Electric Parking Brake Axial Locking Mechanism
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Solution Overview
Problem
The existing electric parking brake systems are limited in their application range, as they require driver intervention for operation, result in slow response times, and increase component durability and weight demands, making them unsuitable for assisting in situations beyond normal parking.
Innovation Solution
An electric parking brake system that automatically applies and releases the parking brake based on vehicle stop detection, using a control device to set the braking force close to the service brake force, incorporating a brake load estimation and inclination angle detection to ensure stable braking and minimize energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a parking brake locking mechanism is arranged at the periphery of the rotor, then the parking brake function is achieved, but the radial dimension becomes large and the weight on the electric motor side becomes heavy
Solution Approach 1:
The locking mechanism is relocated from the radial periphery to the axial direction within the housing. The locking pin engages with locking portions on the gears in the axial direction, changing the spatial dimension from radial to axial, thereby reducing radial dimension while achieving the same locking function
Solution Approach 2:
The locking mechanism components (locking pin, locking portions, pin driving actuator) are nested within the existing housing and gear structure. The locking pin moves axially within the housing to engage with locking portions on the gears, utilizing the existing spatial volume efficiently without increasing overall radial dimension
2Reliability
If a parking brake locking mechanism is arranged at the periphery of the rotor, then the parking brake function is achieved, but the weight on the electric motor side becomes heavy thus causing weight balance degradation
Solution Approach 1:
The locking mechanism is relocated from the radial periphery to the axial direction within the housing. The locking pin engages with locking portions on the gears in the axial direction, changing the spatial dimension from radial to axial, thereby reducing radial dimension while achieving the same locking function
Solution Approach 2:
The locking mechanism components (locking pin, locking portions, pin driving actuator) are nested within the existing housing and gear structure. The locking pin moves axially within the housing to engage with locking portions on the gears, utilizing the existing spatial volume efficiently without increasing overall radial dimension
3Reliability
If the electric motor is kept energized to maintain braking force during parking, then the service brake function is achieved, but power consumption increases extremely
Solution Approach 1:
The locking mechanism is activated before the parking brake is fully applied. The locking pin engages with the locking portions on the gears to pre-lock the gear rotation, preventing the electric motor from needing to remain energized to maintain braking force, thereby significantly reducing power consumption during parking
Solution Approach 2:
The locking mechanism provides a self-sustaining parking brake function. Once the locking pin engages with the locking portions, the gear rotation is mechanically prevented without requiring continuous electrical power, allowing the system to maintain braking force autonomously without external energy input
4Force
If a speed-reducing mechanism is incorporated to increase drive force, then the drive force is increased, but the configuration becomes complex and the actuator enlarges
Solution Approach 1:
The gear reduction mechanism serves dual functions: it provides speed reduction to increase drive force for brake application, and simultaneously provides locking portions for the parking brake locking mechanism. This multi-functionality eliminates the need for separate locking components, simplifying the overall configuration while maintaining both braking and parking brake functions
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 allows for expanded application of the parking brake system as a brake assist in various situations, reducing discomfort to the driver and energy consumption by automatically adjusting braking force to match service brake levels, enhancing safety and reducing component stress.
Implementation Method 1
the planetary rollers are revolved while spinning by frictional contact with the rotation shaft
Implementation Method 2
the outer ring member is axially moved due to engagement of a helical rib formed on the radially inner surface of the outer ring member in a helical groove or circumferential grooves formed in the radially outer surface of each planetary roller
Data Source
Figure 1(a)~1(c)
Figure 2
Figure 3
AI summary
An electric parking brake system includes an electric motor (M); a linear motion mechanism (A) that converts the rotational movement of a rotor shaft (12) of the electric motor (M) to a linear movement of a slide member (5) to operate a brake; a locking mechanism (40) that fixes a position of the slide member (5); a control device (50) that controls the electric motor (M) and the locking mechanism (40); a brake load estimation means (60) that estimates a brake force; and an electric parking brake operation instruction device (70) that is arbitrary operable. The control device (50) automatically executes a parking brake operation when a stop state of the vehicle is detected even if the electric parking brake operation instruction device (70) is not operated; where an automatically applied parking brake force (F1) is set to a value smaller than a normal parking brake force (Fmax) at time of normal parking brake operation by the operation of the parking brake operation instruction device (70), and the application range of the parking brake operation is expanded.