Control system for a hybrid excavator

• US 9,182,312 B2
• Filed: 06/28/2010
• Issued: 11/10/2015
• Est. Priority Date: 06/28/2010
• Status: Active Grant

• Current Assignee: Volvo Construction Equipment AB (Volvo AB)
• Original Assignee: Volvo Construction Equipment AB (Volvo AB)
• Inventors: Kim, Jae-Hong, Lee, Chun-Han
• Primary Examiner(s): Barnes-Bullock, Crystal J
• Application Number:
  US13/639,962
• Publication Number:
  US 20130090771A1
• Time in Patent Office: 1,961 Days
• Field of Search: 180/65.1, 180/65.21, 180/65.265, 180/65.27, 180/65.275, 180/65.28, 180/65.285, 180/65.29, 180/65.25, 180/165, 701/22, 701/51, 701/54, 701/101, 700286-288, 290/7, 290/31, 290/32, 290/34, 290/40.R, 290/40.C, 290/40.F, 903903-907
• US Class Current: 1/1
• CPC Class Codes: B60W 2510/244 Charge state
• CPC Class Codes: E02F 9/2025 Particular purposes of control systems not otherwise provided for E02F3/16, E02F3/26, sub-groups of E02F3/43, E02F3/651, sub-groups of E02F3/84, E02F3/907, E02F5/145 take precedence
• 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 9/2246 Control of prime movers, e.g. depending on the hydraulic load of work tools
• CPC Class Codes: F16H 61/468 for achieving a target input torque
• CPC Class Codes: G01M 1/22 and converting vibrations due to imbalance into electric variables

Abstract

The present invention relates to a control system for a hybrid excavator including an engine, a hydraulic pump driven by the engine to drive a hydraulic actuator by hydraulic fluid, a generator driven by the engine to generate electric energy, and an energy storage device charging the electric energy generated by the generator and supplying the electric energy to an electric actuator, the control system comprising: a required torque detection means for detecting a torque that is required to drive the hydraulic pump; a charge amount detection means for detecting a charge rate (or charge amount) of the electric energy storage device; a memory storing a generation degree (or generation amount) in accordance with the torque and the charge rate (or charge amount); and a hybrid control means for controlling the generator in accordance with the torque value detected by the required torque detection means and the generation amount in a memory means that corresponds to the charge rate value (or charge amount) detected by the charge amount detection means. According to the control system, the fuel efficiency is optimized by driving the electric generator attached to the engine based on the required torque of the hydraulic pump and the preset generation amount value corresponding to the SOC (State Of Charge).

Claims

1. A control system for a hybrid excavator including an engine, a hydraulic pump driven by the engine to drive a hydraulic actuator by hydraulic fluid discharged therefrom, an electric generator driven by the engine to generate electric energy, and an electric energy storage device for storing the electric energy generated by the electric generator and supplying the electric energy to an electric actuator, the control system comprising:

a torque detector configured to detect a torque that is required to drive the hydraulic pump;

a charge detector configured to detect a charge rate (or charge amount) of the electric energy storage device;

a storage device configured to store a degree of electricity generation (or amount of electricity generation) based on the torque and the charge rate (or charge amount); and

a hybrid controller configured to control the electric generator based on the amount of electricity generation stored in the storage device, which corresponds to both the torque value detected by the torque detector and the charge rate (or charge amount) value detected by the charge detector; and

an engine revolution adjuster configured to adjust engine revolution;

wherein;

the electric generator attached to and driven by the engine acts as a motor, to which electric energy is supplied from the electric energy storage device, and operates the hydraulic pump together with the engine;

if the torque detector detects a torque that is lower than a predetermined level, which is determined to correspond to a standby state in which no work is being done by the hybrid excavator, the hybrid controller performs a hybrid control including the following;

when the charge rate or charge amount detected by the charge detector is higher than a predetermined level, the engine revolution adjuster reduces the engine revolution to a low RPM with low fuel consumption; and

when the charge rate or charge amount detected by the charge detector is lower than the predetermined level, the electric generator is driven by operating the engine in an appropriate torque region of a different revolution that is suitable for electricity generation, generates and charges the electric energy storage device, and after the charge rate or charge amount detected by the charge detector becomes higher than the predetermined level, the engine revolution adjuster reduces the engine revolution to a low RPM with low fuel consumption.

2. The control system for a hybrid excavator according to claim 1, further comprising a movement identifier configured to identify movement of an excavator adjustment lever, so that if the adjustment lever is not operated and if the torque detector detects a torque that is not lower than the predetermined level, it is determined that the excavator is in the standby state in which no work is done by the hybrid excavator and the hybrid controller performing the hybrid control.

3. A method for controlling a hybrid excavator including an engine, a hydraulic pump driven by the engine to drive a hydraulic actuator by hydraulic fluid discharged therefrom, an electric generator driven by the engine to generate electric energy, and an electric energy storage device for storing the electric energy generated by the electric generator and supplying the electric energy to an electric actuator, the method comprising:

performing a hybrid control of the hybrid excavator when a torque detector detects that a torque required to drive the hydraulic pump is below a predetermined level, which corresponds to a standby state in which no work is being done by the hybrid excavator;

when the charge rate or charge amount detected by the charge detector is higher than a predetermined level, reducing the engine revolution to a low RPM with low fuel consumption; and

when a charge rate or charge amount detected by a charge detector is lower than the predetermined level, driving the electric generator by operating the engine in a torque region of a revolution that is suitable to generate electricity, generates and charges the electric energy storage device, and after the charge rate or charge amount detected by the charge detector becomes higher than the predetermined level, reducing the engine revolution to the low RPM with low fuel consumption.

4. A control system for a hybrid excavator including an engine, a hydraulic pump driven by the engine to drive a hydraulic actuator by hydraulic fluid discharged therefrom, an electric generator driven by the engine to generate electric energy, and an electric energy storage device for storing the electric energy generated by the electric generator and supplying the electric energy to an electric actuator, the electric generator operates the hydraulic pump together with the engine and is a motor to which electric energy is supplied from the electric energy storage device, the control system comprising:

a torque detector configured to detect a torque that is required to drive the hydraulic pump;

a charge detector configured to detect a charge rate of the electric energy storage device;

a storage device configured to store an amount of electricity generation based on the torque and the charge rate; and

a hybrid controller configured to control the electric generator based on the amount of electricity generation stored in the storage device, which corresponds to both a torque value detected by the torque detector and a charge rate value detected by the charge detector, the hybrid controller performs a hybrid control if the torque detector detects a torque that is lower than a predetermined level, which is determined to correspond to a standby state in which no work is being done by the hybrid excavator;

wherein the hybrid control includes the following;

when the charge rate or charge amount detected by the charge detector is higher than a predetermined level, the engine revolution adjuster reduces the engine revolution to a low RPM with low fuel consumption; and

when the charge rate or charge amount detected by the charge detector is lower than the predetermined value, the electric generator is driven by operating the engine in a torque region of a different revolution that is suitable for electricity generation, generates and charges the electric energy storage device, and after the charge rate or charge amount detected by the charge detector becomes higher than the predetermined value, the engine revolution adjuster reduces the engine revolution to a low RPM with low fuel consumption.