Lock-up clutch engine speed control for smooth engagement

Solution Overview

Problem

The existing fluid-filled power transmitting devices with lock-up clutches experience rough shifts or unacceptable acceleration during the engagement of the lock-up clutch, leading to loss of machine control and degraded driving comfort due to sudden torque transmission from the engine to the transmission.

Innovation Solution

An engine control system that includes a torque converter, engine, transmission, and a lock-up clutch, where an engine control module measures prior engine and transmission speeds and adjusts the engine speed incrementally to a desired speed lower than the prior engine speed, with the incremental change ranging from 1% to 50% of the speed difference, to minimize acceleration and ensure smooth engagement of the lock-up clutch, thereby improving torque converter efficiency and reducing sudden acceleration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the lock-up clutch is engaged to improve power transmitting efficiency, then torque converter efficiency increases to 100%, but sudden acceleration occurs causing loss of machine control and degraded driving comfort

Engineering Contradiction:

Improvetorque converter efficiencyVSAvoidmachine control

Core Design Contradiction:

Loss of energyVSEase of operation

Solution Approach 1:

The engine control module reduces engine speed before lock-up clutch engagement by a predetermined amount (50-200 RPM). This preliminary speed reduction prevents sudden acceleration when the clutch engages, maintaining machine control while still achieving the efficiency benefits of lock-up engagement.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system applies a counteracting action by reducing engine speed prior to clutch engagement. This preliminary anti-action counterbalances the sudden torque transmission that would otherwise cause abrupt acceleration, thereby preventing the harmful effect while preserving the beneficial efficiency improvement.

Inventive Principle:

Principle #9Preliminary anti-action

2Loss of energy

If the lock-up clutch is engaged to improve power transmitting efficiency, then torque converter efficiency increases to 100%, but driving comfort is degraded due to sudden acceleration

Engineering Contradiction:

Improvetorque converter efficiencyVSAvoiddriving comfort

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The engine control module reduces engine speed before lock-up clutch engagement by a predetermined amount (50-200 RPM). This preliminary speed reduction prevents sudden acceleration when the clutch engages, maintaining machine control while still achieving the efficiency benefits of lock-up engagement.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system applies a counteracting action by reducing engine speed prior to clutch engagement. This preliminary anti-action counterbalances the sudden torque transmission that would otherwise cause abrupt acceleration, thereby preventing the harmful effect while preserving the beneficial efficiency improvement.

Inventive Principle:

Principle #9Preliminary anti-action

3Ease of operation

If engine speed is reduced incrementally by 1% to 50% of the speed difference to ensure smooth engagement, then machine control is maintained, but the engagement process takes longer time

Engineering Contradiction:

Improvemachine controlVSAvoidengagement time

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The engine control module applies a partial speed reduction (50-200 RPM) rather than fully equalizing engine and transmission speeds. This partial action is sufficient to prevent sudden acceleration and maintain control, while avoiding the time penalty of a complete speed matching process.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS9216741B2Lock up clutch controls—high idle set point

Publication Date: 2015.12.22 CATERPILLAR INC

AI summary

An engine control system is provided where the engine control system includes a torque converter, an engine connected to the torque converter, a transmission connected to the torque converter, a lock-up clutch housed in the torque converter wherein the lock-up clutch is configured to mechanically connect the engine and the transmission when the lock-up clutch is engaged, an engine speed sensor configured to obtain a prior engine speed which is measured prior to engagement of the lock-up clutch, a transmission speed sensor configured to obtain a prior transmission speed which is measured prior to the engagement of the lock-up clutch, and an engine control module configured to determine a desired engine speed at a speed lower than the prior engine speed and adjust a speed of the engine to the desired engine speed just prior to the movement of the lock-up clutch for the engagement or as the lock-up clutch moves toward the engagement.