Power Split Transmission Cold Start Control
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Solution Overview
Problem
Power-split transmissions with hydrostats face challenges in efficiently heating the hydraulic medium during cold starts, leading to prolonged start-up times and reduced thermal energy generation compared to converter transmissions.
Innovation Solution
A method that monitors the state of the power-split transmission during cold start steps, adjusting the duration based on pressure sensor values, and sequences through pressure build-up, pressure control, heating, pulsation, and drive preparation steps to effectively heat the transmission and prepare it for starting, ensuring robustness across varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional cold start steps are used in power-split transmissions with hydrostats, then the transmission can be started, but the cold start duration is prolonged due to insufficient thermal energy generation
Solution Approach 1:
The patent applies preliminary action by performing pressure build-up and heating steps before the actual drive operation. The method includes a pressure build-up step that activates the hydrostat pump to generate hydraulic pressure, followed by a heating step that uses the pump's operation to thermally energize the hydraulic medium, ensuring the transmission is properly prepared before full operation begins
Solution Approach 2:
The patent implements periodic action through alternating between pressure build-up steps and heating steps during the cold start sequence. The method periodically cycles through activating the pump for pressure generation, then allowing thermal energy to accumulate in the hydraulic medium, creating a rhythmic pattern of energy input and thermal accumulation that efficiently raises temperature
2Productivity
If the cold start process is accelerated, then the start-up time is reduced, but the thermal energy generation and heating effectiveness may be compromised
Solution Approach 1:
The patent applies feedback by continuously monitoring the hydraulic medium temperature and pressure sensor values during each cold start step. The control unit adjusts the duration and intensity of pressure build-up and heating steps based on real-time sensor feedback, extending or shortening step durations dynamically to ensure adequate heating while maintaining accelerated start-up pace
Solution Approach 2:
The patent implements dynamics by making the cold start process adaptive rather than fixed. The method dynamically adjusts the sequence and duration of pressure build-up and heating steps based on actual transmission state, allowing the system to optimize between speed and heating effectiveness in real-time based on varying operating conditions
3Adaptability or versatility
If the cold start method is made adaptive to different conditions, then the robustness is improved, but the control complexity increases
Solution Approach 1:
The patent applies universality by designing a control unit that handles multiple functions within a single integrated system. The control unit manages pressure build-up steps, heating steps, and drive preparation steps, and coordinates the hydrostat pump and position control valve, consolidating what could be separate control systems into one multi-functional unit that adapts to various cold start conditions
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 a faster and more robust cold start process, independent of cooling variants, oil viscosity, and transmission design, maintaining vehicle comfort with minimal loss, and ensuring proper transmission operation.
Implementation Method 1
Hydraulic pressure can be applied to the hydrostatic units of the hydrostat via the position control valve in order to actuate them
Implementation Method 2
heating the transmission oil by relative rotation of a first clutch plate and a first clutch hub of a first clutch assembly and by relative rotation of a second clutch plate and a second clutch hub of a second clutch assembly
Data Source
Figure 1
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AI summary
Method for carrying out cold starting in a vehicle, which vehicle has a power split gearbox with a hydrostat comprising hydrostatic units, wherein a plurality of cold-starting steps are carried out one after the other for the purpose of cold-starting, wherein the length of at least one of the cold-starting steps is adapted depending on a temperature which represents the starting temperature of the power split gearbox, wherein, during execution of at least one of the cold-starting steps, a state of the power split gearbox which differs from the temperature of the power split gearbox is monitored, and wherein a changeover from the respective cold-starting step to a subsequent cold-starting step is carried out depending on this state, and therefore the duration of the respective cold-starting step is adapted.