Daikin Industries, Ltd.

Hitoshi Horiuchi

Jun Nakatsuji

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.

Load dependent variable speed hydraulic unit

A hydraulic control apparatus has a transistor which is changed over by a control signal inputted to an input terminal thereof; and a solenoid controlled valve having a spool actuated by a DC solenoid to be driven by exciting current whose pulse duration has been controlled by the transistor. The hydraulic control apparatus is characterized by having an adder for adding a command signal and an AC signal having a dither frequency; an oscillator for generating a signal having a constant frequency higher than the maximum frequency of the command signal; a subtractor for subtracting a signal representing pulse duration of the exciting current and inputted through a low-pass filter from a signal outputted from the adder; and a comparator for comparing a signal outputted from the subtractor with a signal outputted from the oscillator, outputting a pulse width-modulated control signal to the input terminal of the transistor so as to control the ON and OFF of the transistor, so that the solenoid controlled valve can be controlled with a fast response and high gain and a small amount of phase delay.

Growing community of inventors

Settsu, Japan

Hitoshi Horiuchi