Hydraulic control system for a tractor transmission

A control system for a transmission having a speed transmission assembly including an input shaft and a plurality of clutch operated means for effecting a plurality of different forward output speeds and at least one reverse output speed, a range transmission assembly including a transmission output shaft and a plurality of clutch operated means, each clutch operated means of said range transmission assembly being capable of modifying the different output speeds of said speed transmission assembly, and a fluid pressure actuated master clutch assembly for selectively coupling said transmission assemblies, said control system comprising:

• a valve body connected to a hydraulic source of fluid pressure;
• operator controlled means arranged in said valve body for selectively directing fluid pressure to various clutch operated means in said speed and range transmission assemblies to condition the transmission into a forward, reverse, or neutral mode of operation;
• and
• means for modulating master clutch operation as a function of various transmission operating conditions.

A control system for a transmission including an operator controlled shift lever, a speed transmission assembly having a rotatable input shaft and a plurality of fluid pressure operated drive assemblies for conditioning the transmission into a creeper, a forward, or a reverse mode of operation as a function of shift lever position, a range transmission assembly including a transmission output shaft and a plurality of fluid pressure operated drive assemblies for conditioning the transmission to operate in various speed ranges as a function of shift lever position, and a master clutch for selectively coupling the speed and range transmission assemblies, said control system comprising:

• a hydraulic valve body connected to a source of fluid pressure;
• operator controlled means arranged in said valve body and operably connected to said shift lever for directing fluid pressure to select drive assemblies as a function of shift lever position, said operator controlled means including a fluid valve apparatus the position of which in said valve body controls the creeper mode of transmission operation;
• and
• means for controlling master clutch operation as a function of various transmission operating conditions.

A control valve for a fluid actuated master clutch of a transmission which is shiftable from a neutral condition to multiple step forward and reverse conditions, said transmission including a speed transmission assembly, a range transmission assembly, with said master clutch operably disposed therebetween for selectively coupling said speed and range transmission assemblies, said control valve comprising:

• a valve body defining an inlet port to which fluid pressure is directed and an outlet port opening to said master clutch;
• a manual master clutch pressure modulation assembly operably arranged in said valve body between said inlet port and said outlet port for regulating operation of said master clutch in response to manual operation of said assembly;
• and
• an automatic master clutch pressure modulation assembly operably arranged in said valve body between said inlet port and said outlet port for automatically regulating operation of said master clutch in response to continuing operating conditions of the transmission.

A control valve for a fluid actuated master clutch of a transmission shiftable from a neutral condition and operable in low, medium and high ranges with each range having a plurality of progressively different speed ratios, said master clutch being operably disposed between speed and range transmission assemblies comprising said transmission, said control valve assembly comprising:

• a valve body having an inlet port to which fluid pressure is directed and an outlet port opening to said master clutch;
• a first valve assembly operably disposed between said inlet and outlet ports for modulating fluid pressue to said master clutch in response to manual manipulation of said first valve assembly;
• and
• a second valve assembly operably disposed between said inlet and outlet ports for automatically modulating fluid pressure to said master clutch during transmission operation including disengagement of the master clutch between shifts in higher speed ratios and subsequent modulated rengagement of the master clutch.