HYBRID WORKING MACHINE

• US 20100170239A1
• Filed: 12/17/2009
• Published: 07/08/2010
• Est. Priority Date: 01/06/2009
• Status: Active Grant

• Current Assignee: Kobelco Construction Machinery Company Limited (Kobe Steel Limited)
• Original Assignee: Kobelco Construction Machinery Company Limited (Kobe Steel Limited)
• Inventors: SORA, Toshio
• Granted Patent: US 8,468,816 B2
• Time in Patent Office: Days
• US Class Current: 60/459
• CPC Class Codes: B60K 6/485 Motor-assist type
• CPC Class Codes: B60W 2510/244 Charge state
• CPC Class Codes: B60Y 2200/41 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 9/2217 with energy recovery arrangements, e.g. using accumulators, flywheels
• CPC Class Codes: E02F 9/2221 Control of flow rate; Load sensing arrangements E02F9/2203 take precedence over E02F9/2221
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: F16H 61/475 for achieving a target power, e.g. input power or output power
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

In a hybrid working machine in which the maximum engine output is set at the average power and the maximum pump input is set to be larger than the maximum engine output in a normal state, in an abnormal state in which the level of charge of a battery decreases and assistance ability of a motor function of a power machine is lost, the minimum pump flow rate is reduced to a value equal to or smaller than a standby flow rate, the standby flow rate being the minimum pump flow rate used in normal state control, and a set value of the maximum pump input is changed such that the maximum pump input is smaller than the maximum engine output.

Claims

1. A hybrid working machine comprising:

an engine;

a hydraulic pump connected to the engine, the hydraulic pump driving a hydraulic actuator;

a power machine connected to the engine, the power machine performing a generator function and a motor function;

an electric storage device charged by the generator function of the power machine, the electric storage device discharging power that drives and makes the power machine perform the motor function so as to assist driving of the hydraulic pump;

pump flow rate instruction means that outputs an instruction of a pump flow rate determined in accordance with an operation amount of operation means for operating the hydraulic actuator or in accordance with a load pressure of the hydraulic pump;

a regulator that controls a flow rate of the hydraulic pump on the basis of the instruction of the determined pump flow rate output from the pump flow rate instruction means; and

a power unit for the hybrid working machine in which a set value of the maximum input of the hydraulic pump is set to be larger than a maximum engine output, the power unit including

level-of-charge detection means for detecting a level of charge of the electric storage device, and

correction means for correcting the determined pump flow rate output from the pump flow rate instruction means in accordance with the level of charge that is detected,

wherein the correction means is configured to change, in an abnormal state, the set value of the maximum input of the hydraulic pump to a value equal to or lower than the maximum engine output by decreasing a minimum pump flow rate to a value equal to or lower than a value in an ordinary state, the abnormal state being a state in which the level of charge that is detected is equal to or lower than a set level, the normal state being a state in which the level of charge that is detected is higher than the set level.

2. The hybrid working machine according to claim 1,

wherein the pump flow rate instruction means

(A) determines and outputs the instruction of the pump flow rate by selecting a lower of a pump flow rate obtained by flow rate control and a pump flow rate obtained by power control, the flow rate control being a method of controlling the pump flow rate in accordance with the operation amount, the power control being a method of controlling the pump flow rate in accordance with the load pressure,

(B) determines and outputs a standby flow rate as a minimum flow rate in the flow rate control, the standby flow rate being lower than a minimum flow rate in the power control, and

(C) sets the minimum pump flow rate at a value lower than the standby flow rate in the abnormal state.