Clutch-operated hill holder brake system

A brake control device for preventing backward movement of a vehicle on an uphill road during operation of a clutch pedal of the vehicle after release of a brake pedal of the vehicle which is connected to a master cylinder and wheel cylinders of the vehicle, said brake control device comprising:

• a cylinder body provided with first and second lateral oil passages, a first brake line connecting port in flow communication with said first oil passage for connection to the master cylinder, and a second brake line connecting port in flow communication with said second oil passage for connection to the wheel cylinders;
• said cylinder body having a longitudinal opening in flow communication with each of said first and second oil passages;
• a hollow plunger reciprocably received within said longitudinal opening of said cylinder body, said hollow plunger being provided with an annular groove around a periphery thereof;
• spring means extending into said hollow plunger to force said hollow plunger into a first position with said annular groove in alignment with each of said first and second oil passages to provide flow communication therebetween so that oil can flow from the master cylinder through said first brake line connecting port, said first oil passage, said annular groove, said second oil passage, said second brake line connecting port, respectively, to the wheel cylinders when the brake pedal is actuated;
• first means to move said hollow plunger against the force of said spring means into a second position with said annular groove out of alignment with each of said first and second oil passages to prevent flow communication therebetween so that the oil is prevented from returning from the wheel cylinders when the clutch pedal is actuated upon release of the brake pedal;
• said first means including an electromagnetic core provided with an electromagnetic coil wound therearound, said electromagnetic core being mounted on said cylinder body for acting on said hollow plunger;
• micro switch means electrically connected to said electromagnetic coil and positioned under the clutch pedal for energizing said electromagnetic coil when the clutch pedal is actuated;
• and
• second means provided in said cylinder body to provide a second oil path from the master cylinder to the wheel cylinders to supply additional oil to the wheel cylinders when said hollow plunger is in said second position and the brake pedal is reactuated for an increased braking force.