Dog Clutch Shifting via Electric Machine Torque Adaptation
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Solution Overview
Problem
Existing methods for shifting dog clutch elements in hybrid vehicle transmissions face challenges such as increased wear and power loss due to frictional synchronization, leading to longer shifting times and higher fuel consumption, especially during uphill travel.
Innovation Solution
The method involves using the electric machine to adapt torque and reduce load on the dog clutch element, allowing it to be disengaged easily, and then re-engaging it when the desired rotational speed is reached, minimizing mechanical synchronization loading and wear, and utilizing a control unit to manage shifting operations within the transmission system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical synchronization devices are used to adapt rotational speeds before dog clutch elements intermesh, then reliable shifting is achieved, but wear increases and shifting time increases
Solution Approach 1:
The patent replaces the mechanical synchronization device with an electric machine that directly adapts the rotational speed of the input shaft. This substitution eliminates the need for friction-based mechanical synchronization, enabling rapid speed adaptation without wear or extended shifting time.
Solution Approach 2:
The electric machine dynamically changes the rotational speed parameter of the input shaft to match the output shaft speed before engagement. This parameter adaptation occurs electrically and rapidly, avoiding the time-consuming and wear-inducing mechanical friction process.
2Reliability
If mechanical synchronization devices are used to adapt rotational speeds, then dog clutch elements can intermesh reliably, but power loss increases due to friction
Solution Approach 1:
The patent substitutes the friction-based mechanical synchronization system with an electric machine that adapts rotational speeds through electromagnetic torque control. This eliminates the frictional power losses inherent in mechanical synchronization devices.
Solution Approach 2:
The electric machine applies periodic or pulsed torque to rapidly adjust the input shaft speed to match the output shaft speed, achieving synchronization without continuous frictional contact and associated energy losses.
3Reliability
If mechanical synchronization devices are used for shifting, then rotational speed adaptation is achieved, but fuel consumption increases
Solution Approach 1:
The patent replaces the energy-intensive mechanical synchronization process with an electrically-controlled speed adaptation using the electric machine. This reduces overall energy consumption and specifically lowers fuel consumption by eliminating frictional losses.
Solution Approach 2:
The patent converts the electric machine, which could be a source of energy consumption, into a beneficial device that reduces overall energy loss by eliminating frictional heating and improving shifting efficiency, thereby reducing fuel consumption.
4Reliability
If mechanical synchronization devices are used, then speed adaptation occurs, but heat generation increases requiring additional cooling
Solution Approach 1:
The patent substitutes the friction-based mechanical synchronization that generates heat with an electric machine-based speed adaptation. This eliminates the primary heat generation source during shifting operations, reducing thermal load on the transmission system.
Solution Approach 2:
The patent converts the potential heat generation issue by using the electric machine to perform speed adaptation without frictional heating, thereby eliminating the harmful thermal effect and reducing cooling system demands.
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 enables rapid, efficient, and comfortable shifting with reduced fuel consumption and wear, minimizing heat losses and enhancing driving performance by directly controlling the internal combustion engine's rotational speed through the electric machine, thus optimizing shifting in hybrid vehicles.
Implementation Method 1
the torque of the input shaft is adapted via the electric machine
Implementation Method 2
The internal combustion engine is subsequently braked or accelerated to the desired target rotational speed via the electric machine
Implementation Method 3
the electric machine operating in the manner of a generator and the electrical energy which is liberated being temporarily stored in an energy accumulator device
Data Source
AI summary
A method performs shifts in a dog clutch element of a transmission system in a hybrid vehicle. The vehicle has an input shaft being connected to a crankshaft of an internal combustion engine, an output shaft being connected indirectly to driven wheels, an electric machine which is in engagement with the input shaft, and an automatic transmission connected between the input and output shafts. The transmission has a dog clutch element for the releasable coupling of two transmission elements. During a desired shifting of the dog clutch element, the torque of the input shaft is adapted via the electric machine, and therefore a reduced load prevails in the region of the dog clutch element and the latter can be disengaged, after which the internal combustion engine is set to a desired target rotational speed, and after which the dog clutch element is engaged when the target rotational speed is reached.