Automatic brake booster

An automatic brake booster, comprising:

• a valve body slidably provided within a shell;
• power pistons provided on said valve body;
• a constant pressure chamber and a variable pressure chamber formed in front of and behind each of said power pistons;
• and
• a valve mechanism for controlling the switching of passages provided in said valve body;
• wherein said valve mechanism includes a first valve seat formed in said valve body, a sleeve slidably fitted into said valve body, a second valve seat formed on said sleeve, valve discs seated respectively on said first and second valve seats, drive means for switching the passages by displacing said sleeve frontward, and a valve plunger which is relatively displaceably provided for said valve body and said sleeve, and which is interlocked with an input shaft, said valve plunger for switching the passages by displacing said sleeve frontward when said input shaft is moved forward;
• wherein an elastic member is disposed by forming a predetermined space between the front side of said sleeve and said valve body;
• and
• wherein said elastic member restrains said sleeve from being displaced frontward such that said elastic member (1) is not compressed when said sleeve is displaced frontward by said drive means and (2) is compressed when said sleeve is displaced frontward by said valve plunger so as to increase the opening amount of said second valve seat.

An automatic brake booster, comprising:

• a valve body slidably provided within a shell;
• power pistons provided on said valve body;
• a constant pressure chamber;
• a variable pressure chamber, said variable pressure chamber and said constant pressure chamber being formed in front of and behind each of said power pistons;
• a valve mechanism provided for said valve body;
• an input shaft for switching the passages of said valve mechanism by reciprocally moving a valve plunger of said valve mechanism;
• an output shaft slidably provided in said valve body;
• a reaction disc;
• and
• a plate plunger, said plate plunger and said reaction disc being installed between the base of said output shaft and said valve plunger;
• wherein said valve mechanism includes a first valve seat formed in said valve body, a sleeve slidably fitted into said valve body, a second valve seat formed on said sleeve, valve discs seated respectively on said first and second valve seats, drive means for switching the passages by displacing said sleeve frontward, and said valve plunger which is relatively displaceably provided for said valve body and said sleeve, and which is interlocked with said input shaft, said valve plunger for switching the passages by displacing said sleeve frontward when said input shaft is moved forward;
• wherein (1) said plate plunger has a first member and a second member which are axially movable with respect to each other and mutually contactable with said reaction disc, (2) said first member mates with said second member and transmits braking counterforce acting on said second member and braking counterforce acting on said first member to said valve plunger during a normal braking operation, and (3) said first member is axially separatable from said second member kept in contact with said valve body to transmit braking counterforce acting on said first member to said sleeve.

An automatic brake booster, comprising:

• a valve body slidably provided within a shell;
• power pistons provided on said valve body;
• a constant pressure chamber;
• a variable pressure chamber, said variable pressure chamber and said constant pressure chamber being formed in front of and behind each of said power pistons;
• a valve mechanism provided for said valve body;
• an input shaft for switching the passages of said valve mechanism by reciprocally moving a valve plunger of said valve mechanism;
• an output shaft slidably provided in said valve body;
• a reaction disc;
• and
• a plate plunger, said plate plunger and said reaction disc being installed between the base of said output shaft and said valve plunger;
• wherein said valve mechanism includes a first valve seat formed in said valve body, a sleeve slidably fitted into said valve body, a second valve seat formed on said sleeve, valve discs seated respectively on said first and second valve seats, drive means for switching the passages by displacing said sleeve frontward, and said valve plunger which is relatively displaceably provided for said valve body and said sleeve, and which is interlocked with said input shaft, said valve plunger for switching the passages by displacing said sleeve frontward when said input shaft is moved forward;
• wherein said plate plunger has a first member and a second member which are axially and relatively displaceable;
• wherein said first member makes contact with said sleeve and transmits braking counterforce acting on said first member via said sleeve to said valve plunger during a normal braking operation and transmits braking counterforce acting on said first member to said sleeve separated from said valve plunger during an automatic braking operation;
• and
• wherein said second member makes contact with said valve plunger and transmits braking counterforce acting on said second member to said valve plunger during the automatic braking operation, and makes contact with said valve body and transmits braking counterforce acting on said second member to said valve body during the normal braking operation.