Taken from “New Features of the Kubota Grand L30 Series Compact Tractors”
The Glide Shift Transmission (GST) is original Kubota technology which provides 12 forward and 8 reverse shift-on-the-go gears without the need for clutch operation. The GST has a hydraulic clutch and transmission gears that are changed by the action of an actuator located in the transmission. When the operator initiates a gear change, the GST automatically performs a series of operations that includes disengaging the hydraulic clutch prior to the gear change, changing the gears and then engaging the hydraulic clutch after the change.
The ECU allows for a single shifting lever that actuates a potentiometer signifying the specific gear selection. In the Grand L30 series tractors, the ECU controls a proportional pressure reducing valve, solenoid valves, and performs a gear change by operating a hydraulic clutch.
With this GST system the pressurization of the hydraulic clutch can be set by a proportional pressure reducing valve for limitless stages, all of which is controlled by the ECU. The tractor is equipped with an engine tachometer sensor and a travel speed sensor, as well as a potentiometer that distinguishes the position of the gear selection lever. Based on digital signals from the engine tachometer sensor and the potentiometer, travel speed after the completion of a gear change is calculated, while the travel speed sensor calculates the actual travel speed. Based on the difference between the two speeds, the pressurization characteristics of the hydraulic fluid supplied to the clutch is set. Thus the Kubota GST brings about a smooth gear change by changing the pressurization characteristic in response to the various patterns of gear operation.
Acceleration of the tractor is calculated based on digital signals from the travel speed sensor. Under conditions when the tractor accelerates rapidly, the pressurization is changed to become slower during the pressurization process. When the tractor accelerates slowly, the pressurization is changed to be more prompt.
After the hydraulic clutch begins engaging and the acceleration of the tractor starts, the acceleration is calculated and the pressurization characteristic is compensated. Tractors may be equipped with a variety of different implements according the context of work users wish to perform. In particular, when an extremely heavy implement is attached to the tractor, acceleration does not occur until the compensation begins, which makes gear change time much longer. Therefore the compensation of the pressurization characteristic based on the total tractor weight is realized. The offset can be input using the “Adjustment Mode” of the IntelliPanel, with the correct offset stored in ROM. The ECU of the GST takes in the correction value by communicating with the ECU of the IntelliPanel and compensates the pressurization characteristic. The offset is just a derivative of the diameter of the tractors tire diameter.
