Hydraulic Control System Engine Speed Adjustment
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Solution Overview
Problem
Hydraulic construction machines, such as excavators, face performance deterioration and reduced working efficiency due to the reduction in pump delivery rate when operating in economy mode, leading to unnatural engine speed variations and increased costs from multiple detection means.
Innovation Solution
A control system that adjusts the prime mover's revolution speed based on load pressure detection, allowing continuous changes in engine speed and pump delivery rate to maintain efficiency and fuel economy, while preventing discontinuous variations and reducing the need for multiple detection means.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine revolution speed is reduced in economy mode, then fuel economy is improved, but the pump delivery rate is reduced causing performance deterioration
Solution Approach 1:
The patent implements dynamic adjustment of pump displacement based on engine revolution speed. The control system continuously monitors engine speed and automatically adjusts the pump displacement to maintain optimal delivery rate across varying engine speeds, resolving the contradiction between reduced engine speed for fuel economy and maintained pump delivery rate for productivity
Solution Approach 2:
The system changes the operational parameters of the hydraulic pump by adjusting its displacement in response to engine revolution speed changes. This parameter adjustment allows the pump to maintain effective delivery rate even when the engine operates at reduced speeds for improved fuel economy
2Productivity
If multiple detection means are provided to automatically select control modes, then the maximum delivery rate is ensured in limited pressure range, but the system complexity increases and performance deteriorates in pump absorption torque control region
Solution Approach 1:
The control system integrates multiple functions into a single control mechanism that can operate across different pressure ranges and operating conditions. The system universally handles both the limited pressure range operation and pump absorption torque control region through unified control logic, eliminating the need for separate detection means for different operating conditions
Solution Approach 2:
The patent extracts the essential control function from complex multi-sensor systems and implements it through a simplified control mechanism that directly responds to engine revolution speed and pump operating conditions, removing unnecessary detection means while maintaining effective delivery rate control
Data Source
AI summary
When a mode selection command selects an economy mode, a mode selector 700e is turned on and outputs an engine revolution speed modification value ΔN0 (ΔN1=ΔN0) computed by an engine-revolution-speed modification value computing section 700d. A subtracter 700f subtracts the engine revolution speed modification value ΔN1 from a rated target revolution speed Nmax, thereby computing a target engine revolution speed NR2. The computing section 700d computes the engine revolution speed modification value ΔN0 depending on a pump delivery pressure mean value Pm. In a table stored in a memory, the relationship between Pm and ΔN0 is set such that when Pm is not higher than PA near a midpoint pressure, ΔN0 is 0 and when Pm exceeds PA, ΔN0 is increased with an increase of Pm. Thus, the revolution speed of a prime mover is reduced by mode selection so as to improve fuel economy.