KR20020009921A - Brake booster - Google Patents

Abstract

PURPOSE: A brake booster of a vehicle is provided to reduce tolerance of clearance between a reaction disk and an end of a plunger, and to prevent sudden increase of output according to changes of clearance by forming an expanded recess in the end of a valve body. CONSTITUTION: A brake booster for a vehicle is composed of a casing having a front cell and a rear cell; a center plate dividing the casing into front and rear compartments; a valve body(60) regulating air inflow to front and rear compartment; an input shaft(40) operating the valve body; an output shaft(50) installed in the end of the valve body; a rubber reaction disk(51) contacted to the end of the valve body; a plunger(70) moving back and forth; and a recess(67) formed in the end(60a) of the valve body, and separated from the center of the reaction disk in braking. The diameter of the recess is formed to be less than the diameter of the reaction disk and more than the diameter of a cylinder part(66) to enlarge clearance between the reaction disk and the end of the plunger. The tolerance of the clearance is reduced with forming the expanded recess in the end of the valve body, and the sudden increase of the output is prevented according to changes of clearance.

Description

Automotive brake booster

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle brake booster, and more particularly, to a vehicle brake booster having one end surface of a valve body directly contacted with a reaction disk to prevent a jump-in value from being distributed.

In general, a brake brake for a vehicle (BRAKE 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 master cylinder assembly is coupled to the front cell to form a braking hydraulic pressure through the amplified force. . 1 shows such a conventional vehicle brake booster.

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 chambers 2a and 2b and the rear. The center plate 1c partitioned into seals 2c and 2d, one end slidably penetrates the center of the center plate 1c, and the other end penetrates the rear cell 1b to protrude outward to control the air inflow. It consists of a valve body 6, an input shaft 4 interlocked by a brake pedal (not shown), and an output shaft 5 receiving a displacement force in accordance with its operation.

The front chambers 2a and 2b are divided into the front hydrostatic chamber 2a and the front transformer chamber 2b by the front diaphragm 3a and the front power piston 3b, and the valve body is provided in the front hydrostatic chamber 2a. A return spring 8 is arranged to elastically support 6 in the restored direction. The rear chambers 2c and 2d are divided into a rear static pressure chamber 2c and a rear transformer chamber 2d by the rear diaphragm 3c and the rear power piston 3d.

The valve body 6 slides integrally with the diaphragms 3a and 3c and the power pistons 3b and 3d. For this purpose, the valve body 6 has a front diaphragm 3a and front power at one end thereof. The piston 3b, the rear diaphragm 3c, the rear power piston 3d, and the center plate 1c are coupled to each other, and the other end of the valve body 6 passes through the center of the rear cell 1b to communicate with the atmosphere. The part 6c is provided. In addition, the valve main body 6 has a constant pressure passage 6a for communicating the constant pressure chambers 2a and 2c and the transformer chambers 2b and 2d, and a transformer passage for communicating the atmosphere with 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 disposed. And the rear end of the output shaft 5 is inserted into the disk-shaped reaction disk (5a) for doubling the force acting due to the cross-sectional area to be transmitted to the output shaft (5) side is fitted. The reaction disk 5a is made of an elastic material, and is in contact with the center of the front end face of one end of the valve body 6, and the predetermined clearance G1 is normally maintained with the front end of the plunger 7.

On the other hand, reference numeral "6d" is an elastic poppet valve which is installed in the air suction part 6c of the valve body 6 and controls the inflow of air in accordance with the operation of the input shaft 4, by the poppet valve 6d. The positive pressure passage 6a and the transformer pressure passage 6b are selectively opened and closed.

Next, the operation of the conventional vehicle brake booster configured as described above will be described.

First, 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 maintained in a vacuum state by a negative pressure source (not shown). When the driver presses the brake pedal a little in this state, the input shaft 4 moves forward and the valve body 6 moves slightly toward the reaction disk 5a together with the plunger 7.

Accordingly, the transformer passage 6b communicates with the outside air, so that the outside air flows into the transformer chambers 2b and 2d through the transformer passage 6b. The external air is instantaneously introduced by the differential pressure, so that the diaphragm 3a, 3c, the power piston 3b, 3d, and the valve body 6 are pushed toward the constant pressure chamber 2a, 2c and amplified than the input. The reaction disk 5a and the output shaft 5 are transferred to a master cylinder assembly (not shown) to generate braking hydraulic pressure.

At this time, the clearance G1 between the reaction disk 5a and the front end face of the plunger 7 is maintained, and the output at this time is suddenly increased without an increase in the input force, which is called a jump-in effect. This jump-in effect is caused by gradually depressing the brake pedal so that the reaction disc 5a is deformed, which causes the reaction disc 5a to fill the clearance G1 with the tip of the plunger 7, i.e., fill the empty space. . Therefore, the clearance G1 space between the reaction disk 5a and the tip of the plunger 7 is called a jump-in space.

This jump-in effect is an important feature of the brake booster and is essential for instant braking action when the brake pedal is activated. Therefore, the automotive industry sets the jump-in value within a certain range so that the initial boost generated by the booster does not reach too high without increasing the force transmitted from the brake pedal.

However, due to a large number of parts constituting the brake booster, that is, production tolerances of the valve body 6, the plunger 7, the reaction disk 5a, the output shaft 5, and the like, the clearance G1 tolerance, that is, the jump Tolerance of the in-space cannot be avoided, and there is a problem in that the jump-in value is significantly dispersed even in the same booster.

The present invention is to solve this problem, the object of the present invention is to improve the diameter of the jump-in space by improving the end surface of the valve body directly in contact with the reaction disk, according to the change of clearance between the reaction disk and the plunger tip It is to provide a vehicle brake booster that can prevent the jump-in change from becoming large.

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

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

3 is an excerpt of the "X" part of FIG.

4 and 5 show the operating state of the brake booster according to the present invention.

6 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 *

10. Casing 40. Input shaft

50. Output shaft 51. Reaction disc

60. Valve body 64. Poppet valve

66. Cylinder part 67. Recess part

70..plunger

The present invention for achieving this object is;

A casing in which the front cell and the rear cell are hermetically coupled, a power piston and diaphragm dividing the casing into a positive pressure chamber and a transformer chamber, and an outer circumference is hermetically coupled to the center of the power piston and diaphragm, and the other end passes through the rear cell. And a plunger which is installed in the axial direction in one end of the valve body in communication with the valve body, the plunger which controls the air inflow into the transformer chamber, and the front end of the plunger is coupled to the shaft by the brake pedal. The output shaft arranged coaxially at one end of the valve body and the rear end of the output shaft to receive the force of the power piston and diaphragm displacement as the input shaft moves forward and the input shaft moves forward. It is in direct contact with the center of the face and maintains a certain clearance from the plunger tip during initial brake operation. In the vehicle brake booster with a reaction disc arranged in an elastic material,

One end surface of the valve body is characterized in that the recess is provided with an extended portion having a predetermined diameter around the cylinder portion to maintain a constant distance on the center of the reaction disk during the initial operation of the brake.

In addition, the bottom surface of the recess is formed to have a predetermined depth so as to maintain the same surface as the plunger tip during the initial operation of the brake.

According to such a structure, in the case of the booster which requires a high power-up ratio, the diameter of a jump-in space can be made large, and it can prevent that jump-in change by the change of clearance between the reaction disc and the plunger tip is large.

Hereinafter, one preferred embodiment according to the present invention will be described in detail with reference to the accompanying drawings. 2 and 3 show the brake booster structure according to the present invention, and FIGS. 4 to 6 show the operating state and the backing characteristics of the brake booster according to the present invention.

Referring to FIG. 2, 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. The center plate 13 partitioned into the rear chambers 23 and 24, and the center plate 13 penetrates so that the center part of the center plate 13 can slide freely, The front chamber 21, 22 and the rear chamber 23 ( The valve body 60 for controlling the inflow of air to the 24, the input shaft 40 for operating the valve body 60 by the operation of the brake pedal (not shown), and the valve body 60 to receive the doubled force An output shaft 50 provided coaxially with a reaction disk 51 made of an elastic material (rubber) is provided at the center of one end surface 60a (see FIG. 3).

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 return spring 14 for restoring the valve body 60 is installed in the front pressure chamber 21, and the front cell 11 wall communicates with the vacuum source so that the front pressure chamber 21 is always maintained in a vacuum state. The vacuum connection tube 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 vacuumed by the rear diaphragm 33 and the rear power piston 34. It is divided into the positive pressure chamber 23 and the rear transformer chamber 24 in which pressure changes.

The valve body 60 is provided in a cylindrical shape consisting of a plurality of outer periphery, one end of the outer diaphragm 31, the front power piston 32 and the center plate 13, the rear diaphragm 33 and the rear power The other end of the piston 34 is fitted into the center portion, and the inside thereof is hollow to form an air suction portion 63, and communicates with the outside air through the center portion of the rear cell 12.

In addition, the valve main body 60 has a constant 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. 62) and a cylinder portion 66 is formed in the central portion in the axial direction. The cylinder portion 66 is provided with a plunger 70 sliding in the axial direction in association with the end of the input shaft 40, and the operation of the input shaft 40 in the valve body 60, that is, the inner circumference of the air suction portion 63, is provided. By the poppet valve 64 of the elastic material which substantially controls the air inlet is installed. The poppet valve 64 has a rear end fixed to the inner circumference of the air suction unit 63, and the front end is configured as a free end. In addition, a first valve seat portion 65 is provided on the inner circumference of the valve body 60 so as to perform a vacuum valve function in combination with the poppet valve 64, so that the tip of the poppet valve 64 has a first valve seat portion 65. When seated in the static pressure passage 61 is closed. In addition, a second valve seat portion 71 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 tip of the poppet valve 64 has the second valve seat portion 71. When seated in the outside air is blocked to flow into the transformer chamber (22, 24).

Meanwhile, the end portion 60a of the valve body 60 in which the plunger 70 is installed to move forward and backward may be recessed to maintain the reaction disc 51 and the predetermined clearance G2 during initial brake operation. In the case of the booster requiring a high power ratio, the diameter of the jump-in space can be configured to be larger, and the detailed structure thereof will be described with reference to FIG. 3.

First, the disc-shaped reaction disk 51 configured to have a predetermined thickness is seated on the rear end of the output shaft 50 so that one surface is in surface contact with one end surface 60a of the valve body 60, and the retraction movement is performed on the cylinder portion 66. The plunger 70, which is possibly installed, is arranged such that the front end surface 72 maintains the reaction disk 51 and the predetermined clearance G2 during the initial brake operation.

In addition, the one end surface 60a of the valve body 60 is recessed so that the recessed portion 67 is formed so that a part of the center does not come into contact with the reaction disk 51 during the initial operation of the brake. The recessed portion 67 has a large diameter of the jump-in space to prevent the jump-in change caused by the change of the clearance G2 between the reaction disk 51 and the front end face 72 of the plunger 70 from increasing. To this end, it is provided to extend in the radial direction about the cylinder portion 66. Further, in order to set the jump-in value within a specific range, the recess portion 67 has a diameter D2 smaller than the reaction disk 51 diameter D3 and larger than the cylinder portion 66 diameter D1, In the initial state of the brake booster, the bottom surface 67a of the brake booster may be formed to have a predetermined depth so as to maintain the same surface as the front end surface 72 of the plunger 70.

As such, when the recessed portion 67 is formed on the front end surface 60a of the valve body 60, production tolerances of the valve body 60, the plunger 70, and the reaction disk 51 may be caused. It is possible to compensate the jump-in space, that is, the tolerance of the clearance G2.

Next, the operation and effects of the vehicle brake booster according to the present invention will be described with reference to FIGS. 4 to 6.

First, in a vehicle equipped with a vehicle brake booster according to the present invention, if the driver slightly presses the brake pedal and the input shaft 40 moves forward in the direction of the arrow Y, as shown in FIG. 4, the plunger 70 may include a reaction disc ( 51, the second valve seat portion 71 is separated from the tip of the poppet valve 64 so that the communication between the constant pressure chambers 21, 23 and the transformer chambers 22, 24 is interrupted and the external air By the pressure difference, the air flows into the transformer chambers 22 and 24 in the vacuum state through the direction of the arrow, that is, through the air suction unit 63 and the transformer passage 62.

The front diaphragm 31 and the front power piston 32 and the rear diaphragm 33 and the rear power piston 34 which are actuated according to this are pushed to the output shaft 50 together with the valve body 60, so that the output is output shaft. It is transmitted to the master cylinder assembly (not shown) through 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. Typically jump these phenomena by the (JUMP IN) effect referred to, and (C ₀ region of Fig. 6), the clearance (G2) between the reaction disc 51 and the plunger 70, the top face 72 is still present, The reaction force of the reaction disk 51 is not transmitted to the input shaft 40 side.

This jump-in phenomenon causes the driver to step on the brake pedal more and the output and reaction force of the reaction disc 51 gradually increase. As a result, the reaction disc 51 is elastically deformed, so that the space of the recess part 67 (aka, Continues to fill the jump-in space until it comes into contact with the tip face 72 of the plunger 70 (input; A₀ -A_Onesection).

When the reaction disc 51 which is elastically deformed by further stepping on the brake pedal completely fills the recess 67, the reaction disc 51 comes into contact with the front end surface 72 of the plunger 70, thereby partially reacting. It is transmitted to the input shaft 40 side through the plunger 70.

At this time, a force transmitted from the plunger 70 and a force transmitted from one end surface 60a of the valve body 60 act on the reaction disk 51 at the same time. Accordingly, the ratio of the force exerted by the driver and the pressure amplified by the pressure difference is that the end face 72 of the plunger 70 with respect to the central area of one end of the valve main body 60 that comes into contact with and applies pressure to the reaction disk 51. It can be represented by the area ratio (C ₁ -C ₂ interval in Figure 6).

On the other hand, as shown in FIG. 5, when the brake pedal is pressed deeper and the input shaft 40 is further advanced in the direction of the arrow Y, the pressure difference between the constant pressure chambers 21 and 23 and the transformer chambers 22 and 24 is further increased. As it increases, the pressure acting on the reaction disk 51 also increases. As a result, the reaction force of the reaction disk 51 no longer affects the moment when the reaction disk 51 reaches the point C ₂ (see FIG. 6) that reaches the front end face 72 of the plunger 70. As a result, the driving force of the driver's brake pedal is lost, and the power at this time is formed by the driver's pressing of the brake pedal as it is, which is the C ₂ -C ₃ section.

When the driver releases the brake pedal, the plunger 70 and the input shaft 40 are restored by the return spring 14 installed in the front pressure chamber 21, and the poppet valve 64 has a second valve seat. It is pushed by the 71 to be separated from the first valve seat portion 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.

The size of the jump-in during operation of the brake booster is a direct function of the jump-in volume (the space between the reaction disk 51 and the plunger 70 tip end face 72), and the smaller the volume of the jump-in space, The jump-in change value with the change value tends to be large.

The power boost ratio of the brake booster is a value obtained by dividing the diameter area of the output shaft 50 by the plunger 70 tip area. Accordingly, the larger the boost ratio, the smaller the jump-in space, and thus the larger the dispersion of the jump-in due to the clearance G2 tolerance.

That is, in the case of the conventional booster, when the volume of the jump-in space is V and the volume change of the jump-in space during the braking action is ΔV, they are expressed as follows.

V = (π / 4) D1 ² × G1 and ΔV = (π / 4) D1 ² × ΔG1.

At this time, "D1" is the tip end diameter (cylinder inner diameter) of the plunger 7, "G1" is the distance between the reaction disk 5a and the end face of the plunger 7, and "ΔG1" is the production tolerance. Is a change value of G1 according to the respective symbols (refer to FIG. 1). Therefore, in the case of the conventional booster, the volume change rate (ΔV / V) of the jump-in space according to the production tolerance is ΔG1 / G1.

On the contrary, in the case of the booster according to the present invention, when the volume of the jump-in space is referred to as V 'and the volume change of the jump-in space according to the production tolerance is referred to as ΔV', they are expressed as follows.

V '= (π / 4) D2 ² x G2, and DELTA V' = (π / 4) D1 ² x DELTA G2.

At this time, "D1" represents the diameter of the front end face 72 (cylinder portion inner diameter) of the plunger 70, "D2" represents the diameter of the recess portion 67, "G2" is the initial state of the booster The distance between the reaction disk 51 and the front end surface 72 of the plunger 70 is shown. And " ΔG2 " is a change value of G2 according to production tolerances (each symbol is shown in Fig. 3).

Therefore, in the case of the booster according to the present invention, the volume change rate (ΔV ′ / V ′) of the jump-in space according to the production tolerance is (D1 / D2) ² × (ΔG2 / G2). At this time, since D2 is larger than D1, it can be seen that in the booster according to the present invention, the volume change of the jump-in space according to the production tolerance is smaller than in the conventional case.

As a result, in the case of a brake booster having a high power ratio, the recess portion 67 having a diameter D2 smaller than the reaction disk 51 and larger than the cylinder portion 66 on the center of one end surface 60a of the valve body 60. ), The jump-in space can be increased, so that the change in the jump-in value due to the change in clearance G2 can be avoided.

As described in detail above, according to the brake booster for a vehicle according to the present invention, when the clearance, that is, the size of the jump-in space has a dispersion due to production tolerances of a plurality of components constituting the booster, In the initial operation of the brake, by providing a recess that extends to have a predetermined diameter around the cylinder to maintain a constant distance from the center of the reaction disk, the tolerance of the jump-in space can be reduced, and the reaction disk and the plunger tip end face It is possible to prevent the change of the jump-in value according to the change of the clearance of the increase.

Claims (2)

A casing in which the front cell and the rear cell are hermetically coupled, a power piston and a diaphragm dividing the casing into a positive pressure chamber and a transformer chamber, and an outer circumference is hermetically coupled to a central portion of the power piston and the diaphragm and penetrates the rear cell. A valve body having the other end in communication with the atmosphere, a plunger installed in the cylinder portion formed in the axial direction inside one end of the valve body to control the air inflow into the transformer chamber, and a front end coupled to the rear end of the plunger And an input shaft that moves forward and backward in the axial direction by a brake pedal, and an output shaft having a rear end coaxially disposed at one end of the valve body to receive the force of the power piston and diaphragm displacement as the input shaft is advanced. It is arranged at the rear end of the output shaft and directly contact with the center of one end surface of the valve body And the plunger tip are in operation in the vehicle brake booster with a reaction disc arranged in the elastic material that a predetermined clearance maintained, One end surface 60a of the valve body 60 has a predetermined diameter D2 about the cylinder portion 66 such that a predetermined distance G2 is maintained at the center of the reaction disk 51 during initial brake operation. Brake booster for a vehicle, characterized in that the recess portion 67 is extended to have a. The method of claim 1, The bottom surface 67a of the recess portion 67 is formed to have a predetermined depth so as to maintain the same surface as the front end 72 of the plunger 70 during initial brake operation.