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Knorr-Bremse Group
PD-203-400
Doc. No. Y250904 (EN - Rev. 000)
July 2016
The information contained herein is subject to alteration without notice and therefore may not be the latest release. Please check our website www.knorr-bremseCVS.com for the latest update or contact your local Knorr-Bremse representative.
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KB4TA System Overview
C o m m e r c i a l V e h i c l e S y s t e m s
Operation
KB4TA provides basic service braking in addition to the ABS function.
ABS Operation
The KB4TA moduleis used to prevent the wheels of a trailer locking whilst braking. The friction between the tyre and
the road is created by relative movement between their two surfaces, i.e. difference in surface speeds of road and
tyre and is referred to as ‚slip‘. It is well known that a wheel operating on a wet surface has reduced friction (adhesion)
and hence can transmit reduced braking effort to the road.
The KB4TA module constantly monitors the rotational speed of all sensed wheels on the trailer by using the wheel
speed sensor outputs. It then calculates an average of these wheel speeds (Reference Speed) and constantly
compares it with the speed of each wheel.
During braking, if one or more wheels is on a slippery surface and is unable to support the level of braking that it
is being asked to contribute, the wheel speed will drop relative to the Reference Speed, i.e. there will be ‘slip’, and
deceleration of that wheel will increase. The KB4TA module will normally detect this during the application of the
brake and, before the wheel becomes locked, send an electrical signal to the appropriate modulator to reduce the
pressure in the service brake actuator(s) on that wheel or group of wheels. Once the wheel starts to accelerate
and the slip is reduced, the KB4TA module will send an electrical signal to the modulator to gradually increase the
pressure until either the wheel again starts decelerating or the requested level of braking is reached. It is therefore
possible to maximise the utilisation of the available adhesion to improve stopping distance whilst maintaining stability.
Normal Braking
During normal braking, the KB4TA module system operates as two standard relay valves in parallel. If the ECU
does not detect excessive wheel slip, ABS control will remain inactive while the vehicle is braked according to driver
demand.
Odometer Function
Odometer
The KB4TA module has an odometer function to provide a means of storing the accumulated mileage of the trailer.
The mileage is computed by utilizing information calculated from the wheel speed sensors. This feature will accurately
store mileage information up to 1,000,000 km. The accuracy of readings higher than this cannot be guaranteed. The
mileage can be displayed using PC diagnostics ECU
talk
®
or through blink codes.
Trip Counter
The KB4TA module provides a counter to record the trip mileage. The feature is accessed through PC diagnostics
ECU
talk
®
.
Service Interval
The KB4TA module provides a feature that can be used to indicate a service interval for the trailer. The service interval
can be accessed via PC diagnostics ECU
talk
®
. If configured, the KB4TA module can flash the warning lamp when
the vehicle is at standstill and the ABS is first powered to indicate when the service interval has been exceeded.
Configuration of the KB4TA Module.
Y026787: 006: EN: Released: Fri Nov 11 11:18:50 CET 2016:
