of a desired wheel speed;
- receiving a signal from the engine in the ratio computation unit indicative of an engine speed;
- determining the transmission ratio of the CVT in the ratio computation unit for the desired wheel speed, wherein the transmission ratio for the desired wheel speed is determined from the position of the lever, the transmission ratio for the desired wheel speed is limited to an upper limit, and the upper limit is determined based on the engine speed and a rate of change of the engine speed;
- and
- transmitting the transmission ratio from the ratio computation unit to a CVT control unit to control the vehicle wheel speed.
An agricultural vehicle comprising:
- an engine,
- a CVT,
- a lever for enabling an operator of the agricultural vehicle to vary vehicle speed,
- a control system connected directly to the engine, the lever, and the CYT, wherein the control system is configured to:
- receive a signal in a ratio computation unit indicative of a position of the lever, the position of the lever indicative of a desired wheel speed;
- receive a signal from the engine in the ratio computation unit indicative of an engine speed;
- determine the transmission ratio of the CVT in the ratio computation unit for the desired wheel speed, wherein the transmission ratio for the desired wheel speed is determined from the position of the lever, the transmission ratio for the desired wheel speed is limited to an upper limit, and the upper limit is determined based on the engine speed and a rate of change of the engine speed;
- and
- transmit the transmission ratio from the ratio computation unit to a CVT control unit to control the vehicle wheel speed.
Dependencies are inferred from the claim text.