Vehicle Brake Fluid Bypass for Regenerative Torque Control
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Solution Overview
Problem
Existing vehicle braking systems face challenges in efficiently managing regenerative braking torque, particularly when energy storage is full or vehicle speed is below the minimum required for regenerative braking, leading to potential lengthening of braking distance and changes in brake feel for the driver.
Innovation Solution
A control device that bypasses the wheel brake caliper by transferring brake fluid from the master brake cylinder to a storage chamber, using a high-pressure switching valve to maintain target braking torque without residual pressure, allowing for seamless modulation of regenerative and hydraulic braking without noticeable changes to the driver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If brake fluid is transferred through the wheel brake caliper during regenerative braking, then the hydraulic brake system can be简单地 expanded with minimal modification, but residual pressure builds up in the wheel brake caliper causing hydraulic residual braking torque
Solution Approach 1:
A bypass channel with a bypass valve is introduced as an intermediary path for brake fluid transfer. The bypass valve directs brake fluid from the master brake cylinder directly to the storage chamber, circumventing the wheel brake caliper during regenerative braking operations. This mediator approach allows the system to achieve fluid transfer without the adverse effect of residual pressure buildup in the caliper, while still maintaining the simple system expansion benefit.
2Reliability
If regenerative braking torque is insufficient (full energy store or low vehicle speed), then the driver experiences changed brake feel and potential lengthening of braking distance, but adding hydraulic braking compensation increases system complexity
Solution Approach 1:
The patent combines regenerative braking and hydraulic braking systems into a unified brake system with shared components. The master brake cylinder, wheel brake calipers, and control unit are共用 by both braking modes. The high-pressure switching valve intelligently directs brake fluid based on the operating mode, merging the benefits of both regenerative and hydraulic braking without requiring entirely separate systems, thus limiting the increase in overall system complexity.
Solution Approach 2:
The system dynamically switches between regenerative braking mode and hydraulic braking mode based on real-time conditions such as energy store status and vehicle speed. The high-pressure switching valve dynamically changes its routing configuration to direct brake fluid either through the wheel brake caliper (hydraulic mode) or directly to the storage chamber (regenerative mode), providing adaptive braking performance that responds to changing operational requirements without permanent increase in complexity.
3Ease of operation
If the brake actuator is mechanically coupled to the master brake cylinder piston, then the driver can feel the counterforce during braking, but during regenerative braking this creates perceptible changes in brake feel
Solution Approach 1:
The mechanical coupling between the brake actuator and master brake cylinder piston is made dynamic rather than static. During regenerative braking, the system allows the piston to move independently to accommodate brake fluid transfer to the storage chamber without transmitting full counterforce to the driver. During hydraulic braking, the mechanical coupling is restored to provide normal brake feel. This dynamic adjustment of mechanical coupling characteristics enables the system to maintain consistent perceived braking performance across different operating modes.
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
Ensures efficient regenerative braking efficiency with minimal additional costs, supports driver modulation, and guarantees safe braking even in fallback modes by preventing power transmission between the brake actuator and master cylinder piston at low actuation forces, maintaining consistent brake feel.
Implementation Method 1
a volume of brake fluid pressed out of the master brake cylinder into the storage chamber
Data Source
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AI summary
The invention relates to a control device (80) for a vehicle brake system, comprising a valve control unit (1) which, taking into account a supplied data signal (2) regarding a generator braking moment currently applied or to be applied by a generator (78), allows at least one high-pressure pilot valve (20a, 20b) of a brake circuit (14a, 14b) of the brake system to be moved in a controlled manner into an at least partly open state in such a way that a volume of brake fluid can be displaced from a master cylinder (10) of the brake system into a storage chamber (18a, 18b) of the brake circuit (14a, 14b) via the at least one high-pressure pilot valve (20a, 20b) that has been moved in a controlled manner into the at least partly open state. The invention further relates to a method for operating a vehicle brake system.