Fluid-pressure and analogous brake systems – Multiple fluid-receiving devices – Multiple motors
Patent
1991-03-05
1992-08-25
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Multiple fluid-receiving devices
Multiple motors
303 969, 303113AP, 303DIG4, B60T 1368, B60T 836, B60T 858
Patent
active
051412926
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a system and a method for brake adaptation between a haulage vehicle and an attached semitrailer.
Prior Art
In relatively heavy vehicle combinations an adaptation must be made between the braking systems of a haulage vehicle and an attached semitrailer. In this connection the principal aim is to let each wheel axle be responsible for the braking of the load which rests on the respective axle in order to obtain an uniform a load as possible on the brakes of the respective wheels. Should one brake absorb too great a share of the total braking work, this results in the brakes being overloaded and being worn abnormally quickly. If, on the other hand, the brakes are underloaded, this results in an unnecessarily long braking distance.
The laws and regulations which determine the braking characteristics of vehicles permit a certain difference to exist between different vehicle parts. In cases where the haulage truck and semitrailer have different braking characteristics this can result, when there is relatively low brake pressure, in only the brakes of the haulage vehicle being applied and thereby having to brake the entire vehicle unit. This disadvantage can be further aggravated for example in older semitrailers, where the brakes can often seize on account of corrosion and poor maintenance. Very few braking operations normally take place with fully applied brakes. Instead, the majority of braking operations take place with low or moderate brake pressure, with the result that the problem discussed above manifests itself. As a result of this the brake linings of the haulage truck are loaded to an unnecessary extent, and they are consequently worn out quickly and therefore have to be frequently changed.
Another point of interest is that, in the case of a semitrailer, part of its load is absorbed by the wheels of the haulage truck and another part by the wheels of the semitrailer. As already mentioned, the principal aim is that each wheel should be responsible for the braking work which is required for the mass resting on the respective wheel. This means that, depending on how the semitrailer is loaded, the haulage truck must absorb different degrees of braking work.
There is at present no satisfactory solution to the problem described. There are certain types of control valves for the brakes of the semitrailer, which valves allow the pressure imparted to the brakes of the semitrailer to be manually adjusted, within certain limits, relative to the pressure imparted to the brakes of the haulage truck. However, such an adjustment requires comprehensive measuring equipment, and even when adjustment is carried out for a particular semitrailer it is not certain that the same adjustment is suitable for another semitrailer. This adjustment can also only be made for a specific load and, in the event of reloading or another freight, the conditions for the adjustment are altered. All these disadvantages of manual adjustment have meant that a single adjustment is made once only which is suitable for the most general driving conditions, and no further adjustment is then made.
In the case of a trailer, which unlike a semitrailer completely supports its own load, it is known to arrange force sensors which, during braking sequences, detect the force acting on it drawbar. If, during a braking sequence, a tensile force is detected acting on the drawbar, this is an indication that the brakes of the trailer are responsible for too large a proportion of the braking work. Correspondingly, a compressive force on the drawbar indicates that the brakes of the trailer are responsible for tool small a proportion of the braking work. Depending on these indications a control valve for the brakes of the trailer is actuated so as to increase or decrease the brake pressure imparted to the brakes of the trailer. This technique cannot however be directly transferred to a semitrailer, since in this case a certain proportion of the load of the semitrailer is to be braked by the brakes of the haulage vehicle.
OBJECT OF TH
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Fredriksson Rolf
Gardell Lars
Magnusson Goran
Muratori Alfred
Oberleitner Robert J.
Saab-Scania Aktiebolag
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