Planetary Brake Transmission with Switchable Reduction Ratios
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Solution Overview
Problem
Electromechanical service brakes in motor vehicles face challenges with a large release clearance that leads to delayed braking response and unequal wear, requiring a transmission with nonlinear ratios to reduce torque and improve response time, while minimizing the need for additional components and space.
Innovation Solution
A transmission assembly with a planetary gear system featuring two reduction ratios, where the first ratio quickly traverses the release clearance with low torque and the second ratio provides sufficient braking force, utilizing a clutch and axial bearing to switch between these ratios based on axial force, allowing for rapid brake application without additional rotation-translation converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large release clearance is provided between the friction lining and the brake disk, then the brake unit can cover possible operating conditions and reduce residual braking torque, but the brake application distance increases and the response time is delayed
Solution Approach 1:
The transmission ratio is made variable through a nonlinear rotation-translation converter that dynamically adjusts the ratio based on the brake piston position. During the release clearance traversal phase, a higher transmission ratio is applied to reduce the required input torque and enable faster traversal. Once the friction lining contacts the brake disk, the transmission ratio transitions to a lower value to provide sufficient braking force. This dynamic adjustment resolves the contradiction by adapting the transmission characteristics to the current operational phase.
Solution Approach 2:
The transmission ratio parameter is changed from a constant value to a variable value that depends on the brake piston position. The nonlinear rotation-translation converter implements this parameter change by converting rotational motion into translational motion with a nonlinear relationship, effectively providing different transmission ratios at different stages of brake application. This parameter change allows the system to optimize both the release clearance traversal and the braking force generation.
2Loss of time
If a nonlinear transmission ratio is used to increase the transmission ratio in the region of the release clearance, then the response time is reduced and the required input power is lowered, but the possible travel is limited and the initial position must be known
Solution Approach 1:
The nonlinear rotation-translation converter is designed to automatically adjust the transmission ratio based on the brake piston position without requiring external control signals or knowledge of the initial position. The mechanical design of the converter inherently provides the nonlinear transmission characteristic, and the system self-regulates the transmission ratio as the brake piston moves through its range of motion. This self-service approach eliminates the need for additional sensors, actuators, or control systems that would otherwise be required to implement a variable transmission ratio.
3Adaptability or versatility
If a second rotation-translation converter is added to provide adjustment for wear, then the working range can be maintained over service life, but the installation space and cost increase
Solution Approach 1:
The nonlinear rotation-translation converter is designed to perform multiple functions: it provides the nonlinear transmission ratio for rapid release clearance traversal, it automatically adapts to wear between the friction lining and brake disk, and it maintains the appropriate working range throughout the service life. By integrating these multiple functions into a single mechanical component, the system achieves wear compensation capability without requiring additional rotation-translation converters or adjustment mechanisms, thereby minimizing installation space and cost.
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 enables quick traversal of the release clearance and rapid brake application with reduced torque requirements, ensuring a timely and reliable braking response while maintaining a compact design and minimizing additional components, thus enhancing the performance and efficiency of electromechanical wheel brakes.
Implementation Method 1
The planet wheels (20) are supported by means of the planet carrier (30) in such a way that they can roll both on the sun wheel (11) and on the annulus (40)
Implementation Method 2
A clutch (50) is provided between the drive shaft (12) and the planet carrier (30)
Implementation Method 3
an axial bearing (60), via which the axial force can be applied to the annulus (40)
Data Source
AI summary
A transmission assembly has more than one reduction ratio. For this purpose, the transmission assembly can comprise a planetary transmission in which the annulus can rotate freely in a first position and in which the annulus is held fixed against rotation in a second position. A method of operating a transmission assembly is also disclosed.