Hybrid Automatic Transmission Speed Control for Power-Split Shifting
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Solution Overview
Problem
Current automatic transmissions in hybrid electric vehicles suffer from inefficiencies due to frictionally engaged shift elements, which generate heat and drag losses, and require significant hydraulic power for operation, reducing overall efficiency.
Innovation Solution
The use of interlocking shift elements and a variator comprising two electric motors for gear ratio adjustment, with an electronic control unit that calculates setpoint speeds to limit speed gradient and curvature, allowing precise control and minimizing 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 heat generation and drag losses increase, reducing overall efficiency
Solution Approach 1:
The patent replaces the traditional friction-based mechanical shift elements with a variator system comprising two electric motors. These electric motors mechanically adjust the gear ratios of the automatic transmission without relying on frictional engagement, thereby eliminating the heat generation and drag losses associated with friction-based shifting mechanisms while maintaining smooth gear ratio transitions.
Solution Approach 2:
The patent changes the operating parameters from friction-based mechanical engagement to electric motor-driven adjustment. The electronic control unit calculates setpoint speeds that limit speed gradient and curvature, enabling precise control of the electric motors to achieve gear ratio adjustments with minimal energy consumption and without the harmful effects of frictional heating.
2Ease of operation
If frictionally engaged shift elements are used, then gear changes are possible, but significant hydraulic power is required for operation, reducing overall efficiency
Solution Approach 1:
The patent substitutes the hydraulic actuation system with an electric motor-driven variator system. Instead of using hydraulic pressure to engage and disengage friction plates, the system employs two electric motors controlled by an electronic control unit to adjust gear ratios. This eliminates the need for significant hydraulic power consumption while maintaining gear change functionality.
3Loss of energy
If interlocking shift elements are used instead of frictional elements, then drag losses are eliminated, but precise speed control is required to prevent damage
Solution Approach 1:
The patent implements a feedback control system where the electronic control unit continuously monitors the actual speeds of the two electric motors and compares them against calculated setpoint speeds. The setpoint speeds are specifically designed to limit speed gradient and curvature, ensuring that the interlocking shift elements engage and disengage smoothly without damage. This feedback mechanism makes the speed control requirement manageable by providing real-time adjustment capabilities.
Solution Approach 2:
The electronic control unit calculates the setpoint speeds in advance, considering the limitations of speed gradient and curvature. This preliminary calculation ensures that when the electric motors adjust the gear ratios, the speed changes remain within safe limits that prevent damage to the interlocking shift elements, thereby eliminating drag losses associated with frictional elements.
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 reducing energy consumption and eliminating drag losses, while enabling continuous power transmission with minimal power requirements, thus improving the overall efficiency of the automatic transmission system.
Implementation Method 1
one of the electric motors is operated as a generator and the other electric motor as a motor. By temporarily converting mechanical energy into electrical energy, the speeds of the two electric motors can be decoupled
Implementation Method 2
one of the electric motors is operated as a generator and the other electric motor as a motor
Data Source
AI summary
A motor vehicle has at least two drive motors, at least one of which is an electric motor, a high-voltage accumulator, and an automatic transmission which has at least one fixed gear ratio and at least one power-split gear ratio for transmission ratio adjustment starting from the at least one fixed gear ratio. The motor vehicle includes an electronic control unit having a speed control module which can be activated during a change of transmission ratio. The speed control module is designed in such a way that a setpoint speed is calculated in advance, by which setpoint speed both the speed gradient and also the speed curvature can be limited, the target speed of the at least one drive motor being continuously compared with a maximum allowed speed gradient and with a maximum allowed speed curvature.