Drum brake device

A drum brake device, comprising:

• a brake drum;
• a pair of brake shoes comprising a primary brake shoe and a secondary brake shoe oppositely disposed within the brake drum, each brake shoe of the pair of brake shoes having a first end and a second end;
• a wheel cylinder for expanding the brake shoes, the wheel cylinder being disposed between the first ends of the brake shoes;
• a master cylinder outputting a hydraulic braking pressure;
• a fluid passage for introducing the hydraulic braking pressure output from the master cylinder to the wheel cylinder, the hydraulic braking pressure being dependent on a brake operation force;
• input detecting means, coupled to the fluid passage, for detecting the hydraulic braking pressure output from the master cylinder and producing a first output signal representative of the detected hydraulic braking pressure, the hydraulic braking pressure being an input force to the brake shoes;
• output detecting means for detecting an anchor reaction force generated by the secondary brake shoe during braking and producing a second output signal representative of the detected anchor reaction force, the detected anchor reaction force being an output force of the secondary brake shoe;
• electromagnetic valves, coupled to the fluid passage, that control the supply of the hydraulic braking pressure output from the master cylinder to the wheel cylinder;
• and
• a control circuit that controls the operations of the electromagnetic valves in accordance with the first and second output signals so that the output force is limited to a force equal to or smaller than a force defined by a predetermined boosting ratio of the output force to the input force.

A drum brake device, comprising:

• a brake drum;
• a pair of brake shoes comprising a primary brake shoe and a secondary brake shoe oppositely disposed within the brake drum, each of the pair of brake shoes having a first end and a second end, and the second ends of the pair of brake shoes being linked together;
• a wheel cylinder for expanding the brake shoes, the wheel cylinder being disposed between the first ends of the brake shoes;
• a master cylinder outputting a hydraulic pressure;
• a fluid passage for introducing the hydraulic braking pressure output from the master cylinder to the wheel cylinder, the hydraulic braking pressure being dependent on a brake operation force;
• an input detector coupled to the fluid passage, the input detector detecting the hydraulic braking pressure output from the master cylinder and producing a first output signal representative of the detected hydraulic braking pressure, the hydraulic braking pressure being an input force to the brake shoes;
• an output detector that detects an anchor reaction force generated by the secondary brake shoe during braking and produces a second output signal representative of the detected anchor reaction force, the detected anchor reaction force being an output force of the secondary brake shoe;
• electromagnetic valves, coupled to the fluid passage, that control the supply of the hydraulic braking pressure output from the master cylinder to the wheel cylinder;
• and
• a control circuit that controls the operations of the electromagnetic valves in accordance with the first and second output signals so that the output force is limited to a force equal to or smaller than the input force multiplied by a predetermined boosting ratio.