JP3774880B2 - Brake booster - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a brake booster used in a brake system of a vehicle, and more particularly, to a brake booster that combines a tandem pneumatic booster and a brake auxiliary device.
[0002]
[Prior art]
Conventionally, as this type of brake booster, there is one described in, for example, SAE 950761 (Efective Saf-ety to Reduce Road Accidents). As shown in FIG. 2, this includes a shell body 1 in which a front shell 2 and a rear shell 3 are connected by a tie rod 4, and the inside of the shell body 1 is divided into two front and rear chambers by a center shell 5. The front and rear two chambers are further divided into constant pressure chambers 10 and 11 and variable pressure chambers 12 and 13 by power pistons 8 and 9 having diaphragms 6 and 7. A cylindrical valve body 14 having a small-diameter shaft hole 14a is fitted and supported in the center of each of the power pistons 8 and 9, and the valve body 14 hermetically seals the center shell 5 and the rear shell 3. In addition, it is slidably inserted and extended rearward of the rear shell 3.
[0003]
The two constant pressure chambers 10 and 11 are communicated with each other through a radial hole 15 provided in the valve body 14, and the two variable pressure chambers 12 and 13 are in a flexible tube 16 surrounding the tie rod 4. The passages 17 communicate with each other. The valve body 14 also has an axial hole (negative pressure passage) 18 that communicates the rear end inside with the front constant pressure chamber 10 and a radial hole (atmosphere passage) that communicates the rear end inside with the rear variable chamber 13. ) 19 is formed.
[0004]
A guide member 20 is housed inside the valve body 14 with a hollow shaft portion fitted in the shaft hole 14a, and an input shaft interlocked with a brake pedal (not shown) is provided in the hollow shaft portion of the guide member 20. A distal end portion of a plunger 22 connected to 21 is slidably inserted. A cylindrical valve seat member 24 having an annular valve seat (atmospheric valve seat) 23 at its rear end is slidably disposed in the shaft hole 14 a in the valve body 14. The valve seat member 24 is normally urged to the rear side by a spring 25 disposed around the plunger 22, and the rear end side engaging portion 24 a is engaged with the plunger 22, thereby the valve seat member. 24 is always interlocked with the plunger 22. An annular valve seat (negative pressure valve seat) 26 including the opening edge of the negative pressure passage 18 is formed on the inner surface of the rear end side of the valve body 14, and the rear end portion is supported by the valve body 14. The poppet valve 27 is configured to be separated from and seated on the valve seat 26 and the atmospheric valve seat 23.
[0005]
Note that a reaction disk 28, a pressure receiving plate 29, and a base end large diameter portion of the output shaft 30 are held on the front side of the guide member 20, and the front end portion of the output shaft 30 is located on the front shell 2. It is inserted into the rear end portion of the master cylinder 31 introduced into the shell body 1 through. Each of the valve body 14 and the input shaft 21 is positioned by the return springs 32 and 33 in the inoperative state shown in the figure.
[0006]
The above-described configuration is the same as that of a conventional general tandem type pneumatic booster except that the valve seat member 24 having the atmospheric valve seat 23 is separated from the plunger 22. When the brake pedal is stepped on from the inoperative state shown in the figure, the input shaft 21 moves forward, the plunger 22 and the valve seat member 24 move integrally to the left in the figure, the atmospheric valve seat 23 opens, The air is introduced into the chambers 13 and 12 through the air passage 19 and the passage 17 in the flexible tube 16. As a result, for example, a differential pressure is generated between the constant pressure chambers 10 and 11 into which the engine negative pressure is introduced and the variable pressure chambers 12 and 13, and the power pistons 8 and 9 on the front side and the rear side are propelled. An output proportional to the pedaling force is transmitted to the output shaft 29 via the valve body 14, while a part of the reaction force at this time is transmitted from the reaction disk 28 to the input shaft 21 via the plunger 22. When there is no pedaling force from the brake pedal, the input shaft 21 is first moved rightward (retracted) by the restoring force of the return spring 33, the plunger 22 is also retracted, the atmospheric valve seat 23 is closed, and the negative pressure is used. The valve seat 26 is opened and negative pressure is introduced into both the variable pressure chambers 13 and 12 to eliminate the above-described differential pressure. Thereafter, the valve body 14 is returned to the original position by the pressing force of the return spring 31.
[0007]
The valve body 14 is embedded with a solenoid 34 that constitutes a brake auxiliary device. When the solenoid 34 is excited during emergency braking, the valve seat member 24 resists the urging force of the spring 25. To move relative to the plunger 22 (advance). As a result, the air valve seat 23 is opened widely, a large amount of air is suddenly introduced into the variable pressure chambers 12 and 11, the output is increased at once, and so-called full braking is performed. A harness 35 for exciting the solenoid 34 is led out to the outside through the front wall of the front shell 2 after the inside of the shell body 1 is routed.
[0008]
[Problems to be solved by the invention]
By the way, the excitation of the solenoid 34 described above has been conventionally controlled based on a signal from a sensor for detecting the depression speed of the brake pedal. Therefore, it is quite troublesome to determine whether or not emergency braking is performed based on the depression speed of the brake pedal.
[0009]
Therefore, in the above-described brake booster, the main body 36a of the stroke sensor 36 is attached to the front surface of the front shell 2, and the tip of the detection rod 36b is brought into contact with the front-side power piston 8, so From the displacement, it is determined whether or not emergency braking is performed, and the solenoid 34 is excited.
However, according to such a mounting structure of the stroke sensor 36, the stroke sensor 36 protrudes greatly from the front surface of the shell body 1, and the whole body is large because it is a tandem type. When mounted, there is a problem that interference easily occurs with other vehicle parts, and mountability is significantly deteriorated.
[0010]
In addition, as a brake auxiliary device, as described above, the valve seat member 24 is shared with the pneumatic booster, and the solenoid 34 for driving the valve seat member 24 is embedded in the valve body 14. A working fluid source is provided separately from the booster, and working fluid is supplied from the working fluid source to the booster chamber of the booster according to the depression speed of the brake pedal. Even in a brake booster equipped with such a brake assist device, the same problem as described above occurs when the stroke sensor 36 is attached as described above.
[0011]
The present invention has been made in view of the above-described conventional problems, and the object of the present invention is to improve the mounting structure of the stroke sensor constituting the brake auxiliary device, thereby improving the mountability to the vehicle. The object is to provide a brake booster.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention divides the inside of a shell body into two front and rear chambers by a center shell, and each of the divided two front and rear chambers is separated from a constant pressure chamber by a power piston provided with a diaphragm. Divided into variable pressure chambers, each power piston supports a valve body that is slidably inserted through the center shell and the shell main body and extends rearward. A tandem pneumatic booster with a valve mechanism that generates a differential pressure between the constant pressure chamber and the variable pressure chamber, and a working fluid in the variable pressure chamber based on a signal from a stroke sensor that detects the displacement of the power piston. A brake booster comprising a brake auxiliary device for supplying the stroke sensor, wherein the stroke sensor is substantially entirely housed in the shell body, Body while being supported by the front wall and the center shell, the detection rod, characterized in that a configuration that is brought into contact with the rear side power piston.
[0013]
In the brake booster configured as described above, since the entire stroke sensor is housed in the shell body of the pneumatic booster, large protrusions are eliminated from the front surface of the shell body.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0015]
FIG. 1 shows a structure of a main part of a brake booster as one embodiment of the present invention. Since the basic structure of the brake booster is the same as that shown in FIG. 2, the same reference numerals are given to the same parts and the description will be made with reference to FIG. . In the present embodiment, the stroke sensor 36 for detecting the displacement of the power pistons 8 and 9 is almost entirely accommodated in the shell body 1, and the tip of the detection rod 36 b is brought into contact with the rear side power piston 9. ing.
[0016]
More specifically, the front side power piston 8 in the shell main body 1 is integrally formed with a cylindrical portion 37 that bulges toward the front shell 2, and the main body 36 a of the stroke sensor 36 is connected to the cylindrical portion 36. Is extended in the axial direction of the valve body 14. Both ends of the main body 36 a of the stroke sensor 36 penetrate the front shell 2 and the center shell 5 and extend slightly outside them, and seal members 38, 39 are attached to the front shell 2 and the center shell 5. Are connected through.
[0017]
The stroke sensor 36 is composed of a linear gauge, a magnescale or the like, and a detection mechanism for detecting the amount of movement of the detection rod 36b is built in the main body 36a. Thus, the signal of the stroke sensor 36 is sent to the control device 40 that controls the energization of the solenoid 34 (FIG. 2) embedded in the valve body 14. The control device 40 compares the function of calculating the propulsion speed (forward speed) of the power pistons 8 and 9 based on the signal from the stroke sensor 36 and the calculation result with a reference value. The solenoid 34 is energized.
[0018]
In the present brake booster, during normal braking, the plunger 22 and the valve seat member 24 are integrally moved to the left in FIG. The seat 23 opens, the atmosphere is gradually introduced into the variable pressure chambers 13 and 12, the differential pressure between the constant pressure chambers 10 and 11 and the variable pressure chambers 13 and 12 gradually increases, and the front and rear power pistons 8 and 9 A boosting action is performed in which the output is proportionally increased in accordance with the pushing force.
[0019]
On the other hand, at the time of emergency braking, the forward speed of the input shaft 21 is increased, so that the opening of the air valve seat 23 is accelerated, and the amount of air introduced into the variable pressure chambers 13 and 12 is increased. The forward speed of the pistons 8 and 9 is increased. The displacement of the rear power piston 9 is monitored by the control device 40 via the stroke sensor 36, and the control device 40 calculates the forward speed of the power piston 9 based on the signal from the stroke sensor 36. When the calculation result exceeds the reference value, it is determined that emergency braking is performed, and a current is sent to the solenoid 34 through the harness 35. Then, the solenoid 34 is energized and the valve seat member 24 moves forward against the plunger 22 against the biasing force of the spring 25, and the atmospheric valve seat 23 is opened widely. The air is suddenly introduced, and the output increases at a stroke regardless of the pedaling force, so-called full braking is performed.
[0020]
The brake booster is attached to the vehicle using a threaded portion 4 a (FIG. 2) at the tip of a tie rod 4 that protrudes rearward from the rear shell 3, but almost the entire stroke sensor 36 is accommodated in the shell body 1. Since there are no large protrusions on the front surface of the shell body 1, interference with other vehicle parts is significantly reduced during this mounting, and therefore mounting on the vehicle is facilitated. Moreover, since the main body 36a of the stroke sensor 36 is inserted through the front side power piston 8 and both ends thereof are supported by the front shell 2 and the center shell 5, the power pistons 8 and 9 and the valve body 14 for the shell main body 1 are provided. The relative rotation of the solenoid 34 is restricted, and the harness 35 of the solenoid 34 as well as the diaphragms 6 and 7 are prevented from being kinked, and the durability of the apparatus is improved.
[0021]
【The invention's effect】
As described above, according to the brake booster according to the present invention, almost the entire stroke sensor constituting the brake auxiliary device is housed in the shell body of the tandem type pneumatic booster, so that it is large from the front of the shell body. Protrusions are eliminated, and the mountability on the vehicle is significantly improved.
Further, since the stroke sensor regulates the relative rotation of the power piston and the valve body with respect to the shell body, an excessive force is not applied to the components, and the durability reliability as the device is improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main structure of a brake booster according to the present invention.
FIG. 2 is a cross-sectional view showing an overall structure of a brake booster to which the present invention is applied and a conventional stroke sensor mounting structure corresponding thereto.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Shell main body 5 Center shell 6, 7 Diaphragm 8, 9 Power piston 10, 11 Constant pressure chamber 12, 13 Variable pressure chamber 14 Valve body 21 Input shaft 22 Valve seat member 23 Atmospheric valve seat 24 Plunger 26 Negative pressure valve seat 27 Poppet valve 28 Reaction disk 30 Output shaft 34 Solenoid 36 Stroke sensor 40 Control device

Claims (1)

The shell body is divided into two front and rear chambers by a center shell, and each of the divided front and rear two chambers is divided into a constant pressure chamber and a variable pressure chamber by a power piston equipped with a diaphragm. A valve body that is slidably inserted through the center shell and the shell main body and extends rearward, and the valve body is coupled with the input shaft so that a difference is provided between the constant pressure chamber and the variable pressure chamber. A brake comprising a tandem pressure booster with a valve mechanism for generating pressure, and a brake auxiliary device for supplying working fluid to the variable pressure chamber based on a signal from a stroke sensor for detecting displacement of the power piston In the booster, the stroke sensor is almost entirely accommodated in the shell body, and the front wall of the shell body and the center shell Optionally with the support, the detection rod, rear brake booster, characterized in that it is in contact with the power piston.

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