David E. Keyser Applications Coordinator
Keith Hogan OEM Sales
MICO, Inc. 1911 Lee Boulevard North Mankato, MN U.S.A. 56003-2507 Fax: +1 507 625 3212 Tel: +1 507 625 6426
ABSTRACT This paper will identify some prerequisites for brake actuation circuit design, describe three basic types of brake actuation circuitry, and will point out some common problems to be avoided in brake actuation circuit design for off-highway vehicles and equipment. It will deal only with the actuation of service brakes (as opposed to parking brake). Service brake selection, pneumatic, and vacuum powered brake systems are beyond the scope of this paper. PREREQUISITES Although we are assuming fully functional and operational brakes, this paper outlines six key prerequisites that need to be known in order to design the brake actuation circuit. These are: (1) stopping parameters, (2) required brake torque, (3) capacity of the service brakes, (4) brake line pressure, (5) volumetric requirements, and (6) required operator input effort. Because there are many brake actuation circuits possible for a given application, this information must be understood in order for the designer to choose the optimal circuit. In selecting the components for a brake actuation circuit the designer needs to start at the foundation (service) brakes and "work backward" to the method of actuation. By working backward the designer avoids the pitfall described below under the heading "Service Brake Capacity". Stopping Parameters The stopping parameters include deceleration rate, stopping distance, percentage of grade for operation, and vehicle speed. The desired stopping parameters, are used to determine the required brake torque. They can be sourced from one of several publications, such as the Society of Automotive Engineers (SAE), the International Standards Organization (ISO), Federal, State, Provincial Government agencies or...