Load dependent variable speed hydraulic unit

• US 6,537,032 B1
• Filed: 05/24/2001
• Issued: 03/25/2003
• Est. Priority Date: 09/24/1999
• Status: Expired due to Term

• Current Assignee: Daikin Industries Ltd
• Original Assignee: Daikin Industries Ltd
• Inventors: Nakatsuji, Jun, Horiuchi, Hitoshi
• Primary Examiner(s): Tyler, Cheryl J.
• Assistant Examiner(s): Solak, Timothy P.
• Application Number:
  US09/856,664
• Time in Patent Office: 670 Days
• Field of Search: 417/18, 417/22, 417/42, 417/44.11, 417/48.2, 417/43
• US Class Current: 417/18
• CPC Class Codes: F04D 15/0066 by changing the speed, e.g. of the driving engine

Abstract

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 25 of a controller 11 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 28 calculates a deviation of this target horsepower and a present horsepower received from a present horsepower calculation unit 26, inputs a control signal representing this deviation to the inverter 3 and controls a rotational number of a variable-speed motor 2 so that the present horsepower coincides with the target horsepower.

Claims

1. An autonomous inverter-driven hydraulic unit comprising:

a hydraulic pump (1);

a variable-speed motor (2) for driving the hydraulic pump (1);

an inverter (3) for driving the variable-speed motor (2);

a load sensor (6) for detection a load of the hydraulic pump (1);

a rotation sensor (5) for detecting a rotation speed of the variable-speed motor (2) or hydraulic pump (1);

a controller (11) for outputting a control signal to the inverter (3) based on outputs from the load sensor (6) and rotation sensor (5) so that a pressure and flow rate of fluid discharged from the hydraulic pump (1) become a pressure and flow rate on a predetermined target pressure-flow rate characteristic line, the controller (11) having a target horsepower calculation unit (25) calculating a target horsepower based on the outputs from the load sensor (6) and rotation sensor (5) and the target pressure-flow rate characteristic line, a present horsepower calculation unit (26) calculating a present horsepower based on the outputs from the load sensor (6) and rotation sensor (5) and a comparison unit (27) comparing the target horsepower and the present horsepower and outputting the control signal to the inverter (3).

2. The autonomous inverter-driven hydraulic unit according to claim 1, wherein the target pressure-flow rate characteristic line is composed of a maximum flow rate (MV), maximum horsepower curve (MHP), and maximum pressure line (MP).

3. The autonomous inverter-driven hydraulic unit according to claim 1, wherein

the load sensor is a current sensor for detecting current flowing to the variable-speed motor (2).

4. The autonomous inverter-driven hydraulic unit according to claim 1, wherein

the load sensor (6) is a pressure sensor (6) for detecting a pressure in a discharge line of the hydraulic pump (1).