Drive transmission system for working vehicle

A drive transmission system for a working vehicle for transmitting power of an engine to running devices through a main clutch, a main change speed device and an auxiliary change speed device, said main change speed device including a first group of hydraulic clutches, and a first group of control valves for operating these clutches, said auxiliary change speed device including a second group of hydraulic clutches, and a second group of control valves for operating these clutches, pressure oil being supplied to selected clutches of said first group of hydraulic clutches and said second group of hydraulic clutches to obtain a desired speed, said drive transmission system comprising:

• (A) shifter means for transmitting a shift command to said main change speed device and said auxiliary change speed device;
• (B) first control means operable in response to said shift command to operate, to a drain position, one of said first group of control valves placed in a supply position prior to transmission of said shift command, and to operate, to a supply position, a different one of said first group of control valves corresponding to said shift command;
• (C) second control means operable in response to said shift command to operate, to a drain position, one of said second group of control valves placed in a supply position, and thereafter to operate said one of said second group of control valves gradually to a supply position, and wherein said second control means is operable in response to said shift command to reduce a working pressure of said second hydraulic clutches to a predetermined low pressure when said one of said second group of control valves is operated to said drain position;
• (D) detection means including:
• an accelerator pedal sensor for detecting a position of an accelerator pedal;
• a rotation sensor for detecting a current rotating rate of said engine;
• a rotation difference detector for detecting a difference between a rotating rate of said engine in no-load condition corresponding to a detection value of said accelerator pedal sensor and said current rotating rate of said engine;
• and
• (E) third control means for setting said predetermined low pressure of said hydraulic clutch reduced by said second control means in response to said difference detected by said rotation difference detector.

A drive transmission system for a working vehicle for transmitting power of an engine to running devices through a main clutch, a main change speed device and an auxiliary change speed device, said main change speed device including a first group of hydraulic clutches, and a first group of control valves for operating these clutches, said auxiliary change speed device including a second group of hydraulic clutches, and a second group of control valves for operating these clutches, pressure oil being supplied to selected clutches of said first group of hydraulic clutches and said second group of hydraulic clutches to obtain a desired speed, said drive transmission system comprising:

• shifter means for transmitting a shift command to said main change speed device and said auxiliary change speed device;
• first control means operable in response to said shift command to operate, to a drain position, one of said first group of control valves placed in a supply position prior to transmission of said shift command, and to operate, to a supply position, a different one of said first group of control valves corresponding to said shift command;
• second control means operable in response to said shift command to operate, to a drain position, one of said second group of control valves placed in a supply position, and thereafter to operate said one of said second group of control valves gradually to a supply position;
• a second auxiliary change speed device disposed downstream of said auxiliary change speed device, which is switchable between low speed, neutral and high speed positions;
• a shift lever mechanically interlocked to said second auxiliary change speed device for operating said second auxiliary change speed device to one of said three positions;
• a lock controller for locking and unlocking said shift lever to/from positions corresponding to said three positions;
• and
• a main clutch control means for operating said main clutch to a disengaged position by draining pressure oil therefrom when said lock controller is in an unlocking position, and for operating said main clutch to an engaged position by supplying pressure oil thereto when said lock controller is in a locking position.

A drive transmission system for a working vehicle for transmitting power of an engine to running devices through a main clutch, a main change speed device and an auxiliary change speed device, said main change speed device including a first group of hydraulic clutches and a first group of control valves for operating these clutches, said auxiliary change speed device including a second group of hydraulic clutches and a second group of control valves for operating these clutches, pressure oil being supplied to selected clutches of said first group of hydraulic clutches and said second group of hydraulic clutches to obtain a desired speed, said drive transmission system comprising:

• shifter means for transmitting a shift command to said main change speed device and said auxiliary change speed device, wherein said shift means includes a shift-up button for shifting said main change speed device to an accelerating position, and a shift-down button for shifting said main change speed device to a decelerating position;
• first control means operable in response to said shift command to operate, to a drain position, one of said first group of control valves placed in a supply position prior to transmission of said shift command, and to operate, to a supply position, a different one of said first group of control valves corresponding to said shift command;
• and
• second control means operable in response to said shift command to operate, to a drain position, one of said second group of control valves placed in a supply position, and thereafter to operate said one of said second group of control valves gradually to a supply position.

A drive transmission system for a working vehicle for transmitting power of an engine to running devices through a main clutch, a main change speed device and an auxiliary clutch, said main change speed device including a first group of hydraulic clutches, a group of control valves for operating these clutches, and a second control valve for operating said auxiliary clutch, said auxiliary clutch being disposed between said running devices and said main change speed device, pressure oil being supplied to a selected one of said first group of said hydraulic clutches to obtain a desired speed, said drive transmission system comprising:

• (A) shifter means for transmitting shift command to said main change speed device;
• (B) first control means operable in response to said shift command to operate at one point of time, to a drain position, one of said first group of control valves placed in a supply position prior to transmission of said shift command, and to operate at a point of time which is earlier than said one point of time, to a supply position, a different one of said first group of control valves corresponding to said shift command;
• and
• (C) second control means operable in response to said shift command to operate at a point of time which is earlier than said one point of time said second control valve gradually to a supply position.