Electromechanical Brake Power Assist Unit with Variable Pedal Lever
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Solution Overview
Problem
Conventional vacuum brake power assist units are inefficient in modern vehicles due to the lack of vacuum energy, requiring additional pumps and space, while electromechanical units face challenges in replicating the pedal feel and dynamics of vacuum systems, especially with high-inertia electric motors that can lead to suboptimal brake assistance.
Innovation Solution
An electromechanical brake power assist unit where the piston rod is supported on a pedal lever, with the axis of rotation of the pedal lever being displaced by an electric motor to adjust the pedal path and reduce driver effort, maintaining similar force requirements without direct motor assistance, ensuring a conventional pedal path and safe braking dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a vacuum brake power assist unit is used, then brake assistance is provided, but additional vacuum pumps and space are required due to lack of vacuum energy in modern vehicles
Solution Approach 1:
The patent replaces the vacuum-based mechanical power assist system with an electromechanical system. The electric motor (7) directly substitutes the vacuum pump and vacuum chamber mechanism, providing brake assistance through electrical power while eliminating the need for vacuum generation equipment and associated space requirements.
Solution Approach 2:
The invention extracts and eliminates the vacuum pump and vacuum chamber components from the brake assist system. By removing these unnecessary elements and replacing them with a compact electromechanical actuator, the system achieves brake assistance without the space and complexity penalties of vacuum-based systems.
2Power
If a high-ratio electric motor is used for brake assistance, then brake power is increased, but dynamics are limited due to high inertia
Solution Approach 1:
The patent implements a dynamically adjustable transmission ratio through the variable ratio transmission mechanism (17). This allows the system to optimize the balance between motor torque and response speed in real-time, enabling a high-ratio electric motor to deliver both high brake power and fast response dynamics by adapting the gear ratio according to braking conditions.
Solution Approach 2:
The system pre-adjusts the transmission ratio based on anticipated braking requirements. By preparing the transmission mechanism in advance to be in an optimal state for the expected braking scenario, the system ensures both sufficient power and rapid response when braking is actually applied, overcoming the inertia limitation of high-ratio motors.
3Power
If direct electric motor assistance is applied to the piston rod, then brake power assist is provided, but pedal feel and dynamics comparable to vacuum systems are difficult to achieve
Solution Approach 1:
The patent introduces a pedal lever (3) with variable ratio transmission mechanism (17) as an intermediary between the electric motor (7) and the master brake cylinder piston rod (2). This intermediary mechanism transforms the motor's direct force application into a more nuanced force profile that replicates the characteristic pedal feel of vacuum systems, including the progressive resistance and feedback drivers expect.
Solution Approach 2:
The system dynamically changes the transmission ratio parameter throughout the pedal stroke. By varying the mechanical advantage at different points in the pedal travel, the system reproduces the characteristic pedal feel curve that drivers are accustomed to from vacuum systems, while still delivering electric power assistance. This includes creating the appropriate pedal hardness progression and feedback characteristics.
4Ease of operation
If the axis of rotation of the pedal lever is displaced by the electric motor, then the pedal path is adjusted to reduce driver effort, but the system complexity increases
Solution Approach 1:
The electric motor (7) serves multiple functions: it provides direct brake power assistance, adjusts the pedal lever axis position to optimize pedal path and reduce driver effort, and controls the variable ratio transmission mechanism. By consolidating these functions into a single actuator, the system reduces overall complexity despite the added capability of dynamic pedal path adjustment.
Solution Approach 2:
The patent merges the functions of brake power application and pedal path optimization into a single integrated system. The electric motor simultaneously controls both the brake force generation and the pedal lever positioning, eliminating the need for separate mechanisms and reducing overall system complexity while achieving multiple objectives.
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 reduces the effort required to build brake pressure by adjusting the pedal path, maintaining comparable pedal feel to vacuum systems and ensuring safe braking, even in the event of system failures, by using an electric motor to control the pedal path rather than direct force application, thus overcoming the inefficiencies of conventional vacuum and electromechanical units.
Implementation Method 1
an electromechanical brake power assist unit having a master brake cylinder with a piston rod, which can be displaced by way of a brake pedal and, in the process, builds up or reduces brake pressure. The piston rod can also be displaced by way of an electric motor
Implementation Method 2
the piston rod is supported on a pedal lever, which may be formed either by the brake pedal itself or by an intermediate element that can be pivoted about an axis of rotation by way of the brake pedal
Data Source
AI summary
An electromechanical brake power assist unit of a vehicle braking system has a master brake cylinder with a piston rod, displaceable by a brake pedal and, in the process, building up brake pressure. The piston rod is also displaceable by an electric motor. The piston rod is supported on a pedal lever, which is formed by the brake pedal itself or an intermediate element pivotable about an axis of rotation by the brake pedal. The piston rod is displaced by a pivotal movement of the pedal lever. An axis of rotation of the pedal lever is displaceable by the electric motor in a moving direction of the piston rod. The pedal ratio is selected such that the driver can slightly displace the piston rod by forces customary in the case of a conventional effective brake power assistance also without an activation of the electric motor, and the pedal path which is large, because of such a pedal ratio without an activation of the electric motor, will then be reduced to a normal extent by the electric-motor-driven displacement of the pedal lever axis rotation.