Hydraulic Pump Control for Hybrid Construction Machine
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Solution Overview
Problem
Hybrid construction machines face issues with engine overload and rapid wear of electric storage devices due to insufficient assistance during high-load pressure conditions, especially when the charge level of the electric storage device declines, leading to a loss of assistance capability and potential stalling.
Innovation Solution
A power source apparatus with a hydraulic pump, generator-motor, engine, and electric storage device, along with a controller that adjusts the flow rate based on specific characteristics to optimize the maximum input setting of the hydraulic pump, ensuring it remains greater than the engine's output during normal conditions and gradually decreases as pressure increases, thereby reducing wear on the electric storage device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the maximum input setting of the hydraulic pump is set to be greater than the maximum output of the engine throughout the whole pressure range (first characteristics), then the hydraulic pump can provide sufficient assistance during high-load pressure conditions, but the electric storage device experiences rapid wear and deterioration due to frequent high-level charging and discharging
Solution Approach 1:
The patent applies dynamics by making the maximum input setting of the hydraulic pump variable rather than fixed. The controller dynamically switches between first characteristics (allowing pump input > engine output) and second characteristics (limiting pump input ≤ engine output) based on real-time detection of discharge pressure and duration. This dynamic adjustment enables the system to provide sufficient assistance during high-load conditions while preventing excessive wear during normal operations.
Solution Approach 2:
The patent changes the parameter of maximum input setting based on operating conditions. By detecting discharge pressure and its duration, the system switches between two sets of characteristics: first characteristics that allow greater pump input for reliability, and second characteristics that limit pump input to protect the electric storage device. This parameter change strategy resolves the contradiction between reliability and component longevity.
2Loss of substance
If the maximum input setting of the hydraulic pump is limited in accordance with the amount of charge in the electric storage device, then the wear of the electric storage device is suppressed during normal work, but the engine becomes overloaded and stalls when the charge level falls below the limit
Solution Approach 1:
The patent implements feedback by continuously detecting the discharge pressure of the hydraulic pump and its duration. Based on this feedback, the controller determines whether to switch between first characteristics (for high reliability) and second characteristics (for reduced wear). This feedback mechanism ensures the system adapts to actual operating conditions, preventing both engine overload and excessive wear.
Solution Approach 2:
The system dynamically adjusts the maximum input setting based on real-time pressure detection rather than static charge level limits. This dynamic approach allows the system to maintain reliability during high-load conditions while protecting the electric storage device during normal operations, avoiding engine overload that occurs with fixed charge-based limits.
3Power
If the flow rate is controlled based on horsepower control alone, then the engine does not become overloaded, but the hydraulic pump cannot provide sufficient assistance during high-load pressure conditions when the electric storage device charge level is low
Solution Approach 1:
The patent segments the operating conditions into two categories: normal work conditions (using second characteristics where pump input ≤ engine output) and high-load pressure conditions (using first characteristics where pump input > engine output). This segmentation allows the system to apply appropriate control strategies for each condition, ensuring both engine protection and sufficient assistance capability when needed.
Solution Approach 2:
The system changes the maximum input setting parameter based on detected discharge pressure and duration. During high-load pressure conditions, the parameter switches to allow pump input greater than engine output, providing sufficient assistance. During normal operations, it limits pump input to protect the electric storage device, thus resolving the contradiction between power management and assistance capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for optimal energy management, preventing engine overload and reducing wear on the electric storage device, maintaining assistance capability during high-load operations and enhancing energy efficiency by avoiding frequent high-level charging and discharging.
Implementation Method 1
a generator-motor (2) capable of operating as an electric generator and an electric motor... capable of supplying charged electric power to the generator-motor in order to cause the generator-motor to operate as an electric motor so as to assist driving of the hydraulic pump
Implementation Method 2
an electric storage device (9) which is charged by operation of the generator-motor (2) as an electric generator
Implementation Method 3
a hydraulic pump (3) which drives a hydraulic actuator (40)... a pump pressure detector (11) which detects a discharge pressure of the hydraulic pump (3)
Data Source
AI summary
A controller carries out horsepower control to determine a flow rate of a hydraulic pump based on first characteristics and second characteristics, which each define a maximum input setting of the hydraulic pump by a discharge pressure of the hydraulic pump and a flow rate of the hydraulic pump, and based on the discharge pressure. When the discharge pressure is less than a set pressure and when a state where the discharge pressure is equal to or greater than the set pressure has not continued for a set time period, then the controller determines the flow rate based on the first characteristics, and when the state where the discharge pressure is equal to or greater than the set pressure has continued for the set time period, then the controller determines the flow rate based on the second characteristics.