Browse Publications Technical Papers 2024-01-3032
2024-09-08

Piston and Guide-Pin Rattle Noise Mitigation in Electro-Mechanical Brake Caliper 2024-01-3032

The hydraulic brake caliper utilizes pressurized brake fluid to actuate one or multiple pistons generating friction between the brake pads and disc. Calipers are classified into floating and fixed type caliper. Floating caliper slides inboard/outboard direction to apply and release pressure on the outer pad. This type of caliper has rubber or spring components to maintain specific clearance for sliding characteristics. Therefore, caliper rattle noise could occur due to wheel vibrations when the vehicle is driven on unpaved roads or rough surfaces. Rattle noise is particularly pronounced in front calipers positioned closer to the driver and its susceptibility tends to increase with the weight of the caliper. The Electro-Mechanical Brake (EMB) caliper has gained substantial attention in automotive industry for its advantages features including reduced brake drag, optimized vehicle layout and precise brake control. Operating without the brake fluid, the EMB caliper applies pressure by amplifying rotational torque and converting it into forward force at the ball-screw. However, increased caliper weight and suboptimal weight distribution render the EMB caliper more vulnerable to rattle noise compared to conventional hydraulic caliper. This study conducts a comprehensive examination of rattle noise characteristics in a prototype EMB caliper. The primary sources of rattle noise are identified at interfaces on the piston and guide-pin sides. Employing piston seal and guide-pin boot emerges as an effective way in significantly improving rattle noise characteristics. The examination reveals that collisions between the piston and ball-screw head can be mitigated by inner piston seal resulting in a significant reduction in rattle noise. The effectiveness of outer piston seal is limited due to sufficient tightening force in the piston boot. Guide-pin side is also recognized as another significant source of rattle noise. Employing and enhancing tightening force in the guide-pin boot demonstrates an improvement in rattle noise characteristics particularly under new pad conditions. Analysis of accelerometer data indicates diminished acceleration variations between the caliper cylinder and pad bracket suggesting reduced collision potential between guide-pin and its hole. The finding for this study pave the way for developing diverse forms of EMB calipers as noise-reducing products.

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