Electro-Hydraulic Circuit With Open-Center Valve for Torque-Limited Actuation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electrified agricultural vehicles face high electricity consumption due to the continuous operation of electric motors driving hydraulic pumps, even when not necessary, which hinders the adoption of electric traction systems over traditional internal combustion engines.
Innovation Solution
An electro-hydraulic circuit with a fixed displacement hydraulic pump and an open center directional control solenoid valve, controlled by a user interface, reduces power consumption by monitoring torque and activating the solenoid valve to neutral when a torque limit is reached, thereby reducing pump flow rate and pressure, and incorporating a selector for load limiting modes based on user input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric motor drives the hydraulic pump continuously to ensure hydraulic system readiness, then the hydraulic system is always ready for operation, but electricity consumption increases significantly
Solution Approach 1:
The motor operates periodically rather than continuously - it runs only when hydraulic actuators need to move or maintain position. The control system activates the motor based on actual demand signals from control valves, creating an on-demand operation pattern that eliminates unnecessary energy consumption while ensuring hydraulic readiness when needed.
Solution Approach 2:
The hydraulic system uses gravity and spring forces to maintain actuator positions when the motor is not running. The load itself (through gravity on hydraulic actuators) and spring elements in the control valves provide the self-service mechanism to maintain system readiness without continuous motor operation.
2Stress or pressure
If the motor operates at minimum rotation speed to maintain system pressure, then the hydraulic system maintains pressure readiness, but unnecessary electricity is consumed
Solution Approach 1:
The motor operates periodically rather than continuously - it runs only when hydraulic actuators need to move or maintain position. The control system activates the motor based on actual demand signals from control valves, creating an on-demand operation pattern that eliminates unnecessary energy consumption while ensuring hydraulic readiness when needed.
Solution Approach 2:
The system changes the operating parameters (motor speed, pump pressure) dynamically based on actual hydraulic demand. Instead of maintaining constant minimum speed and pressure, the motor speed and pump pressure are adjusted according to the position of control valves and actual actuator requirements, consuming energy only when and at the level needed.
3Speed
If the pump delivers maximum flow rate to ensure rapid actuator response, then actuator response speed is improved, but energy consumption increases
Solution Approach 1:
The pump flow rate is made dynamic rather than fixed at maximum. The pump delivers variable flow rate according to the position of control valves and actual actuator demands. When actuators are at end-of-stroke or in stall conditions, the pump flow is reduced to minimum, providing rapid response when needed while conserving energy during idle or low-demand periods.
Solution Approach 2:
The control system uses feedback from valve positions and actuator conditions to regulate pump output. Sensors detect when actuators reach end-of-stroke or when control valves are in neutral position, and this feedback signals the motor controller to reduce or stop motor operation, thereby reducing pump flow rate and energy consumption while maintaining rapid response capability when actuators need to move.
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 approach reduces electric energy consumption by limiting motor power only when needed, adapting to user conditions and maintaining operation below maximum system pressure, thus enhancing energy efficiency in electrified work vehicles.
Implementation Method 1
an open center directional control solenoid valve
Implementation Method 2
a fixed displacement hydraulic pump
Implementation Method 3
hydraulic actuator enslaved to the movement of a hydraulic work member
Data Source
Figure 1
Figure 2~3
AI summary
An electro-hydraulic circuit includes a fixed displacement hydraulic pump (P) and an electric motor (M) arranged to drive the hydraulic pump in rotation, a hydraulic actuator (BOOM, BUCKET, AUX) arranged to move an member or work tool and be powered by the hydraulic circuit, a proportional directional solenoid valve (V1, V2, V3) with open center and comprising a rest condition wherein it isolates the hydraulic actuator by connecting the hydraulic pump with the recovery tank, and a processing unit (STK) configured to receive the electrical signals of an input device (joystick) and generate electrical control signals (Spool Command, Rev, Torque) for the valves (V1, V2, V3) and for the engine (M); and programmed to detect the torque of the motor (M) and, when the torque of the motor (M) exceeds a predefined limit value, it commands the execution of at least one power reduction operation by reducing the number of revolutions of the motor (M) and/or bringing the corresponding solenoid valve (V1, V2, V3) to the neutral position with open center.