Browse Prior Art Database

ABS "FAIL-SAFE" WHEEL CYLINDER CONTROL VALVE

IP.com Disclosure Number: IPCOM000006256D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2001-Dec-19
Document File: 3 page(s) / 112K

Publishing Venue

Motorola

Related People

Mark Libner: AUTHOR

Abstract

Electronically controlIed AntiLock Braking Systems utilize secondary electronic monitoring circuits as "watch- dogs:' When the "watch-dog" circuits detect system fail- ures, they shut-down the ABS system and return the vehicle's braking system to a safe, non-ABS operating mode. However, the complexity of these circuits may degrade the overall reliability ofthe total system.

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m MOTOROLA INC. Technical Developments Volume 14 December 1991

ABS "FAIL-SAFE" WHEEL CYLINDER CONTROL VALVE

by Mark Libner

   Electronically controlIed AntiLock Braking Systems utilize secondary electronic monitoring circuits as "watch- dogs:' When the "watch-dog" circuits detect system fail- ures, they shut-down the ABS system and return the vehicle's braking system to a safe, non-ABS operating mode. However, the complexity of these circuits may degrade the overall reliability ofthe total system.

  If an ABS Electronic Control Module fails to a full output state, the proposed wheel cylinder control valve design incorporates a highly reliable mechanical method to ensure that the vehicle's braking system is returned to the normal, non-ABS operating mode.

  The function of the ABS Fail-Safe Wheel Cylinder Control Valve, hereafter referred to as the control valve, is as follows: (see Figures 1 & 2)

1. During normal braking, without the intervention of the ABS electronic control module, the control valve is in the "Normal Braking" position. No current is supplied to the control valve's piston coil and, the return spring keeps the valve in the fully seated position. In this position, brake fluid flows from the master cylinder directly to the wheel cylinder through ports (M) and (B).

2. During ABS operation, the electronic control mod- ule supplies variable pulse width current to the con- trol valve's piston coil. The electronic control module receives signals from the wheel speed sensors and the control valve position sensor to determine ifthe valve should be in "Nom@' "XBS Hold" or the 'RBS Vent"

mode. In the %BS Hold Mode: the valve is positioned to isolate the fltid input and output ports from each other. This ensures that during braking, the pressure in the wheel cylinder brake lie is held constant when there is stable whee...