JPS63269768A - Reaction mechanism for brake booster - Google Patents

Abstract

PURPOSE:To reduce the axial length by loosely engaging a projecting portion of a push rod connected to a master cylinder with a hole of a valve body mounted to a power piston of a booster, rockably connecting the push rod with the valve body, and specifying a dimensional relationship at an engaged portion. CONSTITUTION:A brake booster includes a power piston 2 partitioning a shell 1 into a low-pressure chamber 4 and a variable-pressure chamber 5, and a valve body 6 mounted at a shaft portion of the power piston 2. A valve plunger 11 in a valve mechanism 7 received in the valve body 6 is operatively connected through a reaction disc 26 to a push rod 27. The push rod 27 is formed at its one end with an engagement portion 27a loosely engaged with a hole 6a formed at a shaft portion of the valve body 6. The valve body 6 is formed with a projecting portion 6b abutting against the disc 26. A length l of the engagement portion 27a is set in such a manner that when the push rod 27 is rocked at a maximum angle, an opening contour portion 6c of the hole 6a abuts against an outer peripheral surface of the engagement portion 27a.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a reaction force mechanism for a brake booster, and more particularly to a reaction mechanism for a brake booster equipped with a reaction disk.

"Prior Art" Conventionally, in order to shorten the axial dimension of the brake booster as a reaction force mechanism for a brake booster equipped with a reaction disk, the reaction disk was housed in a fitting part of a push rod. This is known (Utility Model Application No. 57-28059). That is, in the reaction mechanism of this type of brake booster, the fitting part formed at the end of the push rod is slidably fitted into the hole formed in the shaft part of the valve body, and the fitting part is slidably fitted into the hole formed in the shaft part of the valve body. A recess is formed in the joint portion and a reaction disk is accommodated in the recess, and the valve body is further formed with a protrusion that is fitted into the recess and abuts the reaction disk.

When the brake booster is activated, the brake reaction force applied from the master cylinder to the push rod is transmitted to the reaction disc, and a part of the brake reaction force transmitted to the reaction disc is received by the protrusion. , and the other part is transmitted to the brake pedal via a valve plunger constituting a valve mechanism and an input shaft connected to the valve plunger. At this time, the push rod moves forward together with the valve body, compressing the reaction disk and retreating relative to the valve body, so the fitting part of the push rod slides into the hole in the valve body. The protruding portion is slidably fitted into the recess.

By the way, due to assembly errors and manufacturing errors between the brake booster and the master cylinder, it is difficult to accurately arrange the axis of the brake booster and the master cylinder on the same straight line. The tip of the push rod of the force device is interlocked with the piston of the master cylinder at a position offset from the axis of the brake booster.

As a result, the push rod is installed in an inclined state with respect to the axis of the brake booster, and the valve body is also installed so that it can move forward and backward completely on the axis of the brake booster. Since the brake booster is built in such a way that it can tolerate some degree of rocking, as the push rod tilts, it moves forward and backward in a tilted state with respect to the axis of the brake booster.

When the push rod is moved forward and backward relative to the valve body in an inclined state, if the axial length of the fitting portion, that is, the sliding portion of the push rod that slides against the valve body is short, There is a possibility that the valve body and the push rod may bend and stick at the fitting part, and if the valve body and push rod stick, the brake reaction force will not be transmitted to the brake pedal, resulting in a no-reaction force state, making it impossible to perform smooth brake control.

``Problems to be Solved by the Invention'' For this reason, conventionally, the axial length of the fitting portion of the push rod is set to a predetermined length corresponding to its diameter to prevent the sticking. As a result, the axial length of the fitting portion becomes long, resulting in an increase in the axial dimension of the brake booster.

In particular, the fitting part of the push rod is loosely fitted into the hole of the valve body, and the protrusion formed on the valve body is slidably fitted into the recess formed in the fitting part of the push rod. In this case, since the gap between the protrusion and the recess becomes small, there is an advantage that the reaction disk accommodated in the recess can be prevented from being caught in the gap without taking any special measures. However, on the other hand, with such a configuration, not only does the axial dimension of the brake booster increase, but also when the push rod is moved forward and backward with respect to the valve body in an inclined state,
Since a bending moment acts on the base of the relatively small-diameter protrusion, cracks are likely to occur in that part, resulting in a decrease in the durability of the valve body.

"Means for Solving Problems" In view of such circumstances, the present invention connects the push rod to the valve body in a swingable manner, and at the same time, when a brake reaction force acts on the push rod, the push rod A rotational force is generated so that the valve body and the valve body are aligned in a straight line to prevent sticking, thereby shortening the axial dimension of the fitting part and reducing the axial dimension of the brake booster. It has been made possible to do so.

That is, in the reaction force mechanism of the brake booster, the present invention provides a structure in which there are The push rod is swingably connected to the valve body by forming a gap, and the push rod is fitted so that the opening contour of the hole in the valve body comes into contact with the outer peripheral surface of the fitting part when the push rod swings at its maximum. Set the axial dimension of the outer circumferential surface of the mating part, and roughly define the size of the gap so that the outer circumferential surface of the mating part abuts the opening contour of the hole and the recess when the push rod swings to its maximum. The opening contour is set to a size such that it comes into contact with the outer circumferential surface of the protrusion, and at the same time, the point of action of the brake reaction force on the tip of the push rod is formed by extending the outer circumferential surface of the protrusion in the axial direction. It is set to be inside the virtual cylindrical surface.

"Action" According to such a configuration, as will be explained in more detail later,
When a brake reaction force is applied to the above point of action, the point of action is inside the virtual cylindrical surface along the outer circumferential surface of the protrusion, so the push force connected to the piston of the master cylinder and inclined The valve body is rotated with respect to the rod in a direction in which the push rod and the valve body are aligned in a straight line, that is, in a direction in which sticking is prevented, around the contact area between the outer circumferential surface of the fitting portion and the opening contour of the hole. Thus, the push rod can slide smoothly against the valve body without sticking.

In addition, by setting the gap between the inner peripheral surface of the recess and the outer peripheral surface of the protrusion to a suitable value, the reaction disk accommodated in the recess can be bitten into the gap without taking any special measures. At the same time, it is possible to prevent the bending moment from acting on the base of the protrusion, thereby preventing the occurrence of cracks in that part, thereby improving the durability of the valve body.

``Embodiment'' The present invention will be described below with reference to an illustrated embodiment. In FIG. 1, a power piston 2 is slidably provided in a shell 1 of a brake booster, and a diaphragm 3 is attached to the back surface of the power piston 2. The inside of the shell 1 is divided into a constant pressure chamber 4 at the front and a variable pressure chamber 5 at the rear by the power piston 2 and the diaphragm 3. A valve body 6 is integrally attached to the shaft of the power piston 2.
A valve mechanism 7 for switching the flow path is housed within the valve body 6.

The valve mechanism 7 has a first valve seat 10 formed on the valve body 6.
, the rear side of the power piston 2, that is, the first valve seat 12 and both valve seats 10.
Valve body 1 is seated from the right side of the figure by the elastic force of spring 13
It is equipped with 4. Then, the first valve seat 10 and the valve body 14
The outside of the seat part communicates with the constant pressure chamber 4 through a passage 15 formed in the valve body 6, and the inside of the constant pressure chamber 4 is connected to the engine intake manifold through a negative pressure introduction pipe 16 provided in the shell 1. It is connected to a negative pressure source such as

On the other hand, the first valve seat lO, the valve body 14, and the second valve seat 1
2 and the valve body 14, the valve body 6
It communicates with the variable pressure chamber 5 through a passage 17 formed in , and further communicates with the atmosphere through a filter 18 inside the seat portion between the second valve seat 12 and the valve body 14 .

Further, the valve plunger 11 constituting the valve mechanism 7 is connected to an input shaft 24 that is linked to a brake pedal (not shown), and the valve plunger 11 is connected to a push rod 27 via a plate 25 and a reaction disk 26 made of an elastic body. I'm trying to make it work together. This push rod 27 passes through the seal member 28 and projects to the outside of the shell 1, and is interlocked with a piston of a master cylinder (not shown). Furthermore, the power piston 2 and valve body 6
etc. are normally held in the non-operating position shown by a return spring 29.

As shown in an enlarged view in FIG. 2, the large-diameter fitting portion 27a formed at the distal end of the push rod 27 is slidably and loosely fitted into the hole 6a formed in the shaft portion of the valve body 6. The reaction disk 26 has a recess 27 formed in the fitting portion 27a of the push rod 27.
It is accommodated in b. Further, the valve body 6 has a protrusion 6b formed on the shaft portion within the hole 6a, which is loosely fitted into the recess 27b and abuts against the reaction disk 26.

Therefore, the push rod 27 has its fitting portion 27
There is a gap δ1 between the outer circumferential surface of the hole 6a of the valve body 6 and the inner circumferential surface of the hole 6a of the valve body 6, and there is also a gap δ2 between the inner circumferential surface of the recess 27b and the outer circumferential surface of the protrusion 6b. In other words, the push rod 27 is swingably connected to the valve body 6 at the fitting portion 27a.

The axial dimension of the outer circumferential surface of the fitting portion 27a is determined by the opening contour of the hole 6a of the valve body 6 even when the brake booster is in operation when the push rod 27 swings at the maximum angle. The dimensions are set such that the portion 6c abuts the outer circumferential surface of the fitting portion 27a, that is, the outer circumferential surface of the fitting portion 27a projects outward from the hole 6a.

Further, the sizes of the gaps δ1 and δ2 are such that when the push rod 27 swings at its maximum, the size of the gaps δ1 and δ2 is determined so that the fitting portion 27
The size is set such that the outer circumferential surface of the hole 6a abuts the opening contour 6C of the hole 6a, and the opening contour 27c of the recess 27b abuts the outer circumferential surface of the protrusion 6b.

In other words, when the push rod 27 swings to the maximum angle, the two outer circumferential surfaces of the fitting portion 27a do not come into contact with the inner circumferential surface of the hole 6a as shown in FIG. As shown in FIG. 5, the size is set so that the two inner peripheral surfaces of the recess 27b do not come into contact with the outer peripheral surface of the protrusion 6b.

Furthermore, the sizes of the gaps δ1 and δ2 are such that, as shown in FIG. It is set to be inside a virtual cylindrical surface 31 formed by extending the outer circumferential surface of the cylinder in the axial direction.

Next, to describe an example of the specific dimensions of the above-mentioned parts, in FIG.
The axial dimension 1' between the opening contour 6c is 3 to 13I.
Ill, the axial dimension 1″ from the right end surface of the reaction disk 26 to the opening contour portion 27c is 0.94 to 4.39.
mm, and the thickness of the reaction disk 26 is 3 to 8 mm.
It can be made into mm.

Furthermore, when considering the surface pressure and jumping characteristics of the reaction disk 26, the inner diameter dimension d1 of the recessed portion 2'7b that accommodates it is preferably 18 to 32 mm, and based on this, the outer diameter dimension d2 of the fitting portion 27a is set to 20 to 32 mm. 38 mm, and the inner diameter dimension d3 of the hole 6a can be 20.2 to 39.6 mm.

Further, the size of the gap δ2 is at least 0.0 mm for smooth sliding between the push rod 27 and the valve body 6.
A gap of 0.05 mm or more is required, but in order to prevent the reaction disk 26 from getting caught in the gap δ2 and reducing durability without taking special measures, the gap should be 0.35 mm or more.
It is desirable that the thickness be less than mm. However, when a ring 35 for preventing jamming is provided, the gap δ2 can be expanded to 1 oIn.

On the other hand, regarding the gap δ1, even if it is possible to make it 1.6 mm or more, if it is made too large, the characteristics may become unstable, so it is desirable to make it less than that, and it is preferable to make it larger than the gap δ2. desirable. Therefore, the relationship between the gaps δ1 and δ2 is 0.05nuo≦δ2
The maximum value of the gap δ2 at this time varies depending on the presence or absence of the ring 35 for preventing jamming, as described above.

In the above configuration, when the brake pedal (not shown) is depressed and the input shaft 24 and the valve plunger 11 are moved to the left, the valve body 14 is seated on the first valve seat lO of the valve body 6 and is connected to the variable pressure chamber 5 at a constant pressure. Communication between the chambers 4 is cut off, and the valve body 14 is separated from the second valve seat 12 of the valve plunger 11 to allow communication between the atmosphere and the variable pressure chamber 5. As a result, atmospheric air is supplied into the variable pressure chamber 5, and the pressure difference between the front and rear sides of the power piston 2 causes the power piston 2 to move forward against the elastic force of the return spring 29, similar to a conventional brake booster. , a braking action is performed.

At this time, the brake reaction force applied to the push rod 27 is transmitted from the push rod 27 to the reaction disc 26, and part of it is received by the protrusion 6b of the valve body 6, and the rest is received by the plate 25,
It is transmitted to a brake pedal (not shown) via the valve plunger 11 and the human power shaft 24.

By the way, as mentioned above, due to assembly errors and manufacturing errors between the brake booster and the master cylinder (not shown),
The point of contact between the tip of the push rod 27 and the piston of the master cylinder, that is, the point of application of the brake reaction force 3
0 deviates from the axis 32 of the brake booster, the push rod 27 will be assembled at an angle with respect to the 'l1lh line 32.

However, even if the push rod 27 is assembled at the maximum inclination angle shown in FIG.
When a brake reaction force is applied to , the point of application 30 is inside the virtual cylindrical surface 31 along the outer circumferential surface of the protrusion 6b, so that the tip is connected to the piston of the master cylinder and relatively With respect to the push rod 27 whose inclination angle is fixed, the valve body 6 moves counterclockwise in FIG. In other words, push rod 27
and the valve body 6 are now rotated in a direction in which they are aligned in a straight line.

As a result, the opening contour 27c of the recess 27b becomes the protrusion 6b.
Since the push rod 27 can move to the right relative to the valve body 6 while being prevented from biting into the outer peripheral surface of the valve body 6, the push rod 27 can be prevented from being stuck to the valve body 6. .

On the other hand, in the state shown in FIGS. 4 and 5, or in FIG. 3, the axial dimension 2 of the outer peripheral surface of the fitting portion 27a is short;
In a state where the outer peripheral surface corner portion 34 is in contact with the inner peripheral surface of the hole 6a, it is not possible to apply the above-mentioned rotational force to the valve body 6, and therefore the push rod 27 and the valve body 6 are The sliding resistance becomes large, resulting in sticking in the worst case. This also applies when the point of action 30 is outside the virtual cylindrical surface 31 along the outer peripheral surface of the protrusion 6b when the push rod 27 swings at its maximum.

Next, FIGS. 6 and 7 show another embodiment of the present invention. In this embodiment, the passage 15 is communicated with the hole 6a, and as a result, the inner circumference of the hole 6a is Part of the surface is missing. Therefore, in this embodiment, the passage 15
A generally T-shaped stopper member 36 is attached therein, and the stopper member 36 and the valve body 6 form an opening contour 6C of the hole 6a. As shown in FIG. 8, a stopper member 36' provided in the passage 15
may be formed by bending a strip-shaped thin plate material into an appropriate shape.

In the embodiment shown in FIGS. 9 and 10, the passage 15 is connected to the hole 6.
a, the opening side of the hole 6a is enlarged in diameter, and a ring-shaped stopper member 37 is provided at the opening of the hole 6a. This ring-shaped stopper member 37 has a large number of through holes 38 that communicate with the passage 15, and the inner peripheral edge of the center hole 37a of the stopper member 37 forms the opening contour 6c of the hole 6a. ing. In this case, the gap δ1 between the inner peripheral edge of the center hole 37a and the outer peripheral surface of the fitting portion 27a of the push rod 27 is important; The gap with the surface can be made larger than the gap δ1.

"Effects of the Invention" As described above, according to the present invention, the axial length of the push rod fitting part, which was conventionally required, can be set to less than the length required to prevent sticking. Since sticking can be prevented by satisfying the necessary conditions of the present invention, it is possible to achieve the effect that the axial dimension of the brake booster can be shortened compared to the conventional brake booster.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG.
3 is an enlarged view of the figure, FIG. 3 is a cross-sectional view exaggerating the tilted state of the push rod, FIGS. 4 and 5 are cross-sectional views corresponding to FIG. 3, which do not satisfy the conditions of the present invention, respectively, FIG. 6 is a front view of main parts showing another embodiment of the present invention, FIG. 7 is a sectional view of FIG. 6, and FIGS. 8 and 9 are main parts showing still other embodiments of the present invention. 10 is a sectional view of FIG. 9. 1... Shell 6... Valve body 6a...
Hole 6b...Protrusion 6c---Opening contour 26--Reaction disk 27...Push rod 27a--Fitting part 27b--Concave part
27c - Opening contour part 30 - Point of action 3
1-... Virtual cylindrical surface δ1, δ2... Gap 1...
Axial dimensions Fig. 3 Fig. 8 Fig. 9 Fig. 10

Claims (1)

[Claims] A fitting portion formed at the end of the push rod is slidably fitted into a hole formed in the shaft portion of the valve body, and a recess is formed in the fitting portion. In the reaction mechanism of the brake booster, the reaction mechanism of the brake booster has a reaction disk accommodated therein, and a protrusion formed in the hole of the valve body to fit into the recess and come into contact with the reaction disk, the inner circumferential surface of the hole. and the outer circumferential surface of the fitting part, and between the inner circumferential surface of the recess and the outer circumferential surface of the protrusion, respectively, to connect the push rod to the valve body in a swingable manner. The axial dimension of the outer peripheral surface of the fitting part is set so that the opening contour of the hole in the valve body comes into contact with the outer peripheral surface of the fitting part when the rod swings at maximum, and the size of the gap is set so that the opening contour of the hole in the valve body comes into contact with the outer peripheral surface of the fitting part. At the same time, the push rod is set to a size such that the outer peripheral surface of the fitting portion contacts the opening contour of the hole and the opening contour of the recess contacts the outer peripheral surface of the protruding portion when the rod swings at its maximum. A reaction force of a brake booster, characterized in that the point of action of the brake reaction force on the tip part is set to be inside a virtual cylindrical surface formed by extending the outer peripheral surface of the protruding part in the axial direction. mechanism.