Hybrid Driveline Propshaft Spin-Up Control
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Solution Overview
Problem
Conventional hybrid vehicles experience an unacceptable 'jerk' and delay when dynamically reconnecting from two wheel drive to four wheel drive mode due to frictional drag and incomplete spinning up of the driveline components.
Innovation Solution
The use of an electric motor to spin up the propshaft to a predetermined speed before reconnecting it to the engine and rear wheels, ensuring a smooth transition by synchronizing rotational speeds and minimizing jerkiness, achieved through a control system that activates the electric motor and clutch mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the propshaft is disconnected from the engine and rear wheels during two wheel drive mode, then fuel efficiency is improved by reducing driveline drag, but the reconnection to four wheel drive mode produces an unacceptable jerk and delay
Solution Approach 1:
The electric motor spins up the propshaft to the required operating speed before the clutch engages to connect the driveline components. This preliminary acceleration of the propshaft eliminates the jerk that would otherwise occur during engagement, allowing smooth transition from two-wheel to four-wheel drive mode while maintaining the fuel efficiency benefits of disconnection during two-wheel drive operation
2Adaptability or versatility
If conventional clutch arrangements are used to reconnect the propshaft, then the transition from two wheel drive to four wheel drive can be made, but a jerk is still felt and there is a delay in transferring modes
Solution Approach 1:
The electric motor pre-accelerates the propshaft to match the rotational speed required for four-wheel drive operation before the clutch engages. This preliminary action ensures that when the clutch connects the driveline, there is no speed mismatch to cause jerk or discomfort to the driver, while also minimizing the time required for mode transition
Solution Approach 2:
The electric motor acts as an intermediary device between the engine and the propshaft during the transition phase. It provides the additional torque needed to spin up the propshaft quickly and smoothly, bridging the gap between the disconnected two-wheel drive state and the connected four-wheel drive state without subjecting the driver to jerk or delay
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 seamless dynamic driveline reconnection while driving, reducing fuel inefficiencies and enhancing driver comfort by eliminating noticeable jerks during mode changes.
Implementation Method 1
an electric motor coupled to the auxiliary driveline... the control means firstly activates the electric motor causing it to spin the propshaft up to a predetermined speed
Data Source
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AI summary
A hybrid motor vehicle (10) has a four wheel drive arrangement in which the front wheels (12 and 13) are driven by the engine (11) in two wheel drive mode and all four wheels (12-15) in four wheel drive mode. The engine is connected to the rear wheels (14 and 15) through an auxiliary driveline which includes a first clutch (22) to connect to the engine (11), a propshaft (23) and a differential (25). An electric motor (28) is connected to the propshaft (23) for the purpose of driving the vehicle either with or without the assistance of the engine (11). A second clutch (27) is located between the propshaft (23) and the differential (25). When the vehicle is in two wheel drive mode, the propshaft (23) is disconnected from both the engine (11) and the rear wheels (14 and 15) and on switching to four wheel drive mode when the vehicle is moving the propshaft (23) is firstly spun up to a speed matching that of the engine (11) and rear wheels (14, 15) by the action of the electric motor (28). Then the auxiliary driveline (21) is reconnected by engaging the first and second clutches (22, 27). This reduces any acceleration jerk perceived by the driver.