Hydrostatic Transmission Braking Control via Dynamic Pivot Angle Adjustment
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Solution Overview
Problem
Existing hydrostatic transmissions for mobile working machines do not bring the internal combustion engine to its maximum rotational speed during braking operations, resulting in inefficient braking power dissipation due to the need to protect the engine from overspeeding.
Innovation Solution
A hydrostatic transmission system with closed-loop control of the pivot angle and swept volume of the primary unit, using an electrical control unit to support the braking torque from the secondary unit to the driveshaft, ensuring the internal combustion engine reaches and maintains its maximum rotational speed without overspeeding, while utilizing pressure-limiting valves to manage braking power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the primary unit is set to a fixed pivot angle to protect the internal combustion engine from overspeeding, then the engine is protected from damage, but the braking power dissipation efficiency deteriorates because the engine cannot reach its maximum rotational speed
Solution Approach 1:
The pivot angle of the primary unit is changed from a fixed static setting to a dynamic variable that changes over time during braking operation. The control unit adjusts the pivot angle in multiple stages: initially setting it to a first value that limits engine speed to prevent overspeeding, then transitioning to a second value that allows the engine to reach maximum rotational speed for efficient braking power dissipation, while continuously monitoring engine speed to maintain safety constraints.
Solution Approach 2:
A feedback control system is implemented where the control unit continuously monitors the actual rotational speed of the internal combustion engine and adjusts the pivot angle of the primary unit accordingly. The control unit compares the actual engine speed with the maximum permissible speed and dynamically modifies the pivot angle to maintain engine speed within safe limits while optimizing braking performance.
2Reliability
If the primary unit operates at a limited pivot angle during braking, then the engine speed is constrained to safe levels, but the braking performance deteriorates due to reduced power transmission capability
Solution Approach 1:
The system dynamically adjusts the pivot angle of the primary unit during braking operation, transitioning from an initial limited angle that constrains engine speed to a subsequent optimized angle that maximizes power transmission. This dynamic adjustment allows the system to achieve both engine protection and optimal braking performance by adapting the pivot angle to the current operating conditions and engine speed.
Solution Approach 2:
The control unit预先 sets the pivot angle to a first value before full braking engagement to prevent engine overspeeding, then transitions to a second value that optimizes power transmission. This preliminary action of setting the pivot angle to a safe initial value ensures engine protection is established before braking power is fully applied, then optimizes performance as conditions allow.
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 maximizes braking power transmission to the internal combustion engine while preventing overspeeding, allowing for efficient and effective braking operations without excessive energy dissipation through pressure-limiting valves.
Implementation Method 1
a hydrostatic pump (primary unit) and a hydrostatic motor (secondary unit) are fluidically connected to one another by means of a closed circuit
Implementation Method 2
a considerable part of the braking power to be dissipated by means of the pressure-limiting valve of the high-pressure line
Data Source
AI summary
A hydrostatic transmission with which a braking operation is realized in which at least one traction motor which acts as a pump is supported via a closed circuit on an adjustable axial piston pump which acts as a motor, and which in turn is supported on an internal combustion engine. Since overspeeding of the latter should be avoided, pilot control is performed with a rotational speed that is subcritical for the internal combustion engine, and thereafter closed-loop control is performed with a closed-loop controller which outputs a corrective value in a manner dependent on the rotational speed deviation between the present rotational speed and the maximum and thus ideal rotational speed of the internal combustion engine.