EBD CONTROL OPERATION

id041300185700

•  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 ABS 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 ABS 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.

Status

Rear wheel slip ratio determination

EBD control

Solenoid valve

Comment
0
No slip
No control
Pressure increase
—
1
α%—β%
Control
Pressure maintained
—
2
β% or more
Control
Reduction/maintained
—
3
After EBD control, slip ratio is γ%
Control
Increase/maintain
—
4
Front wheel slip ratio is δ% or more
Control
Pressure reduction/maintained/ increase
ABS control operates

α—δ  :Specified value

Operating Condition Transition Diagram

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