Two types of combined ABS combining CBS and ABS
Honda is now using two types of ABS for motorcycles, ABS using circulating type modulator widely used in automobiles and ABS used exclusively by motorcycles with modulators driven directly by motors. There are cases of using those two types of ABS as they are for the conventional brake system and of using them in combination with CBS as combined ABS, aiming at installation of ABS on many models. For the combined ABS for large scooters, circulating type modulators partially improved for motorcycles were adopted for “Combi brake”. For large tourers, combined ABS capable of giving higher braking force was completed, combining modulators directly driven by motors with dual CBS.
Combined ABS for large scooters
Combined ABS combining “Combi brake” and circulating type modulators. In this system prepared in one body with the electric control unit (ECU), a motor-driven pump generates hydraulic pressure and pressure is controlled by the solenoid valve. The system is characterized by a simple construction, which enables a unit to control brakes on the front and rear wheels.
Combined ABS for large sports and tourers
Combined ABS for large sports and tourers are the brake systems combining dual CBS with ABS modulators driven directly by motor, which were developed exclusively for the purpose. The ABS modulators will control hydraulic pressure by directly lifting up and down the position of the piston with a motor. A modulator controls the brake hydraulic pressure of one wheel. The modulators are installed one each on the front and rear wheel.
Comparison of characteristics of two types of ABS
The above figure compares the control of two types of ABS. The red line at the bottom denotes the changes in brake hydraulic pressure while the black line on top represents motorcycle body speed, and the blue line indicates wheel speed.
With the increase in hydraulic pressure, wheels start decelerating by the braking force. However, when wheel speed drops down excessively against motorcycle body speed, that is, wheels are nearing lock conditions, the modulators will lower hydraulic pressure receiving a signal from the ECU. As the wheel speed gets close to motorcycle body speed, the hydraulic pressure will be raised once again. This is repeated time and again in one second.
Hydraulic pressure fluctuation is smaller in the ABS directly driven by a motor, so that wheel speed is much smoother and finely controlled. As the result, the pitching of the motorcycle body is reduced.