Hybrid Vehicle Shifting Control for Smooth Transitions
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Solution Overview
Problem
Conventional hybrid vehicle transmissions experience slippage and vibration when shifting from park or neutral to drive or reverse, leading to reduced durability and poor shifting performance due to rotational speed differences and frictional forces.
Innovation Solution
A shifting control method that includes releasing clutches and brakes into a neutral position, controlling engine and motor/generator operations to synchronize rotational speeds, and using a controller to determine the appropriate clutch or brake operation for smooth transitions, ensuring the second ring gear is not rotated or rotated at the engine's output speed based on predetermined conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If clutches and brakes are released in conventional CVT during park or neutral mode, then the transmission can be shifted to drive or reverse, but slippage occurs due to rotational speed difference causing vibration and noise
Solution Approach 1:
The controller synchronizes the rotational speeds of the engine and motor/generator before shifting from park or neutral to drive or reverse. By pre-aligning the rotational speeds, the clutch engagement occurs without speed differential, preventing slippage and the associated vibration and noise.
Solution Approach 2:
The system dynamically adjusts the rotational speed parameters of the engine and motor/generator to match each other before clutch engagement. This parameter synchronization ensures that when the clutch connects the rotational elements, there is no speed mismatch to cause harmful slippage.
2Ease of operation
If clutches and brakes are released during shifting, then gear transition is enabled, but frictional force reduces durability of transmission components
Solution Approach 1:
The controller performs preliminary speed synchronization of the engine and motor/generator before clutch engagement. This advance preparation ensures that the clutch connects rotational elements at matched speeds, minimizing frictional wear and extending transmission component durability.
3Object-affected harmful factors
If rotational speed synchronization is implemented before shifting, then slippage and vibration are reduced, but control complexity increases
Solution Approach 1:
The controller continuously monitors the rotational speeds of the engine and motor/generator and dynamically adjusts their operation to maintain speed synchronization. This feedback control automatically manages the complexity of coordinating multiple power sources while achieving smooth shifting without vibration.
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 method minimizes shift shock and slippage, enhancing shifting feel and safety by preventing rotational speed mismatches and reducing wear on transmission components.
Implementation Method 1
a first motor/generator that is disposed to rotate the first ring gear
Implementation Method 2
a second motor/generator that is disposed to rotate the second sun gear
Implementation Method 3
an engine that is disposed to rotate the first carrier of the first planetary gear unit
Implementation Method 4
a first planetary gear unit having a first sun gear, a first planetary gear, a first ring gear, and a first carrier; a second planetary gear unit having a second sun gear that rotate together with the first sun gear, a second planetary gear, a second ring gear, and a second carrier that transfers a toque to an output shaft
Data Source
AI summary
A system and method for shifting a hybrid vehicle is provided which utilizes one or more controllers to release one or more clutches and brakes when a transmission is shifted into neutral or park and then prevents a rotational element from being rotated by controlling an engine and a motor/generator when the transmission is in neutral or park. Accordingly, shift shock or slip is minimized when a transmission is shifted from a park or a neutral to a drive or a reverse, thus improving a shifting feeling and safety of the vehicle.