Refuse Vehicle Hydraulic Pump Torque Limiting Under High Load
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Solution Overview
Problem
Refuse vehicles face challenges in preventing over-torqueing and stalling of hydraulic pumps during increased load demands, which can lead to motor damage and inefficiencies in waste collection operations.
Innovation Solution
A torque limiting hydraulic circuit system that includes sensors to monitor pressure and swashplate position, and a spool valve to divert hydraulic fluid and adjust the swashplate angle, reducing pump output and torque when pressure exceeds thresholds, thereby preventing over-torqueing and stalling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the hydraulic pump operates at high torque to meet increased load demands, then the lifting system can handle heavier waste receptacles, but the pump may stall or suffer motor damage
Solution Approach 1:
The system uses pressure sensors to continuously monitor hydraulic circuit pressure and provides feedback to the controller. When pressure exceeds a predetermined threshold indicating high load conditions, the controller activates the torque limiting valve to reduce pump torque, preventing pump stalling and motor damage while maintaining reliable operation.
Solution Approach 2:
A torque limiting valve is introduced as an intermediary component between the hydraulic pump and the lifting system. This valve acts as a mediator that limits the maximum torque output of the pump during high load conditions, preventing direct transmission of excessive torque that could cause pump stalling or motor damage.
2Stress or pressure
If the hydraulic pump delivers high pressure fluid to actuators, then the lifting system has sufficient force to lift heavy receptacles, but the pump may over-torque and stall
Solution Approach 1:
The system dynamically adjusts pump torque based on real-time pressure conditions. The controller continuously monitors hydraulic pressure and activates the torque limiting valve when pressure thresholds are exceeded, creating a dynamic response that maintains adequate power for lifting while preventing over-torque conditions that would cause stalling.
Solution Approach 2:
The torque limiting valve changes the operational parameters of the hydraulic pump by limiting maximum torque output during high pressure conditions. This parameter change allows the system to maintain sufficient pressure for lifting heavy receptacles while preventing the pump from operating in an over-torqued state that would lead to stalling.
3Reliability
If the valve directs fluid to reduce hydraulic pressure, then the pump torque is limited to prevent damage, but the lifting force is reduced
Solution Approach 1:
The torque limiting valve provides preliminary protection by preemptively limiting pump torque when pressure thresholds are exceeded, preventing over-torque damage before it occurs. This preliminary anti-action ensures pump reliability while the system can still maintain adequate lifting force through coordinated control of multiple actuators.
Solution Approach 2:
The system applies partial torque limitation only when and where needed (during high load conditions exceeding pressure thresholds). During normal operating conditions, the pump operates at full torque capacity, providing excessive torque capability when needed while applying limitation only partially during extreme conditions to prevent damage.
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
The system effectively prevents pump stalling and motor damage by reducing torque and maintaining efficient pump performance during high load conditions, ensuring continuous operation and reducing the risk of component failure.
Implementation Method 1
A variable displacement pump is positioned within or adjacent the vehicle body and is configured to pump hydraulic fluid from a hydraulic fluid reservoir into a high pressure line of a hydraulic circuit
Implementation Method 2
Fluid pressure within the high pressure line moves the torque limiting valve between the first open position, the blocking position, and the second open position
Data Source
AI summary
A refuse vehicle includes a chassis and a vehicle body. A variable displacement pump is positioned within the vehicle body and is configured to pump hydraulic fluid from a hydraulic fluid reservoir into a high pressure line of a hydraulic circuit. A lifting system on the vehicle includes at least one actuator in fluid communication with the variable displacement pump, which delivers pressurized hydraulic fluid from the hydraulic fluid reservoir to the actuator through the high pressure line to adjust a position of the actuator. A valve is positioned downstream of the variable displacement pump. In a first valve position, the valve restricts flow outward from the high pressure line. In a second valve position, the valve directs fluid from the high pressure line into a lower pressure line to reduce a hydraulic pressure within the high pressure line and adjust an output parameter of the variable displacement pump.