MPXM2102AS datasheet(559/670 Pages) MOTOROLA

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Motorola Sensor Device Data

www.motorola.com/semiconductors

AN4007

New Small Amplified Automotive

Vacuum Sensors

A Single Chip Sensor Solution

for Brake Booster Monitoring

Prepared by: Marc Osajda

Automotive Sensors Marketing

Sensor Products Division

Motorola Semiconductors S.A.

Toulouse France

BRAKING SYSTEMS

Different types of braking principles can be found in vehicles

depending on whether the brake system is only activated by

muscular energy or power assisted (partially or completely).

Muscular activated brakes are mostly found on motorcycles

and very light vehicles. The driver’s effort on the hand lever

or pedal is directly transmitted via a hydraulic link to the brake

pads.

Power assisted brakes are found on most passenger cars

and some light vehicle trucks. In this case, the driver’s effort

is amplified by a

brake booster to increase the force applied

to the brake pedal.

BRAKE BOOSTER OPERATION PRINCIPLE

The vacuum brake booster is a system using the differential

between atmospheric pressure and a lower pressure source

(vacuum) to assist the braking operation. The brake booster

is located between the brake pedal and the master cylinder.

Figure 1 shows a simplified schematic of a vacuum brake

booster.

When no brake pressure is applied on the push rod (brake

pedal side), the air intake valve is closed and the vacuum

valve open. Thus, both the vacuum and working chambers

are at the same pressure, typically around –70 kPa (70 kPa

below atmospheric pressure). Vacuum is generated by either

the engine intake manifold or by an auxiliary vacuum pump.

Figure 1. Brake Booster Simplified Schematic

CONNECTION TO VACUUM PUMP

OR ENGINE INTAKE MANIFOLD

PUSH ROD FROM

AIR INTAKE VALVE

WORKING CHAMBER

VACUUM CHAMBER

VACUUM VALVE

THE BRAKE PEDAL

PISTION

RUBBER MEMBRANE

PUSH ROD TO

MASTER CYLINDER

MOTOROLA

SEMICONDUCTOR APPLICATION NOTE

REV 1

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

MPXM2102AS Datasheet(PDF) 559 Page - Motorola, Inc

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