Hydrostatic Transmission Throttle Valve Control
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Solution Overview
Problem
Existing hydrostatic drive deceleration methods do not optimally utilize the entire brake or drag power available at the drive motor, as they fail to account for power consumption by additional consumers and power losses, leading to inefficiencies and potential overspeeding, and are characterized by complex and costly designs.
Innovation Solution
A method and device that dynamically adjusts the throttle valve in the hydraulic lines to match the hydraulic power with the maximum power supported by the drive motor, considering auxiliary consumer power and losses, to maintain the drive motor at its maximum admissible rotational speed during coasting, thereby optimizing the use of available drag power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed throttle valve or pilot pressure relief valve is used to limit pressure in the return line, then the drive motor is protected from overspeeding, but the entire available brake power at the drive motor is not utilized optimally and hydraulic fluid volume is lost from the working circuit
Solution Approach 1:
The throttle valve is made dynamically adjustable based on operating conditions. The control unit receives signals from sensors monitoring drive motor speed, hydraulic motor speed, and auxiliary consumer power consumption, then automatically adjusts the throttle cross-section to optimize brake power utilization while preventing overspeeding. This dynamic adjustment replaces fixed pressure limiting with adaptive control.
Solution Approach 2:
A feedback control system is implemented where sensors continuously monitor the actual operating parameters (drive motor rotational speed, hydraulic motor rotational speed, auxiliary consumer power consumption) and feed this information to a control unit. The control unit compares actual values with target values and adjusts the throttle valve position accordingly, creating a closed-loop control system that optimizes brake power utilization while maintaining safety limits.
2Stress or pressure
If a pilot pressure relief valve is used to control throttle valve, then pressure is limited, but hydraulic fluid volume is withdrawn from the hydrostatic drive and cannot be transformed into mechanical power
Solution Approach 1:
The harmful function of the pilot pressure relief valve (withdrawing hydraulic fluid from the working circuit) is eliminated by extracting the pressure control function and implementing it through a different mechanism. Instead of using a pilot pressure relief valve that opens to a tank, the patent uses a control unit with sensors that adjusts the throttle valve position based on actual operating conditions, keeping all hydraulic fluid within the working circuit.
Solution Approach 2:
The purely mechanical pilot pressure relief valve system is replaced with a hybrid control system that uses electronic sensors and a control unit to make informed decisions about throttle valve positioning. This substitution allows for more precise control and eliminates the need for hydraulic fluid to be diverted from the working circuit, as the control system can optimize throttle positioning based on real-time data about auxiliary consumer power consumption.
3Speed
If the throttle cross section is reduced to limit hydraulic power, then drive motor speed is controlled, but excess hydraulic power is transformed into heat energy
Solution Approach 1:
The throttle valve cross-section is dynamically adjusted based on real-time operating conditions rather than being fixed or controlled by a simple pressure relief mechanism. The control unit continuously optimizes the throttle opening to match the actual brake power capacity of the drive motor, considering auxiliary consumer power consumption, thereby minimizing energy waste as heat while maintaining speed control.
Solution Approach 2:
The system changes the throttle valve opening parameter dynamically based on operating conditions. By monitoring drive motor speed, hydraulic motor speed, and auxiliary consumer power consumption, the control unit adjusts the throttle cross-section to allow maximum useful power transmission while preventing overspeeding, thereby reducing the portion of power that must be dissipated as heat compared to fixed throttle or pressure relief valve systems.
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 ensures that all available consumer power and friction losses are utilized for deceleration, preventing overspeeding and reducing the need to convert excess hydraulic power into heat, while maintaining a robust and cost-effective design.
Implementation Method 1
a throttle valve (16) arranged in the return line (7), which is adjustable in its flow rate cross-section and which is dynamically adapted in its flow rate cross-section
Implementation Method 2
The hydraulic motor converts the hydraulic power supplied by the hydraulic pump into mechanical power for the propulsion of a consumer
Implementation Method 3
a hydraulic pump is driven by the drive motor, e.g. a combustion engine in particular a diesel engine and provides the hydraulic motor with hydraulic power in form of supplying a hydraulic fluid flow under high pressure
Data Source
AI summary
Method for deceleration of a hydrostatic transmission 3 driven by a drive motor 2 comprising a closed hydraulic fluid circuit, in which a hydraulic pump 4 coupled mechanically with the drive motor 2 and a hydraulic motor 5 are arranged. Two hydraulic lines 6, 7 connect the hydraulic pump 4 and the hydraulic motor 5 and constitute for the hydraulic motor 5 according to the drive direction of the hydrostatic transmission 3 a supply line 6 and a return line 7. In at least one of the two hydraulic lines 6, 7 a throttle valve 16 is arranged being adjustable in its throttle cross section which, if the corresponding hydraulic line 7 is a return line 7 for hydraulic fluid under high pressure towards the hydraulic pump 4 is being adaptable in its throttle cross section dynamically such that the adjustable hydraulic power in return line 7 downstream of throttle valve 16 at any time during a coasting mode corresponds to the maximum power being supportable at the drive motor 2 in consideration of the power consumption of auxiliary consumers 100 and power losses.