Hydraulic Pump Calibration Using Pressure Peaks at Target Flow
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Solution Overview
Problem
Existing calibration methods for hydraulic pumps in working machines, such as hydraulic excavators, face challenges in accurately calculating calibration values for minimum and maximum flow rates due to low pressure at minimum flow rates and potential engine output drops at maximum flow rates, leading to inferior calibration accuracy.
Innovation Solution
A calibration system and method that includes a pressure detection means and a relief oil path connected to the output side of a flow control valve, allowing for the calculation and calibration of pump control current values based on peak changes in pump pressure during a sweeping increase, thereby achieving precise calibration across the entire range of flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If calibration is performed at minimum flow rate, then calibration can be completed, but pressure is too low making accurate pressure displacement point difficult to find
Solution Approach 1:
The patent changes the calibration approach from using minimum flow rate (low pressure) to using maximum flow rate (high pressure) as the calibration point. This parameter change allows accurate detection of pressure displacement points while maintaining calibration effectiveness.
Solution Approach 2:
Instead of calibrating at minimum flow rate as conventionally done, the patent inverts the approach by calibrating at maximum flow rate, where pressure conditions are favorable for accurate measurement.
2Productivity
If calibration is performed at maximum flow rate, then calibration can be completed, but engine output may drop making accurate pressure displacement point difficult to find
Solution Approach 1:
The patent performs preliminary actions by setting the control valve to a predetermined opening ratio before calibration, and preparing the relief valve to maintain constant differential pressure. These preliminary setups ensure stable pressure conditions during maximum flow rate calibration, enabling accurate pressure displacement point detection without engine output drops.
3Ease of manufacture
If conventional calibration methods are used, then calibration can be performed without specialized equipment, but calibration accuracy is inferior
Solution Approach 1:
The patent introduces feedback mechanisms by using pressure sensors to detect pressure displacement points and using the detected information to calculate accurate calibration values. The system continuously monitors pressure changes and uses this feedback to refine calibration accuracy while maintaining operational simplicity.
Solution Approach 2:
The patent replaces conventional mechanical calibration approaches with an electronic control and detection system that uses pressure sensors and microprocessor-based calculations to determine calibration values, achieving higher accuracy without requiring complex specialized equipment.
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 enables high-precision calibration of hydraulic pump flow rates, improving accuracy and reliability without requiring specialized equipment, and allows for efficient calibration with a simple structure.
Implementation Method 1
a pressure compensation valve that is disposed on an upstream side of the flow control valve and is actuated to maintain differential pressure before and after the flow control valve to be constant
Implementation Method 2
a relief oil path is connected an output side of the flow control valve to flow an output flow rate to an oil tank at low back pressure
Implementation Method 3
a pressure detection means for detecting pump pressure of the hydraulic pump is provided
Data Source
AI summary
Problem: Calibrating a correspondence relationship between a pump control current value and a pump flow rate of the hydraulic pump in a hydraulic system including a variable capacity hydraulic pump whose capacity is variably controlled according to the pump control current value, a flow rate control valve whose opening area is variably controlled according to a valve control current value, and a pressure compensation valve that maintains differential pressure before and after the flow control valve to be constant is made in a precise and simple manner. Solution: The spool valve has a configuration in which the pump control current value is sweepingly increased and the peak of a change of pump pressure during the sweeping increase is calibrated as the pump control current value of the pump flow rate of the target flow rate, with the spool valve held in the aperture area corresponding to the spool valve output flow rate of the arbitrary target flow rate. With the spool valve maintained at an opening area corresponding to an output flow rate of the spool valve of an arbitrary target flow rate, the pump control current value sweepingly increases, and the peak of the change of the pump pressure during the sweeping increase is calibrated as the pump control current value of the pump flow rate of the target flow rate.