Backup Power Source Device for Shift-by-Wire Systems
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Solution Overview
Problem
Existing back-up power source devices for shift-by-wire systems in vehicles require high capacity to supply power from the time of battery failure to user-initiated switching to the parking range, leading to increased size and complexity.
Innovation Solution
A back-up power source device with a failure detection unit, monitor unit, and control unit that only starts power supply to the shift control unit when a user instruction to switch to the parking range is detected, allowing for efficient use of the back-up power source and reducing its capacity and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the back-up power source supplies power from the time of battery failure to when the parking range is switched, then the shift control unit can operate continuously, but the capacity and size of the back-up power source must be high
Solution Approach 1:
The system performs preliminary detection of battery failure and monitors user input before activating the back-up power source. The failure detection unit detects battery failure in advance, and the monitor unit waits for user input signal before starting power supply, ensuring the back-up power is activated only when needed rather than continuously from the moment of failure.
Solution Approach 2:
Instead of supplying power continuously from battery failure moment, the system provides partial action by monitoring user input and only activating power supply when the user actually intends to switch to parking range. This avoids excessive power supply during the period when the user is still deciding or when switching is not required.
2Duration of action of moving object
If the back-up power source capacity is increased to cover the period from battery failure to parking range switching, then sufficient power is available, but the back-up power source becomes larger and more complex
Solution Approach 1:
The system implements preliminary detection of battery failure and monitoring of user input signals before activating the back-up power source. This ensures power is supplied only for the necessary duration from user input to parking range switching, rather than from the moment of battery failure, thereby reducing the required power supply duration and associated system complexity.
Solution Approach 2:
The monitor unit provides feedback by detecting user input signals (such as door opening or parking brake application) to determine when the user intends to switch to parking range. This feedback mechanism allows the back-up power source to be activated precisely when needed, optimizing both duration and complexity.
3Reliability
If a dedicated switch instructing unit is added for battery failure scenarios, then user input can be reliably detected, but the device complexity increases
Solution Approach 1:
The system utilizes existing multi-functional switches already present in the vehicle (door switches, parking brake switches, etc.) for the dual purpose of their original functions and for detecting user intent during battery failure. This eliminates the need for dedicated switch instructing units while maintaining reliable detection of user input.
Solution Approach 2:
The monitor unit leverages existing vehicle switches that naturally indicate user intent (such as door opening or parking brake application) to serve the additional function of triggering back-up power supply. The system uses the vehicle's own existing components to detect user input, avoiding additional dedicated hardware.
Data Source
AI summary
A back-up control unit of a back-up power source device executes: a battery failure determination process of determining whether or not a battery failure has been detected by a failure detecting unit; when it is determined that battery failure has been detected in the battery failure determination process, a switching instruction determination process for determining, on the basis of an instruction signal from a monitor circuit, whether or not an instruction to switch to a P range has been made by a user; and when it is determined that a switching instruction has been made in the switching instruction determination process, a shifting instruction process for starting power supply from a back-up power source to a shift control unit and instructing the shift control unit to shift to the P range.