Braking Force Regulator
One always speaks of dynamic axle load distribution. It means that during braking the front axle is more loaded and the rear axle is relieved, progressively ascending with stronger braking. More load on the front axle
leads to an over-braking of the rear axle. The result of over-braking or even blocking: Lateral guidance is lost. This is to be prevented.
There are valves that regulate depending on the brake pressure or the axle load. Are the brake circuits separated between front and rear axle, the valve has two connections, in the case of diagonal separation four of
them. If you enlarge the images above, you can partially see inputs or outputs marked by arrows. The x-axis of the following graph shows p1, the pressure of the front axle, the y-axis p2, the
pressure of the rear axle.
The line 3 indicates the unregulated pressure as if no valve would be present. The two branching lines 7 and 8 show pressure gradients in pressure relief (8) and pressure control (7) with increasing pressure from the
master cylinder.
In the case of load-sensitive regulation and increasing rear axle load the line 7 shifts up to the line 5 within the range of adjustment 9. It is important that the branching point and the whole line
remain under the curve 4 (loaded). Curve 6 applies for the unladen vehicle. A pressure-controlled gradient definitely must remain underneath.
First, let the influence of the rear suspension away and just take care of the piston above. It is stepped to form two different sized surfaces and thus create the required pressure difference. The smaller area below
needs a relatively high pressure to displace the piston, less presser is needed for the full piston surface above. The connection from the master cylinder to the rear wheel brake cylinders is only open when the piston
abuts against the top and the pin opens the spring-loaded valve.
If the pressure above increases too much, the piston is moved downwards and the connection is broken. If the upper spring is more compressed by lowering of the car body, this branching point is shifted towards
more pressure. 03/16
| Test over-braking rear axle with empty luggage compartment. |
| This regulation is also possible in vehicles with ABS. |
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