Electric Parking Brake Motor Control via Rotational Load Feedback
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Solution Overview
Problem
Existing electric parking brake devices face issues with inadequate or excessive return of the parking lever during brake release, leading to failures like brake drag and response delays, due to discrepancies between the time electric current reaches no-load and the lever's return position.
Innovation Solution
An electric parking brake device with a motor control unit that manages the electric motor's rotation based on rotational loads, using a converting mechanism for linear movement and a load applying mechanism to ensure precise positioning of the parking lever, eliminating the need for a sensor to detect the lever's state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the electric motor is stopped when electric current reaches no-load current during reverse rotating state, then power consumption is reduced, but the parking lever may return inadequately or excessively due to time discrepancy with the lever's actual position
Solution Approach 1:
The patent applies feedback control by detecting the rotational load of the electric motor during reverse rotation and comparing it against predetermined thresholds. The motor control unit continuously monitors load changes and adjusts motor stopping timing based on this feedback, ensuring the parking lever returns to the correct position while optimizing power consumption.
Solution Approach 2:
The patent implements preliminary action by predicting the optimal stopping point before the motor actually stops. The control unit detects when the rotational load reaches a first threshold value, indicating the parking lever is approaching the returning position. It then continues rotation until a second threshold is reached, ensuring precise positioning before motor shutdown, rather than stopping immediately at no-load current.
2Measurement precision
If a sensor is added to detect the parking lever state, then return position accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses the electric motor's rotational load as an intermediary indicator to infer the parking lever's position. Instead of directly sensing the lever's position with a sensor, the system measures the motor's load characteristics, which change predictably as the lever moves. This indirect measurement approach achieves accurate position detection without adding sensors.
Solution Approach 2:
The electric motor serves dual functions: it both drives the parking lever and provides the sensing mechanism through its own rotational load characteristics. The motor's electrical properties are exploited to detect position information, eliminating the need for separate sensing components and reducing overall system complexity.
3Device complexity
If the motor control is simplified to use only current value, then device complexity is reduced, but manufacturing precision of lever positioning deteriorates
Solution Approach 1:
The patent transitions from static current-threshold control to dynamic load-based control. Instead of using a fixed current value threshold, the system continuously monitors rotational load variations and adapts the stopping decision based on real-time load changes. This dynamic approach maintains simple control logic while achieving precise positioning.
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
Prevents inadequate or excessive return of the parking lever, thereby preventing brake drag and response delays, while maintaining a consistent parking-brake force and eliminating the need for a sensor to control the electric motor.
Implementation Method 1
an electric motor which can be rotationally driven in a normal/reverse direction
Implementation Method 2
a converting mechanism which can convert a rotational movement into a linear movement
Implementation Method 3
a return spring which biases a brake shoe to the returning position
Data Source
AI summary
Provided is an electric parking brake device in which a parking lever is driven by an electric actuator. The electric actuator includes: an electric motor which can be rotationally driven in a normal/reverse direction and of which an operation is controlled by a motor control unit in accordance with rotational loads; a converting mechanism which can convert a rotational movement into a linear movement and which can move the parking lever from a returning position to an operating position in accordance with normal rotation of the electric motor and which can move the parking lever from the operating position to the returning position in accordance with reverse rotation of the electric motor; and a load applying mechanism (a stopper, a friction material) which drives components of the converting mechanism and which applies predetermined rotational loads to the electric motor, in a state where the parking lever is moved from the operating position to the returning position in accordance with reverse rotation of the electric motor.