Binary Clutch Slip Verification for NVH Reduction
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Solution Overview
Problem
Binary clutch assemblies in motor vehicle transmissions often fail to release properly due to torsional loads and friction, leading to unintended engagement and potential noise, vibration, and harshness (NVH) issues during shifts, as existing methods lack effective verification of release states.
Innovation Solution
A transmission control module (TCM) is used to verify the release of a binary clutch assembly by monitoring slip across the clutch assembly via speed sensors, determining if the slip exceeds a calibrated threshold, and delaying or executing shifts only when the clutch is confirmed released, thereby ensuring proper engagement of friction clutches and minimizing NVH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a binary clutch assembly is used to provide on/off torque transfer, then the transmission control is simplified and shift response is improved, but the clutch may fail to release properly due to torsional loads and friction
Solution Approach 1:
The system continuously monitors slip across the binary clutch assembly using speed sensors and compares it against threshold values. This feedback mechanism detects whether the clutch has properly released by verifying that slip exceeds a calibrated threshold, allowing the control module to identify release failures and prevent unintended engagements.
Solution Approach 2:
The system performs preliminary verification of clutch release status before allowing transmission shifts to proceed. By checking slip conditions in advance and delaying shift execution until release is confirmed, the system prevents unintended engagements and ensures reliable operation before the actual shift occurs.
2Ease of operation
If the binary clutch assembly is commanded to release, then the transmission can shift to the next gear, but without verification the clutch may remain engaged causing noise, vibration, and harshness
Solution Approach 1:
Speed sensors continuously monitor the rotational speeds of components across the binary clutch assembly, and the control module calculates slip by comparing these speeds. This real-time feedback allows the system to verify whether the clutch has actually released, preventing shifts from occurring when the clutch remains engaged and thus eliminating NVH issues.
Solution Approach 2:
The system replaces direct mechanical verification of clutch release with an electronic monitoring system that measures slip through speed sensors and computational logic. This substitution allows for precise, non-intrusive detection of release status without adding mechanical complexity to the clutch assembly itself.
3Measurement precision
If slip monitoring is implemented to verify clutch release, then release accuracy is improved, but the device complexity increases due to additional sensors and control logic
Solution Approach 1:
The control module performs multiple functions using the same slip monitoring infrastructure: it verifies clutch release status, detects release failures, prevents unintended engagements, and controls shift timing. By making the control module multi-functional, the system achieves high measurement precision without proportionally increasing device complexity.
Solution Approach 2:
The system uses existing speed sensors and the controller's computational resources to perform clutch release verification, rather than requiring dedicated verification hardware. The controller already processes speed data for other transmission control functions, so it self-services the verification function using existing infrastructure.
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
The method ensures accurate verification of binary clutch release, preventing unintended engagements and reducing noise, vibration, and harshness (NVH) by confirming the clutch assembly's release state before proceeding with shifts, thus enhancing transmission control and reliability.
Implementation Method 1
A typical binary clutch assembly includes a freewheeling element and an on/off binary device such as a selectable one-way clutch or a dog clutch. When the binary device is unloaded upon a commanded release, the binary clutch assembly freewheels in at least one rotational direction.
Implementation Method 2
Application of the binary device, typically via deployment of spring-loaded struts, sprags, or other torque-holding pieces into engagement with recesses in a race of the binary device, thus effectively locks the binary clutch assembly to thereby present undesired rotation.
Implementation Method 3
The TCM monitors the amount of slip across the binary clutch assembly, e.g., via receipt and processing of speed signals from a pair of speed sensors positioned with respect to the binary clutch assembly.
Data Source
AI summary
A vehicle includes an engine and transmission assembly, the latter having a stationary member, a plurality of gear sets, an input member, a friction clutch, a binary clutch assembly, and a transmission control module (TCM). The binary clutch assembly includes a freewheeling element and a binary device such as a selectable one way clutch or dog clutch. The TCM selectively delays a release of the binary clutch assembly via a binary clutch indicator method by detecting a requested shift of the transmission requiring an engagement of the friction clutch, and commanding the release of the binary clutch assembly. The TCM determines an amount of slip across the binary clutch assembly and executes the requested shift of the transmission only when the determined amount of slip exceeds a calibrated slip threshold. Slip may be measured or calculated.