Electric Brake Thrust Zeroing for Premature Brake Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In electric brakes, fluctuations in thrust force sensor signals due to piston direction changes cause incorrect zero point settings, leading to unintended braking force generation before the brake pedal is operated, resulting in discomfort for vehicle occupants.
Innovation Solution
An electric brake system that includes a control device which sets the thrust force zero point based on detection values obtained 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 accurate thrust force control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thrust force zero point is set when the piston moves toward the thrust force increasing direction, then the sensor signal fluctuation depending on moving direction is eliminated, but braking force is generated before the brake pedal is operated causing occupant discomfort
Solution Approach 1:
The control device performs preliminary action by moving the piston toward the thrust force increasing direction before setting the zero point. This preliminary movement eliminates internal machine sliding resistances and ensures the sensor signal reflects the true zero thrust state, preventing premature braking while maintaining measurement accuracy
Solution Approach 2:
Instead of setting the zero point when the piston moves toward the thrust force decreasing direction (conventional approach), the invention inverts the approach by setting it when the piston moves toward the thrust force increasing direction. This inversion resolves the signal fluctuation issue caused by sliding resistances during retraction
2Object-affected harmful factors
If the thrust force zero point is set when the piston moves toward the thrust force decreasing direction, then the braking force is not generated prematurely, but the sensor signal value fluctuates depending on the moving direction of the piston
Solution Approach 1:
The invention extracts and eliminates the harmful factor of sliding resistances by performing a preliminary piston movement toward the thrust force increasing direction before zero point setting. This separation of the preliminary movement from the zero point setting process removes the source of signal fluctuation
Solution Approach 2:
The invention changes the operational parameter (piston movement direction) before setting the zero point. By moving the piston toward the thrust force increasing direction, the internal machine sliding resistances are eliminated, changing the sensor signal characteristics to a stable state that accurately represents zero thrust
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided is 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.