Vehicle Drive Assembly Coasting Mode via Power Shift Element
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Solution Overview
Problem
Existing drive arrangements for vehicles with two equivalent travel directions face challenges in smoothly transitioning between powered and coasting modes, leading to wear on components and potential shocks due to the need for precise differential speed control and frequent neutral shifts.
Innovation Solution
A method that uses a change-speed gearbox with multiple planetary gear sets and power shift elements, where the power flow is interrupted by opening power shift elements to enable coasting or towing mode without actuating the reversing set, and a secondary oil pump ensures lubrication during these operations, reducing wear and minimizing shocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drive train is disconnected by means of the form-fit shifting element in the reversing set to enable coasting mode, then the drive motor is decoupled from the drive train, but this causes wear on the shifting element and potential tooth-on-tooth positioning issues requiring multiple attempts
Solution Approach 1:
The patent extracts the coasting function from the reversing set and relocates it to the change-speed gear. By opening a power shift element in the change-speed gear instead of using the form-fit shifting element in the reversing set, the drive motor is decoupled without causing wear on the reversing set's shifting elements, thus eliminating the harmful wear effect while maintaining reliable coasting mode switching
Solution Approach 2:
The patent introduces the change-speed gear as an intermediary mechanism to achieve coasting mode. Instead of directly disconnecting the drive train through the reversing set's form-fit shifting element, the power shift element in the change-speed gear acts as an intermediary to interrupt power flow, thereby protecting the reversing set from wear while enabling reliable coasting operation
2Ease of operation
If the differential speed is controlled to a narrow window to achieve jerk-free gearshifts when coasting mode is switched off, then smoother transitions are achieved, but this requires complex targeted motor control and may still result in tooth-on-tooth position issues
Solution Approach 1:
The patent replaces the mechanical form-fit shifting element disengagement with a friction-based power shift element opening. When switching from coasting to driven mode, the power shift element is closed using friction engagement rather than positive locking, which eliminates the need for precise differential speed control and complex motor adjustments, thereby reducing control complexity while maintaining smooth transitions
Solution Approach 2:
The patent changes the engagement parameter from form-fit (positive locking) to friction-based engagement. This parameter change allows for more tolerant speed matching during mode transitions, as friction clutches can accommodate a wider range of speed differences without causing tooth-on-tooth positioning issues, thus simplifying the control requirements while ensuring smooth transitions
3Adaptability or versatility
If frequent neutral shifts are performed by shifting the positive-locking shifting device, then coasting mode can be switched on and off, but this leads to additional wear on sliding surfaces and other components
Solution Approach 1:
The patent extracts the coasting control function from the reversing set's positive-locking shifting device and relocates it to the change-speed gear's power shift elements. This extraction prevents the frequent actuation of the reversing set's form-fit shifting element, thereby eliminating wear on its sliding surfaces while maintaining full adaptability for coasting mode switching through the change-speed gear's friction-based power shift elements
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 allows for quicker, smoother transitions between modes, reducing wear on components and eliminating shocks, while maintaining adequate lubrication and pressure for shifting elements, thus enhancing the operational efficiency and comfort of the vehicle.
Implementation Method 1
a secondary pump for supplying oil to at least the transmission is switched on or put into operation
Data Source
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AI summary
The invention relates to a method for operating a drive assembly (1) of a vehicle having two equivalent directions of travel in a coasting or towing mode, wherein the drive assembly (1) has a variable-speed transmission (4) for realising different transmission ratios and a reversing set (8) for reversing the direction of rotation. The variable-speed transmission comprises (4) a plurality of planetary gear sets (5) and a plurality of load-shifting elements (6). The reversing set (8) comprises at least one interlocking shifting device (7). According to the proposed method, at least one load-shifting element (6) in the variable-speed transmission (4) is opened in order to activate the coasting or towing mode. The invention also relates to a corresponding drive assembly (1).