Daikin Industries, Ltd.

Jun Nakatsuji

Hitoshi Horiuchi

Yoshiyuki Ochi

A first pump of small capacity and a second pump of large capacity are connected directly with each other and are driven by a variable-speed motor. The rotational speed of the variable-speed motor is controlled by a control device. In a first mode, a first discharge line of the first pump and a second discharge line of the second pump are disconnected with each other, making the first pump unloaded. With the first pump in the unloaded state, a constant-horsepower operation is performed, where the discharge fluid is brought into a high pressure by relatively small torque. In a second mode, the first discharge line and the second discharge line are connected with each other by a switching valve. With the first and second discharge lines in the connected state, a constant-horsepower operation is performed, where a high flow rate of discharge fluid is discharged at relatively low rotational speed.

Pump unit with multiple operation modes

There is provided an autonomous inverter-driven hydraulic unit in which a command pressure and command flow rate do not need to be inputted from outside and a pressure and flow rate can be autonomously controlled without requiring any input signal wire. A target horsepower calculation unit of a controller judges which of a plurality of regions a point representing a present operating state belongs to and calculates a target horsepower represented by a point on a target pressure-flow rate characteristic line based on the present pressure and present flow rate. A comparison unit calculates a deviation of this target horsepower and a present horsepower received from a present horsepower calculation unit , inputs a control signal representing this deviation to the inverter and controls a rotational number of a variable-speed motor so that the present horsepower coincides with the target horsepower.

Growing community of inventors

Settsu, Japan

Jun Nakatsuji