Title: Fluid control system for hydraulically operated transmissions and master clutch

• Summary
• Claims
• Description
• View all

Abstract: The power train between the engine and drive wheels of a motor grader, for example, comprises a normally engaged main engine clutch, a high-low power shift range transmission, and a four speed reversible power shift main transmission. The main engine clutch is releasable manually by a clutch pedal or releasable automatically by a hydraulically operated clutch release cylinder. The range transmission is shiftable into high or low by supplying hydraulic fluid to power shift clutches therein. The main transmission is shiftable into forward, reverse or neutral by manual operation of a direction selector valve. The main transmission is also shiftable into each of its speed ranges by axially moving the spool of a speed selector valve. The spool of the speed selector valve is axially movable into four positions by a hydromechanical linkage comprising three hydraulic shift cylinders. A fluid logic control system is provided to operate the main engine clutch, the range transmission and the main transmission automatically in a predetermined sequence so as to provide eight speed ranges in either forward or reverse. The control system comprises a high range shifter valve; a low range shifter valve; and an engine clutch sequence valve which operate in concert in response to manual operation of the spool of a speed control valve (having eight speed positions and neutral) to supply fluid to operate the engine clutch release cylinder and the range transmission shift clutches in a predetermined sequence. The three hydraulic shift cylinders are operated by the speed control valve. In accordance with the sequence, the normally engaged main engine clutch is automatically disengaged while either of the transmissions is undergoing a shifting operation so as to provide for smoother shifting and to relieve loads on the power shift clutches in the transmission. Furthermore, the range transmission automatically shifts twice (high and low) in each of the four speed ranges of the main transmission to provide a total of eight possible speed ranges.


Do you think this is a good invention? Vote now: