Vehicle braking system

A method of controlling a braking system of a vehicle, in which the braking system comprises a master cylinder including at least one pumping piston operatively connected to a brake pedal,

• a brake pedal actuating the pumping piston to supply pressurized fluid into a delivery line of the master cylinder, so as to cause activation of a hydraulically-operated brake device associated with a respective wheel of the vehicle,
• a pressure transfer device transferring hydraulic pressure from the delivery line of the master cylinder to an hydraulic actuating line of the brake device, said pressure transfer device comprising:
• a cylinder, with a movable member within the cylinder between a first upstream chamber, communicating with the delivery line of the master cylinder, and a downstream chamber, communicating with the hydraulic actuating line of the brake device, so that the pressure generated by said master cylinder in said delivery line, following an intervention on the brake pedal, causes a movement of the movable member of the pressure transfer device, which generates a resulting pressure in the hydraulic actuating line of the brake device,
• said pressure transfer device also comprising a second upstream chamber, operatively arranged in parallel with said first upstream chamber,
• an electrically-operated fluid pressure source, communicating with said second upstream chamber of said pressure transfer device,
• the electrically-operated fluid pressure source arranged in such a way that, regardless of the pressure in the delivery line of the master cylinder, the movable member of the pressure transfer device operable by said electrically-operated fluid pressure source to generate a pressure in the hydraulic actuating line of the brake device,
• a solenoid valve for enabling/disabling the master cylinder arranged in the delivery line of the master cylinder, between an outlet of the master cylinder and said first upstream chamber of the pressure transfer device, said solenoid valve for enabling/disabling the master cylinder having a first operating condition, wherein the outlet of the master cylinder is in communication with said first upstream chamber of the pressure transfer device, and a second operating condition, in which the first upstream chamber of the pressure transfer device is placed in communication with a discharge and supply reservoir, and in which the outlet of the master cylinder is placed in communication with the discharge reservoir through a restricted passage,
• an electronic controller controlling said solenoid valve for enabling/disabling the master cylinder and said electrically-operated fluid pressure source in such a way as to be able to selectively activate one or more of the following operating modes:
• a basic braking operating mode, in which said solenoid valve for enabling/disabling the master cylinder is in its first operating condition enabling the master cylinder, and the electrically-operated fluid pressure source is inactive, so that the brake device is operated by the brake pedal by means of the master cylinder,
• an assisted-braking operating mode, in which said solenoid valve for enabling/disabling the master cylinder is in its first operating condition enabling the master cylinder, and the electrically-operated fluid pressure source is active, so that the brake device is operated by the brake pedal by means of the master cylinder, but the fluid pressure supplied to the brake device is the result of both the pressure generated by the master cylinder and the pressure generated by the electrically-operated fluid pressure source,
• an automatic braking operating mode, in which said solenoid valve for enabling/disabling the master cylinder is in its second operating condition disabling the master cylinder, and the electrically-operated fluid pressure source is active, so that the brake device is only operated by the pressure generated by said electrically-operated fluid pressure source, and
• an operating mode for activating an ABS effect, in which, following detection by the electronic controller of a condition of incipient locking of a vehicle wheel during braking controlled by the brake pedal through the master cylinder or automatically, said solenoid valve for enabling/disabling the master cylinder is switched from its first enabling operating condition to its second operating condition disabling the master cylinder and said electrically-operated fluid pressure source is activated to generate reduced pressure in the supply line of the brake device, in order to avoid locking of the wheel during braking.