Hydro-Mechanical Park Shift Actuation for Smooth Transmission Braking

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Solution Overview

Problem

Existing park systems in transmissions face challenges in efficiently and reliably braking the output shaft, particularly in achieving smooth transitions between engaged and disengaged states.

Innovation Solution

A hydro-mechanically actuated park system that includes an input shaft, an output shaft, a park assembly, an electro-hydraulic valve assembly, and an actuation linkage with a piston that translates axially in response to fluid pressures, driving the operation of the park assembly through the actuation linkage in both engaged and disengaged states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional mechanical park system is used, then the structure is simple, but the transition between engaged and disengaged states is not smooth and reliability is reduced

Engineering Contradiction:

Improvereliability of park systemVSAvoidcomplexity of actuation mechanism

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies hydraulic actuation using a piston and fluid pressure to replace traditional mechanical cable-based park systems. The electro-hydraulic valve assembly delivers fluid pressure to the piston, enabling smooth and reliable transition between engaged and disengaged states while eliminating cable friction and mechanical wear issues.

Inventive Principle:

Principle #29Pneumatics and hydraulics

Solution Approach 2:

The patent replaces the traditional mechanical cable-based actuation system with a hydro-mechanical system. The electro-hydraulic valve assembly and piston mechanism substitute for mechanical cables and linkages, providing more controlled and reliable park system operation with reduced mechanical wear.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If a hydro-mechanically actuated park system is implemented, then smooth transitions between states are achieved, but the device complexity increases

Engineering Contradiction:

Improvesmoothness of state transitionVSAvoidcomplexity of park assembly

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The hydraulic actuation system using piston and fluid pressure provides smooth and controlled transition between park states. The fluid-based actuation eliminates the jerky motion associated with mechanical cable systems, achieving ease of operation despite the added hydraulic components.

Inventive Principle:

Principle #29Pneumatics and hydraulics

Solution Approach 2:

The piston acts as an intermediary between the electro-hydraulic valve assembly and the park assembly. This intermediary component translates fluid pressure into mechanical motion, enabling smooth state transitions while isolating the complexity of the hydraulic system from the park mechanism.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If an electro-hydraulic valve assembly is used, then precise control of park engagement is achieved, but manufacturing complexity increases

Engineering Contradiction:

Improveprecision of park engagement controlVSAvoidease of manufacturing park system

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The electro-hydraulic valve assembly replaces mechanical control mechanisms with electro-hydraulic control, enabling precise control of park engagement. While this increases manufacturing complexity, it eliminates the need for complex mechanical linkages and cable tensioning mechanisms.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The use of fluid pressure through the electro-hydraulic valve assembly provides precise and controllable actuation. The hydraulic system enables accurate positioning and engagement control that would be difficult to achieve with purely mechanical systems.

Inventive Principle:

Principle #29Pneumatics and hydraulics

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 system effectively resists rotation of the output shaft in the engaged state and permits rotation in the disengaged state, enhancing the operational efficiency and reliability of the transmission's park mode.

Implementation Method 1

an electro-hydraulic valve assembly to deliver one or more fluid pressures, and an actuation linkage having a piston that is axially translatable along a longitudinal axis in response to the one or more fluid pressures

Methodology Applied

Scientific EffectHydraulic pressure: Pressure Increase

Implementation Method 2

The actuation linkage may include a biasing element surrounding the rotational axis that applies a biasing force to the plate to urge interaction between the plate and the piston

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS20250189036A1Hydro-mechanical park-by-wire shift systems, transmissions incorporating the same, and methods for transmissions

Publication Date: 2025.06.12 ALLISON TRANSMISSION INC

AI summary

Transmissions, park systems for transmissions, and methods for transmissions are envisioned. A transmission includes an input shaft to receive torque from a drive unit, an output shaft to transmit torque to a load, and a park system to selectively brake the output shaft. The park system includes a park assembly, an electro-hydraulic valve assembly to deliver one or more fluid pressures, and an actuation linkage having a piston axially translatable along a longitudinal axis in response to the one or more fluid pressures delivered thereto from the electro-hydraulic valve assembly.