Automatic Transmission Park Lock With Two-Piston Emergency Release

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Solution Overview

Problem

Existing parking lock systems for automatic transmissions lack an effective emergency release mechanism that does not compromise the compact design and reliability, particularly in scenarios where hydraulic or electrical failures occur, leading to potential unintentional disengagement or inability to disengage the parking lock.

Innovation Solution

A parking lock system with a bi-stable detent device and two axially displaceable pistons, where the second piston is mechanically connected to the selector lever, allowing for manual disengagement through an emergency release mechanism that maintains the compact design and ensures the parking lock can be released even in failure scenarios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a hydraulic system with solenoid valve and detent mechanism is used for parking lock control, then the parking lock can be reliably engaged and disengaged under normal operation, but the system becomes vulnerable to unintentional disengagement or failure to disengage when hydraulic or electrical failures occur

Engineering Contradiction:

Improveparking lock control reliabilityVSAvoidunintentional disengagement risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a mechanical emergency release mechanism as an intermediary system that operates independently of the hydraulic and electrical systems. This manual release mechanism provides a backup path for disengaging the parking lock when the primary hydraulic-electrical system fails, thereby eliminating the vulnerability to unintentional disengagement while maintaining normal operational reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements a mechanical emergency release mechanism that is pre-configured and ready to operate independently of the hydraulic system. This beforehand cushioning ensures that if hydraulic or electrical failures occur, there is already a functional backup mechanism in place to prevent unintentional disengagement or failure to disengage the parking lock

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Adaptability or versatility

If a mechanical emergency release mechanism is added to the parking lock system, then manual disengagement is possible in failure scenarios, but the device complexity increases

Engineering Contradiction:

Improveemergency disengagement capabilityVSAvoidparking lock system complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The connecting bar serves multiple functions: it transmits force from the selector lever to the locking pawl during normal operation, and also serves as the actuating mechanism for the emergency release when pulled by the release element. This multi-functionality allows the emergency release capability to be added without proportionally increasing device complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the emergency release mechanism with existing components of the parking lock system. The release element connects to the connecting bar, which is already part of the force transmission path. By combining the emergency release function with the existing connecting bar and selector lever assembly, the overall device complexity is minimized while still providing the required adaptability

Inventive Principle:

Principle #5Merging (Combining)

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

Enables reliable manual disengagement of the parking lock without compromising the compact design, ensuring the parking lock remains secure and can be released in case of system failures, thus preventing unintentional disengagement and maintaining vehicle safety.

Implementation Method 1

The interlocking element is spring-mounted on the connecting bar via a spring element

Methodology Applied

Scientific EffectSpring force: Spring

Implementation Method 2

the cylinder chamber of the parking lock cylinder is pressurized and pushes the parking lock piston

Methodology Applied

Scientific EffectHydraulic pressure: Hydraulic Press

Data Source

PatentUS11215282B2Park lock for an automatic transmission in a motor vehicle

Publication Date: 2022.01.04 ZF FRIEDRICHSHAFEN AG

AI summary

A parking lock includes a locking pawl (2) and an interlocking element (6) arranged on a connecting bar (5) to a selector lever (4). During engagement of the parking lock, the selector lever (4) is rotated by a spring (9). A hydraulically actuatable actuator (10) including two pistons (11, 12). A first piston (11) is pressurized in order to disengage the parking lock and axially displace the second piston (12) against a spring (9). Axial movement of the second piston (12) rotates the selector lever (4) and vice versa. A detent device (13) of the actuator (10), is actuatable by an electromagnet (13a). An emergency release device (15) is operatively connectable with the selector lever (4) so that the second piston (12) is axially displaceable by the selector lever (4) without displacing the first piston (11).