Hydrostatic Drive Control Device for Constant Power
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Solution Overview
Problem
Existing hydrostatic drive systems with closed hydraulic circuits face challenges in maintaining constant drive power and avoiding overload, particularly when the rotational speed of the variable displacement pump fluctuates, and require complex and costly pressure relief valves to limit maximum capacity.
Innovation Solution
A control device that uses a double-sided servo control unit with a control piston in a double-sided control cylinder, where the control piston is deflected to adjust the displacement volume of the hydraulic pump, and a preload element limits the pressure to maintain constant power delivery without the need for pressure relief valves, using a simple pressure return line to counteract the preload force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressure relief valves are used to limit maximum capacity, then overload protection is achieved, but device complexity and cost increase
Solution Approach 1:
The control piston automatically regulates the servo control unit's pressurization by balancing spring force and hydraulic pressure, eliminating the need for external pressure relief valves. The system self-regulates by returning operating pressure to the control piston, which automatically adjusts the servo control based on pressure conditions.
Solution Approach 2:
The invention extracts and eliminates the pressure relief valve component from the system by integrating its pressure-limiting function directly into the control piston mechanism through the spring force counterbalance approach.
2Reliability
If pressure relief valves are used to limit maximum capacity, then overload protection is achieved, but manufacturing cost increases
Solution Approach 1:
The control piston automatically regulates the servo control unit's pressurization by balancing spring force and hydraulic pressure, eliminating the need for external pressure relief valves. The system self-regulates by returning operating pressure to the control piston, which automatically adjusts the servo control based on pressure conditions.
Solution Approach 2:
The invention extracts and eliminates the pressure relief valve component from the system by integrating its pressure-limiting function directly into the control piston mechanism through the spring force counterbalance approach.
3Adaptability or versatility
If the rotational speed of the variable displacement pump fluctuates, then adaptability to operating conditions is improved, but drive power stability deteriorates
Solution Approach 1:
The invention implements a feedback mechanism where operating pressure from the hydraulic circuit is returned to the control piston. This creates a closed-loop system where pressure fluctuations automatically adjust the control piston position, which in turn regulates the servo control unit to maintain stable drive power despite pump speed variations.
Solution Approach 2:
The system dynamically adjusts the control parameter (control piston position) in response to changing operating conditions. By returning operating pressure to the control piston, the system automatically modifies the servo control unit's pressurization level to compensate for pump speed fluctuations and maintain stable power delivery.
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 provides constant drive power to consumers like fans, maintains power levels regardless of rotational speed fluctuations, and is self-regulating, eliminating the need for pressure relief valves, thus being more efficient and cost-effective.
Implementation Method 1
control pressure by means of pressurized drive fluid supplied by a feed pump
Implementation Method 2
a preload element limits the pressure to maintain constant power delivery
Implementation Method 3
pressurized drive fluid supplied by a feed pump
Data Source
AI summary
The invention concerns a hydrostatic drive with a closed hydraulic fluid circuit comprising a hydraulic motor and a variable displacement pump. A feed pump feeds hydraulic fluid under pressure. A control device regulates pressure to a double-sided servo control unit comprising a control piston in a double-sided control cylinder so that the control piston can open a feed line for hydraulic fluid to one side while opening a discharge line on the other. The control device comprises an actuator at the cylinder by means of which force can be exerted onto the piston. A preload element exerts force onto the piston. The pressure generated by the variable displacement pump returns via a return line such that force is exerted in the direction of the piston, if inactive, the piston is maintained by the preload element and the pressure of the variable displacement pump.