| 摘要 |
PURPOSE:To prevent a prime mover from over-run due to a motor action of a variable pump in descend along a steep slope by increasing a pressure in a hydraulic pump circuit when the rotational frequency of the prime mover exceeds a set governor range by a throttle lever. CONSTITUTION:When an engine is in a limit point of controlling the rotational frequency increased by a motor action of a variable capacity type pump and the output characteristics of a function generator 11b is set such that the out-signal of the function generator 11b has a maximum value, the engine is driven by the motor action of the hydraulic pump. When the rotational frequency of the engine reaches point B', the out-signal more than zero is generated from the function generator 11b. The signal is amplified by an amplifier 11c to drive an electromagnetic proportion relief valve 8 for increasing the circuit pressure in a fixed type hydraulic pump. When the circuit pressure is increased, load on the hydraulic pump is increased and applied to the engine so that the increase of rotational frequency of the engine is restrained. Also, when the rotational frequency exceeds point B' the corresponding out-signal is increased so that the load on the hydraulic pump is increased to prevent the engine from over-run. |
