Electric motor-driven wheel brake for vehicles

#The invention pertains to an electric motor-driven wheel brake for vehicles wherein an electronic control unit transmits drive signals for electric motor driven actuators as a function of the driver's command, the actuators being supplied with current by at least two independent voltage sources.

#Electric motor-driven wheel brakes for vehicles are known. WO A 94/24,453, for example, describes a wheel brake in which the brake application force is produced by an electric motor. When the brake system of a vehicle is designed with electric motor-driven brakes, special attention must be paid to the reliability with which a brake system of this type will operate, the key point being the reliability of the voltage supply made available by the batteries.

#The object of the invention is to minimize the load on the batteries for electric motor driven wheels brakes while still maintaining the braking action. This is achieved by supplying actuators of the wheel brakes of each vehicle axle or each vehicle diagonal with current from a separate voltage source, and by actuating the wheel brakes of the front axle before the brakes of the rear axle in at least one braking situation.

#FIG. 1 shows an overall circuit diagram of a preferred design of a brake system, which can be driven by an electric motor;

#FIG. 2 shows a flow diagram, which illustrates a realization of the brake control system in the form of a computer program; and

#FIG. 3 shows time graphs which illustrate how the brake control system works.

#FIG. 1 shows a preferred design of an electric motor-driven brake system for vehicles. In FIG. 1, four wheel brakes are illustrated, which are assigned to the four wheels of the vehicle. Wheel brake 100 is assigned to the right rear wheel, (RR) wheel brake 102 to the left front wheel, wheel (LF) brake 104 to the left rear wheel, (LR) and wheel brake 106 to the right front wheel (RF). The wheel brakes are connected by way of mechanical lines 108, 110, 112, 114 to electric motor-driven actuators (M) 116, 118, 120, 122, one of which is assigned to each of the wheel brakes. The electric motor-driven actuators are driven by an electronic control unit 124 transmitting over output lines 126, 128, 130, 132. For reasons of safety and reliability, the on-board electrical system supplying voltage to the actuators is designed redundantly. The brakes on each pair of diagonally opposite wheels are connected to one of the two batteries; the associated actuators are supplied with power by the battery assigned to the diagonal in question. Thus actuators 116 and 118 at the right rear and left front wheels are connected by way of feed lines 134, 136 to positive pole 138 of a first battery 140. In a corresponding manner, actuators 120, 122 at the left rear and right front wheels are connected by feed lines 142, 144 to positive pole 146 of a second battery 148.

#At least one signal representing the degree to which the brake pedal has been actuated is sent to electronic control unit 124 from a pedal sensor 152 over an input line 150. In addition, input lines 154-156 from measuring devices 158-160 are also connected to electronic control unit 124; these devices measure operating variables of the brake system and/or of the vehicle. Such operating variables include, for example, the wheel loads, variable for the actual value of the braking action produced at each wheel brake (e.g., current, brake moment, braking power, slip, wheel rpm's, etc.), the wheel rpm's, the vehicle velocity, the wear on the brake linings, etc. In addition, electronic control unit 124 is supplied with power by at least one of the batteries 140, 148. The corresponding connecting line is not shown in FIG. 1 for reasons of clarity.

#In addition to the illustrated diagonal division of the brake circuits, it is also possible in other advantageous exemplary embodiments for the brake circuit to be divided in such a way that the wheel brakes of one side of the vehicle or of one axle are combined into one brake circuit. A voltage source would then be assigned to the actuators belonging to each of the two different pairs of wheels.