EBD CONTROL OPERATION


BHE041543750T12

• EBD control detects the slip ratio between the front and rear wheels from the ABS wheel-speed sensor signals. If the slip ratio of the rear wheels as compared to the front wheels is larger than the fixed limit, the DSC HU/CM reduces brake pressure being distributed to the rear wheels. Due to this, brake pressure distribution is constantly controlled in the proper proportion and in relation to vehicle load, road surface conditions and vehicle speed.

• Determination of the rear wheel slip ratio, based on a comparison of the lowest front wheel speed and the estimated vehicle speed with the rear wheel speeds, is divided into conditions 0-4 shown in the table below.

• The DSC HU outlet and inlet solenoid valves are operated and the brake fluid pressure controlled according to these conditions.

• If ABS control conditions are met during EBD control, EBD control is stopped and ABS control is given priority.

Condition

Rear wheel slip ratio determination

EBD control

Solenoid valve

Comment

0
No slip
No control
Pressure increase
-
1
a%-b%
Control
Pressure maintained
-
2
b% or more
Control
Pressure reduction/maintained
-
3
After EBD control, slip ratio is g%
Control
Pressure increase/maintained
-
4
Front wheel slip ratio is d% or more
Control
Pressure reduction/maintained/ increase
ABS control operates

a-d  :
Specified value

Operating Condition Transition Diagram

1
Speed
2
Rear solenoid valve control
3
Pressure reduction
4
Pressure maintained
5
Pressure increase
6
Brake fluid pressure
7
High
8
EBD initial control value
9
ABS initial control value
10
Vehicle speed
11
Wheel speed (rear)
12
Wheel speed (front)
13
Time
14
Front brake fluid pressure
15
Rear brake fluid pressure
16
EBD control area
17
ABS control area