Vehicle Start Clutch Control for Torque Gradient Limiting
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Solution Overview
Problem
Existing starting operations in motor vehicles with internal combustion engines face challenges in reliably establishing a drive connection between the engine and the drive wheels, particularly when the starting element is overloaded due to excessive torque, leading to potential failure or damage.
Innovation Solution
A method and control device that adjust the torque gradient during the closing operation of the starting element to a lower closing gradient than the preset gradient, ensuring the speed difference between input and output speeds falls below a defined limit, thereby preventing excessive torque and reducing stress on the starting element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the starting element is closed to establish a drive connection between the internal combustion engine and the drive wheels, then the motor vehicle can start from a standstill, but excessive torque may overload the starting element causing potential failure or damage
Solution Approach 1:
The control device dynamically adjusts the torque gradient parameter during the closing operation. Instead of applying the full requested torque gradient, the control device modifies it to a reduced gradient that ensures the starting element is not overloaded while still enabling the drive connection to be established. This parameter change resolves the contradiction by allowing reliable starting operation without exceeding the starting element's load capacity.
2Productivity
If the torque gradient is increased to meet the requested torque quickly, then the starting operation is faster, but the speed difference between input and output speeds increases causing excessive torque on the starting element
Solution Approach 1:
The control device dynamically adjusts the torque gradient based on the current speed difference between the input and output sides of the starting element. As the closing operation progresses and the speed difference decreases, the torque gradient can be increased. This dynamic adaptation allows the starting operation to be completed efficiently while preventing excessive torque from being applied when the speed difference is still large, thus resolving the contradiction between starting speed and torque protection.
3Productivity
If the starting element is closed rapidly to establish drive connection, then the starting operation is more efficient, but heat input to the starting element increases causing potential damage
Solution Approach 1:
By controlling the torque gradient parameter throughout the closing operation, the control device prevents excessive slip and associated heat generation in the starting element. The torque gradient is adjusted to match the evolving speed conditions, ensuring that the starting element closes efficiently without generating excessive heat that could lead to damage. This resolves the contradiction between starting efficiency and temperature control.
Data Source
AI summary
A method of starting a motor vehicle is initiated as soon as a requested torque is preset on the driver's side when the vehicle is at a standstill. During starting, a starting element in the drive train is closed, establishing a drive connection between an internal combustion engine connected to a drive side of the starting element and an output of the drive train connected to an output side of the starting element, thereby adjusting an output speed at the output side to an input speed at the drive side of the starting element. While closing the starting element, a torque gradient used to adjust a target torque is changed to a closing gradient until a lower limit value is undershot by a difference between the input speed and the output speed. The closing gradient is set below a preset gradient defined based on the preset requested torque.