Kubota Corporation

Hironobu Kubota

Akihiro Asada

Mitsuhiko Obe

Akio Inamori

Shigeo Sakamoto

Kazushige Komori

During a shifting operation to slide a shift gear of an auxiliary change speed device, clutches of a backward and forward drive switching device acting also as a propelling clutch and of a main change speed device are automatically disengaged to place these devices in neutral state. After the shift gear is switched to a high-speed position or low-speed position, the clutches of the main change speed device are automatically engaged to return the main change speed device to a transmitting state. After the main change speed device returns to the transmitting state, the clutches of the backward and forward drive switching device are automatically engaged to return the backward and forward drive switching device to a transmitting state.

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 is disclosed. The main change speed device includes a first group of hydraulic clutches and a group of control valves for operating these clutches. The auxiliary change speed device includes a second group of hydraulic clutches and control valves for operating these clutches. Pressure oil is supplied to selected clutches of the first and second groups of hydraulic clutches to obtain the desired speed. The drive transmission system includes a shifter mechanism for transmitting a shift command to the main and auxiliary change speed devices; a first controller operable in response to the shift command to operate one of the first control valves to a drain position which was placed in a supply position prior to transmission of the shift command, and to operate to a supply position a different one of the first control valves corresponding to the shift command; and a second controller operable in response to the shift command to operate one of the second control valves to a drain position which was placed in a supply position, and thereafter to operate one of the second control valves gradually to a supply position.

Drive transmission system for working vehicle

A hydraulic circuit for a working vehicle comprising a first pump, a second pump, a first actuator, a second actuator, and a selector valve having a plurality of control positions. The selector valve is switchable between a first position for connecting the first pump to the first actuator and the second pump to the second actuator, and a second position for connecting the first pump and the second pump to the second actuator. This circuit includes a first relief valve disposed between the selector valve and the first pump, and a second relief valve disposed between the selector valve and the second pump. The first relief valve is set to a higher relief pressure than the second relief valve.

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Sakai, Japan

Hironobu Kubota