JPH04257760A - Gas pressure booster for brake - Google Patents

Abstract

PURPOSE:To provide a gas pressure booster for a brake which changes a boosting ratio in two stages and has excellent durability of a reaction disc. CONSTITUTION:During forward movement of a power piston, a subplunger 94 is first brought into contact with a reaction disc 78, and boosting is effected with a high boosting ratio when an input is high. When an input is increased, the subplunger 94 is gradually retracted in a plunger body 86 as a resistance force increased with the increase of the reaction force of the reaction disc 78 is exerted on the subplunger from a rubber block 98. Finally, the plunger body is brought into contact with the reaction disc 78 in a state that the plunger body 86 is positioned flush with the subplunger 94, and a boosting ratio is decreased. Unreasonable deformation does not occur to the reaction disc 78 in a region where a force is high and service-life is prevented from decreasing.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a pressure booster for brakes that uses gas pressure to boost the operating force of a brake device, and particularly relates to a pressure booster for brakes that uses gas pressure to boost the operating force of a brake device. This relates to improving the durability of reaction discs.

0002

[Prior Art] Generally, a pneumatic booster for brakes is
It is composed as follows. (a) a housing; (b) a power piston that is disposed movably in the axial direction within the housing and operates according to the pressure difference between a variable pressure chamber and a constant pressure chamber formed on both sides; and (c) a power piston. a plunger axially movably fitted and connected to the input member; (d) an output member axially movable relative to the housing and the power piston; and (e) reaction from the output member. a reaction disk made of an elastic body that distributes and transmits force to the power piston and plunger;
(f) It is held by the power piston, and by relative movement of the plunger with respect to the power piston, the variable pressure chamber and the constant pressure chamber are brought into communication with each other so that the pressure difference between the two chambers is zero, and the communication is cut off and the pressure difference between the two chambers is reduced to 0. The control valve device is configured to switch to a state in which a pressure difference is generated by allowing inflow of working gas.

In this booster, when an input is applied to the input member and the plunger moves forward, the control valve device is switched, a pressure difference is created between the variable pressure chamber and the constant pressure chamber, the power piston moves forward, and the input of the input member is increased. is boosted and output from the output member. The power piston stops at a position where the forward force due to the pressure difference between the variable pressure chamber and the constant pressure chamber is balanced with the reaction force applied from the reaction disk, and the input applied to the input member is determined by the pressure receiving area of the plunger against the reaction disk and the output. The output is multiplied by a multiplication factor determined by the ratio of the pressure receiving area of the member to the reaction disk.

[0004] Japanese Utility Model Application Publication No. 56-62268 describes a gas pressure booster in which the above-mentioned boosting factor can be changed in two stages. In this gas pressure booster, the plunger is provided with a protrusion that protrudes from the center of its tip surface, and when the plunger moves forward due to input to the input member, the protrusion first contacts the reaction disk and then advances further. As a result, the entire tip surface of the plunger comes into contact with the reaction disk. If only the protrusion contacts the reaction disk and the annular portion around the protrusion is away from the reaction disk, the protrusion receives part of the reaction force that the annular portion should receive from the reaction disk, and the rest is absorbed by the annular portion. The reaction force that the power piston receives and is applied to the plunger is smaller than when its entire tip surface contacts the reaction disk, and a larger power factor is obtained when only the protrusion contacts the reaction disk. If the input applied to the input member increases and the entire tip surface of the plunger comes into contact with the reaction disk, the boost factor will be the ratio of the area of the entire tip surface to the pressure receiving area of the reaction disk, and if only the protrusion comes into contact As the input member becomes smaller, the operation feeling of the input member becomes harder, and the user can understand that a large output is obtained.

[0005]

[Problems to be Solved by the Invention] However, in this gas pressure booster, when the entire tip surface of the plunger comes into contact with the reaction disk, the protrusion bites into the reaction disk and deforms it into a concave shape. There was a problem that it easily deteriorated under stress and had poor durability.

[0006] The present invention has been made with the object of providing a gas pressure booster that can change the boost factor in two stages and has a highly durable reaction disk.

[0007]

[Means for Solving the Problems] In order to solve the above problems, the gas pressure booster of the present invention includes a plunger body and a fitting hole opened at the center of the tip of the plunger body in the axial direction. It is arranged between a movably fitted sub-plunger and the sub-plunger and the plunger body, and the sub-plunger is kept protruding from the plunger body while the reaction force applied from the reaction disk is small, and the reaction force is reduced. The gist of the present invention is to include a resistance force imparting member that allows retraction into the fitting hole as the amount of retraction increases, and provides a resistance force that increases as the amount of retraction increases.

[0008]

[Operation] In the brake pneumatic booster configured as described above, when an input is applied to the input member and the plunger moves forward, the sub-plunger first comes into contact with the reaction disk, and the input from the input member produces a large boost. The output is multiplied by a certain percentage. After the sub-plunger contacts the reaction disk, when the input increases and the plunger moves forward, the sub-plunger retracts into the fitting hole due to the increased reaction force from the reaction disk. Since the sub-plunger is provided with a resistance force that increases as the reaction force from the reaction disk increases, the sub-plunger gradually retracts into the plunger body while resisting. Therefore, the plunger body does not initially come into contact with the reaction disk, and the sub-plunger acts in the same way as the protrusion in the pneumatic booster, resulting in a large boost factor. However, the plunger body eventually comes into contact with the reaction disk, and the power factor decreases thereafter. At this point, if the tip surface of the sub-plunger is aligned with the tip surface of the plunger body and the sub-plunger is prevented from retracting any further, the entire plunger will be on a flat surface in the area of high pressure within the reaction disk. It comes into contact with the reaction disk.

However, this is not essential. Even when the sub-plunger remains protruding from the plunger body even in a region where the pressure inside the reaction disk is high, the amount of deformation of the reaction disk is reduced by the amount that the sub-plunger is retracted into the plunger body. Conversely, in regions of high pressure within the reaction disk, the sub-plunger may retract into the plunger body. In this case, the central portion of the reaction disk will bulge, but there is no problem as long as the amount is small.

0010

As described above, in the brake pneumatic booster of the present invention, the boost factor can be changed in two stages. Moreover, in a region where the pressure of the reaction disk is high, the amount of protrusion of the sub-plunger from the plunger body becomes 0, decreases, or is slightly retracted,
In any case, the protrusions do not dig into the reaction disk as much as in the past, and the durability of the disk is improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a case in which the present invention is applied to a brake vacuum booster will be explained in detail with reference to the drawings. In FIG. 3, 10 is a housing. This housing 10 has an airtight chamber formed by a front shell 20 and a rear shell 22, and the chamber is divided into two by a diaphragm type power piston 24 into a constant pressure chamber 26 and a variable pressure chamber 28. The constant pressure chamber 26 is a pipe joint 30
It is connected to a negative pressure source such as the engine's intake manifold or vacuum pump, and is constantly under negative pressure.
The variable pressure chamber 28 is selectively communicated with the constant pressure chamber 26 or the atmosphere by a control valve device to be described later, so that the internal pressure thereof is controlled. The power piston 24 also includes a bowl-shaped diaphragm plate 36 and a diaphragm plate 36.
Consisting of a diaphragm rubber 38 whose periphery is fixed within the empty chamber and a power piston main body 40 fixed to the center of the diaphragm plate 36, the constant pressure chamber 2
The variable pressure chamber 28 is driven in the axial direction based on the pressure difference between the variable pressure chamber 28 and the variable pressure chamber 28. 41 is a return spring that urges the power piston 24 to the rearward end position shown in the figure.

The power piston body 40 is provided with a control valve device 42 and a relay mechanism 44. Control valve device 4
2 is a first valve seat 4 formed on the power piston body 40;
6 and is slidably fitted to the power piston body 40,
A second valve seat 52 formed on a valve plunger 50 connected to an input rod 48 as an input member, and both valve seats 46
. In addition, the power piston body 40
Air flow passages 56 and 58 communicating with the constant pressure chamber 26 and the variable pressure chamber 28 are formed in the chamber. Therefore, when the valve element 54 is seated on the second valve seat 52, the air flow passages 56 and 58 pass through the constant pressure chamber 22.
and the variable pressure chamber 28, and the pressure difference is 0. However, as the input rod 48 is moved forward, the valve element 54 and the second valve seat 52 are separated, and the valve element 54 is connected to the first valve seat 52. When seated on the valve seat 46, the air flow passage 5
6 is closed, and the atmosphere is communicated with the variable pressure chamber 28 through the air flow passage 58, and a pressure difference is created between the two chambers 26 and 28, causing the power piston 24 to move forward.

A stopper key 62 is inserted into a cutout hole 60 provided in the power piston body 40, and is prevented from being pulled out by a stopper ring (not shown). This stopper key 62 engages with an annular groove 64 formed in the middle portion of the valve plunger 50 to restrict the forward end and the backward end of the valve plunger 50. Also,
The input rod 48 has an end opposite to the side connected to the valve plunger 50 connected to the air filter 6 held at the end protruding from the housing 10 of the power piston body 40.
6 and protrudes from the spring 68.
is urged in the backward direction by Air filter 66
is for purifying the air flowing into the variable pressure chamber 28. A boot 70 covers a portion of the power piston body 40 that protrudes from the rear shell 22.

An output rod 72 serving as an output member is fitted into the front shell 20 so as to be movable in the axial direction while penetrating the center thereof. The auxiliary force of the power piston 24 corresponding to this is transmitted to the output rod 72 via the relay mechanism 44. The relay mechanism 44 includes a small-diameter plunger portion 7 formed at the front end of the valve plunger 50.
4, a large-diameter plunger portion 76 provided at the rear end of the output rod 72, and a reaction disk 78 made of rubber. A stepped hole is formed in the power piston body 40, and the small diameter plunger portion 74 is fitted into the small diameter hole portion 80 (see FIG. 1(A)) of the stepped hole so as to be slidable in the axial direction. The large diameter plunger portion 76 has a large diameter hole portion 82 (
(see FIG. 1(A)), and the reaction disk 78 is disposed between the large-diameter plunger portion 76 and the bottom surface of the large-diameter hole portion 82.

FIG. 1A shows an enlarged view of the tip of the small-diameter plunger portion 74. A bottomed fitting hole 88 that opens toward the reaction disk 78 is formed in the center of the tip of the plunger body 86 of the small-diameter plunger portion 74 . This fitting hole 88 has a stepped shape, and the tip surface 9 facing the reaction disk 78 of the small diameter plunger portion 74
A sub-plunger 94 is fitted into the small-diameter hole 92 that opens at 0 so as to be movable in the axial direction. In addition, the fitting hole 88
A rubber block 98 as a resistance force imparting member is disposed in the large diameter hole 96 . This rubber block 98 has a cylindrical shape with the same diameter as the sub-plunger 94, and is fitted into and fixed in a recess 102 formed at the bottom of the fitting hole 88 at a protrusion 100. The small diameter plunger portion 74 is in the position shown in FIG.
protrudes a short distance from the tip surface 90 of the plunger body 86 and is maintained a short distance away from the reaction disk 78.

A radially outward flange 104 is formed at the protruding end of the sub-plunger 94. on the other hand,
A counterbore 106 is formed at the opening of the fitting hole 88, and the flange 104 is accommodated in the counterbore 106 when the sub-plunger 94 is retracted the most into the fitting hole 88. In this state, the sub-plunger 94
The distal end surface of the plunger body 86 and the distal end surface of the plunger body 86 are positioned on the same plane, and the engagement between the flange 104 and the counterbore portion 106 prevents the sub-plunger 94 from retracting further.

In the vacuum booster configured as described above, when the brake pedal is not depressed, the valve element 54 is seated on the second valve seat 52 and the first valve seat 46 and the valve element 54 are separated. Therefore, the variable pressure chamber 26 and the constant pressure chamber 28 communicate with each other, and no pressure difference is generated on both sides of the power piston 24. Therefore, the power piston body 40 and the output rod 7
2 is positioned at the rearmost position by the biasing force of the return spring 41. FIG. 3 shows this state.

When the input rod 48 is moved forward by operating the brake pedal from this state, the valve plunger 50 is moved forward relative to the power piston body 40, and the valve element 54 is seated on the first valve seat 46. At the same time, the second valve seat 52 and the valve element 5
4 are separated. For this reason, the atmosphere is caused to flow into the variable pressure chamber 28 according to the opening degree of the control valve device 42, a pressure difference is generated on both sides of the power piston 24, and the power piston 24 is moved forward together with the valve plunger 50.
The movement of the power piston 24 is transmitted to the output rod 72 via the reaction disk 78, and the output rod 72
2 is advanced. As a result, the brake fluid in the master cylinder is supplied to a brake system (not shown), the brake clearance disappears, and a braking effect begins to appear.

At this time, due to the brake reaction force applied to the output rod 72, as shown in FIG. Because the sub-plunger 94 and the small-diameter plunger 74 bulge toward the valve plunger 50 side, and the sub-plunger 94 and the reaction disc 78 come into contact with each other, a brake reaction force is applied from the output rod 72 to the reaction disc 78. is the power piston body 40 and the sub-plunger 9
It is distributed between 4 and 4. The annular portion around the sub-plunger 94 of the small-diameter plunger portion 74 is the reaction disk 7.
8, the reaction force that this annular portion would have received from the reaction disk 78 is partially received by the sub-plunger 94, and the rest is received by the power piston body 40, and the input is as shown in FIG. As shown by the straight line X in the graph, the signal is multiplied at a high multiplication factor and output.

When the brake pedal is further depressed from this state, the valve plunger 50 advances further, and the plunger body 86 advances, while the reaction force applied from the reaction disc 78 to the sub-plunger 94 increases, causing the sub-plunger to move forward. 94 is retracted into the fitting hole 88. At this time, the sub-plunger 94 has a rubber block 98.
As a result, a resistance force that increases as the amount of retraction of the sub-plunger 94 increases, the sub-plunger 94 is gradually retracted, and during this period, the plunger body 86 and the reaction disk 78 do not come into contact with each other. However, the plunger body 86 eventually comes into contact with the reaction disk 78, and at about the same time, the sub-plunger 94 is prevented from retracting due to the engagement between the flange 104 and the counterbore 106. The plunger body 86 and the sub-plunger 94 come into contact with the reaction disk 78 on one plane as if they were an integral member (FIG. 1(C)).
reference). In this state, the input power is multiplied by the ratio of the cross-sectional area of the small-diameter plunger portion 74 and the cross-sectional area of the large-diameter plunger portion 76. The relationship between input and output in this case is as shown by the straight line Y in the graph of FIG. The sensation becomes harder and you can see that a large braking force is being generated.

Once the pressure difference between both sides of the power piston 24 reaches its limit, any change in the operating force applied to the brake pedal is transmitted as is as a change in the output of the output rod 72. That is, when the auxiliary force of the power piston 24 reaches its limit, the valve plunger 50 moves to the stopper key 6.
2, the power piston 24 engages with the power piston 24 through the output rod 72, and both move together, and the power piston 24 transmits a constant assisting force to the output rod 72 regardless of changes in the operating force. Therefore, the force output from the output rod 72 is the operating force applied to the input rod 48 plus the constant assisting force. In such a state, the multiplication factor of the output with respect to the input is 1, and the relationship between the input and the output is shown by the straight line Z in FIG.

As described above, in the vacuum booster of this embodiment, the boost factor can be changed in two stages, and the tip surfaces of the plunger main body 86 and the sub-plunger 94 are Since it comes into contact with the reaction disk 78 in a single plane, the reaction disk 78 is not partially strongly depressed, and a reduction in its lifespan is prevented.

In the above embodiment, the resistance force imparting member was a rubber block 98, but as shown in FIG. It may be set to 110. In this case, when the sub-plunger 94 is retracted into the fitting hole 112, the block 110 is compressed to allow the sub-plunger 94 to be retracted. There is no need to make the hole 112 stepped. Note that the elastic force of the block 110 is such that when the plunger body 86 comes into contact with the reaction disk 78, the tip surface of the sub-plunger 94 and the plunger body 8
The distal end surface of the sub-plunger 94 is set to a size such that it is in one plane and comes into contact with the reaction disk 78, and the retraction of the sub-plunger 94 is not restricted by providing a flange 104 and a counterbore 106 as in the above embodiment. It's okay.

Furthermore, as shown in FIG.
4 and the bottom surface of the fitting hole 116 may be provided as a resistance force applying means. The spring load of the disc spring 118 is set to be similar to the elastic force of the block 110 in the embodiment shown in FIG.

Further, in each of the above embodiments, the present invention is applied to a vacuum booster in which the power piston operates due to the difference between negative pressure and atmospheric pressure. The present invention can be applied to a gas pressure booster that operates a power piston due to a pressure difference between a negative pressure and a positive pressure, and a gas pressure booster that operates a power piston due to a pressure difference between a negative pressure and a positive pressure.

In addition, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art without departing from the scope of the claims.

[Brief explanation of the drawing]

[Fig. 1] A state in which the valve plunger of a vacuum booster that is an embodiment of the present invention is separated from the reaction disk, a state in which the sub-plunger is in contact with the reaction disk, and a state in which the entire tip surface of the small diameter plunger portion of the valve plunger is in the reaction state. FIG. 3 is a diagram showing a state in which it is in contact with a disk.

FIG. 2 is a graph showing the relationship between input and output in the vacuum booster.

FIG. 3 is a front sectional view showing the vacuum booster.

FIG. 4 is a front sectional view showing another embodiment of the resistance force imparting member.

FIG. 5 is a front sectional view showing still another aspect of the resistance force imparting member.

[Explanation of symbols]

10 Housing 24 Power piston 26 Constant pressure chamber 28 Transformation room 42 Control valve device 48 Input rod 50 Valve plunger 72 Output rod 78 Reaction Disc 86 Plunger body 88 Fitting hole 90 Tip surface 94 Sub plunger 98 Rubber block 110 block 112 Fitting hole 116 Fitting hole 118 Disc spring

Claims (1)

[Claims] 1. A housing; a power piston that is disposed movably in the axial direction within the housing and operates according to a pressure difference between a variable pressure chamber and a constant pressure chamber formed on both sides;
a plunger that is axially movably fitted into the power piston, is connected to an input member, and has a protrusion protruding from the center of a distal end surface, and is axially relative to the housing and the power piston. a movable output member; a reaction disk made of an elastic body that distributes and transmits reaction force from the output member to the power piston and the plunger; and a reaction disk held by the power piston and relative to the power piston. By the movement, the variable pressure chamber and the constant pressure chamber are brought into communication with each other so that the pressure difference between the two chambers is zero, and the communication is cut off and a working gas is allowed to flow into the variable pressure chamber to create a pressure difference. In the brake pneumatic booster including a control valve device that switches between states, the plunger is fitted into a plunger body and a fitting hole opened at the center of the tip of the plunger body so as to be movable in the axial direction. A sub-plunger, which is disposed between the sub-plunger and the plunger body, keeps the sub-plunger protruding from the plunger body while the reaction force applied from the reaction disk is small, and as the reaction force increases. A pneumatic pressure booster for brakes, characterized in that it includes a resistance force applying member that is allowed to be retracted into the fitting hole and that applies a resistance force that increases as the amount of retraction increases.