KR20010077767A - Brake booster for car - Google Patents

Abstract

PURPOSE: A vehicle brake booster is provided to brake efficiently with stepping on a brake pedal by improving a plunger applying pressure to a reaction disk. CONSTITUTION: A brake booster of a vehicle is composed of a casing(10) combined with a front cell(11) and a rear cell(12) to close; a center plate(13) dividing the casing into front chambers(21,22) and rear chambers(23,24); a valve body(60) penetrating the center plate with sliding, and controlling air inflow to front and rear chambers; an input shaft(40) operating the valve body by operating a brake pedal; and an output shaft(50) having a rubber reaction disk(51). The pressure on the reaction disk is increased in increasing pressure difference between static and variable pressure chambers by stepping on the brake pedal. A moving plunger(80) compresses a supporting spring(82), and moves to a plunger(70) to increase pressure. The brake booster brakes stably and efficiently by stepping on the brake pedal lightly in an emergency.

Description

Brake booster for car}

The present invention relates to a vehicle brake booster, and more particularly to a vehicle brake booster to improve the end of the plunger to form a plurality of power ratio.

The vehicle brake booster (BOOSTER) is a device that generates a large braking force with a small force by using a pressure difference between the vacuum and the atmosphere, the braking hydraulic pressure is formed through the amplified force because the master cylinder is coupled to the front cell. Figure 1 is a side cross-sectional view showing a conventional brake booster (BRAKE BOOSTER) for this function.

As shown in FIG. 1, a conventional brake booster for a vehicle includes a casing 1 in which the front cell 1a and the rear cell 1b are hermetically coupled, and the inside of the casing 1 with the front chamber 2a and 2b and the rear chamber. Center plate (1c) partitioned by (2c) (2d), one end slidably penetrates the center of the center plate (1c) and the other end is mounted to protrude out through the open center of the rear cell (1b) The valve body 6 for controlling the inflow, the input shaft 4 is interlocked by the brake pedal (not shown) and the output shaft 5 receives the force of displacement in accordance with its operation.

The front chambers 2a and 2b are divided into the front static pressure chamber 2a and the front transformer chamber 2b by the front diaphragm 3a and the front power piston 3b, and the rear chambers 2c and 2d are The rear diaphragm 3c and the rear power piston 3d are divided into the rear static pressure chamber 2c and the rear transformer chamber 2d.

The valve main body 6 has a front diaphragm 3a, a front power piston 3b, a rear diaphragm 3c, a rear power piston 3d, and a center plate 1c at one end of the outer periphery. The other end in which the portion 6c is formed passes through the central portion of the rear cell 1b and communicates with the atmosphere. Inside the valve body 6, a pressure passage 6a communicating with the constant pressure chambers 2a and 2c and the transformer chambers 2b and 2d, and a transformer passage communicating with the atmosphere and the transformer chamber 2b and 2d. 6b is formed, and a plunger 7 which is engaged with the end of the input shaft 4 and slides in the axial direction is provided. A reaction disk 5a is provided between the output shaft 5 and the tip of the plunger 7 to double the force applied due to the difference in the cross-sectional area and to transmit it to the output shaft 5. Reference numeral 6d is an elastic poppet valve installed in the valve body 6 to control the inflow of air according to the operation of the input shaft 4, and the positive pressure passage 6a and the transformer passage 6b by the poppet valve 6d. ) Is selectively opened and closed.

Next, the operation of the conventional vehicle brake booster configured as described above will be described. When the driver has not stepped on the brake pedal, each of the positive pressure chambers 2a and 2c and the transformer chambers 2b and 2d is kept in a vacuum state at the negative pressure source. In this state, when the driver presses the brake pedal, the input shaft 4 moves forward, causing the plunger 7 to be pushed back, which causes the front end of the plunger 7 to push the reaction disk 5a directly. In addition, when the transformer passage 6b communicates with the outside air by the movement of the plunger 7, external air flows into the transformer chambers 2b and 2d through the transformer passage 6b. As the external air is instantaneously introduced by the differential pressure, each of the diaphragms 3a, 3c, the power pistons 3b, 3d, and the valve body 6 is pushed toward the positive pressure chamber 2a, 2c, The output amplified from the input is transmitted to the master cylinder assembly (not shown) through the liquid crystal disk 5a and the output shaft 5 to generate braking hydraulic pressure.

At this time, the force transmitted from the plunger 7 and the force transmitted from the valve body 6 simultaneously act on the reaction disk 5a. The ratio of the force directly applied by the driver and the force formed by the pressure difference is the reaction disk. It is determined by the area ratio of the contact surface of the valve body 6 and the front end surface of the plunger 7, which are in contact with (5a) to apply pressure directly.

However, in the conventional brake booster, when the driver presses the brake pedal more than a certain level, the additional power effect is lost, and the brake pedal's pressing force is transmitted as it is. Referring to FIG. . 2 is a power characteristic graph showing the relationship of the output to the input of the conventional brake booster for generating a single power ratio.

That is, the ratio of the input applied through the brake pedal and the output obtained by the pressure difference is determined by the ratio of the tip area of the plunger 7 directly contacting the reaction disk 5a and the contact area ratio of the valve body 6 as described above. In the conventional booster, since the area of the component that determines the power ratio is set, the output also increases at a constant rate from B1 to B2 while the input rises to the A1-A2 interval, so that only a single power ratio (C1-C2 interval) is achieved. Occurs.

In fact, in the early stage of braking, reducing the deceleration of the vehicle and increasing the braking force in the late braking phase have a great effect on the stopping distance and the direction stability of the vehicle.However, in the conventional booster that generates a single power ratio, more power from the driver It must be delivered to this brake pedal. Section C2-C3 shows the phenomenon that when the driver presses the brake pedal more than a certain level, the power effect is lost and the step is transmitted to the reaction disc 5a.

Therefore, since the conventional booster forms only a certain power ratio, the inclination of the driver has an inconvenience in that the driver must step on the brake pedal considerably heavy in an emergency situation in which the braking force is increased or a large braking force is required.

The present invention is to solve such a problem, an object of the present invention is to improve the plunger to apply pressure to the reaction disk, if a large braking force is urgently required, a brake booster for a vehicle that can generate a large power ratio even if you step on the brake pedal lightly To provide.

1 is a cross-sectional view of a conventional vehicle brake booster.

2 is a force characteristic graph of a conventional brake booster.

3 is a cross-sectional view of the vehicle brake booster according to the present invention.

FIG. 4 is an enlarged view illustrating an extract of part G of FIG. 3.

5 is an operational state diagram illustrating a process of forming a first power ratio of the brake booster according to the present invention.

6 is an operational state diagram showing a secondary power ratio forming process of the brake booster according to the present invention.

7 is a force characteristic graph of the brake booster according to the present invention.

* Description of the symbols for the main parts of the drawings *

40. Input shaft 50. Output shaft 51. Reaction disc

60.Valve body 70.Plunger 70b.Outward flange

70c. First protrusion 80. Operation plunger 80a. Outward flange

80b .. 2nd projection 81..Guide 81a, 81b.

82. Support spring

The present invention for achieving this purpose, the casing is a front cell and the rear cell is hermetically coupled, the power piston and the diaphragm partitioning the inside of the casing into a constant pressure chamber and the transformer chamber, once the center of the power piston and the diaphragm is coupled to the outer periphery The other end penetrates the rear cell and communicates with the atmosphere, and a plunger is installed in the cylinder hole formed in the axial direction inside one end of the valve body to control the air inflow into the transformer chamber, and the other end is coupled to the plunger and the other end. In a brake booster for a vehicle having an input shaft coupled with a brake pedal, and an output shaft disposed at a center of one end of the valve body via a reaction disc to receive the force of the power piston and the diaphragm displacement when the input shaft moves forward,

The movable plunger is installed at the tip of the plunger so as to be able to move back and forth at a predetermined interval, and the tip presses the reaction disk so that a plurality of force ratios are formed according to the advancement degree of the input shaft, and one end of the movable plunger is guided to guide the retracting motion of the movable plunger. And a cylindrical guide tube coupled to the other end to surround the front end of the plunger, which is installed in the guide tube and has a support spring for elastically supporting the rear end of the movable plunger.

According to such a structure, when a plunger is compressed and a relatively large braking force is calculated | required, even if a brake pedal is lightly pressed, a power-up ratio can be produced large.

Hereinafter, one preferred embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 3, the brake booster for a vehicle according to the present invention may include a casing 10 in which the front cell 11 and the rear cell 12 are hermetically coupled to each other, and the inside of the casing 10 with the front chambers 21 and 22. Center plate 13, which is divided into rear chambers 23 and 24, is disposed to penetrate freely to move the center of the center plate 13, and the front chambers 21, 22 and the rear chambers 23, 24 The valve body 60 for controlling the inflow of air to the air), the input shaft 40 for operating the valve body 60 by the brake pedal (not shown) operation and the reaction disk 51 made of rubber material to receive the doubled force An output shaft 50 is provided.

The front chambers 21 and 22 are formed in the space between the front cell 11 and the center plate 13, which are again formed by the front diaphragm 31 and the front power piston 32. ) And front transformer chamber (22). In addition, a restoring spring 14 for restoring the valve body 60 is installed in the front constant pressure chamber 21, and a vacuum connection pipe communicating the front pressure chamber 21 and a negative pressure source on the outer wall of the front cell 11. 15) is mounted. In addition, the rear chambers 23 and 24 are formed in the space between the center plate 13 and the rear cell 12, which are also formed by the rear diaphragm 33 and the rear power piston 34. ) And the rear transformer chamber (24).

And the valve body 60 is provided in a multi-stage stepped cylindrical shape, once the front diaphragm 31, the front power piston 32 and the center plate 13, the rear diaphragm 33 and the rear power piston The central portion of the 34 is fitted and coupled, and the other end on which the air suction portion 63 is formed passes through the central portion of the rear cell 12 and communicates with the outside air.

In addition, the valve main body 60 has a positive pressure passage 61 for communicating the constant pressure chambers 21, 23 and the transformer chambers 22, 24, and a transformer passage for communicating the outside air with the transformer chambers 22, 24. The cylinder 66 is formed in the axial direction at 62 and one center part. The cylinder hole 66 is provided with a plunger 70 sliding in the axial direction in association with the end of the input shaft 40, and the inlet of the valve body 60 substantially allows the inflow of air by the operation of the input shaft 40. The poppet valve 64 of elastic material to control is installed.

That is, the first valve seat portion 65 is provided on the inner circumference of the valve body 60 so as to perform the vacuum valve function in combination with the poppet valve 64, so that the front end of the poppet valve 64 has the first valve seat portion 65. ), The positive pressure passage 61 is closed. In addition, a second valve seat portion 70a is provided at the rear end of the plunger 70 so as to perform an air valve function in combination with the poppet valve 64, so that the front end of the poppet valve 64 has a second valve seat portion 70a. When it is seated in) is blocked from entering the air in the variable pressure chamber 22, 24 of the outside air.

On the other hand, a movable plunger 80 and a support spring 82 are installed at the front end of the plunger 70 so as to increase the power ratio by contacting the reaction disk 51 when the force of the input shaft 40 exceeds a predetermined size. do. Since the movable plunger 80 and the support spring 82 are combined into one assembly at one end of the plunger 70 through the guide tube 81, the gap between the movable plunger 80 and the reaction disk 51 can be kept constant and the assembly work can be performed. It may be facilitated, the detailed structure thereof is as follows.

Referring to FIG. 4, the guide tube 81 has one end coupled to the rear end of the movable plunger 80 and the other end coupled to surround the front end of the plunger 70, so that the movable plunger 80 is mounted in a retractable motion therein. do. In order to install the guide tube 81, the outward flanges 80a and 70b having the diameters are respectively provided at the rear end of the movable plunger 80 and the front end of the plunger 70, and are provided outwardly at both ends of the guide tube 81. Locking jaws 81a and 81b that are bent to surround the flanges 80a and 70b are formed. Accordingly, the movable plunger 80 is installed in the guide tube 81 so as to move forward and backward and is prevented from being separated by the locking jaw 81a and 81b.

And, the support spring 82 is installed in the guide tube 81 so as to elastically support the rear end of the movable plunger 80. In order to install the support spring 82, a rod-shaped first protrusion 70c protruding toward the movable plunger 80 is provided at the front end of the plunger 70 so that the one end of the support spring 82 is fitted thereinto. At the rear end of the support 80, the other end of the support spring 82 is inserted and supported, and at the same time, a rod-shaped second protrusion 80b protruding to the rear side is spaced apart from the first protrusion 70c by a predetermined interval. Therefore, the movable plunger 80 is normally spaced apart from the plunger 70 by the elastic support force of the support spring 82, and the front end portion of the guide tube 81 is protruded to the outside and spaced apart from the reaction disk 51. Is maintained.

Next, the operation and effects of the vehicle brake booster according to the present invention will be described.

First, in a vehicle equipped with a vehicle brake booster according to the present invention, when the driver slightly presses the brake pedal and the input shaft 40 advances in the direction of the arrow, as shown in FIG. 5, the plunger 70 is the reaction disk 51. By slightly pushing toward the side, the second valve seat portion 70a and the poppet valve 64 are spaced apart so that communication between the constant pressure chambers 21, 23 and the transformer chambers 22, 24 is interrupted, and the outside air is sucked in at the same time. It flows into each transformer chamber 22 (24) of a vacuum state through the part 63 and the transformer passage 62.

Accordingly, the front diaphragm 31, the front power piston 32, the rear diaphragm 33, and the rear power piston 34, which are operated by the pressure difference, are pushed toward the output shaft 50 together with the valve body 60. As a result, the output is transmitted to the master cylinder assembly (not shown) through the reaction disk 51 and the output shaft 50 to generate a braking pressure. At this time, the output increases dramatically even though the input through the input shaft 40 is substantially the same. This phenomenon is commonly referred to as a jump-in effect (F0 section in FIG. 7), and the clearance between the reaction disk 51 and the tip of the movable plunger 80 still exists, so that the reaction force of the reaction disk 51 is reduced by the input shaft 40. ) Is not delivered to the side.

Further, when the brake pedal is further pressed, the output and reaction force of the reaction disk 51 gradually increase. As a result, the reaction disk 51 is compressed and the center thereof comes into contact with the tip of the movable plunger 80, whereby the reaction disk ( Part of the reaction force of 51 is transmitted to the input shaft 40 through the movable plunger 80 and the plunger 70.

At this time, two forces transmitted from the movable plunger 80 to the reaction disk 51 and from the center of the valve body 60 are acted upon. Therefore, the ratio of the force applied by the driver and the force amplified by the pressure difference is represented by the ratio of the area of the tip of the movable plunger 80 to the central area of one end of the valve main body 60 which contacts the reaction disk 51 and exerts a pressure thereon. (F1-F2 section in FIG. 7).

Subsequently, when the brake pedal is stepped deeper and the pressure difference between the positive pressure chambers 21 and 23 and the transformer chambers 22 and 24 becomes larger, the pressure acting on the reaction disk 51 as shown in FIG. As it increases, the movable plunger 80 is pushed toward the plunger 70 while compressing the support spring 82 due to the reaction force of the reaction disk 51. At this time, the distance between the reaction disc 51 and one end of the valve body 60 proximate to the movable plunger 80 increases.

Accordingly, a second jump-in effect occurs in which the power ratio increases sharply than the initial stage (F2-F3 section in FIG. 7), and the movable plunger 80 is pushed as the input force increases in the F2-F3 section. The two projections 80b continue to contact the first projections 70c of the plunger 70.

On the other hand, when the brake pedal is stepped more deeply and the second projection 80b of the movable plunger 80 reaches the point F3 (see FIG. 7) that reaches the first projection 70c, the reaction force of the support spring 82 is no longer present. Instead of affecting, the movable plunger 80 and the plunger 70 abut together to produce an integral effect. When the movable plunger 80 and the plunger 70 are in contact with each other, the effect of the driver's stepping on the brake pedal is lost, and the force at this time is formed by the driver's stepping on the brake pedal. , This is the interval F3-F4.

When the driver releases the brake pedal, the plunger 70 and the input shaft 40 are restored by the restoring spring 14 installed in the front pressure chamber 21, and the poppet valve 64 has a second valve seat. It is pushed by the 70a to be separated from the first valve seat 65, and serves as an air valve to prevent the inflow of air. In addition, as the poppet valve 64 is separated from the first valve seat 65, the positive pressure passage 61 communicates with each other, so that the air in the front transformer chamber 22 and the rear transformer chamber 24 is vacuumed in the front pressure chamber. (21) and the rear constant pressure chamber (23), and the constant pressure chambers (21) and (23) are vacuumed by the negative pressure source to be the initial state of the brake booster.

As described in detail above, according to the brake booster for a vehicle according to the present invention, the movable plunger is installed at the end of the plunger in contact with the reaction disk so as to be able to move back and forth in an axial direction, so that the driver presses the brake pedal at a predetermined level. If exceeded, the movable plunger is compressed to produce a larger power ratio. Accordingly, the braking force is generated at the initial stage of braking to reduce the vehicle safely, and after a certain deceleration, the braking force is rapidly increased and the stopping distance is shortened. In addition, even in an emergency situation where a large braking force is required, sufficient braking force is formed even if the brake pedal is lightly stepped on, so that applying this to an antilock brake system or the like can further improve braking distance and braking stability.

Claims (3)

A casing in which the front cell and the rear cell are hermetically coupled, a power piston and a diaphragm dividing the inside of the casing into a positive pressure chamber and a transformer chamber, and a central portion of the power piston and the diaphragm is hermetically coupled to an outer circumference thereof, and the other end penetrates the rear cell. A plunger which is installed in the axial direction of the valve body in communication with the atmosphere, one end of the valve body is installed in the axial direction to control the air flow into the transformer chamber, one end is coupled to the plunger and the other end is the brake pedal and In the brake booster for a vehicle having a coupled input shaft, an output shaft disposed at the center of one end of the valve body via a reaction disk to receive the force of the power piston and diaphragm displacement when the input shaft is advanced, A movable plunger 80 installed at the distal end of the plunger 70 so as to move forward and backward at a predetermined interval and having a plurality of power ratios formed according to the advancement degree of the input shaft 40; Cylindrical guide tube 81, one end of which wraps around the rear end of the movable plunger 80 and the other end surrounds the front end of the plunger 70 so as to guide the forward and backward movement of the movable plunger 80, And a support spring (82) installed in the guide tube (81) to elastically support the rear end of the movable plunger (80). The method of claim 1, At the front end of the plunger 70 and the rear end of the movable plunger 80 are provided outward flanges (70b, 80a) of expanded diameter, Both end portions of the guide tube 81 are bent to surround the outward flanges 70b and 80a, respectively, and locking jaws 81a and 81b are provided to prevent separation of the movable plunger 80. Car brake booster. The method of claim 1, A rod-shaped first protrusion 70c protruding toward the movable plunger 80 is provided at the front end of the plunger 70 so that one end of the support spring 82 is fitted therein. At the rear end of the movable plunger 80, the other end of the support spring 82 is inserted and supported, and at the same time, a rod-shaped second protrusion 80b protruding to the rear side is spaced apart from the first protrusion 70 by a predetermined interval. Brake booster for cars.