Clutched Hydraulic System for Refuse Vehicles
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Solution Overview
Problem
Hydraulic systems in vehicles experience wear on components like bearings and pistons due to increased pump speed at higher engine speeds, leading to reduced operational lifespan.
Innovation Solution
A hydraulic system with a variable displacement pump and a clutch controlled by a controller that reduces pump stroke and disengages the clutch when engine speed exceeds a threshold, minimizing wear by decoupling the pump from the engine during high-speed operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump speed increases at higher engine speeds, then the hydraulic system can meet higher flow demands, but wear on bearings and pistons increases
Solution Approach 1:
The pump is designed with variable displacement capability, allowing the pump stroke to be dynamically adjusted based on engine speed and hydraulic demand. This enables the system to maintain optimal pump speed across varying operating conditions, reducing wear while meeting flow demands.
Solution Approach 2:
The system changes the pump stroke parameter in response to engine speed changes. By reducing the pump stroke at high engine speeds, the system limits pump RPM and consequently reduces wear on internal components while still providing adequate hydraulic flow when needed.
2Reliability
If the pump stroke is reduced before clutch disengagement, then clutch wear is reduced, but hydraulic system response time increases
Solution Approach 1:
The system uses periodic or staged action by implementing a two-step process: first reducing pump stroke, then disengaging the clutch. This staged approach balances the need to protect the clutch while maintaining acceptable system response time for hydraulic operations.
Data Source
AI summary
A hydraulic system for a vehicle includes a variable displacement pump configured to pressurize a fluid based on a pump stroke, a clutch, and a controller that is coupled to the variable displacement pump and the clutch. The clutch is positioned to selectively couple the variable displacement pump with an engine when engaged and selectively decouple the variable displacement pump from the engine when disengaged. The controller is configured to generate a first command signal to decrease the pump stroke and thereafter generate a second command signal to disengage the clutch.