Transmission Hydraulic Backup Pressure for Park Lock Hold
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Solution Overview
Problem
The hydraulic system of a vehicle transmission is vulnerable to operational interruptions of the transmission control unit (TCU), which can inadvertently engage the park lock system, leading to safety and operational issues.
Innovation Solution
A hydraulic system with a back-up system that maintains hydraulic pressure above a predetermined threshold for a predetermined period, using an energy storage unit like a capacitor to power the electric pump controller, ensuring the park lock system remains actuated during TCU resets or interruptions, thus preventing unintended park lock engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the hydraulic actuator is directly connected to the first hydraulic circuit for actuation using line pressure, then the park lock system can be actuated, but an operational interruption of the TCU can cause inadvertent engagement of the park lock system
Solution Approach 1:
A second hydraulic circuit is introduced as an intermediary system between the TCU and the hydraulic actuator. This second circuit includes a backup pump and energy storage unit that can independently maintain hydraulic pressure when the TCU is operational, thereby preventing inadvertent park lock engagement while still allowing controlled actuation when needed.
Solution Approach 2:
The energy storage unit (capacitor) is charged in advance during normal TCU operation to store sufficient electrical energy. This beforehand cushioning ensures that when a TCU interruption occurs, the backup pump can immediately continue operating without interruption, maintaining hydraulic pressure and preventing unintended park lock engagement.
2Reliability
If a back-up system is implemented to maintain hydraulic pressure during TCU interruptions, then the park lock system remains safe during interruptions, but the device complexity increases
Solution Approach 1:
The backup hydraulic circuit is merged with the existing first hydraulic circuit at the hydraulic actuator. Both circuits share common components including the hydraulic actuator itself, hydraulic lines, and control logic, thereby reducing overall system complexity while still providing redundant pressure maintenance capability during TCU interruptions.
Solution Approach 2:
The second hydraulic circuit with backup pump and energy storage unit serves multiple functions: it maintains hydraulic pressure during TCU interruptions, provides a safety backup for the primary TCU-controlled circuit, and can independently actuate the park lock system if needed. This multi-functionality justifies the added complexity by providing comprehensive safety and reliability.
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 ensures the park lock system remains functional and safe during TCU resets or interruptions, maintaining the desired operational state and preventing safety risks by maintaining hydraulic pressure and actuation of the park lock system.
Implementation Method 1
the back-up system includes an energy storage unit configured to store an amount of energy usable for independently powering at least the pump controller for the predetermined period of time
Implementation Method 2
an electric pump, the electric pump being operated by means of a pump controller
Implementation Method 3
a hydraulic circuit arranged for generating a pressure, a hydraulic actuator arranged for engaging a park lock system, wherein the hydraulic actuator is hydraulically connected to the hydraulic circuit for actuation of the hydraulic actuator using the pressure
Data Source
AI summary
The invention relates to a hydraulic system for a vehicle transmission, comprising: a hydraulic circuit arranged for generating a pressure, a hydraulic actuator arranged for engaging a park lock system, wherein the hydraulic actuator is hydraulically connected to the hydraulic circuit for actuation of the hydraulic actuator using the pressure, and a back-up system configured to keep the pressure above a predetermined pressure threshold for maintaining an actuation of the hydraulic actuator for a predetermined period of time in case of an operational interruption of a transmission control unit of the vehicle.