Electric Parking Brake Gear Layout for Self-Locking Ball-Screw Actuation
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Solution Overview
Problem
Conventional electric parking brakes (EPBs) face challenges in providing high-efficiency parking braking force for large trucks due to low torque conversion efficiency and require multiple motors and power transmission structures, which increase weight and cost, and are difficult to install in narrow spaces.
Innovation Solution
An electric parking brake system utilizing a single motor with a ball-screw type power conversion unit and a combination of cross helical and worm gear assembly structures in the gear units to achieve high-efficiency parking braking force and self-locking functionality, maintaining the parking state when power is off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a ball-screw type power conversion unit is used to increase torque conversion efficiency, then the efficiency of converting motor torque into parking force is improved, but the self-locking function is lost and parking force cannot be maintained
Solution Approach 1:
The patent merges the ball-screw type power conversion unit (for high efficiency) with a separate self-locking mechanism comprising a worm gear and worm wheel. The motor drives the ball-screw mechanism through a coupling device that also engages the worm gear, combining both functions in one integrated system. This allows the ball-screw to provide efficient torque conversion while the worm gear-worm wheel assembly provides the necessary self-locking capability to maintain parking force.
2Force
If two motors and two power transmission structures are used to meet high output requirements, then the braking force is sufficient, but weight and cost increase and installation space requirements are not met
Solution Approach 1:
The patent combines the functions of two motors and two power transmission structures into a single motor with an integrated dual-function transmission system. The ball-screw mechanism and worm gear assembly work together within one motor unit, providing the equivalent braking force of a dual-motor system while significantly reducing overall weight and simplifying the power transmission structure.
Solution Approach 2:
The single motor is designed with a multi-functional transmission system that performs both high-efficiency torque conversion (via ball-screw) and self-locking (via worm gear). This universal design allows one motor to replace two motors while maintaining the required braking force output, reducing system complexity and weight.
3Force
If two motors and two power transmission structures are used to meet high output requirements, then the braking force is sufficient, but device complexity and cost increase
Solution Approach 1:
The patent integrates multiple power transmission functions into a single unified structure. The ball-screw mechanism and worm gear assembly are combined within one motor housing, sharing common components such as the motor shaft and coupling device. This merging reduces the number of separate power transmission structures from two to one, simplifying the overall device complexity while maintaining sufficient braking force.
4Force
If two motors and two power transmission structures are used to meet high output requirements, then the braking force is sufficient, but the system volume increases and installation becomes difficult
Solution Approach 1:
The patent consolidates two separate motor assemblies into a single integrated motor unit with combined ball-screw and worm gear mechanisms. This merging significantly reduces the overall system volume, making it suitable for installation in the narrow spaces available in large trucks, while still providing the high braking force required.
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
The system provides high-efficiency parking braking force with a single motor, reduces noise, maintains the parking state without power, and minimizes system volume and weight, while ensuring efficient power transmission and self-locking functionality.
Implementation Method 1
a ball-screw type power conversion unit installed in a caliper housing to convert a rotational force into a linear motion
Implementation Method 2
a cross helical gear assembly may be used. The cross helical gear assembly is commonly used in the EPBs because it is easy to switch a rotational direction and has a good contact ratio of gears, which may reduce noise considerably
Implementation Method 3
the first and second gear units are configured to perform a self-locking function when a parking braking force is generated
Data Source
AI summary
Disclosed herein an electric parking brake including a ball-screw type power conversion unit installed in a caliper housing to convert a rotational force into a linear motion. The electric parking brake includes a motor configured to generate a rotational force, a first gear unit including a first connection portion, the first connection portion directly connected to a main helical gear provided on a motor shaft of the motor, a second gear unit including a second connection portion, the second connection portion spaced apart from the first connection portion by a predetermined distance and directly connected to the main helical gear, and a reduction gear unit connected to any one of the first gear unit and the second gear unit and configured to transmit the rotational force generated from the motor to a spindle of the power conversion unit, wherein any one of the first and second gear units is configured to perform a self-locking function when a parking braking force is generated.