Variable Hydraulic Pressure Relief Valve for Material Handling Vehicles
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Solution Overview
Problem
Conventional hydraulic pressure relief systems in material handling vehicles are not adequately adjustable to accommodate varying load elevations, leading to inefficient pressure management and potential system overload.
Innovation Solution
A hydraulic control system with a variable pressure relief valve controlled by a controller, which adjusts the pressure relief threshold based on the height of the fork assembly, using a solenoid and spring mechanism to provide multiple pressure relief settings, and a calibration method to determine the optimal control signal parameters for target pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed pressure relief valve is used in the hydraulic system, then the system structure is simple, but the pressure relief threshold cannot be adjusted to accommodate varying load elevations, leading to inefficient pressure management and potential system overload
Solution Approach 1:
The patent applies the dynamics principle by replacing a fixed pressure relief valve with a variable pressure relief valve whose threshold can be dynamically adjusted based on fork assembly elevation. The controller receives height sensor signals and automatically modifies the pressure relief threshold to match the current operating height, enabling the system to adapt to varying load elevations and prevent overload conditions that would occur with a fixed threshold valve.
Solution Approach 2:
The patent implements parameter changes by varying the pressure relief threshold parameter according to the fork assembly elevation. The system changes the pressure threshold parameter dynamically - lowering it at higher elevations where the load is lighter and raising it at lower elevations where the load is heavier. This parameter adaptation resolves the contradiction by enabling pressure relief adjustability while maintaining a relatively simple overall system architecture through electronic control.
2Productivity
If a variable pressure relief valve with multiple settings is implemented, then pressure management efficiency improves, but the device complexity and calibration requirements increase
Solution Approach 1:
The patent applies the self-service principle by implementing an automatic calibration mode that eliminates the need for manual calibration of the variable pressure relief valve. During normal operation, the system automatically correlates height sensor readings with pressure sensor readings at each elevation level and stores these calibrated values in memory. This self-calibrating capability resolves the contradiction by enabling efficient variable pressure management while minimizing the complexity of calibration procedures - the system calibrates itself without external intervention.
Solution Approach 2:
The patent implements feedback by using pressure sensors to monitor actual system pressure at different elevations and feeding this information back to the controller. The controller uses this feedback to automatically adjust the pressure relief threshold and to perform automatic calibration by comparing expected versus actual pressure values. This feedback mechanism enables efficient pressure management while reducing calibration complexity through automated adjustment based on real-time system state monitoring.
3Strength
If the pressure relief threshold is set high for maximum load capacity, then the system can handle heavy loads, but the system may overload at lower elevations with lighter loads, creating safety risks
Solution Approach 1:
The patent resolves this contradiction through parameter changes by dynamically adjusting the pressure relief threshold parameter based on fork assembly elevation. At lower elevations where the load is heavier, the system raises the pressure relief threshold to allow higher load handling capacity. At higher elevations where the load is lighter, the system lowers the pressure relief threshold to prevent overload conditions. This dynamic parameter adaptation enables the system to maintain both high load handling capacity and safety across all operating elevations.
Solution Approach 2:
The patent applies dynamics by making the pressure relief threshold a dynamic parameter rather than a static one. The threshold automatically changes in response to elevation changes detected by the height sensor, creating a dynamic safety mechanism that adapts to current operating conditions. This dynamic adjustment ensures that the pressure relief threshold always matches the appropriate safety level for the current load weight, resolving the contradiction between maximizing load capacity and preventing overload at varying elevations.
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 manages pressure relief at varying fork assembly elevations, ensuring safe operation and efficient load handling by accurately adjusting pressure thresholds, thereby preventing system overload and optimizing hydraulic performance.
Implementation Method 1
supplying, via the controller, a minimum current magnitude to a solenoid of the variable pressure relief valve
Implementation Method 2
using a solenoid and spring mechanism to provide multiple pressure relief settings
Data Source
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AI summary
A method for controlling a hydraulic control system that includes a variable pressure relief valve (324) and is configured for a material handling vehicle may include steps for calibrating the hydraulic control system. The hydraulic control system may be calibrated by controlling, with a controller (218), the variable pressure relief valve to move to a fully open position and then increasing a fluid pressure in a supply passage with a pump. The controller can control the variable pressure relief valve to incrementally move from the fully open position toward a fully closed position by adjusting a control signal supplied to the variable pressure relief valve. The controller may monitor a pressure detected by a pressure sensor (217); and can record a parameter of the control signal valve when the pressure detected by the pressure sensor reaches a target pressure.