Patent ID: 9506225
Filing Date: 2016-11-29
CPC Classification: E02F,F15B

Claim Text:
1. An actuator displacement measuring system in an electro-hydraulic system for a construction machine, including an electric motor, a hydraulic pump driven by the electric motor, a hydraulic actuator connected to the hydraulic pump, a load holding valve installed in a flow path between the hydraulic pump and the actuator, a relief valve installed in a branch flow path connected in parallel to the flow path, and a controller controlling driving of the electric motor, the actuator displacement measuring system comprising: controlling the driving of the electric motor according to a control signal from the controller; determining whether the electric motor is driven, and if the electric motor is driven, calculating a flow rate of the hydraulic pump; determining whether a displacement value of the actuator that is always detected by a detection signal input from a position detection sensor to the controller deviates from a zero value that is set as a reference position; determining whether a set pressure value of the relief valve is larger than or equal to a measured pressure value of the hydraulic system if the actuator displacement value deviates from the set zero value; setting the actuator displacement value to a previous value if the pressure value of the hydraulic system is larger than or equal to the pressure value of the relief valve, and calculating the actuator displacement value using a rotating speed of the electric motor, a sectional area of the actuator, and a supply flow rate of the hydraulic pump if the pressure value of the hydraulic system is smaller than the pressure value of the relief valve; and finishing the calculation after storing the actuator displacement value calculated up to now in the controller if a power-off request of the hydraulic system is input, and moving to an initial stage if the power-off request of the hydraulic system is not input.