Clutch Disengagement via Acceleration Limiting
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Solution Overview
Problem
In power shift transmissions, centrifugal head pressure can cause disengaged clutches to lock up, reducing functionality, and existing solutions like the Centrifugal Head Internal Relief Port (CHIRP) prevent engagement but not release at high rotational speeds, especially when transmission oil is cold, leading to slow clutch piston retraction.
Innovation Solution
A system and method that uses a controller to determine engine speed and hydraulic fluid temperature to limit the acceleration of a work vehicle, employing a hydrostatic unit to control speed and allow the clutch piston to retract, thereby enabling the CHIRP to open and disengage the clutch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a CHIRP port is added to the clutch piston tank to prevent centrifugal head pressure buildup, then clutch engagement at high rotational speeds is prevented, but clutch disengagement at high rotational speeds is inhibited
Solution Approach 1:
The controller proactively limits vehicle acceleration before the clutch disengagement problem occurs. By detecting cold hydraulic fluid conditions and high engine speeds, the system preemptively reduces acceleration demands on the transmission, allowing the clutch piston sufficient time to retract and disengage without being overwhelmed by centrifugal head pressure
Solution Approach 2:
The system continuously monitors hydraulic fluid temperature and engine speed to dynamically adjust acceleration limits. This feedback loop ensures that acceleration restrictions are applied only when necessary (cold fluid conditions), allowing normal operation when fluid temperature is adequate, thus resolving the contradiction between preventing engagement and enabling disengagement
2Productivity
If the vehicle accelerates rapidly after a gear shift, then power transmission efficiency is improved, but the clutch piston cannot retract in time due to centrifugal head pressure
Solution Approach 1:
The system prepares for potential clutch disengagement issues by monitoring hydraulic fluid temperature beforehand. When cold conditions are detected, acceleration limits are preemptively applied during gear shifts, ensuring the clutch piston has adequate time to retract even though this temporarily reduces power transmission efficiency
Solution Approach 2:
The acceleration limit is not a fixed constraint but a dynamic control parameter that adjusts based on real-time operating conditions. The system applies acceleration restrictions only during cold fluid conditions and high-speed gear shifts, allowing full acceleration capability during normal operating temperatures, thus balancing productivity requirements with clutch protection needs
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 ensures timely clutch disengagement by limiting acceleration, preventing next gear from spinning at high rotational speeds and allowing the clutch piston to retract, thus effectively managing centrifugal head pressure and improving clutch functionality.
Implementation Method 1
a centrifugal head may build up in clutches rotating at high speed when they are not engaged. The centrifugal head may generate enough pressure to cause a disengaged clutch to lock up
Data Source
AI summary
A system of a work vehicle includes an engine, a transmission that includes a hydrostatic unit, and a clutch coupled to the transmission. The system also includes a controller communicatively coupled to the engine, the transmission, and the clutch. The controller, in operation, receives a command to disengage the clutch. The controller, in operation, determines an engine speed of the engine. The controller, in operation, also determines a temperature of hydraulic fluid in the clutch. The controller, in operation, further determines a magnitude and time to limit acceleration of the work vehicle based on the engine speed and the temperature. The controller, in operation, also commands the clutch to disengage. The controller, in operation, further limits the acceleration of the work vehicle using the hydrostatic unit based on the magnitude for the time determined.