Construction Machine Hydraulic Circuit Without a Charge Pump
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Solution Overview
Problem
The use of a closed hydraulic circuit in construction machines leads to increased costs and energy wastage due to the inclusion of a charge pump, which is always driven by the drive source even when hydraulic oil replenishment is not required.
Innovation Solution
A hydraulic circuit design incorporating an open circuit and a closed circuit, utilizing a variable-volume hydraulic pump, bidirectional hydraulic pump, and a charge line connecting the open and closed circuits, eliminating the need for a charge pump by controlling hydraulic oil supply through directional switching valves, check valves, and proportional bypass valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge pump is provided in the closed circuit to supply hydraulic oil, then the hydraulic circuit can maintain proper oil levels and cooling, but the cost of the hydraulic circuit increases due to the charge pump and external filter
Solution Approach 1:
The patent merges the charge pump function into the main hydraulic pump by utilizing the discharge port and return line of the existing hydraulic pump. The charge line branches from the return line upstream of the return check valve and connects to the closed circuit through check valves, eliminating the need for a separate charge pump and external filter while maintaining hydraulic oil supply reliability.
Solution Approach 2:
The hydraulic pump is designed to serve dual functions: powering the open circuit hydraulic actuator and supplying hydraulic oil to the closed circuit through the charge line. The return line and return check valve are utilized to provide both return flow for the open circuit and charge flow for the closed circuit, reducing the need for dedicated components.
2Reliability
If a charge pump is always driven by the drive source, then the hydraulic circuit maintains continuous oil circulation, but energy is wasted when the charge of hydraulic oil to the closed circuit is not required
Solution Approach 1:
The system uses the hydraulic pump's own discharge and return lines to automatically supply hydraulic oil to the closed circuit when needed. The check valves in the charge line automatically control the flow direction, allowing the closed circuit to charge from the open circuit without requiring a separately controlled charge pump, thus eliminating unnecessary energy consumption.
Solution Approach 2:
The charge pump (hydraulic pump) operates periodically based on the actual needs of the closed circuit. When the closed circuit requires hydraulic oil charging or cooling, the pump supplies oil through the charge line. When not required, the pump only maintains the open circuit operation, reducing energy waste while ensuring continuous circulation when needed.
3Reliability
If a charge pump and external filter are included in the closed circuit, then proper hydraulic oil filtration and replenishment is ensured, but the number of components increases leading to higher maintenance complexity
Solution Approach 1:
The patent combines the filtration function into the existing open circuit hydraulic system. The return line with return check valve serves dual purposes: returning oil to the tank for the open circuit and providing filtered oil through the charge line to the closed circuit via check valves, eliminating the need for a separate external filter in the closed circuit.
Solution Approach 2:
The invention extracts the essential function of the charge pump (supplying hydraulic oil to the closed circuit) and implements it using existing components from the open circuit. By taking out the charge pump and external filter from the closed circuit and replacing them with a charge line utilizing the open circuit's pump and return line, the maintenance complexity is reduced while maintaining filtration 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 design reduces costs by eliminating the charge pump and external filter, minimizes energy consumption, and facilitates maintenance by reducing components, while ensuring efficient hydraulic oil supply to the closed circuit.
Implementation Method 1
a charge line is provided between the open circuit and the closed circuit that connects a portion of the return line on an upstream side of the return check valve to the first line via a first check valve, and connects a portion of the return line on an upstream side of the return check valve to the second line via a second check valve
Implementation Method 2
a return check valve provided in the return line
Implementation Method 3
an electromagnetic proportional bypass valve provided in the bypass line
Implementation Method 4
a variable-volume hydraulic pump configured to discharge hydraulic oil sucked from a hydraulic oil tank
Implementation Method 5
a variable-volume bidirectional hydraulic pump having a first port and a second port
Data Source
AI summary
Problem to be solved: To provide a hydraulic circuit for a construction machine capable of supplying hydraulic oil to a closed circuit without a charge pump. Means for solving the problem: The open circuit of the hydraulic circuit includes a hydraulic pump, a hydraulic actuator operated by hydraulic oil discharged from the hydraulic pump, a directional switching valve for switching a flow direction of the hydraulic oil from the hydraulic pump to the hydraulic actuator, a return line connecting the directional switching valve and a hydraulic oil tank, and a return check valve provided in the return line. The closed circuit of the hydraulic circuit includes a bidirectional hydraulic pump having a first port and a second port, a hydraulic motor operated by hydraulic oil discharged from the bidirectional hydraulic pump, a first line connecting the first port of the bidirectional hydraulic pump and the hydraulic motor, and a second line connecting the second port of the bidirectional hydraulic pump and the hydraulic motor. Between the open circuit and the closed circuit, a charge line connecting the return line and the first line via a first check valve and connecting the return line and the second line via a second check valve is provided.