Electric Brake Thrust Zero Learning for Stable Brake Control
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Solution Overview
Problem
In electric brakes, fluctuations in the thrust force sensor signal due to piston direction changes lead to incorrect zero point settings, causing unintended braking force generation before the brake pedal is operated, resulting in occupant discomfort.
Innovation Solution
An electric brake system that includes a control device which sets the thrust force zero point based on detection values from the thrust force sensor when the electric motor moves the piston towards the disc in a range where the brake pads are not in contact, eliminating direction-dependent signal fluctuations and ensuring the zero point is learned under a non-thrust force state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the thrust force zero point is set based on sensor signal when piston moves toward thrust force reducing direction, then the zero point learning is simple, but the sensor signal fluctuates depending on piston moving direction causing incorrect zero point setting
Solution Approach 1:
The patent applies local quality by identifying that the sensor signal characteristics differ depending on the piston moving direction. It specifically selects the signal characteristics when the piston moves toward the thrust force increasing direction (brake pad pressing direction) as the reference, rather than using a generic zero-point detection method. This localized approach to signal evaluation eliminates the direction-dependent fluctuations and ensures accurate zero point setting.
2Measurement precision
If the zero point is set when piston moves toward thrust force increasing direction, then the sensor signal fluctuation is eliminated, but braking force may be generated before brake pedal operation causing occupant discomfort
Solution Approach 1:
The patent applies preliminary action by performing zero point learning during a specific preliminary phase: when the brake pads are not in contact with the disc (clearance state) but the piston is moving toward the thrust force increasing direction. This preliminary positioning ensures that the zero point is established under controlled conditions before actual braking operations, preventing premature braking force generation while maintaining signal accuracy.
Solution Approach 2:
The patent utilizes the dynamic state of the piston movement toward the thrust force increasing direction (even without brake contact) as the basis for zero point learning. Rather than using a static position, it leverages the dynamic movement phase where the piston is approaching the disc but maintaining clearance, thereby capturing the sensor signal characteristics under realistic operating conditions while avoiding actual brake engagement.
3Manufacturing precision
If the clearance between disc and brake pads is reduced to zero, then the piston position is precisely determined, but the sensor signal becomes unstable due to contact forces
Solution Approach 1:
The patent maintains the useful action of piston movement toward the disc (which provides precise positioning information) while avoiding the harmful effect of actual contact. By learning the zero point during the continuous movement phase when clearance is maintained but piston position is precisely determined, the system captures accurate sensor signals without the instability introduced by contact forces.
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 approach stabilizes the thrust force control by eliminating signal fluctuations related to piston direction, preventing premature braking force generation and enhancing user comfort by accurately setting the zero point during non-thrust conditions.
Implementation Method 1
a thrust force sensor configured to detect the thrust force applied to the piston
Implementation Method 2
a brake mechanism configured to transmit a thrust force generated through drive of an electric motor to a piston
Data Source
AI summary
An electric brake including: a brake mechanism configured to transmit a thrust force generated through drive of an electric motor to a piston, the piston being configured to move brake pads to be pressed against a disc rotor; a thrust force sensor configured to detect the thrust force transmitted to the piston; and an ECU for rear electric brake configured to control, based on a detection value obtained by the thrust force sensor, the drive of the electric motor in accordance with a brake command. The ECU for rear electric brake is configured to learn, as a reference point of a piston thrust force, a detection value obtained by the thrust force sensor when the electric motor is driven to move the piston in a direction for pressing the piston against the disc rotor in a range in which the brake pads are not in contact with the disc rotor.