Torque Converter Clutch Third Hydraulic Chamber Back Pressure

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Solution Overview

Problem

Torque converter clutches face inefficiencies due to back pressure, which counteracts the fuel economy benefits gained by engaging the clutch, as the transmission pump must work harder to overcome this pressure, negating some of the efficiency gains.

Innovation Solution

The design incorporates a torque converter with a third hydraulic chamber that is sealed from the first and second chambers, allowing for restricted hydraulic flow, and includes a piston plate with an orifice to limit clutch cooling flow, thereby reducing back pressure on the lockup clutch piston plate by de-pressurizing the third chamber.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If the transmission pump increases hydraulic pressure to overcome back pressure on the torque converter clutch, then the clutch apply pressure is sufficient to engage the clutch, but the transmission pump consumes more energy, negating fuel economy benefits

Engineering Contradiction:

Improveclutch apply pressureVSAvoidtransmission pump energy consumption

Core Design Contradiction:

ForceVSUse of energy by moving object

Solution Approach 1:

The hydraulic system is segmented into two separate circuits: a first hydraulic circuit that maintains pressure for clutch engagement, and a second hydraulic circuit that is de-pressurized to reduce back pressure. This segmentation allows the transmission pump to maintain sufficient clutch apply pressure while reducing the energy required to overcome back pressure, as the second circuit does not require high pressure maintenance.

Inventive Principle:

Principle #1Segmentation

2Reliability

If the transmission pump works harder to increase clutch apply pressure, then the torque converter clutch engages properly, but the fuel economy benefit is reduced due to increased energy consumption

Engineering Contradiction:

Improveclutch engagement reliabilityVSAvoidfuel economy

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

By dividing the hydraulic system into two independent circuits with different pressure requirements, the system ensures reliable clutch engagement through the first circuit while minimizing energy loss through the de-pressurized second circuit. This allows the clutch to engage properly without requiring the transmission pump to work harder against high back pressure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the pressure parameter in the second hydraulic circuit by de-pressurizing it, thereby reducing the back pressure that opposes clutch engagement. This parameter change allows the transmission pump to maintain sufficient clutch apply pressure with lower energy consumption, preserving fuel economy benefits.

Inventive Principle:

Principle #35Parameter changes

3Stress or pressure

If the hydraulic chamber is sealed to restrict flow, then back pressure on the piston plate is reduced, but the complexity of the hydraulic chamber configuration increases

Engineering Contradiction:

Improveback pressure on piston plateVSAvoidhydraulic chamber configuration

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

The hydraulic chamber is segmented and sealed to create distinct first and second hydraulic circuits. This segmentation allows the second circuit to be de-pressurized, reducing back pressure on the piston plate. While this does increase configuration complexity, it provides a straightforward method to control pressure distribution and reduce opposing forces on the clutch mechanism.

Inventive Principle:

Principle #1Segmentation

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 configuration reduces the back pressure on the lockup clutch piston plate, allowing for more efficient engagement and operation of the torque converter clutch, thereby enhancing fuel economy by minimizing the energy required to overcome opposing pressures.

Implementation Method 1

the piston plate has an orifice and a clutch cooling flow from the second chamber to the third chamber is limited by the orifice

Methodology Applied

Scientific EffectFluid flow restriction through orifice: Pressure Drop

Implementation Method 2

the third chamber is for being de-pressurized to reduce a back pressure on the lockup clutch piston plate

Methodology Applied

Scientific EffectDe-pressurization: Depressurisation

Data Source

PatentUS9494221B2Torque converter clutch with low back pressure

Publication Date: 2016.11.15 SCHAEFFLER TECHNOLOGIES AG & CO KG

AI summary

A torque converter includes an impeller shell and a backing plate defining at least a portion of a first hydraulic chamber, a cover and a piston plate defining at least a portion of a second hydraulic chamber, and a third hydraulic chamber. The third chamber is sealed from the first and second hydraulic chambers such that a hydraulic flow between the third chamber and the other chambers is at least restricted. In some example embodiments, the torque converter includes a turbine, a stator, and an impeller disposed within the first hydraulic chamber, and a lockup clutch including a piston plate. The first chamber is for being pressurized to prevent cavitation in the turbine, stator, or impeller, the second or third chamber is for being pressurized to engage the lockup clutch, and the other of the second or third chamber is for being de-pressurized to reduce a back pressure on the lockup clutch piston plate.