Four-wheel traveling system for tipper

A four-wheel drive traveling system for a tipper having rear wheels and front wheels, an engine with an output side connected to the rear wheels via a power transmission, at least one variable hydraulic motor drivingly coupled with the front wheels, and a variable hydraulic pump driven by the engine and coupled in a circuit with the at least one variable hydraulic motor, said four-wheel drive traveling system comprising a control system including:

• means for controlling displacement of the variable hydraulic pump;
• means for controlling capacity of the at least one variable hydraulic motor;
• a main controller having a normal travel mode and an abnormal travel mode, and a mode changeover switch,
• wherein during said normal travel mode, said main controller controls displacement of the variable hydraulic pump and capacity of the at least one variable hydraulic motor depending upon a rear wheel rotation speed, and
• wherein during said abnormal travel mode, said main controller operates to make the displacement of the variable hydraulic pump and the capacity of the at least one variable hydraulic motor maximum upon receipt of a transmission neutral signal.

A four-wheel drive traveling system for a tipper having rear wheels and front wheels, an engine with an output side connected to the rear wheels via a power transmission, at least one variable hydraulic motor drivingly coupled with the front wheels, and a variable hydraulic pump driven by the engine and coupled in a closed circuit with the at least one variable hydraulic motor via first and second primary circuits, said four-wheel drive traveling system comprising a hydraulic drive abnormality detection system including:

• means for detecting pressures of the first and second primary circuits, respectively;
• means for ascertaining an abnormal value of the pressures detected by said detecting means;
• and
• a display device for displaying an abnormality signal when an abnormal value of the pressures detected by said detecting means is ascertained by said ascertaining means.

A four-wheel drive traveling system for a tipper having rear wheels and front wheels, an engine with an output side connected to the rear wheels via a power transmission, at least one variable hydraulic motor drivingly coupled with the front wheels, and a variable hydraulic pump driven by the engine and coupled in a circuit with the at least one variable hydraulic motor, said four-wheel drive traveling system comprising a control system including:

• means for controlling displacement of the variable hydraulic pump;
• means for setting a discharge pressure of said variable hydraulic pump at either a high discharge pressure or a low discharge pressure;
• means for detecting a steering angle of said front wheels;
• means for detecting rear wheel slippage by comparing the front wheel rotation speed with the rear wheel rotation speed, the front wheel rotation speed being determined by obtaining a rotation speed value by dividing a sum of the rotation speeds of the left and right front wheels in half and then correcting the rotation speed value by multiplying the rotation speed value by a correction coefficient corresponding to the steering angle detected by said steering angle detecting means;
• and
• means for controlling said setting means so that the discharge pressure of said variable hydraulic pump is set at said low discharge pressure when no rear wheel slippage is detected, and so that the discharge pressure of said variable hydraulic pump is set at said high discharge pressure when rear wheel slippage is detected.

A four-wheel drive traveling system for a tipper having rear wheels and front wheels, an engine with an output side connected to the rear wheels via a power transmission, at least one variable hydraulic motor drivingly coupled with the front wheels, and a variable hydraulic pump driven by the engine and coupled in a circuit with the at least one variable hydraulic motor, said four-wheel drive traveling system comprising a control system including:

• means for controlling displacement of the variable hydraulic pump;
• means for setting a discharge pressure of said variable hydraulic pump at either a high discharge pressure or a low discharge pressure;
• means for detecting rear wheel slippage;
• means for controlling said setting means so that the discharge pressure of said variable hydraulic pump is set at said low discharge pressure when no rear wheel slippage is detected, and so that the discharge pressure of said variable hydraulic pump is set at said high discharge pressure when rear wheel slippage is detected;
• means for detecting a braking state of the tipper;
• and
• means for causing said displacement controlling means to reduce displacement of said variable hydraulic pump to a magnitude which causes a pumping effect of said at least one variable hydraulic motor such that said at least one variable hydraulic motor causes a braking resistance of the front wheels, upon detection of a braking state by said braking state detecting means.

A four-wheel drive traveling system for a tipper having rear wheels and front wheels, an engine with an output side connected to the rear wheels via a power transmission, at least one variable hydraulic motor drivingly coupled with the front wheels, and a variable hydraulic pump driven by the engine and coupled in a circuit with the at least one variable hydraulic motor, said four-wheel drive traveling system comprising a control system including:

• means for controlling displacement of the variable hydraulic pump;
• means for setting a discharge pressure of said variable hydraulic pump at either a high discharge pressure or a low discharge pressure;
• means for detecting rear wheel slippage;
• means for controlling said setting means so that the discharge pressure of said variable hydraulic pump is set at said low discharge pressure when no rear wheel slippage is detected, and so that the discharge pressure of said variable hydraulic pump is set at said high discharge pressure when rear wheel slippage is detected;
• and
• means for setting the discharge pressure of said variable hydraulic pump at respectively different levels in an empty state of the tipper, a loaded state of the tipper, a hill-climbing state of the tipper and a hill-descending state of the tipper.

A four-wheel drive traveling system for a tipper having rear wheels and front wheels, an engine with an output side connected to the rear wheels via a power transmission, at least one variable hydraulic motor drivingly coupled with the front wheels, and a variable hydraulic pump driven by the engine and coupled in a circuit with the at least one variable hydraulic motor, said four-wheel drive traveling system comprising a control system including:

• means for controlling displacement of the variable hydraulic pump;
• means for setting a discharge pressure of said variable hydraulic pump;
• means for detecting an actual input pressure to said at least one variable hydraulic motor;
• means for outputting a capacity control signal for said displacement controlling means on the basis of a difference between the discharge pressure set by said discharge pressure setting means and the actual input pressure detected by said actual input pressure detecting means;
• and
• means for setting the discharge pressure of said variable hydraulic pump at respectively different levels in an empty state of the tipper, a loaded state of the tipper, a hill-climbing state of the tipper and a hill-descending state of the tipper.