Abstract: In a negative pressure boosting device 1 of the present invention, a movable valve seat 28 is air-tightly and slidably disposed in a concavity of a valve body 4. The movable valve seat 28 and a valve element 12 compose a vacuum valve 15. The movable valve seat 28 and a control spring 29 compressed and disposed between the movable valve seat 28 and the valve body 4 compose a servo ratio changing means. The servo ratio changing means is provided on a valve mechanism (the vacuum valve 15). During operation, the valve element 12 comes in contact with the movable valve seat 28. However, the movable valve seat 28 does not move in a low-input range so that the servo ratio in this state is relatively large ratio i.e. the servo ratio for the normal operation. In the high-input range, the control spring 29 starts to be compressed to allow the movement of the movable valve seat 28, thereby changing the servo ratio to a small servo ratio.

Abstract: A tubular member 18 is slidably fitted into a valve body, and is formed with a vacuum valve seat 21. The tubular member 18, a valve plunger 16 and the valve body 3 are maintained in their inoperative positions shown by abutment against a key member 13. A holder 14 is formed with a tapered surface 14a to assist in allowing an elastic deformation of a reaction disc 15. Immediately after the commencement of operation of a valve mechanism 7 as an input shaft 8 is driven forward, the input shaft 8 and the tubular member 18 are maintained in their inoperative positions until a rear end face of a variable pressure passage 28 abuts against the key member 13. The operating stroke of an input shaft 6 can be chosen to be less than the operating stroke of an output shaft 11 while preventing the jumping value from increasing to an excessively high value.

Abstract: A brake system 1 of the present invention comprises a brake operating means 2 such as a brake pedal for carrying braking operation, a fluid variable stroke means 3 which variably controls the stroke of the brake operating means 2 by using fluid, and a braking force output means 4 which is actuated by the operation of the brake operating means 2 to produce braking forces. By manipulating the brake operating means 2, the braking force output means 4 performs the braking operation. The traveling rang of the brake operating means 2 i.e. the stroke can be changed variously by the fluid variable stroke means 3 using fluid. Since the stroke of the brake pedal can be changed as mentioned above, a proper pedal stroke can be obtained.

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: During a normal brake operation, a brake reaction from a reaction disc 12 is transmitted to a valve plunger 15 through an outer plunger 17 and an inner plunger 18.

Abstract: A tubular member 21 is disposed within a valve body 6, and has a resilient retainer 69 mounted around the outer periphery thereof. The inner periphery of the valve body 6 is formed with an annular groove 68. When a brake pedal is quickly depressed, an input shaft 23 and the tubular member 21 are driven forward through more than a given stroke relative to the valve body, whereby a projection 69a of the retainer 69 becomes engaged with the annular groove 68. This produces and maintains a large opening in an atmosphere valve 32. Accordingly, an output from a tandem brake booster 1 can be increased immediately in response to a quick depression of the brake pedal.

Abstract: A hydraulic-pressure counter-force mechanism 37 which produces a counter force when a brake booster is operated is made up of an input-side member 38 slidable disposed within a valve body 3, a second constant-pressure chamber 39 formed on the rear side of the input-side member and into which a pressure is introduced from a constant pressure chamber A, and a second constant-pressure chamber 39 formed on the front side of the input-side member and into which a pressure is introduced from a variable pressure chamber B. The counter force from the hydraulic-pressure counter-force mechanism 37 is reduced by an orifice passage 43 as counter-force reducing means in rapid operation for brake.

Abstract: An electrically driven brake booster 1 includes an input member 4 disposed in operative association with a brake pedal 12, an output member 5 disposed in operative association with the master cylinder 6, and drive transmitting means 10 for translating a rotating motion of a motor 9 into a linear motion to be transmitted to the output member 5. The drive transmitting means 10 comprises a rack 23 formed on the output member 5, and pinions 21, 22 disposed in operative association with the motor 9 and in meshing engagement with the rack 23. Also, reaction transmitting means 8 which transmits a brake reaction to the input member 4 and the output member 5 at a given proportion is provided. In comparison to conventional drive transmitting means, the drive transmitting means 10 of the present invention has a simple construction, a reduced weight and a better transmission efficiency. The provision of reaction transmitting means allows a correct brake control to be achieved on the basis of a brake reaction.

Abstract: In a brake booster of the present invention, by depression of a brake pedal 3, an input shaft 4 travels to the left, a pedal input converter generates thrust, and a valve element 5a moves to the left. A valve passage 5a1 is shut off from a valve passage 5b1 and a valve passage 5a2 is connected to a valve passage 5b2 so as to develop output pressure Pr at an output port 5c of a control valve 5 because of the pressure of a pressure source. The output pressure Pr is supplied to a wheel cylinder 7, thereby actuating the brake. At this point, since the displacement of the input shaft 4 required for operating the control valve 5 is defined only by the converter 6, the input side is not affected by the brake rigidity of a circuit from the control valve 5 to the wheel cylinder 7. The output pressure Pr of the control valve 5 acts on the valve element 5a through a first reaction receiving portion 8 and is regulated to pressure proportional to the thrust of the converter 6.

Abstract: As the primary piston 3 is driven forward, a cup seal 32 moves forwardly of a communication path 17c in a first sleeve 17 to interrupt a communication between a first reservoir chamber 11 and the first liquid pressure chamber 5, thus generating a liquid pressure in the first liquid pressure chamber 5. As the secondary piston 10 is driven forward, a cup seal 25 moves forwardly of a communication path 18c, interrupting a communication between a second reservoir chamber 19 and a second liquid pressure chamber 6, thus generating a liquid pressure in the second liquid pressure chamber 6. The invention provides a master cylinder 1 which is simple in construction and inexpensive to manufacture.

Abstract: A brake system including an intensifying arrangement which allows a master cylinder pressure to be intensified by feeding a discharge pressure from a pump to an intensifying chamber. The brake system includes a master cylinder having a primary piston, on the rear portion of which a sleeve is fitted, with a spool valve slidably fitted into the sleeve. The spool valve has a rear end which abuts against the bottom of a bottomed opening formed in an input shaft. The invention allows a misalignment between the axes of the primary piston and the input shaft.

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: An automatic brake booster includes a solenoid and a solenoid plunger which allow a flow path in a valve mechanism to be switched without depression of a brake pedal. The solenoid plunger comprises a rear member on which an atmosphere valve seat is formed, a front member which is disposed to be displaceable with respect to the rear member, and a first spring disposed between the both members. When a current fed to the solenoid is less than a given value, the first spring remains inactive while when the current exceeds the given value, the first spring becomes flexed to reduce a clearance between the rear member and a holder which forms part of a magnetic path of the solenoid together with the rear member. When the booster operates as an automatic brake, a gentle brake operation which allows a precise control with a reduced brake output and a quick brake operation with an increased brake output can be simultaneously achieved in a preferred manner.

Abstract: An automatic brake booster 1 includes a solenoid 8 which causes a back-and forth movement of a solenoid plunger 31 to switch a valve mechanism 6. A second vacuum valve seat member 11 including a second vacuum valve seat 12 which is juxtaposed with a first vacuum valve seat 10 on a valve body 3 and a pressure responsive area 34 subject to a pressure of a variable pressure chamber and a pressure of a constant pressure chamber is slidably mounted on the valve body. The effect of the pressure differential acting upon the pressure responsive area is balanced with the force resulting from the excitation of the solenoid plunger 31 to deliver a brake output which corresponds to the force. The invention enables a high accuracy control of a brake output during an automatic brake operation.

Abstract: A tubular member 21 is disposed within a valve body 6, and has a resilient retainer 69 mounted around the outer periphery thereof. The inner periphery of the valve body 6 is formed with an annular groove 68. When a brake pedal is quickly depressed, an input shaft 23 and the tubular member 21 are driven forward through more than a given stroke relative to the valve body, whereby a projection 69a of the retainer 69 becomes engaged with the annular groove 68. This produces and maintains a large opening in an atmosphere valve 32. Accordingly, an output from a tandem brake booster 1 can be increased immediately in response to a quick depression of the brake pedal.

Abstract: A brake system contains a safety mechanism which terminates an automatic brake upon detecting that unnecessary braking force is developed as a result of a failure in an automatic brake controller. In the event a braking output is developed when neither a brake pedal nor the automatic brake controller is operated, the safety mechanism determines the occurrence of an abnormality, and interrupts a communication between the master cylinder and the wheel cylinder while decompressing the oil pressure in the wheel cylinder by discharging it into a low pressure accumulator. The safety mechanism allows the automatic braking to be terminated, thus allowing a risk of a collision by a succeeding vehicle to be avoided and allowing a vehicle to continue running.

Abstract: A detection switch is mounted on an input shaft through a clevis for detecting the operation of an automatic brake unit without the depression of a brake pedal. The detection switch may also be mounted on the brake pedal. The clevis and the brake pedal are connected together in a manner to permit a relative displacement therebetween through an operating stroke of the detection switch. When the brake pedal is depressed, the brake pedal is maintained at an advanced position relative to the input shaft, and the detection switch detects a retracting movement of the brake pedal with respect to the input shaft from the advanced position during an automatic brake operation. The arrangements allow the detection switch to be mounted on either the input shaft or the brake pedal, does not require design of a small size and facilitates the mounting of the detection switch.

Abstract: A valve mechanism of an automatic brake booster comprises a vacuum valve seat formed on a valve body to face forward, an atmosphere valve seat formed on the rear portion of a valve plunger, and a valve element adapted to be seated on the both valve seats from the front side thereof. The valve plunger is associated with a solenoid plunger which allows the valve plunger to extend therethrough to permit a relative displacement therebetween and which is integrally connected thereto at an advanced end position thereof. A resilient member is provided which normally maintains the solenoid plunger at the advanced end position relative to the valve plunger. This simplifies a valve mechanism in comparison to a conventional automatic brake booster, thus improving the reliability.

Abstract: In an automatic brake booster, a sleeve 18 constituting a valve mechanism 15 has a drive portion 50 disposed on the front side, a valve portion 51 forming a second valve seat 19, a mating portion 52 for mating with a valve seat portion when the drive portion is moved forward, and a conical spring 53 disposed between the drive portion and the valve seat portion and used for separating both members from each other. The conical spring is compressed during the normal braking operation so as to make the opening amount of the second valve seat greater than that during the automatic braking operation. Moreover, a plate plunger 40 for transmitting braking counterforce is relatively displaceably provided and a first member 71 and a second member 71 for mutually contacting a reaction disc 41 is also provided, so that the braking counterforce of the first member is transmitted to the sleeve during the automatic braking operation.

Abstract: As the primary piston 3 is driven forward, a cup seal 32 moves forwardly of a communication path 17c in a first sleeve 17 to interrupt a communication between a first reservoir chamber 11 and the first liquid pressure chamber 5, thus generating a liquid pressure in the first liquid pressure chamber 5. As the secondary piston 10 is driven forward, a cup seal 25 moves forwardly of a communication path 18c, interrupting a communication between a second reservoir chamber 19 and a second liquid pressure chamber 6, thus generating a liquid pressure in the second liquid pressure chamber 6. The invention provides a master cylinder 1 which is simple in construction and inexpensive to manufacture.