Abstract: A first vacuum valve seat 17 is formed on a valve body 3, and a second vacuum valve seat 18 is formed on a tubular member 21 which is slidably mounted on the valve body 3. A lever member 41 is provided between the tubular member 21 and a valve plunger 14, and when the valve plunger 14 strokes through a given stroke or more relative to the valve body 3, the lever member 41 moves angularly to retract the tubular member 21 rearward relative to the valve body 3. When a brake pedal is quickly depressed, the lever member 41 moves angularly to cause an engaging tab 41f to engage an engaging recess 44 formed in the valve body 3, thus retaining the tubular member 21 at a position which is reached as it is retracted rearward relative to the valve body 3. This allows an atmosphere valve 33 to be opened to a greater opening than during a usual operation, allowing an increased output to be obtained rapidly.

Abstract: A first vacuum valve seat 17 is formed on a valve body 3, and a second vacuum valve seat 18 is formed on a tubular member 21 which is slidably mounted on the valve body 3. A lever member 41 is provided between the tubular member 21 and a valve plunger 14, and when the valve plunger 14 strokes through a given stroke or more relative to the valve body 3, the lever member 41 moves angularly to retract the tubular member 21 rearward relative to the valve body 3. When a brake pedal is quickly depressed, the lever member 41 moves angularly to cause an engaging tab 41f to engage an engaging recess 44 formed in the valve body 3, thus retaining the tubular member 21 at a position which is reached as it is retracted rearward relative to the valve body 3. This allows an atmosphere valve 33 to be opened to a greater opening than during a usual operation, allowing an increased output to be obtained rapidly.

Abstract: A valve seat (50) is provided on and along the end face of the end tubular portion (16a) of the valve body (16) of a power brake device. A valve member (49) is slidably put on the input shaft (8). The valve member (49) is moved forward and backward by an actuator (51). When the valve member (49) is seated on the valve seat (50), the valve member (49) closes a pressure path (35). In this state, the operation of amplifying a braking force by the power brake device is not performed. The brake system may be incorporated into a vehicle with a regenerative brake device. The operation of amplifying a braking force by the power brake device can be interrupted. Therefore, the brake system produces a braking force optimal for a current loading state of a vehicle. The braking force amplifying operation of the power brake device can be stopped until the regenerative brake device produces a large regenerative braking force. Therefore, the regenerative braking force can be effectively used.