JP2561507B2 - Tandem brake booster - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a tandem brake booster used in a brake system of an automobile or the like.

(Prior art) In recent years, in response to higher engine speed and higher output, many vehicles use a brake booster that utilizes the negative pressure of the intake pipe of the engine to double the pedal effort of the brake pedal and output it to the master cylinder. The device is installed. Then, when a particularly large output is required, a tandem brake booster is used.

For example, as a conventional tandem type brake booster,
There is one disclosed in JP-A-60-154952,
This tandem brake booster 1 will be described with reference to FIG. 2. The inside of the main body 4 formed of the front shell 2 and the rear shell 3 is divided into two parts by the center plate 5 into the front and rear chambers. The room has a front diaphragm 6
A front constant pressure chamber 8 and a front variable pressure chamber 9 are defined by a front power piston 7 having a rear constant pressure chamber 12 and a rear variable pressure chamber 13 by a rear power piston 11 having a rear diaphragm 10. It is defined as
Further, the front shell 2 is provided with a negative pressure introducing pipe 14 for connecting a negative pressure source such as an intake manifold (not shown) to the front constant pressure chamber 8.

Inside the body 4, the valve body is movable in the axial direction.
15 is provided, and the hub of the valve body 15 is
Are fitted. A stopper portion 16a is formed at the rear portion of the hub 16 to prevent the hub 16 from coming off forward, and a recess portion 16b is formed at the front portion. The flange portion 18a of the output shaft 18 is slidably fitted in the recess 16b of the hub 16 with the reaction disc 17 interposed.

A center body 19 is fitted on the outer circumference of the hub 16, and the inner peripheral end portions of the rear power piston 11 and the rear diaphragm 10 are provided between the rear end surface of the center body 19 and the front end surface of the valve body 15. It is pinched. A cylindrical portion 7a is formed on the inner peripheral side of the front power piston 7, the rear end of which extends radially inward and is sandwiched between the hub 16 and a nut 20 screwed onto the hub 16. Then, by tightening this nut 20, the stopper portion 16a of the hub 16 is
The valve body 15, the rear power piston 11, the rear diaphragm 10, the center body 19, and the front power piston 7 are integrally connected to each other between the and the nut 20. The front diaphragm 6 is fixed to the front power piston 7 on the inner peripheral side by rivets 21 and the like.

Reference numeral 22 is a return spring interposed in a portion extending inside the rear end of the front shell 2 and the tubular portion 7a of the front power piston 7. The return spring 22 allows the front power piston 7 and the rear power piston 11 is always biased backwards.

Next, the valve mechanism 23 will be described.
Has a rear end protruding from the body 4 to the outside, and the protruding portion is formed in a cylindrical shape. And inside,
A plunger 25 connected to the input shaft 24 is slidably fitted.

Inside the valve body 15, a poppet valve 26 is provided, and its tip is attached to a valve seat 15a formed on the inner circumference of the valve body 15 and a valve seat 25a formed on the rear end of the plunger 25. It is located so that it can be seated.

A passage 19a is formed in the center body 19 to connect the rear variable pressure chamber 13 and the front variable pressure chamber 9. Further, a communication hole 27 that connects the front constant pressure chamber 8 and the rear constant pressure chamber 12 is formed between the center body 19 and the hub 16. Also,
The valve body 15 is formed with a passage 15b which communicates the inside of the valve body 15 with the rear constant pressure chamber 12 and a passage 15c which communicates with the rear variable pressure chamber 13.

According to the tandem brake booster 1 having the above configuration, when the brake pedal is depressed and the input shaft 24 is moved forward, the plunger 25 moves forward relative to the valve body 15 and the valve seat 25a of the plunger 25. The poppet valve 26 is separated and the atmosphere is introduced into the rear variable pressure chamber 13 through the passage 15c.
Further, the atmosphere is also introduced into the front variable pressure chamber 9 through the passage 19a of the center body 19. As a result, the front constant pressure chamber 8 and the rear constant pressure chamber 12 are always under negative pressure,
A differential pressure is generated between the front constant pressure chamber 8 and the front variable pressure chamber 9, and between the rear constant pressure chamber 12 and the rear variable pressure chamber 13, and the front power piston 7 and the rear power piston 11 move forward.
As a result, the valve body 15 and the hub 16 are advanced by a large force, and the thrust is transmitted to the output shaft 18.

(Problems to be solved by the invention) By the way, in automobiles and the like, it is desired to reduce the weight of the vehicle body in order to improve the fuel efficiency and the acceleration performance. And miniaturization is required.

However, in the conventional tandem brake booster 1, the nut 20 is used to sandwich the valve body 15, the rear power piston 11, the rear diaphragm 10, the center body 19 and the front power piston 7 with the stopper portion of the hub 16. However, since they are integrally connected to each other, the shape of each member is restricted, and the structure is complicated.

Further, since the front power piston 7 and the front diaphragm 6 are fixed on the inner peripheral side by the rivets 21 and the like, the number of parts is large.

Therefore, there is a problem that sufficient weight reduction cannot be expected.

The present invention has been made in view of the above problems, and an object thereof is to reduce the weight of a tandem brake booster by simplifying the configuration and reducing the number of parts. is there.

(Means for Solving the Problem) As means for achieving the above object, in a tandem brake booster, a cylindrical portion is provided so as to extend rearward on the inner peripheral side of the front power piston, and Fit a cylindrical center body on the outer periphery, sandwich the center body between the pressure receiving surface side of the front power piston and the bent part formed at the rear of the cylindrical part, and fix it to the front part of the center body. The formed latching portion and the pressure receiving surface sandwich and fix the inner peripheral end portion of the diaphragm provided in the front power piston.

(Operation) With the above configuration, since the center body is fixed to the front power piston by itself, other members are less restricted by the mounting shape of the center body, and the structure can be simplified. .

Furthermore, the fixing of the front power piston and the center body and the fixing of the front power piston and the front diaphragm do not require separate fixing means such as nuts, and the number of parts can be reduced.

(Embodiment) Next, an embodiment of the present invention will be described with reference to FIG. It should be noted that the same or corresponding members as those described in the related art are designated by the same reference numerals and the description thereof will be omitted.

The front power piston 28 is provided on the inner peripheral side so as to extend rearward of the tubular portion 28a, and the rear end thereof extends radially inward. Further, the base portion 30a of the output shaft 30 is fitted into the recess 29a formed at the front end of the valve body 29 with the reaction disc 17 interposed. Base 30a of output shaft 30
Protrudes forward from the recess 29a of the valve body 29, and a plurality of protrusions 30b are formed in the circumferential direction of the protruding portion.

Corresponding to the protrusion 30b, a cut-and-raised portion 28b is formed at the rear end of the tubular portion 28a of the front power piston 28, and the protrusion 30b is sandwiched between the portion 28c extending radially inward. Causes the front power piston 28 to move the output shaft 30
Fixed to. 29b is the valve body 29 of the output shaft 30.
In order to prevent it from coming off, it is a claw portion formed on the valve body 29, and has a shape capable of penetrating the front power piston 28 and locking the base portion 30a of the output shaft 30. Note that 29c is a valve seat that is seated on and off the poppet valve 26, 29d is a passage that connects the inside of the valve body 29 and the rear constant pressure chamber 12, and 29e is a passage that connects the inside of the valve body 29 and the rear variable pressure chamber 13.

A cylindrical center body 31 is fitted on the outer periphery of the cylindrical portion 28a of the front power piston 28. The center body 31 is provided on the pressure receiving surface side of the front power piston 28 and on the rear portion of the cylindrical portion 28a. It is fixed by sandwiching it with the formed bent portion 28d. The bent portion 28d is formed by being cut and raised, and the front constant pressure chamber 8 and the rear constant pressure chamber 12 are communicated with each other through the hole 32 formed by this cut and raised.

Further, in the front part of the center body 31, there is formed a hooking part 31a having a concave shape for fixing the inner peripheral end part of the front diaphragm 6 with the pressure receiving surface of the front power piston 28. The inner peripheral side of the diaphragm 6 is fixed to the front power piston 28 without using a rivet or the like.

A holding portion 28e for holding the other end of the return spring 33 whose one end abuts on the front shell 2 is cut and raised at a plurality of circumferential positions on the tubular portion 28c of the front power piston 28.

Next, a means for connecting the front variable pressure chamber 9 and the rear variable pressure chamber 13 will be described.

Holes 5a and 11a are formed in the center plate 5 and the rear power piston 11, respectively, and bellows 34 having a bellows shape are engaged with the holes. And this bellows 34
Is made of an elastic material, the rear power piston 11
It expands and contracts as the vehicle moves, and the front transformer room 9 and the rear transformer room 13 can always be communicated with each other.

According to the tandem type brake booster having the above configuration,
By depressing the brake pedal and advancing the input shaft 24, the valve mechanism 23 introduces the atmosphere into the rear variable pressure chamber 13 through the passage 29e, and further, the atmosphere is introduced into the front variable pressure chamber 9 through the bellows 34. It

As a result, a pressure difference is generated between the negative pressure and the constant pressure chambers 8 and 12, and the power pistons 11 and 28 move forward to transmit the boosted force to the output shaft 30.

When the depression force of the brake pedal is released, the valve mechanism 23 cuts off the communication between the atmosphere and the constant pressure chambers 9 and 13, and further connects the variable pressure chambers 9 and 13 to the constant pressure chambers 8 and 12. The pressure difference between the chambers disappears and the return spring 33
Thereby, each power piston 11, 28 is returned to the initial position.

Then, according to the present embodiment, the following unique effects are exhibited.

First, since the respective members of the valve body 29, the output shaft 30, the front power piston 28, and the center body 31 are combined without using separate parts such as the nut 20 and the rivet 21, the number of parts can be reduced.

Further, the center body 31 does not need to have a mounting structure for the valve body 29 or a passage for communicating the variable pressure chambers 9 and 13, and is a cylinder whose outer peripheral surface merely slides on the inner peripheral surface of the center plate 5. Since the plate-like shape is sufficient, the plate thickness can be made simple and the weight can be reduced.

Also, a holding portion that holds the other end of the return spring 33.
Since 28e is formed by cutting and raising from the cylindrical portion 28a of the front power piston 28, the position of the holding portion 28e can be freely set in the axial direction, and a compact return spring is provided.
33 can be used.

(Effects of the Invention) As described in detail above, the present invention is a tandem brake booster, in which a cylindrical center body is fitted to the outer periphery of the cylindrical portion of the front power piston, and It is sandwiched between the pressure receiving surface side of the piston and the bent part formed at the rear part of the tubular part, and fixed,
Since the inner peripheral end of the diaphragm provided on the front power piston is sandwiched and fixed by the front hooking portion of the center body and the pressure receiving surface, the structure can be simplified, and the parts can be The number of points can be reduced.

Therefore, the weight of the tandem brake booster can be reduced, the assembly can be facilitated, and the productivity can be improved and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of a tandem type brake booster of the present invention, and FIG. 2 is a vertical sectional view showing an example of a conventional tandem type brake booster. 2 ... Front shell 3 ... Rear shell 5 ... Center plate 6 ... Front diaphragm 8 ... Front constant pressure chamber 9 ... Front transformer chamber 10 ... Rear diaphragm 11 ... Rear power piston 12 ... Rear constant pressure chamber, 13 …… Rear transformer chamber 23 …… Valve mechanism, 24 …… Input shaft 28 …… Front power piston 28a …… Cylindrical part, 28d …… Bending part 30 …… Output shaft, 31 …… Center body 31a …… Hook Stop

Claims (1)

(57) [Claims] 1. A main plate formed by a front shell and a rear shell is divided into a front chamber and a rear chamber by a center plate,
Furthermore, the front and rear chambers are respectively divided into a front constant pressure chamber and a front variable pressure chamber, and a rear constant pressure chamber and a rear variable pressure chamber by means of a front power piston and a rear power piston each equipped with a diaphragm, and each constant pressure chamber is always kept in a negative pressure state. ,
Atmosphere is introduced into each of the variable pressure chambers by the movement of the input shaft by the valve mechanism, and the power pistons are moved forward due to the pressure difference between the constant pressure chambers and the variable pressure chambers, and the boosted thrust is transmitted to the output shaft. In the tandem-type brake booster, a cylindrical portion is extended rearward on the inner peripheral side of the front power piston, and a cylindrical center body is fitted on the outer periphery of the cylindrical portion, The body is fixed by being sandwiched between the pressure receiving surface side of the front power piston and the bent portion formed at the rear portion of the tubular portion, and the catching portion formed at the front portion of the center body and the pressure receiving surface. A tandem brake booster characterized in that an inner peripheral end portion of a diaphragm provided in the front power piston is sandwiched and fixed.