Hybrid Automatic Gearbox Torque Unloading for Drag-Loss-Free Shifting
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Solution Overview
Problem
Current hybrid electric vehicle transmissions experience inefficiencies due to drag losses and energy consumption in frictionally engaged shift elements, which are not effectively addressed by existing hybridization methods.
Innovation Solution
The implementation of a motor vehicle with at least two drive motors, including an electric motor and an internal combustion engine, featuring a variator with two electric motors for continuous gear ratio adjustment between fixed gear ratios, and an electronic control unit that manages torque loads to disengage shift elements efficiently, reducing energy consumption and drag losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If frictionally engaged shift elements are used for gear ratio adjustment, then gear changes can be achieved, but drag losses and energy consumption increase during operation
Solution Approach 1:
The transmission system is segmented into distinct functional areas: frictionally engaged shift elements are separated from the variator system. The variator handles continuous gear ratio adjustment independently, while shift elements only engage/disengage at discrete fixed gear ratios, minimizing their operational time and associated energy losses.
Solution Approach 2:
The patent extracts the continuous gear ratio adjustment function from the friction-based shift elements and assigns it to the variator system. This removes the harmful drag losses from continuous operation, as shift elements only operate briefly during discrete gear changes rather than continuously.
2Power
If hydraulic pressure is applied to friction plates for power transmission, then torque can be transmitted in closed state, but power consumption increases due to hydraulic pump operation
Solution Approach 1:
The hydraulic system operates periodically rather than continuously. The hydraulic pump activates only during discrete gear change events to engage or disengage shift elements, then remains inactive during normal operation. This periodic operation dramatically reduces overall power consumption while maintaining torque transmission capability when needed.
Solution Approach 2:
The patent extracts the continuous torque transmission function from the hydraulic friction system and assigns it to the variator. The hydraulic system is reduced to only performing discrete engagement/disengagement actions, eliminating continuous power consumption while preserving essential gear ratio adjustment capability.
3Ease of operation
If friction work is converted to heat during slip operation, then gear changes can occur, but heat dissipation requirements increase
Solution Approach 1:
The patent segments the gear ratio adjustment process into two distinct phases: brief discrete gear changes using shift elements, and continuous smooth adjustment using the variator. This segmentation limits the duration of friction-based operations, thereby reducing total heat generation and simplifying thermal management requirements.
Solution Approach 2:
The shift elements complete their friction-based slip operation as quickly as possible during discrete gear changes, then immediately transition to the variator for continuous adjustment. By rushing through the heat-generating friction phase and minimizing its duration, the system reduces overall heat generation while maintaining gear change capability.
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 solution enhances the efficiency of gear ratio adjustments by minimizing energy consumption and eliminating drag losses during gear changes, maintaining high overall efficiency and tractive force while shifting between fixed gear ratios.
Implementation Method 1
the variator comprises, for example, two electric motors. One electric motor may also suffice. In this case, the variator consists of the electric motor and a high-voltage accumulator
Implementation Method 2
comprising a high-voltage accumulator and comprising an automatic transmission
Implementation Method 3
In these transmissions, at least one shift element is operated under slip during gear changes. The friction work during slip operation is converted here into heat
Data Source
AI summary
A motor vehicle has at least two drive motors, at least one drive motor being an electric machine; a high-voltage accumulator; and an automatic gearbox, having at least one fixed transmission ratio and at least one power-split transmission ratio for transmission regulation starting from the at least one fixed transmission ratio. The motor vehicle further includes an electronic control unit, which is designed such that, when a gear change command is present, the shifting element to be opened of the fixed transmission ratio to be disengaged is unloaded in a torque-controlled manner by at least two of the drive motors. For the shifting element to be opened, the torque load is calculated and observed. The torque load is observed with the objective of bringing about a load change by way of a zero crossing in order to produce a no-load state at the shifting element. For producing the no-load state of the shifting element to be opened, a first drive motor and a second drive motor are controlled in a power split manner such that they, in terms of rotational speeds, maintain the transmission of the previously engaged fixed transmission ratio, and, in terms of torque, put the shifting element to be opened in an at least nearly no-load state, and a load change is brought about at the shifting element to be opened by a differential rotational speed, opposite the calculated torque load at the shifting element to be opened, being specified at the shifting element.