Powershift transmission system with torque-mapped shifts

A method for shifting a powershift transmission in an off-road vehicle, the powershift transmission having at least one proportionally-modulatable, directional clutch coupled to an engine having a turbocharger and operating at an engine speed, the method comprising the steps of:

• generating a data table representing a known engine load as a function of a known engine speed and a known turbo boost pressure for a plurality of operating conditions of the engine;
• monitoring a turbo boost pressure developed by the turbocharger and generating a turbo boost signal therefrom;
• monitoring the engine speed and generating an engine speed signal therefrom;
• comparing the turbo boost signal and the engine speed signal with the data table to estimate the load being experienced by the engine and to produce an engine load value therefrom;
• generating a shift profile signal based on the engine load value;
• and
• modulating the directional clutch into engagement at a desired rate of engagement based on the shift profile signal to shift the transmission.

A method of generating a data table having a known engine load, a known engine speed and a known turbo boost pressure for a plurality of operating conditions to be used in an electronic transmission controller for shifting a powershift transmission of an off-road vehicle having at least one proportionally-modulatable, directional clutch coupled to an engine having a turbocharger and operating at an engine speed, the method comprising the steps of:

• setting an operating condition for the engine, including a throttle condition, a loading condition and an engine speed;
• measuring measured values for the turbo boost pressure, the engine speed and the engine load to determine the known turbo boost pressure, the known engine speed and the known engine load for the operating condition;
• and
• storing the known turbo boost pressure, the known engine speed and the known engine load as a data point in the data table to create a sparsely populated data table;
• whereby an engine load value which estimates the load being experienced by the engine can be determined as a function of the known engine speed and the known turbo boost pressure.

An electronic transmission controller for use in an off-road vehicle of the type having an engine including a turbo charger, a turbo boost pressure sensor and an engine speed sensor, and a powershift transmission system having at least one directional clutch which is proportionally modulatable in response to a shift profile signal for shifting the powershift transmission system, the electronic transmission controller comprising:

• a turbo boost signal generator for generating a turbo boost signal from the turbo boost pressure sensor;
• an engine speed signal generator for generating an engine speed signal from the engine speed sensor;
• means for estimating the load being experienced by the engine as a function of the turbo boost signal and the engine speed signal and producing an engine load value;
• and
• a shift profile signal generator for generating a shift profile signal from the engine load value,
• whereby the shift profile signal proportionally modulates said at least on directional clutch for shifting the powershift transmission.