Brake Pressure Control via Hydraulic Pump Activation
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Solution Overview
Problem
Existing electronically controllable brake systems in motor vehicles experience a 'hard pedal' feeling due to stepped pressure increases from valve switching or pump operations, leading to discomfort and reduced actuating speed, especially under low engine vacuum conditions.
Innovation Solution
A method that detects the approach of the operating point of the vacuum brake booster and activates the additional pressure source when the pressure gradient exceeds a predetermined limit, allowing for smooth pressure buildup and maintaining a comfortable pedal feel by adjusting the operating point and activating the hydraulic pump accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If valve switching operations or pump operations are used for active pressure increase, then brake pressure can be increased, but stepped pressure increase occurs causing a hard pedal feeling and reduced actuating speed
Solution Approach 1:
The patent implements continuous pressure increase by controlling the hydraulic pump to operate continuously or in closely spaced intervals rather than through discrete switching operations. The control unit monitors the operating point of the vacuum brake booster and activates the hydraulic pump to maintain continuous pressure buildup, eliminating the stepped pressure increases that cause hard pedal feeling.
2Power
If valve switching operations or pump operations are used for active pressure increase, then brake pressure can be increased, but noticeable delay occurs reducing actuating speed
Solution Approach 1:
The control unit detects the approach of the operating point of the vacuum brake booster in advance and activates the hydraulic pump before the vacuum booster reaches its maximum capacity. This preliminary activation ensures that pressure buildup begins early, eliminating noticeable delays and maintaining high actuating speed.
3Force
If the vacuum brake booster reaches maximum boosting force, then additional brake force is needed, but the system becomes less responsive to driver input
Solution Approach 1:
The control unit continuously monitors the operating point of the vacuum brake booster and uses this feedback information to determine when to activate the hydraulic pump. By detecting the approach of the operating point, the system responds proactively to maintain optimal performance and responsiveness throughout the braking process.
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
Enables quick and sufficient brake pressure increase without noticeable delay, maintaining a comfortable pedal feel and reducing the 'hard pedal' sensation, thus improving braking performance and driver experience.
Implementation Method 1
The hydraulic pressure, which results in the hydraulic master brake cylinder from the brake force that is introduced by the driver by way of depression of the brake pedal and boosted by means of a vacuum brake booster, is increased in addition by the hydraulic pump.
Implementation Method 2
Vacuum brake boosters require vacuum supply from the motor in order to assist the pedal force that has to be generated by the driver.
Implementation Method 3
The pressure difference over the membrane in the vacuum brake booster is lower than would be the case e.g. with a quasi-stationary gradient.
Data Source
AI summary
In a method for controlling the pressure buildup in an electronically controllable brake system, preferably for use in motor vehicles, including a master brake cylinder, in particular a tandem master brake cylinder (TMC), a vacuum brake booster (booster), at least one additional pressure source for brake force assistance, preferably a hydraulic pump which is drivable by a controlling unit and the pressure of which can be applied to wheel brakes of the vehicle, an approach of a point where the auxiliary-force to actuating-force ratio (operating point) of the vacuum brake booster (booster) falls below a predetermined ratio is detected, that a pressure gradient in the master brake cylinder (TMC pressure gradient) is detected, and that in the event of a detected approach of the operating point of the booster and when a pressure gradient limit value of the detected TMC pressure gradient is exceeded, the additional pressure source is activated for brake force assistance, for the purpose of building up additional brake pressure.