Excavator Pump Flow Control Without a Hydraulic Joint Line
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Solution Overview
Problem
Existing hydraulic excavators with joint lines for supplying pressurized fluid to boom cylinders experience hydraulic pressure loss and inefficiency during swinging/boom raising operations, as they require a joint line that increases energy consumption and reduces operability.
Innovation Solution
A work machine design that eliminates the need for a physical joint line by using a controller to simulate a hypothetical joint line, adjusting the flow rates of two variable-displacement-type hydraulic pumps to achieve equivalent operability and energy efficiency, by computing hypothetical flow rates and target flow rates based on operation amounts of boom and swing devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a joint line is provided to supply pressurized fluid from the second pump to the boom cylinder, then the boom can be raised at sufficient speed during swinging/boom raising operation, but hydraulic pressure loss occurs in the joint line
Solution Approach 1:
The patent creates a virtual copy of the joint line function through software control. Instead of physically connecting the second pump to the boom cylinder via a joint line, the controller calculates the flow contribution that would have come through the joint line and adds it to the first pump's flow rate. This virtual modeling achieves the same functional effect without the physical infrastructure that causes pressure loss.
Solution Approach 2:
The patent replaces the mechanical joint line system with a computational control system. The physical hydraulic connection (mechanical system) is substituted by electronic sensors, a controller that performs calculations, and software algorithms that dynamically adjust pump flow rates. This substitution eliminates the pressure loss inherent in physical hydraulic lines while maintaining the boom raising capability.
2Ease of operation
If a joint line is incorporated to supply pressurized fluid during swinging/boom raising operation, then operability is maintained, but the system complexity increases
Solution Approach 1:
The patent uses virtual modeling to replicate the joint line's operational effect without its physical complexity. The controller creates a digital representation of the joint line's flow characteristics and uses this model to determine appropriate flow rate adjustments, thereby maintaining operability while avoiding the complexity of actual joint line installation and maintenance.
Solution Approach 2:
The patent maintains operability by dynamically changing the flow rate parameter of the first pump based on real-time operating conditions. Instead of adding a physical joint line, the system adjusts the first pump's delivery flow rate to compensate for the absence of the joint line, using sensor data and controller calculations to maintain the necessary hydraulic flow for boom raising during swinging operations.
3Loss of energy
If the delivery flow rate of the first pump is increased to compensate for the absence of joint line, then energy saving ability is improved, but the pump may exceed its maximum flow rate capacity
Solution Approach 1:
The patent implements a dynamic control system that continuously monitors operating conditions and adjusts the first pump's flow rate in real-time. The controller calculates the required flow rate based on current swing speed, boom position, and load conditions, ensuring the pump operates within its capacity limits while maximizing energy efficiency. This dynamic adjustment prevents the pump from exceeding its maximum flow rate while still achieving energy savings compared to a fixed joint line system.
Solution Approach 2:
The patent employs feedback control where sensors monitor the actual flow rates, pressures, and operational parameters, and this information is fed back to the controller. The controller uses this feedback to continuously optimize the first pump's delivery flow rate, ensuring it remains within capacity limits while achieving the desired energy efficiency. The feedback mechanism allows the system to adapt to changing conditions and prevent overload situations.
Data Source
AI summary
There is provided a work machine that is capable of realizing operability and energy saving ability that are equivalent to those of work machines that have a joint line to be used during swinging/boom raising operation, without incorporating a joint line for supplying a pressurized fluid from a second pump to a bottom-side chamber of a boom cylinder. The controller is configured to compute a hypothetical flow rate representing a flow rate in a hypothetical joint line, compute a first pump provisional target flow rate on the basis of an operation amount of a boom operation device, compute a second pump provisional target flow rate on the basis of an operation amount of a swing operation device, compute a first pump final target flow rate by adding the hypothetical flow rate to the first pump provisional target flow rate, and compute a second pump final target flow rate by subtracting the hypothetical flow rate from the second pump provisional target flow rate.