Parking Lock Actuator Damping for Interlock Wear Reduction

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Solution Overview

Problem

Existing parking lock actuators in automatic transmissions suffer from wear due to pressure fluctuations and peaks, which can lead to mechanical damage and reduced reliability, especially when the parking lock is disengaged or engaged.

Innovation Solution

The implementation of a choke unit with an orifice and non-return valve in the pressure line, combined with a pressure limiting valve and hydraulic damper, to regulate and dampen pressure fluctuations, thereby reducing wear on the mechanical interlock and enhancing the reliability and service life of the actuator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If system pressure is applied to the actuator piston to disengage the parking lock, then the parking lock can be reliably disengaged, but pressure fluctuations and peaks cause wear to the mechanical interlock

Engineering Contradiction:

Improveparking lock disengagement reliabilityVSAvoidwear on mechanical interlock

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A hydraulic damper is integrated into the actuator to cushion pressure fluctuations and peaks before they reach the mechanical interlock. The damper absorbs excessive pressure energy through hydraulic damping, preventing harmful pressure spikes from damaging the mechanical interlock components while maintaining sufficient pressure for reliable parking lock disengagement.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The hydraulic damper acts as an intermediary element between the pressure supply system and the mechanical interlock. It mediates the pressure transmission by filtering out harmful fluctuations while allowing controlled pressure application, thus protecting the mechanical interlock without compromising the actuator's functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If the actuator piston is mechanically interlocked in the disengaged position, then unintentional movement is prevented, but pressure peaks during reconnection cause wear at the mechanical piston interlock

Engineering Contradiction:

Improveactuator piston position stabilityVSAvoidwear at mechanical piston interlock

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The hydraulic damper provides beforehand cushioning by absorbing pressure peaks that occur during reconnection of the pressure supply. This cushioning effect protects the mechanically interlocked piston from wear-causing pressure spikes while maintaining the stability of the interlocked position.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The hydraulic damper converts harmful pressure fluctuations and peaks into beneficial damping effects. By transforming the harmful pressure energy into controlled hydraulic resistance, the damper protects the mechanical interlock while the pressure supply is reconnected, turning a potentially damaging situation into a protective mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 solution effectively reduces wear on the actuator's mechanical interlock by damping pressure fluctuations and peaks, ensuring the parking lock operates reliably and prolongs the actuator's service life.

Implementation Method 1

pressure fluctuations—in particular, brief pressure drops and brief pressure peaks—in the system pressure can result in wear at the mechanical piston interlock

Methodology Applied

Scientific EffectHydraulic damping: Damping

Data Source

PatentUS11746901B2Device for operating a parking lock of a motor vehicle transmission

Publication Date: 2023.09.05 ZF FRIEDRICHSHAFEN AG

AI summary

A device for operating a parking lock (34) of a transmission (3) includes an engagement spring (345) for engaging the parking lock (34), a hydraulic actuator (340) for disengaging the parking lock (34), an electrohydraulic control unit (35) for hydraulically actuating the actuator (340), and an electronic control unit (36) for electrically actuating the actuator (340) and the electrohydraulic control unit (35). The actuator (340) includes a hydraulic piston (341) operatively connected to the parking lock (34), is actuatable by system pressure (P_sys) of the electrohydraulic control unit (35) via a pressure line (347) upon disengagement of the parking lock (34), and is mechanically interlockable by an interlocking device (342). A choke unit (353) includes an orifice (353) and a non-return valve (354) and is installed in the pressure line (347) downstream from the hydraulic piston (341).