Hybrid Vehicle Launch Torque Disturbance Reduction
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Solution Overview
Problem
In hybrid vehicles, stopping the engine and electric machine can lead to driveline torque disturbances due to gaps between gear surfaces and reduced oil pressure, causing wear and impacting vehicle efficiency.
Innovation Solution
Adjusting the electric machine from zero speed to a first speed to fill the torque converter and close gear clutches, allowing a small torque transfer to reduce gaps before full torque is applied, thereby minimizing driveline torque disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electric machine is accelerated directly from zero speed to high speed to meet driver demand, then the vehicle can respond quickly to propulsion requests, but torque disturbances occur through the driveline causing gear impact and wear
Solution Approach 1:
The system performs preliminary action by first rotating the electric machine at a first speed sufficient to fill the torque converter and close gear clutches before accelerating to the second speed. This preliminary rotation establishes proper lubrication and component engagement, preventing torque disturbances when full power is applied.
Solution Approach 2:
The acceleration process is segmented into two distinct speed stages. The first speed stage handles torque converter filling and clutch engagement, while the second speed stage provides full propulsion. This segmentation separates the lubrication function from the propulsion function, eliminating the conflict between quick acceleration and driveline protection.
2Loss of energy
If the engine and electric machine are stopped to conserve fuel and electrical energy, then vehicle efficiency improves, but spaces open up between gear surfaces and oil pressure reduces causing driveline wear
Solution Approach 1:
Before stopping the engine and electric machine, the system performs preliminary action by rotating the electric machine at the first speed to fill the torque converter with oil and close gear clutches. This ensures lubrication is established before the powertrain shuts down, protecting driveline components during the energy-saving idle period.
Solution Approach 2:
The system provides beforehand cushioning by using the first speed rotation to pressurize transmission fluid and engage clutches before shutdown. This creates a cushion of pressurized oil that maintains lubrication and prevents metal-to-metal contact during the period when the powertrain is stopped, reducing wear despite energy conservation.
3Loss of energy
If oil pressure is reduced to save energy when the transmission pump is not operating, then energy consumption decreases, but application force on gear clutches is reduced creating gaps and wear
Solution Approach 1:
The system performs preliminary action by rotating the electric machine at the first speed, which drives the transmission pump to build up oil pressure and close gear clutches before shutdown. This preliminary pressurization ensures clutches are fully engaged and lubricated before the pump stops, maintaining component protection without continuous energy input.
Solution Approach 2:
The system uses dynamic control by temporarily operating the transmission pump at first speed to establish proper clutch application force, then reducing pump operation to save energy. The dynamic sequence ensures clutches are engaged during the high-pressure phase, and the engaged state is maintained even when pump pressure is reduced, balancing energy savings with component protection.
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 reduces driveline torque disturbances, wear on components, and improves vehicle efficiency by conserving energy and reducing the impact of gear engagement during vehicle launches.
Implementation Method 1
a transmission pump pressurizes transmission fluid to a level sufficient to begin closing gear clutches and that allows torque to be transmitted from the torque converter impeller to the torque converter turbine
Implementation Method 2
a transmission pump pressurizes transmission fluid to a level sufficient to begin closing gear clutches
Implementation Method 3
application of gear clutches may not be maintained and space and/or a reduction in application force may develop between clutch friction surfaces
Data Source
AI summary
Systems and methods for improving launching of a stopped hybrid vehicle are presented. The systems and methods adjust speed of a motor to reduce the possibility of noticeable impact between driveline gears during vehicle launch. In one example, motor speed is adjusted to a pump pressurization speed where driveline components may be moved to reduce impact between driveline gears during vehicle launch.