Abstract: During idling control with an acceleration switch ON, operation of the accelerator pedal is stopped. When stoppage of the operation of the accelerator pedal is detected for a predetermined time period, along with closing a slowdown switch, an idling changeover switch is changed over to its contact a. And the engine rotational speed is gradually slowed down by a command from a slowdown control section. On the other hand, when stoppage of the operation of an operation lever is detected for a predetermined time period, the idling changeover switch is changed over to its contact c. Due to this, the engine rotational speed is instantly controlled to the idling rotational speed.

Abstract: Control valves are respectively provided in a pair of variable displacement hydraulic pumps. If an ultra low speed travel signal is issued in response to an ultra-low-speed switch turned on, one of the control valves is fixed to a neutral position by a solenoid valve. And a displacement amount of a travel motor is fixed at a maximum displacement by another solenoid valve. In this way, an upper limit for motor rotation speed is significantly reduced. As a result, it is possible to realize the ultra low speed travel with maximum operation of an accelerator pedal, without the need for subtle operation of the accelerator pedal.

Abstract: A brake release unit is provided between a transmission control unit for controlling a transmission and a clutch device. Pressure oil supplied from a hydraulic pressure source to the clutch device is also guided to an accumulator of the brake release unit. When the engine is stopped, pressure oil from the clutch device is collected in a reservoir, and the transmission operates as a parking brake. Pressure oil accumulated in the accumulator is kept as it is. If a solenoid switching valve of the brake release unit is driven as a result of operation of a switch in the operator's cabin, pressure oil accumulated in the accumulator is supplied to the clutch device. As a result, it is possible to easily release the parking brake.

Abstract: Control valves are respectively provided in a pair of variable displacement hydraulic pumps. If an ultra low speed travel signal is issued in response to an ultra-low-speed switch turned on, one of the control valves is fixed to a neutral position by a solenoid valve. And a displacement amount of a travel motor is fixed at a maximum displacement by another solenoid valve. In this way, an upper limit for motor rotation speed is significantly reduced. As a result, it is possible to realize the ultra low speed travel with maximum operation of an accelerator pedal, without the need for subtle operation of the accelerator pedal.

Abstract: A brake release unit is provided between a transmission control unit for controlling a transmission and a clutch device. Pressure oil supplied from a hydraulic pressure source to the clutch device is also guided to an accumulator of the brake release unit. When the engine is stopped, pressure oil from the clutch device is collected in a reservoir, and the transmission operates as a parking brake. Pressure oil accumulated in the accumulator is kept as it is. If a solenoid switching valve of the brake release unit is driven as a result of operation of a switch in the operator's cabin, pressure oil accumulated in the accumulator is supplied to the clutch device. As a result, it is possible to easily release the parking brake.

Abstract: During idling control with an acceleration switch ON, operation of the accelerator pedal is stopped. When stoppage of the operation of the accelerator pedal is detected for a predetermined time period, along with closing a slowdown switch, an idling changeover switch is changed over to its contact a. And the engine rotational speed is gradually slowed down by a command from a slowdown control section. On the other hand, when stoppage of the operation of an operation lever is detected for a predetermined time period, the idling changeover switch is changed over to its contact c. Due to this, the engine rotational speed is instantly controlled to the idling rotational speed.