Shift Drum Parking Lock Blocking Mechanism
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Solution Overview
Problem
In 2-ratio transmissions, there is a risk of inadvertent selection of the parking lock function, which can lead to the transmission locking up during travel, posing safety concerns due to incorrect operation of the actuator.
Innovation Solution
A mechanically acting apparatus is provided in the shift drum that blocks the selection of the parking lock position in one direction of rotation and releases the blockage in the opposite direction, preventing inadvertent selection by requiring a specific movement sequence to engage the parking lock function, utilizing a combination of movable base parts, flexible stops, and spring mechanisms to ensure safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the parking lock function is enabled without directional control, then the parking lock can be engaged, but the transmission may lock up during travel due to inadvertent selection
Solution Approach 1:
The patent applies asymmetry by implementing different operational requirements for engaging versus disengaging the parking lock. The shift drum can only be rotated in a first direction (e.g., clockwise) to engage the parking lock position, while rotation in a second direction (e.g., counter-clockwise) is blocked by the mechanically acting apparatus. This asymmetric control mechanism prevents inadvertent engagement while allowing intentional disengagement, thereby improving reliability without significantly compromising ease of operation.
Solution Approach 2:
The mechanically acting apparatus provides preliminary anti-action by blocking the shift drum rotation in the first direction before the parking lock position can be inadvertently selected. The blockage occurs in advance of any potential harmful engagement, preventing the transmission from locking up during travel. This preemptive blocking mechanism ensures that only deliberate actions in the permitted direction can engage the parking lock.
2Reliability
If a mechanically acting apparatus is added to block inadvertent selection, then safety is improved, but the device complexity increases
Solution Approach 1:
The patent merges the mechanically acting apparatus with the existing shift drum structure. The blocking mechanism is integrated into the shift drum assembly rather than being a completely separate system. The apparatus includes components such as a blockage element and a release mechanism that work in conjunction with the shift drum's existing slots and actuators, thereby reducing overall system complexity compared to a fully independent blocking system.
Solution Approach 2:
The mechanically acting apparatus serves as an intermediary between the shift drum rotation and the parking lock engagement. It mediates the rotational movement by allowing it only in the permitted direction while blocking it in the hazardous direction. This intermediary mechanism adds a layer of safety without requiring complete redesign of the shift drum or parking lock system, thus limiting the increase in device complexity.
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 solution effectively prevents the transmission from locking up during travel by ensuring that the parking lock position can only be selected intentionally, thereby enhancing safety and preventing unintended locking, allowing for smooth shifting between transmission ratios.
Implementation Method 1
spring mechanisms to ensure safe operation
Data Source
AI summary
A device and method for preventing inadvertent selection of a parking lock function in a 2-ratio transmission. Here, the shift positions of the transmission and the parking lock function thereof can be selected by way of a shift drum. A mechanically acting apparatus is provided which, in the event of rotation of the shift drum in a first direction of rotation, blocks the selection of a parking lock position of the shift drum, subsequently, in the event of rotation of the shift drum in a second direction of rotation opposite to the first direction of rotation, releases the blocking, and subsequently, in the first direction of rotation opposite to the second direction of rotation, permits selection of the parking lock position. The device does not require a separate parking lock wheel.