Brakes – Wheel – Transversely movable
Patent
1998-10-09
2000-11-07
Mar, Michael
Brakes
Wheel
Transversely movable
188 7956, 188 78, 188326, F16D 5100
Patent
active
061422711
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a servo friction brake of the type as disclosed in European patent application No. 0 195 922. The special feature of the prior art friction brake is that a valve for sensing wheel lock is interposed between the two friction linings. As soon as the wheel associated with the respective brake locks, the valve will generate hydraulic pressure which is used to actuate a second valve that permits change-over of effective surfaces provided within the wheel brake cylinder. The result is a reduction of the actuating force applied to the linings so that an anti-lock effect is ensured this way.
It is a shortcoming in the prior art friction brake that hydraulic intervention in the wheel brake cylinder becomes effective only in a case of wheel lock. The intervention includes a simple change-over action so that the brake of the art exhibits a high degree of friction coefficient sensitivity despite the intervention.
Therefore, an object of the present invention is to provide measures permitting a major reduction of the friction coefficient sensitivity. An additional objective is to achieve a great servo effect, especially in the range close to the wheel lock limit.
SUMMARY OF THE INVENTION
According to the present invention, this object is achieved by the provision of means which permit variations in the servo effect during operation of the brake and, preferably, are configured as an adjusting mechanism which permits changes of the angle between the connecting line of the central point of force application between the friction lining and the friction surface with a central force support point of the friction lining, on the one hand, and the direction of the normal force which acts upon the friction lining, on the other hand.
Further, a method of controlling the servo effect of a servo friction brake is disclosed in the present invention, wherein the components of the actuating force, which act vertically on the friction lining, and the boosting force which is due to the servo effect are added to the normal force, and the friction force acting between the friction lining and the friction surface is generated by the effect of the normal force. According to the present invention, a signal representative of the friction force is produced and sent, along with a signal representative of the desired servo effect and a signal representative of the actuating force, as input quantities to a controller. The output quantity of the controller serves to actuate an actor with a view to influencing the boosting force.
Further details, features and advantages of the present invention can be taken from the following description of an embodiment making reference to the accompanying drawings wherein corresponding individual parts have been assigned like reference numerals.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings,
FIG. 1 is a friction or duplex brake according to the present invention.
FIG. 2 is an enlarged view of a cross-section taken along line `C--C` of FIG. 1.
FIG. 3 is a schematic view of the function principle of the duplex brake shown in FIGS. 1 and 2.
FIG. 4 is a view of a simplified control circuit for implementing the method of controlling the servo effect of the duplex brake shown in FIGS. 1 to 3 according to the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
The drum or duplex brake shown in the FIG. 1 embodiment includes a brake carrier 1 on which two brake shoes 2, 3 equipped with brake linings are radially opposed. Brake shoes 2, 3 are operable by way of pivoted clamping cams 4, 5 by an actuating device 6, i.e., are movable into engagement with a brake drum (not shown) . The clamping cams 4, 5 act on an end of the brake shoe 2, 3 by way of each one force-transmitting element 7, 8 screwed to the brake shoe 2, 3. The other end of brake shoe 2, 3 is supported on the brake carrier 1 by way of a central force support point A (see FIG. 3). The force-transmitting element 7, 8 is preferably provided with force-measuring elements, for example, wi
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Bill Karlheinz
Dusil Vladimir
Leber Matthias
ITT Manufacturing Enterprises Inc.
Mar Michael
Sy Mariono
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