Lockup Clutch Pressure Control for Fast, Low-Slip Engagement
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Solution Overview
Problem
Existing control devices for lockup clutches in automatic transmission mechanisms of vehicles face challenges in rapidly engaging the clutch while minimizing slip ratio and slip amount, leading to inefficiencies in engagement time and potential vibrations during acceleration and deceleration.
Innovation Solution
A control device that supplies hydraulic pressure to the lockup clutch to maintain a differential pressure lower than a reference level in the disengaged state, increasing it as the filling ratio of the oil passage decreases, thereby reducing engagement time without excessively increasing the slip ratio or slip amount, and employing hysteresis in opening and closing the oil passage to prevent frequent changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If higher hydraulic pressure is temporarily supplied to the lockup clutch to maintain the engaged state, then response characteristics are improved and engagement time is shortened, but slip ratio and slip amount increase excessively
Solution Approach 1:
The patent applies dynamics by making the hydraulic pressure supply dynamic rather than static. The control device adjusts the differential pressure based on the filling ratio of the oil passage, which changes over time during engagement. By dynamically adapting the pressure to the current state (filling ratio), the system achieves rapid engagement while controlling slip, resolving the contradiction between fast response and excessive slip.
Solution Approach 2:
The patent changes the parameter of differential pressure based on the filling ratio. Instead of applying a fixed high pressure, the system varies the pressure level according to how full the oil passage is. This parameter change allows the system to optimize engagement speed while minimizing slip ratio and slip amount, as the pressure is adjusted to match the actual state of the clutch engagement process.
2Object-generated harmful factors
If differential pressure is kept low in the disengaged state, then slip ratio is reduced, but engagement response becomes slower
Solution Approach 1:
The patent applies preliminary action by preparing the hydraulic pressure in advance based on the filling ratio. Before full engagement occurs, the system has already adjusted the differential pressure according to the oil passage filling state. This preliminary preparation ensures that when engagement is commanded, the pressure is already optimized for rapid response, eliminating the delay that would occur with low pressure maintenance.
Solution Approach 2:
The system transitions from a static low-pressure state to a dynamic pressure adjustment based on filling ratio. The differential pressure is not fixed but changes dynamically as the oil passage fills, allowing the system to maintain low slip ratio during disengagement while preparing for rapid engagement response when needed.
3Loss of time
If hydraulic pressure is increased rapidly to shorten engagement time, then response characteristics improve, but vibrations occur during acceleration and deceleration
Solution Approach 1:
The patent changes the pressure application parameter from a sudden step-change to a gradual adjustment based on filling ratio. By controlling the differential pressure to increase progressively as the oil passage fills, the system avoids the shock and vibration that would result from abrupt pressure application, while still achieving rapid engagement through the optimized pressure trajectory.
Solution Approach 2:
The system applies beforehand cushioning by preparing the hydraulic pressure in advance according to the filling ratio. The differential pressure is adjusted progressively before full engagement occurs, cushioning against the sudden pressure surge that would cause vibrations. This preliminary pressure preparation smooths the engagement process while maintaining fast response.
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 effectively shortens engagement time, reduces vibrations during acceleration and deceleration, and maintains a suitable differential pressure by accurately calculating slip ratio and slip amount based on input and output rotation speeds and heat generation, ensuring precise control of the lockup clutch.
Implementation Method 1
a control part (CM) supplying hydraulic pressure to the lockup clutch (LC) and controlling differential pressure of the lockup clutch (LC)
Data Source
AI summary
A control device controls a lockup clutch interposed between an engine and an automatic transmission mechanism of a vehicle. The control device includes a control part supplying hydraulic pressure to the lockup clutch and controlling differential pressure of the lockup clutch. The control part supplies the hydraulic pressure to the lockup clutch so that the differential pressure is lower than a reference differential pressure in a disengaged state of the lockup clutch. In a case of shifting the lockup clutch from the disengaged state to an engaged state, the control part supplies the hydraulic pressure to the lockup clutch so that the differential pressure increases as a filling ratio of an oil passage of the lockup clutch decreases. The reference differential pressure is a lower limit of the differential pressure that increases a slip ratio of the lockup clutch or reduces a slip amount of the lockup clutch.