Hydraulic Accumulator Preload Check via Pump-Off Pressure Drop
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Solution Overview
Problem
Hydraulic accumulators in agricultural and forestry vehicles face challenges in reliably detecting degradation of their energy storage capacity, which can lead to functional impairments due to gas leaks or loss of preload force.
Innovation Solution
A method to check the state of hydraulic accumulators by monitoring pressure drops in the hydraulic system when the pump is switched off, calculating preload pressure, and comparing it to a target value, with temperature compensation using hydraulic fluid temperature as an auxiliary variable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the hydraulic accumulator uses a compression means (gas spring) for energy storage, then the energy storage capacity is improved, but the reliability deteriorates due to gas leaks and loss of preload force
Solution Approach 1:
The control device performs a functional check of the hydraulic accumulator during system operation or at idle times by monitoring the pressure curve behavior when the hydraulic pump is switched off. This preliminary detection allows identifying degradation of the compression means before complete failure occurs, enabling timely maintenance while the accumulator still provides reliable energy storage capacity.
Solution Approach 2:
The control device continuously monitors the pressure curve in the hydraulic system and uses the characteristic jump in pressure (delta p) as feedback to assess the state of the compression means. By comparing the measured pressure drop against expected values, the system provides continuous feedback on the accumulator's health status, allowing adaptive maintenance scheduling.
2Device complexity
If no functional check is performed, then the device complexity is reduced, but the measurement precision of accumulator state deteriorates
Solution Approach 1:
The hydraulic accumulator's own pressure behavior serves as the measurement signal for detecting its own degradation. When the hydraulic pump is switched off, the natural pressure drop and the characteristic jump in pressure (caused by the compression means relaxing) provide self-diagnostic information about the accumulator's state, eliminating the need for external test equipment or complex sensing systems.
Solution Approach 2:
The control device acts as an intermediary that processes the pressure curve data from the hydraulic system. By analyzing the pressure drop behavior and the characteristic jump (delta p) using stored reference values or target values, the control device translates raw pressure measurements into diagnostic information about the compression means' health without requiring direct physical access to the accumulator internals.
3Measurement precision
If the pump is switched off for checking, then the measurement precision of preload force is improved, but the productivity is reduced due to system downtime
Solution Approach 1:
The functional check requires only a brief interruption of the hydraulic pump operation rather than complete system shutdown. The control device monitors the pressure curve during this short period when the pump is switched off, capturing the characteristic pressure jump behavior. This partial action (brief pump shutdown) provides sufficient data for accurate preload force measurement while minimizing impact on overall system productivity.
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
Enables prompt and reliable detection of hydraulic accumulator malfunctions, ensuring timely maintenance or replacement, thereby maintaining hydraulic system functionality.
Implementation Method 1
a fluid chamber (20), which can be compressively preloaded in opposition to the resetting effect of a compression means (18) for the reversible storage of hydraulic energy
Implementation Method 2
the compression means is formed by an elastic diaphragm (38) made of metal or an elastomer, which, during the filling of the fluid chamber (20), can be deflected in opposition to the resetting effect of a compressible gas
Implementation Method 3
a motor-driven hydraulic pump (24), which serves for the hydraulic supply to a hydraulic system (22)
Implementation Method 4
a control device (56) monitors a pressure drop in the hydraulic system (22) in relation to a jump in the pressure curve (XA, XB), which is characteristic of reaching a fully relaxed state of the compression means (18)
Data Source
AI summary
A method for checking the state of a hydraulic accumulator having a fluid chamber, which communicates with a hydraulic system supplied with hydraulic fluid from a hydraulic reservoir by a motor-driven hydraulic pump, includes monitoring via a control unit a pressure drop in the hydraulic system in relation to a jump in the pressure curve, which is characteristic of reaching a fully relaxed state of the hydraulic accumulator, when the motor drive of the hydraulic pump is switched off, ascertaining via the control unit a hydraulic pressure corresponding to the jump in the pressure curve, calculating via the control unit a preload pressure exerted by the hydraulic accumulator by starting with the ascertained hydraulic pressure, and concluding via the control unit a malfunction of the hydraulic accumulator when the preload pressure does not reach a specified target value.