HYDRAULIC UNIT AND CONSTRUCTION MACHINE INCLUDING THE SAME

• US 20100115800A1
• Filed: 04/30/2008
• Published: 05/13/2010
• Est. Priority Date: 05/02/2007
• Status: Active Grant

• Current Assignee: Daikin Industries Ltd
• Original Assignee: Daikin Industries Ltd
• Inventors: Sakai, Toshiyuki, Kawata, Kenichi
• Granted Patent: US 8,136,271 B2
• Time in Patent Office: Days
• US Class Current: 37/348
• CPC Class Codes: E02F 9/2075 of the hybrid type for vehicles in general B60W20/00
• CPC Class Codes: E02F 9/2239 using two or more pumps with cross-assistance
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: F04B 1/26 Control
• CPC Class Codes: F04B 17/03 driven by electric motors
• CPC Class Codes: F04B 49/06 Control using electricity regulating by means of floats actuating electric switches F04B49/04
• CPC Class Codes: F04B 49/20 by changing the driving speed

Abstract

A hydraulic unit is switched among a first region A where a flow rate is adjusted by controlling a rotational speed of an electric motor while maintaining a displacement of a variable displacement pump at a maximum value, a second region B where the flow rate is adjusted by changing the displacement of the variable displacement pump while maintaining the rotational speed of the electric motor at a minimum value lower than the rotational speed in the first region A, and a third region C where, in a range where a discharge pressure of the variable displacement pump is larger than that in the first region A, the flow rate is adjusted by changing the rotational speed of the electric motor in a range larger than the minimum rotational speed, while maintaining the displacement of the variable displacement pump at an allowable maximum value that is derived from the discharge pressure and a maximum shaft torque of the electric motor.

Claims

1. A hydraulic unit, comprising:

a variable displacement pump (38);

an electric motor (37) capable of controlling its rotational speed, for driving the variable displacement pump (38); and

flow rate adjusting means (51) for switching among

a first region A where a flow rate is adjusted by controlling the rotational speed of the electric motor (37) while maintaining a displacement of the variable displacement pump (38) at a maximum value,

a second region B where the flow rate is adjusted by changing the displacement of the variable displacement pump (38) while maintaining the rotational speed of the electric motor (37) at a minimum value lower than the rotational speed in the first region A, and

a third region C where, in a range where a discharge pressure of the variable displacement pump (38) is larger than that in the first region A, the flow rate is adjusted by changing the rotational speed of the electric motor (37) in a range larger than the minimum rotational speed, while maintaining the displacement of the variable displacement pump (38) at an allowable maximum value that is derived from the discharge pressure and a maximum shaft torque of the electric motor (37).

2. The hydraulic unit of claim 1, wherein

the control of the rotational speed of the electric motor (37) is performed by inverter control.

3. A construction machine, comprising:

the hydraulic unit (50) of claim 2;

an engine (31); and

an electric generator (32) that is driven by the engine (31), wherein

electric power of the electric generator (32) is supplied to the electric motor (37) through an inverter (34).

4. The construction machine of claim 3, wherein

the construction machine is a hydraulic shovel (1).