Vehicular Lockup Clutch Precharge Control for Hydraulic Responsiveness
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Solution Overview
Problem
Existing control devices for vehicular lockup clutches face insufficient responsiveness during flexible start control, particularly at ultralow or ultrahigh temperatures, leading to degraded drivability and fuel consumption due to engine revolution speed overshoot and hydraulic pressure controllability issues.
Innovation Solution
A control device for a vehicular lockup clutch that includes a precharge control mechanism, where a predetermined preparation pressure is established in the linear solenoid valve before flexible start control, ensuring a sufficient increase in hydraulic pressure and preventing unnecessary engine speed increases, along with a switching valve to maintain the disengaged state of the lockup clutch until vehicle movement begins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the control hydraulic pressure is raised to the initial engagement pressure at the initial stage of flexible start control, then the responsiveness of hydraulic control is improved, but a hydraulic pressure overshoot easily occurs and controllability of hydraulic pressure degrades
Solution Approach 1:
The invention applies preliminary action by performing a precharge control before the flexible start control to establish a standby state with a predetermined preparation pressure in the linear solenoid valve. This preliminary pressurization ensures that when the flexible start control begins, the hydraulic system is already primed and responsive, eliminating the need to rapidly raise pressure during the actual engagement phase, thus avoiding overshoot while maintaining controllability.
2Speed
If the hydraulic pressure command value is set high in the fast-fill mode, then the responsiveness of engagement hydraulic pressure is improved, but a hydraulic pressure overshoot easily occurs and controllability of hydraulic pressure degrades
Solution Approach 1:
The precharge control establishes a preparation pressure in advance, so when fast-fill mode is activated during flexible start control, the system starts from a pressurized state rather than from zero pressure. This reduces the pressure differential that would otherwise cause overshoot, while still enabling rapid pressure increase when needed.
Solution Approach 2:
The invention dynamically adjusts the hydraulic pressure command based on the operational phase. During precharge control, a moderate preparation pressure is applied. When flexible start control begins, the system transitions to a different pressure profile that accounts for the already-pressurized state, preventing overshoot while maintaining the necessary responsiveness for engagement.
3Use of energy by moving object
If the responsiveness of hydraulic control is low, then fuel consumption is improved through reduced hydraulic pressure fluctuations, but drivability is degraded by overshoot of engine revolution speed
Solution Approach 1:
By pre-charging the linear solenoid valve with a preparation pressure before flexible start control, the system ensures immediate responsiveness when engagement is commanded. This eliminates delays that would cause engine revolution speed overshoot, improving drivability without requiring excessive pressure fluctuations that would waste fuel.
Solution Approach 2:
The control device monitors the actual hydraulic pressure and compares it with the command pressure, adjusting the linear solenoid valve input accordingly. This feedback mechanism ensures that the hydraulic pressure follows the desired profile closely, preventing both overshoot (which degrades drivability) and excessive pressure variations (which waste fuel).
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 precharge control ensures improved responsiveness and reduced fuel consumption by inhibiting rapid engine speed increases and maintaining the disengaged state of the lockup clutch until vehicle movement, thereby enhancing drivability and fuel efficiency.
Implementation Method 1
a linear solenoid valve that controls an engagement hydraulic pressure for engaging and actuating the lockup clutch
Implementation Method 2
a hydraulic transmission device constituting part of a power transmission path between an engine and drive wheels
Data Source
AI summary
A control device for a vehicular lockup clutch, including a lockup clutch that directly connects an input rotation member and an output rotation member of a hydraulic transmission device constituting part of a power transmission path between an engine and drive wheels, a linear solenoid valve that controls an engagement hydraulic pressure for engaging and actuating the lockup clutch, and a controller that is configured to perform a flexible start control for slip-engaging the lockup clutch when a vehicle starts moving, and to perform, before starting the flexible start control, a precharge control for establishing a standby state in which a predetermined preparation pressure is indicated to the linear solenoid valve.