Transmission Range Shifting Using Parking Lock Pre-Engagement

Solution Overview

Problem

Existing methods for shifting the downstream range group of a motor vehicle's transmission while stationary are unreliable due to drag losses in the powershiftable main transmission group, which can prevent the downstream range group from being shifted into the desired range.

Innovation Solution

Engaging the parking lock of the main transmission group to immobilize its output shaft, allowing the downstream range group to be safely shifted into neutral, and then reliably into the desired range, while preventing excessive rotation speed of the main transmission group's output shaft.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the main transmission group is powershiftable with frictional shifting elements, then shifting operations can be performed during vehicle operation, but drag losses cause the output shaft to accelerate to rotation speeds that prevent the downstream range group from being shifted

Engineering Contradiction:

Improveshifting capabilityVSAvoidshifting reliability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent applies preliminary action by engaging the parking lock before shifting the downstream range group. This pre-engagement immobilizes the main transmission group's output shaft, preventing drag losses from accelerating it to problematic rotation speeds. The parking lock is activated in advance to create the necessary stationary condition for reliable downstream range group shifting, directly resolving the contradiction between shifting capability and shifting reliability.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the driver switches off the drive aggregate to shift the downstream range group, then the downstream range group can be shifted without excessive rotation speed, but there is no longer sufficient hydraulic pressure to shift it if it is hydraulically shifted

Engineering Contradiction:

Improveshifting reliabilityVSAvoidhydraulic pressure availability

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies preliminary action by engaging the parking lock before shifting the downstream range group. This pre-engagement immobilizes the main transmission group's output shaft, preventing drag losses from accelerating it to problematic rotation speeds. The parking lock is activated in advance to create the necessary stationary condition for reliable downstream range group shifting, directly resolving the contradiction between shifting capability and shifting reliability.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If the downstream range group is shifted while the motor vehicle is stationary, then range changes can be made without moving the vehicle, but the output shaft of the main transmission group can accelerate due to drag losses preventing the shift

Engineering Contradiction:

Improverange switching flexibilityVSAvoidoutput shaft rotation speed

Core Design Contradiction:

Adaptability or versatilityVSSpeed

Solution Approach 1:

The patent applies preliminary action by engaging the parking lock before shifting the downstream range group. This pre-engagement immobilizes the main transmission group's output shaft, preventing drag losses from accelerating it to problematic rotation speeds. The parking lock is activated in advance to create the necessary stationary condition for reliable downstream range group shifting, directly resolving the contradiction between shifting capability and shifting reliability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses the parking lock as an intermediary device between the drive aggregate and the downstream range group. The parking lock acts as a mediator that immobilizes the main transmission group's output shaft, creating a stable intermediate state that allows the downstream range group to be shifted without being affected by rotation speed issues. This intermediary mechanism enables range switching flexibility while preventing excessive output shaft acceleration.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12209659B2Method and control apparatus for operating a motor vehicle

Publication Date: 2025.01.28 ZF FRIEDRICHSHAFEN AG

AI summary

A motor vehicle transmission is connected between a drive aggregate and a drive output, and includes a powershiftable main transmission group with a plurality of forward gears and at least one reversing gear. A hydrodynamic starting element is connected between the drive aggregate and the transmission. The main transmission has frictional shifting elements of which, in each gear, a first number are closed and a second number are open. The main transmission has a parking lock that, when engaged, immobilizes an output shaft of the main transmission group.A downstream range group includes at least one interlocking shifting element and can be shifted between a first range and a second range. When the motor vehicle is stationary with the drive aggregate running, to shift the downstream range group the parking lock is first engaged, and then the downstream range group is shifted into neutral from a range to be disengaged.