Hybrid construction machine

• US 8,924,100 B2
• Filed: 08/18/2011
• Issued: 12/30/2014
• Est. Priority Date: 09/08/2010
• Status: Active Grant

• Current Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Inventors: Imura, Shinya, Ishida, Seiji, Satake, Hidetoshi, Kajita, Yusuke, Fujishima, Kazuo, Ooki, Takatoshi
• Primary Examiner(s): Dager, Jonathan M
• Application Number:
  US13/817,913
• Publication Number:
  US 20130197768A1
• Time in Patent Office: 1,230 Days
• US Class Current: 701/50
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 10/103 of fluid type
• CPC Class Codes: B60W 10/30 including control of auxiliary equipment, e.g. air-conditioning compressors or oil pumps
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 2300/17 Construction vehicles, e.g. graders, excavators
• CPC Class Codes: E02F 9/2075 of the hybrid type for vehicles in general B60W20/00
• CPC Class Codes: E02F 9/2091 Control of energy storage means for electrical energy, e.g. battery or capacitors energy recovery arrangements in hydraulic or pneumatic drives E02F9/2217
• CPC Class Codes: E02F 9/2235 including an electronic controller
• CPC Class Codes: E02F 9/2246 Control of prime movers, e.g. depending on the hydraulic load of work tools
• CPC Class Codes: F02D 29/04 peculiar to engines driving pumps
• CPC Class Codes: F02D 31/007 controlling fuel supply
• CPC Class Codes: F02D 41/021 Introducing corrections for particular conditions exterior to the engine conjoint control of vehicle sub-units for propelling the vehicle B60W30/18
• CPC Class Codes: G05B 13/02 electric
• CPC Class Codes: G06F 17/00 Digital computing or data processing equipment or methods, specially adapted for specific functions information retrieval, database structures or file system structures therefor G06F16/00
• CPC Class Codes: Y02T 10/40 Engine management systems
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A hybrid construction machine is provided with a variable displacement hydraulic pump 1 which supplies hydraulic oil to a hydraulic actuator, an engine 2 which is provided to be able to drive and rotate the hydraulic pump 1, an electric motor 3 which is provided to be able to drive and rotate the hydraulic pump 1, an engine control dial 4, a controller 4 and an operating lever 5. The controller changes the rotation speed of the engine 2 to reduce fuel consumption according to power generated by the engine 2, and changes displacement of the hydraulic pump 1 based on the rotation speed of the engine 2, the dial position of the engine control dial 4 and the amount of operation on the operating lever 5.

Claims

1. A hybrid construction machine comprising:

a variable displacement hydraulic pump which discharges hydraulic oil for a hydraulic actuator;

an engine which drives the hydraulic pump;

an electric motor which is driven by the engine to charge generated electric power into an electric storage device and which is driven by the electric power charged in the electric storage device so as to assist the engine to drive the hydraulic pump; and

a controller which controls driving of the hydraulic pump, the engine and the electric motor;

characterized in that;

the controller includes an engine power calculating unit which calculates power generated by the engine, a first rotation speed calculating unit which calculates a rotation speed of the engine to minimize fuel required for generating the engine power, a second rotation speed calculating unit which determines a lower limit of a target rotation speed of the engine, a target rotation speed calculating unit which selects a larger one of a first rotation speed outputted from the first rotation speed calculating unit and a second rotation speed outputted from the second rotation speed calculating unit, an engine control unit which controls the engine so as to make a real rotation speed of the engine approach the target rotation speed, a target flow rate calculating unit which calculates a target flow rate of the hydraulic oil discharged from the hydraulic pump, and a hydraulic pump control unit which controls displacement of the hydraulic pump based on the real rotation speed or the target rotation speed of the engine so that a flow rate of the hydraulic oil discharged from the hydraulic pump approaches the target flow rate;

a target maximum total power calculating unit which calculates a target maximum value of total power of the engine and the electric motor is provided;

the second rotation speed calculating unit calculates a minimum rotation speed of the engine required for generating the target maximum total power in the engine and the electric motor; and

the target maximum total power calculating unit calculates the target maximum total power based on a dial position of an engine control dial.

2. A hybrid construction machine according to claim 1, characterized in that:

the target flow rate calculating unit calculates the target flow rate based on a dial position of an engine control dial and an amount of operation on an operating lever.

3. A hybrid construction machine according to claim 1, characterized in that:

the engine power calculating unit calculates the engine power based on an amount of fuel injection in the engine and the rotation speed of the engine.

4. A hybrid construction machine according to claim 1, characterized in that:

the engine power calculating unit calculates the engine power based on the discharge flow rate and a discharge pressure of the hydraulic pump, the power of the electric motor and a load of accessories.

5. A hybrid construction machine according to claim 1, characterized in that:

the second rotation speed calculating unit calculates a minimum rotation speed of the engine required for securing the target flow rate of the hydraulic pump.

6. A hybrid construction machine according to claim 1, wherein the controller increases displacement of the hydraulic pump when the real rotation speed of the engine decreases, and the controller decreases the displacement of the hydraulic pump when the real rotation speed of the engine increases.

7. A hybrid construction machine comprising:

a variable displacement hydraulic pump which discharges hydraulic oil for a hydraulic actuator;

an engine which drives the hydraulic pump;

an electric motor which is driven by the engine to charge generated electric power into an electric storage device and which is driven by the electric power charged in the electric storage device so as to assist the engine to drive the hydraulic pump; and

a controller which controls driving of the hydraulic pump, the engine and the electric motor;

characterized in that;

the controller includes an engine power calculating unit which calculates power generated by the engine, a first rotation speed calculating unit which calculates a rotation speed of the engine to minimize fuel required for generating the engine power, a second rotation speed calculating unit which determines a lower limit of a target rotation speed of the engine, a target rotation speed calculating unit which selects a larger one of a first rotation speed outputted from the first rotation speed calculating unit and a second rotation speed outputted from the second rotation speed calculating unit, an engine control unit which controls the engine so as to make a real rotation speed of the engine approach the target rotation speed, a target flow rate calculating unit which calculates a target flow rate of the hydraulic oil discharged from the hydraulic pump, and a hydraulic pump control unit which controls displacement of the hydraulic pump based on the real rotation speed or the target rotation speed of the engine so that a flow rate of the hydraulic oil discharged from the hydraulic pump approaches the target flow rate;

a target maximum total power calculating unit which calculates a target maximum value of total power of the engine and the electric motor is provided;

the second rotation speed calculating unit calculates a minimum rotation speed of the engine required for generating the target maximum total power in the engine and the electric motor;

a third rotation speed calculating unit which calculates a minimum rotation speed of the engine required for securing the target flow rate of the hydraulic pump is further provided; and

the target rotation speed calculating unit selects a largest value from the first rotation speed outputted from the first rotation speed calculating unit, the second rotation speed outputted from the second rotation speed calculating unit and a third rotation speed outputted from the third rotation speed calculating unit.