Dog Clutch Switching Control for Four-Wheel Drive Vehicles
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Solution Overview
Problem
Four-wheel drive vehicles face difficulties in smoothly switching the dog clutch from a non-meshing state to a meshing state when a speed difference exists between wheels, particularly during turning, due to rotation speed differences between the power transmitting member and the sub-drive wheels, leading to potential switching issues or noticeable noise.
Innovation Solution
A control device calculates the rotation speed differences between the drive-power-source-side and sub-drive-wheel-side meshing teeth, and if within a predetermined range, it couples the sub-drive wheel with the smaller difference to the central axle to facilitate smooth switching, while prohibiting switching if the differences are outside the range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If one-sided chamfers are provided on meshing teeth to allow meshing when power transmitting member speed exceeds central axle speed, then meshing is enabled under normal conditions, but smooth switching cannot be achieved when speed difference exists between wheels during turning
Solution Approach 1:
The patent applies parameter changes by providing two different chamfer configurations: first chamfers for normal operation and second chamfers for turning conditions. The control device changes the effective chamfer geometry by selecting which set of chamfers engages based on detected wheel speed differences, thereby adapting the meshing characteristics to match the operational conditions and enable smooth switching during turning.
Solution Approach 2:
The patent segments the chamfer structure into two distinct sets: first chamfers on the power transmitting member side and second chamfers on the central axle side. This segmentation allows each set to be optimized for different operational scenarios, with the control device selecting the appropriate engagement configuration based on real-time speed difference detection.
2Ease of operation
If control coupling on outer wheel side is selected during turning, then coupling is achieved, but dog clutch cannot switch from non-meshing to meshing state when first rotation speed difference is negative
Solution Approach 1:
The control device continuously monitors the rotation speed difference between the power transmitting member and the central axle, and based on this feedback, dynamically selects which control coupling to engage and which chamfer configuration to use. This feedback mechanism ensures that the dog clutch switching is performed under optimal speed difference conditions, preventing switching failures during turning operations.
Solution Approach 2:
The system dynamically adjusts the engagement configuration by switching between different control couplings and chamfer sets based on real-time operating conditions. The control device can change which left or right control coupling is active and which chamfer geometry is engaged, adapting the mechanical configuration to match the current speed difference conditions.
3Ease of operation
If control coupling on inner wheel side is selected during turning, then coupling is achieved, but noticeable switching sound is generated when second rotation speed difference is relatively large
Solution Approach 1:
The patent reduces harmful switching sounds by changing the effective chamfer geometry parameter. When turning conditions are detected, the control device selects the second chamfers on the central axle side, which have different angular parameters optimized for reduced impact and noise during engagement under speed difference conditions.
4Productivity
If dog clutch switching is attempted under large speed difference conditions, then four-wheel drive engagement is achieved, but switching smoothness deteriorates and noise increases
Solution Approach 1:
The control device acts as an intermediary that manages the transition process. It detects speed difference conditions and either selects appropriate chamfer configurations to facilitate smooth engagement or temporarily prohibits switching until conditions improve, thereby mediating between the need for four-wheel drive engagement and the requirement for smooth, noise-free operation.
Data Source
AI summary
A four-wheel drive vehicle in which, when a switching request is made for switching from a non-meshing state to a meshing state, the control device calculates a first rotation speed difference between the drive-power-source-side meshing teeth and the sub-drive-wheel-side meshing teeth, and a second rotation speed difference between the drive-power-source-side meshing teeth and the sub-drive-wheel-side meshing teeth. If at least one of the calculated first and second rotation speed differences is within a predetermined range set in advance, the control device couples the sub-drive wheel corresponding to the rotation speed difference within the predetermined range, to the central axle by the control coupling to switch the dog clutch from the non-meshing state to the meshing state. And, if neither the calculated first nor second rotation speed difference is within the predetermined range, the control device prohibits switching of the dog clutch from the non-meshing state to the meshing state.