JP2001063549A - Negative pressure booster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative pressure booster having a simple structure and capable of promptly introducing a large quantity of atmospheric air into an operating chamber to make an input rod exercise high output, a booster limit, during emergent braking. SOLUTION: An input plunger 18 connecting with a reaction mechanism 24 is connected to an input rod 20, and a valve piston 33 having an atmospheric air introducing valve seat 31 at its back end is engaged with the outer periphery of the input plunger 18 so as to be movable between a retreat position R and a forward position F and is energized toward the retreat position R by a return spring 44. First and second permanent magnets 51, 52 are respectively annexed to a valve cylinder 10 and the valve piston 33, generate repulsion for energizing the valve piston 33 toward the retreat position R when the valve piston 33 does not cover a specified distance (s) at the time of its advancement toward the valve cylinder 10 and generate attraction for moving the valve piston 33 to the forward position F when the valve piston 33 advances, covering a distance exceeding the specified distance (s).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative pressure booster used for boosting operation of a brake master cylinder of an automobile, and more particularly, to a booster shell having a front negative pressure chamber connected to a negative pressure source. A booster piston partitioned into a rear working chamber is accommodated, and a valve cylinder slidably supported on the rear wall of the booster shell is connected to the booster piston, and the valve cylinder can be moved back and forth in the valve cylinder. An input rod and a control valve for switching the working chamber between a negative pressure chamber and the atmosphere in accordance with the forward and backward movement of the input rod are disposed, and are slidable on the valve cylinder, the input rod, and the booster shell. A reaction force mechanism for transmitting a resultant force of the input to the input rod and the thrust of the booster piston due to the pressure difference between the working chamber and the negative pressure chamber to the output rod. What did you do?

[0002]

2. Description of the Related Art Conventionally, in such a negative pressure booster, as disclosed in, for example, Japanese Patent Application Laid-Open No. 9-2246, the amount of operation of a control valve is increased by exciting a solenoid device during emergency braking. 2. Description of the Related Art There has been known an apparatus in which a large amount of air is quickly introduced into a room so that an output rod exhibits a high output of a boosting limit.

[0003]

In the negative pressure booster disclosed in the above publication, not only an expensive solenoid device,
Since a sensor that detects the emergency braking condition is required,
There are disadvantages in that the configuration is complicated and the cost is high.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and only by adding a simple and inexpensive structure, during an emergency brake, a large amount of air is quickly introduced into the working chamber to boost the output rod. It is an object of the present invention to provide the above-mentioned negative pressure booster capable of exhibiting a maximum high output.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a booster piston having a booster shell, the interior of which is divided into a front negative pressure chamber connected to a negative pressure source and a rear working chamber. And a valve cylinder slidably supported on the rear wall of the booster shell is connected to the booster piston, and an input rod movable forward and backward and a longitudinal movement of the input rod are provided in the valve cylinder. And a control valve for switching the working chamber between the negative pressure chamber and the atmosphere in accordance with the control valve, between the valve cylinder and the input rod and the output rod slidably supported by the booster shell.
In a negative pressure booster provided with a reaction force mechanism for transmitting to the output rod a resultant force of the input to the input rod and the thrust of the booster piston due to the pressure difference between the working chamber and the negative pressure chamber,
An input plunger connected to the reaction force mechanism is connected to the input rod, and a valve piston is fitted on the outer periphery of the input plunger so that the valve piston can move between a retracted position and an advanced position along the axial direction with respect to the input plunger. At the same time, the valve piston is urged toward the retracted position by a return spring, and the valve piston is moved to the control valve, and when the valve piston advances to the forward position, the control valve is moved to the working chamber and the atmosphere. The first permanent magnet and the second permanent magnet which are connected so as to be switched to the maximum communication state, and which move relative to each other in the axial direction while overlapping each other in the radial direction according to their relative movement in the axial direction. The first of these
And a second permanent magnet for moving the valve piston (33) to the retracted position by causing the same polarity to oppose each other in the radial and axial directions when the advancement of the valve piston from the retracted position with respect to the input plunger is less than a predetermined distance. When a repulsive force is generated that urges the valve piston toward the input plunger and the advancement of the valve piston from the retracted position exceeds a predetermined distance, the opposite ends of the valve piston are radially and axially opposed to each other to move the valve piston to the advanced position. The first feature is that it is configured to generate a suction force for moving the suction force.

According to this first feature, during normal braking in which the advance of the valve piston with respect to the valve cylinder is less than a predetermined distance, the first and second permanent magnets maintain a repulsive state, and their repulsive force is reduced by the valve piston. Continue to bias in the backward direction,
The set load of the return spring that biases the valve piston toward the retracted position can be set small. Therefore, at the time of emergency braking for rapidly moving the input rod, the first and second permanent magnets are repelled by the valve piston moving forward with the input rod and exceeding a predetermined distance with respect to the valve cylinder due to the operation delay of the valve cylinder. As soon as the state is switched from the suction state to the suction state, the valve piston is quickly advanced without much resistance of the return spring due to the attraction force of the first and second permanent magnets, and the control valve is moved to the maximum between the working chamber and the atmosphere. Switch to the communication state. As a result, a large amount of air is introduced into the working chamber at once, and the pressure difference between the working chamber and the negative pressure chamber is maximized, thereby immediately increasing the thrust of the booster piston, that is, the output of the output rod, to the boosting limit point. be able to. By adopting such a simple configuration,
A strong braking force corresponding to emergency braking can be generated.

Further, in addition to the above-mentioned features, the present invention further comprises the steps of caulking and connecting the spherical front end of the input rod to the input plunger so as to swing, and covering the caulked connection with the valve piston. An air introduction valve seat formed at a rear end, a negative pressure introduction valve seat formed on the valve cylinder so as to surround the air introduction valve seat with an annular passage interposed therebetween, and attached to the valve cylinder so as to be movable back and forth. The control valve is formed by a valve body having a front end valve portion opposed to the negative pressure introduction valve seat and the air introduction valve seat, and a valve spring for urging the valve portion of the valve body in the seating direction of the two valve seats. A first port communicating the inside of the valve body to the atmosphere and communicating the negative pressure introducing valve seat to the negative pressure chamber, and a second port communicating the annular passage to the working chamber. The outer peripheral surface of the valve piston facing the annular passage is provided on the valve cylinder. That it has tapered to a smaller diameter toward the end as a second feature.

According to the second feature, since the outer peripheral surface of the valve piston is formed in a tapered shape having a smaller diameter toward the air introduction valve seat, when the air introduction valve seat is fully opened, a large amount of air is supplied to the valve piston. Can smoothly guide into the working chamber by the tapered outer peripheral surface, which can contribute to the improvement of the responsiveness of the booster piston. In addition, the valve piston covers the caulked joint of the input rod and the input plunger, and the caulked portion The generation of wind noise can be suppressed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

FIG. 1 is a longitudinal sectional view of a tandem type negative pressure booster according to an embodiment of the present invention, FIG. 2 is an enlarged view of a part of FIG. 1, and FIG.
FIG. 4 is an explanatory diagram of the operation of the negative pressure booster, and FIG. 4 is a diagram showing boosting characteristics of the negative pressure booster.

In FIG. 1 and FIG. 2, a booster shell 1 of a negative pressure booster B is sandwiched between a pair of front and rear shell halves 1a and 1b connecting opposite ends to each other, and between both shell halves 1a and 1b. And a partition plate 1c that partitions the inside of the booster shell 1 into a front shell chamber 2 and a rear shell chamber 3.
The rear shell half 1b is fixedly supported by bolts 8 to the vehicle interior front wall F, and the front shell half 1a is
The cylinder body Ma of the brake master cylinder M operated by the booster B is fixed by bolts 9.

The front shell chamber 2 has a front booster piston 4 accommodated therein so as to be able to reciprocate back and forth, and is bonded to and overlapped with a rear surface thereof, and has a front shell half 1a and a partition plate 1c.
The front diaphragm 5 sandwiched therebetween partitions into a front front negative pressure chamber 2a on the front side and a rear front working chamber 2b on the rear side.
The front negative pressure chamber 2a is connected to a negative pressure source V (for example, the inside of an intake manifold of an internal combustion engine) via a negative pressure introducing pipe 14.

The rear shell chamber 3 is connected to a rear booster piston 6 housed in the rear shell chamber 3 so as to be able to reciprocate back and forth, and is fixed together with the partition plate 1c between the two shell halves 1a and 1b. The rear diaphragm 7 defines a front rear negative pressure chamber 3a on the front side and a rear operating chamber 3b on the rear side.

The front and rear booster pistons 4, 6 are each formed in a ring shape from a steel plate, and are integrally connected via a synthetic resin valve cylinder 10 fixed to the center. The valve cylinder 10 is slidably supported by a partition plate 1c via a seal member 11 and a rear extension cylinder 12 formed at the center of the rear shell half 1b via a seal member 13. The retreat limit of both booster pistons 4, 6 is defined by a large number of raised projections 7 a abutting the rear wall of the booster shell 1 on the rear surface of the rear diaphragm 7.

The front end of the valve cylinder 10 is formed on a large-diameter piston 15 and is formed at the center of the large-diameter piston 15.
A small-diameter piston 17 reduced in diameter at a fixed rate from the large-diameter piston 15 is slidably fitted in a bottomed cylinder hole 16 opened in the front surface thereof. The front end of the input plunger 18 that slidably penetrates the center of the section abuts.

A spherical portion 20a at the front end of an input rod 20 inserted from the rear end of the valve cylinder 10 is fitted into a connecting tube portion 19 formed at the rear end of the input plunger 18 and is prevented from coming off. Due to this, a part 19a of the connecting tubular portion 19 is crimped inward. Thus, the input rod 20 is swingably connected to the input plunger 18.

A cup 21 is provided on the outer periphery of the large-diameter piston 15.
The cup body 21 is filled with a flat elastic piston 22 opposed to the large-diameter and small-diameter pistons 15 and 17.

One of the opposed end surfaces of the large-diameter piston 15 and the elastic piston 22 (in the illustrated example, an annular step 23 is formed at the front end of the large-diameter piston 15).

In the above, the large-diameter piston 15, the small-diameter piston 17, the elastic piston 22, and the cup 21 are a reaction force mechanism for transmitting the combined force of the input to the input rod 20 and the thrust of the booster pistons 4, 6 to the output rod 25. 24.

An output rod 25 protrudes from the front surface of the cup body 21. The output rod 25 is connected to the brake master cylinder M.
Of the piston Mb. In addition, a retainer 26 is provided in contact with the cup body 21 and the front end face of the valve cylinder 10, and a valve cylinder return spring 27 is contracted between the retainer 26 and the front wall of the booster shell 1.

The valve cylinder 10 has front and rear negative pressure chambers 2a and 3a.
A first communication passage 28a for communicating between
b, 3b, a first port 29a communicating with the first communication passage 28a and opening on the inner peripheral surface of the valve cylinder 10, and a first port 29a communicating with the second communication passage 28b. A second port 29b that opens to the inner peripheral surface of the valve cylinder 10 further forward is formed. Their first and second ports 2
An annular negative pressure introduction valve seat 30 is formed on the inner peripheral surface of the valve cylinder 10 in the middle in the front-rear direction of 9a and 29b. A cylindrical valve piston 33 is slidably fitted on the inner peripheral surface of the front part of the valve cylinder 10, and a second port 29b is provided at the rear end of the valve piston 33.
An annular air introduction valve seat 31 is formed which is surrounded by a negative pressure introduction valve seat 30 with an annular passage 32 connected thereto, and one common valve opposed to the negative pressure introduction valve seat 30 and the atmosphere introduction valve seat 31. A body 34 is disposed in the valve sleeve 10. This valve body 34
The annular valve portion 34a facing the negative pressure introducing valve seat 30 and the atmosphere introducing valve seat 31 so as to be seated is at the front end, the annular mounting bead portion 34b is at the rear end, and the two portions 34a, 34b are axially opposed to each other. Displaceably connected diaphragm portions 34c are formed in the middle portions, respectively.
4b is attached to the inner peripheral surface of the valve cylinder 10 by the front end of a cylindrical valve holder 35 fitted to the inner peripheral surface of the rear part of the valve cylinder 10. A valve spring 36 for urging the valve portion 34a in the seating direction between the valve seats 30 and 31 is provided between the valve portion 34a and the input rod 2.
It is contracted between 0.

In the above, the two valve seats 30, 31, the valve element 34 and the valve spring 36 constitute a control valve 38.

The outer peripheral surface 32a of the valve piston 33 constituting the annular passage 32 has a smaller diameter toward the air introduction valve seat 31, and is formed in a tapered shape continuous with the inner peripheral surface of the second port 29b. .

At the rear end of the rear extension cylinder 12, an inward flange 12a having an air inlet 39 opened at the center is integrally formed. The input rod 20 is retracted by contacting the inner surface of the flange 12a. A stopper plate 40 defining a limit is fixed to the input rod 20 so as to be adjustable in the front-rear direction, and the input rod 20 is biased toward the retreat limit by an input return spring 41 supported by the valve holder 35.

An air filter 42 is mounted on the inner periphery of the rear end of the valve cylinder 10, and the inner periphery of the air introduction valve seat 31 is always in communication with the air introduction port 39 through the air filter 42. The air filter 42 has flexibility so as not to prevent the input rod 20 from moving back and forth with respect to the valve cylinder 10.

The input plunger 18 has an outward flange 18a slidably fitted on the inner peripheral surface of a cylindrical valve piston 33 via a seal member 43.
Has an inward flange 33a which is slidably fitted to the outer peripheral surface of the connecting cylindrical portion 19 of the input plunger 18, and is integrally formed between the two flanges 18a, 33a. Return spring 4 for urging
4, the stopper ring 45 receiving the rear end face of the inward flange 33a is locked to the connecting tubular portion 19.
The inner peripheral surface of the valve piston 33 has an outward flange 18.
a abutting step 4 which is opposed to the rear end face with a predetermined gap g
6 are formed. Within the range of the gap g, the valve piston 33 is moved backward to contact the inward flange 33a against the stopper ring 45 (see FIG. 2), and is moved forward to contact the contact step 46 to the outward flange 18a. It can move between the position F (see FIG. 3).

The set load of the return spring 44 is set larger than that of the valve spring 36. Therefore, when the input plunger 18 is retracted by the input rod 20, the valve portion 34a of the valve body 34 can be displaced rearward by the valve piston 33 against the set load of the valve spring 36 without compressing the return spring 44. .

In the valve piston 33, the inner diameter D1 of the inner peripheral surface on which the outward flange 18a is fitted and the effective diameter D2 of the air introduction valve seat 31 on which the valve body 34 is seated are set to be equal to each other. In this case, the valve body 34 is connected to the air introduction valve seat 31.
When the seat is seated, even if the negative pressure in the negative pressure chambers 2a, 3a acts on the front and rear of the valve piston 33 from the first port 29a, the thrust due to the negative pressure acting on the front end and the rear end of the valve piston 33 can be reduced. Can offset each other.

A cylindrical portion 50 surrounding the input plunger 18 is formed in the valve cylinder 10 in front of the outward flange 18a, and an annular first permanent magnet 51 is provided on the outer periphery of the cylindrical portion 50 with a locking ring 53. The first permanent magnet 5
An annular second permanent magnet 52 that can move relatively in the axial direction while overlapping with the radial direction 1 is fixed to the front end of the valve piston 33 by bonding or the like. These first and second permanent magnets 51,
52 has both poles N and S at both ends in the axial direction, but the N and S poles of the first and second permanent magnets 51 and 52 have opposite directions. That is, in the illustrated example, the first permanent magnet 51 has S and N poles at the front and rear ends, and the second permanent magnet 52 has N and S poles at the front and rear ends. Moreover, the first and second
When the forward movement of the valve piston 33 from the retreat position R with respect to the input plunger 18 is less than a predetermined distance s, the permanent magnets 51 and 52 cause the valve piston 33 to have the same pole, that is, the N and N poles in the radial and axial directions to face each other. When a repulsive force for urging the valve piston 33 toward the retreat position R is generated, and the advance of the valve piston 33 from the retreat position R with respect to the input plunger 18 exceeds a predetermined distance s, the opposite poles, i. It is arranged so as to generate a suction force for moving the valve piston 33 to the forward position F in the axial direction. The set load of the input return spring 41 is set to be larger than the attraction force generated when both the permanent magnets 51 and 52 are in the attraction state.

Next, the operation of this embodiment will be described. [Suspension of Negative Pressure Booster] In the rest state of the negative pressure booster B, as shown in FIG. 1, the input rod 20 is located at the retreat limit.
The control valve 38 allows the front and rear working chambers 2b, 3b to be connected to both the negative pressure chambers 2a, 3a and the air introduction port 39 by seating the valve body 34 on the atmosphere introduction valve seat 31 and the negative pressure introduction valve seat 30. In the neutral state in which the operation is interrupted, the negative pressure of the negative pressure source supplied through the negative pressure introducing pipe 14 is stored in the two negative pressure chambers 2a and 3a by the control valve 38, and the two operating chambers 2b and 3
At b, a negative pressure appropriately diluted with the atmosphere is maintained. Thus, a small forward force is applied to the front and rear booster pistons 4 and 6 due to a slight pressure difference between the front negative pressure chamber 2a and the working chamber 2b and between the rear negative pressure chamber 3a and the working chamber 3b. However, these forward forces are balanced with the force of the valve-cylinder return spring 27, and the booster pistons 4, 6 are stopped when they slightly advance from the retreat limit. [Normal brake] The brake pedal P is depressed at a normal speed to brake the vehicle, and the input rod 20 and the input plunger 18 are depressed.
If the air introduction valve seat 31 is moved forward via the valve piston 33 and the booster pistons 4 and 6 are initially immobile, the air introduction valve seat 31 immediately separates from the valve body 34,
The second port 29b is connected to the air inlet 3 through the annular passage 32.
Communicate with 9. As a result, the valve cylinder 1
The air that has flowed into the chamber passes through the air introduction valve seat 31, and
It is quickly introduced into both working chambers 2b, 3b through the port 29b, and the chambers 2b, 3b are made higher in pressure than the two negative pressure chambers 2a, 3a. , 6 move forward with the movement of the input rod 20 against the force of the valve cylinder return spring 27 with the valve cylinder 10 and the large-diameter piston 15. The forward thrust of the booster pistons 4 and 6 is transmitted from the large-diameter piston 15 to the elastic piston 22 and pushes the cup body 21, that is, the output rod 25, forward. It can be activated without delay and brake the vehicle.

During the braking, the thrust of the booster pistons 4 and 6 applied to the large-diameter piston 15 and the pedaling force of the operator applied to the small-diameter piston 17 from the input rod 20 are applied to the rear end face of the elastic piston 22. Acts on the front end face thereof, and the reaction force of the output rod 25 acts thereon, whereby the elastic piston 22 is compressed back and forth. As a result, a part of the operation reaction force of the output rod 25 is transmitted to the input rod 20 via the elastic piston 22, and the operator can control the output rod 2.
5, the magnitude of the braking force can be sensed.

Until the output of the output rod 25 reaches the boosting limit (see the line ab in FIG. 4), the valve cylinder 10 integrated with the booster pistons 4, 6 moves the input rod 20 forward. Only when the input rod 20 stops moving forward.
Together with the valve body 34, which is moved forward, is seated again on the air introduction valve seat 31 to prevent the air from being further introduced into the working chambers 2b, 3b. A corresponding boost output will be obtained. By the way, the large-diameter piston 15 initially has its front end surface excluding the annular step portion 23 abutting on the elastic piston 22, but when the output of the output rod 25 exceeds a predetermined value, the annular step portion 23 is also moved by the elastic piston. As the pressure-receiving area ratio of the large-diameter piston 15 and the small-diameter piston 17 to the elastic piston 22 changes, the boosting ratio increases from the middle as shown by the line abc in FIG. I do.

When the output of the output rod 25 exceeds the boosting limit, the thrust due to the pressure difference between the booster pistons 4 and 6 is maximized, and the air introduction valve seat 31 remains separated from the valve body 34. The output of the output rod 25 is determined by the maximum thrust due to the pressure difference between the booster pistons 4 and 6 and the brake pedal P
And the thrust of the input rod 20 due to the treading force (see the line cd in FIG. 4).

As described above, when the valve cylinder 10 follows the advance of the input rod 20 with almost no delay, the relative displacement between the first permanent magnet 51 of the valve cylinder 10 and the second permanent magnet 52 of the valve piston 33. Does not exceed the predetermined distance s, and the two permanent magnets 51 and 52 continue to repel each other in the axial direction. Therefore, as shown in FIG.
a is held at the retracted position R where the a contacts the stopper ring 45 of the input plunger 18. This means that the valve piston 33
Means that the set load of the return spring 44 for urging the spring toward the retreat position R side can be set small. [Emergency brake] During emergency braking in which the brake pedal P is rapidly depressed, the valve cylinder 1
0, the valve piston 33 advances with the input rod 20, and the second permanent magnet 52 advances more than a predetermined distance s with respect to the first permanent magnet 51, as described above.
2, the front and rear end poles (S and N poles) are radially and axially opposed to the front and rear end poles (N and S poles) of the first permanent magnet 51. 52 is switched from the repulsive state to the suction state, so that the suction force causes the valve piston 33 to advance against the set load of the return spring 44 and to be in the forward position F in contact with the outward flange 18a (the state shown in FIG. 3).
Until the air introduction valve seat 31 is maximally separated from the valve body 34 to bring it into a fully opened state.

Here, it should be noted that the set load of the return spring 44 is, as described above, the two permanent magnets 51,5.
2 is set small by utilizing the repulsive force when in the repulsive state, so that as soon as the two permanent magnets 51 and 52 switch from the repulsive state to the attracted state, they do not significantly resist the set load of the return spring 44. That is, the valve piston 33 is rapidly advanced instantaneously, and the air introduction valve seat 31 is fully opened immediately.

As a result, the two working chambers 2
Since a large amount of air is introduced into the b and 3b all at once, the thrust of the brake pistons 4 and 6 due to the pressure difference between the working chambers 2b and 3b and the negative pressure chambers 2a and 3a, that is, the output of the output rod 25 is doubled. It increases immediately to the force limit, and the brake master cylinder M can be operated quickly and powerfully. As shown by P1, P2, and P3 in FIG. 4, such an emergency brake operation is performed at the same time as the start of braking, during the normal braking, or after the boosting ratio changes during the normal braking. If you do this,
From then on, the output can be increased immediately to the boost limit.

The outer peripheral surface 32a of the valve piston 33 facing the annular passage 32 is a tapered surface that is continuous with the inner peripheral surface of the second port 29b and has a smaller diameter toward the air introduction valve seat 31. When a large amount of air flows into the second port 29b from the annular passage 32 with the full opening of the air introduction valve seat 31, the flow of the air is smooth without being disturbed, and the valve piston 33 is connected to the input rod 20 and the input plunger 18. Covering the caulking connection portion 19a can also suppress the generation of noise such as wind noise.

As described above, when the input rod 20 is rapidly advanced by the brake pedal P, the atmospheric pressure is generated by the attractive force between the first and second permanent magnets 51 and 52 attached to the valve cylinder 10 and the valve piston 33, respectively. By adopting a simple configuration in which the introduction valve seat 31 is fully opened, a negative pressure booster B that can cope with emergency braking can be provided at low cost. [Release of emergency brake] When the pedaling force is released from the brake pedal P to release the emergency brake state, the input rod 2
0 and the input plunger 18 are retracted by the force of the input return spring 41. At this time, since the set load of the input return spring 41 is set to be larger than the attraction force between the two permanent magnets 51 and 52, the input plunger 18 retracts the valve piston 33 against the attraction force. When the two permanent magnets 51 and 52 are repelled by the retraction, the repulsive force and the force of the return spring 44 cause the valve piston 33 to move the inward flange 33 a to the stopper ring 4 of the input plunger 18.
5 can be immediately returned to the retracted position R where it abuts.
Then, the valve piston 33 connects the air introduction valve seat 31 to the valve body 34.
And the valve body 34 is connected to the negative pressure introducing valve seat 30.
After that, both working chambers 2b and 3b are connected to the second port 2 in the same manner as when the normal brake is released.
9b, the annular passage 32 and the first port 29a communicate with both negative pressure chambers 2a and 3a. As a result, both working chambers 2b,
3b is prevented from being introduced into the atmosphere, while both working chambers 2b,
3b is sucked into the negative pressure limit V through the two negative pressure chambers 2a, 3a, and the pressure difference between them is eliminated. Therefore, the booster pistons 4, 6 also retreat with the force of the valve cylinder return spring 27, and the master cylinder M Cancel the operation of.

When the input rod 20 moves backward until the stopper plate 40 comes into contact with the inward flange 12a of the rear extension cylinder 12, the rear booster piston 6 once moves the projection 7a of the rear diaphragm 7 to the rear of the booster shell 1. Returning to the retreat limit to be brought into contact with the wall, the negative pressure introduction valve seat 30 is seated on the valve body 34 and the valve body 34 is moved to the atmosphere introduction valve seat 31 this time.
The air is again introduced into the two working chambers 2b and 3b, but if the booster pistons 4 and 6 advance slightly due to the resulting pressure difference, the negative pressure introducing valve seat 3 will be released.
At 0, the valve body 34 is seated, and the control valve 38 is returned to the initial neutral state. In this way, the working chambers 2b and 3b hold the negative pressure diluted with the atmosphere, and the negative pressure booster B enters the rest state shown in FIGS.

The present invention is not limited to the above embodiment, and various design changes can be made without departing from the gist of the present invention. For example, in the first permanent magnet 51, N,
While the S pole is provided, the second permanent magnet 52 has S, N
Poles can also be arranged. Further, the negative pressure booster B may be configured as a single type having a single booster piston. Further, the stopper plate 40 of the input rod 20 and the inward flange 12a of the rear extension cylinder 12 are eliminated, and when the negative pressure booster B is stopped, the operating chambers 2b and 3b are kept open while the negative pressure introducing valve seat 30 is kept open. The communication with the negative pressure chambers 2a and 3a may be maintained. In addition, the annular step portion 23 can be eliminated to keep the pressure receiving area of the elastic piston 22 constant and to keep the boost ratio constant.

[0041]

As described above, according to the first aspect of the present invention, when the input rod is rapidly advanced by the brake pedal, the attraction force of the first and second permanent magnets respectively attached to the valve cylinder and the valve piston is increased. By adopting a simple configuration in which the air introduction valve seat is fully opened by using the same, a negative pressure booster capable of coping with emergency braking can be provided at low cost. In particular, at the time of normal braking in which the advance of the valve piston with respect to the valve cylinder is less than a predetermined distance, the first and second permanent magnets maintain a repulsive state, and the repulsive force urges the valve piston in the backward direction. Therefore, it is possible to reduce the set load of the return spring that urges the valve piston to the retracted position side. As a result, during emergency braking, the valve piston moves forward beyond a predetermined distance with respect to the valve cylinder. As soon as the first and second permanent magnets are switched from the repelled state to the attracted state, the attraction force of the first and second permanent magnets causes the valve piston to quickly move forward without much resistance of the return spring, The control valve is switched to the maximum communication state between the working chamber and the atmosphere, a large amount of air is introduced into the working chamber at once, and the output of the output rod is immediately increased to the boosting limit point, so that emergency braking can be properly handled. It is possible.

According to the second feature of the present invention, since the outer peripheral surface of the valve piston facing the annular passage is formed in a tapered shape having a small diameter toward the air introduction valve seat, when the air introduction valve seat is fully opened. A large amount of air can be smoothly guided to the working chamber by the tapered outer peripheral surface of the valve piston, which can contribute to the improvement of the response of the booster piston. In addition, the valve piston connects the input rod and the caulked joint of the input plunger. Since the cover is covered, the generation of wind noise by the caulking portion can be suppressed, and the smooth flow of the atmosphere into the working chamber can be effectively reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a tandem type negative pressure booster according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a part of FIG.

FIG. 3 is an explanatory diagram of an operation of the negative pressure booster.

FIG. 4 is a diagram showing boost characteristics of the negative pressure booster.

[Explanation of symbols]

B: Negative pressure booster F: Advance position of valve piston R: Retreat position of valve piston V: Negative pressure source s: Repel first and second permanent magnets A predetermined distance at which the valve piston moves forward to switch from the state to the suction state 1... Booster shell 2a... Negative pressure chamber (front negative pressure chamber) 3a. ... working chamber (front working chamber) 3b ... working chamber (rear working chamber) 4 ... booster piston (front booster piston) 6 ... booster piston (rear booster piston) 10 ...・ Valve cylinder 18 ・ ・ ・ Input plunger 20 ・ ・ ・ Input rod 24 ・ ・ ・ Reaction mechanism 25 ・ ・ ・ Output rod 29a ..First port 29b ··· Second port 30 ··· Negative pressure introduction valve seat 31 ··· Atmospheric introduction valve seat 32 ··· Annular passage 33 ··· valve piston 34 ··· valve body 34a ··· valve part 36 ··· valve Spring 38 ・ ・ ・ Control valve 44 ・ ・ ・ Return spring 51 ・ ・ ・ First permanent magnet 52 ・ ・ ・ Second permanent magnet

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroki Kawakami 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (Reference) 3D048 BB21 BB29 BB31 CC27 EE00 EE15 EE16 EE20 EE25 MM02 NN04 QQ08

Claims (2)

[Claims] 1. A booster piston which partitions a booster shell (1) into a front negative pressure chamber (2a, 3a) connected to a negative pressure source (V) and a rear working chamber (2b, 3b). (4,6), and this booster piston (4,6)
A valve cylinder (10) slidably supported on the rear wall of the booster shell (1) is connected to the valve shell (1).
An input rod (20) that can be moved back and forth, and the working chambers (2b, 3b) are moved according to the forward and backward movement of the input rod (20) into the negative pressure chambers (2a, 2a).
3a) and a control valve (38) for switching between communication with the atmosphere, the valve cylinder (10) and the input rod (20), and the output rod slidably supported by the booster shell (1). (2
5) between the input to the input rod (20) and the thrust of the booster pistons (4, 6) due to the pressure difference between the working chambers (2b, 3b) and the negative pressure chambers (2a, 3a). In a negative pressure booster provided with a reaction force mechanism (24) for transmitting a resultant force to the output rod (25), an input plunger (18) connected to the reaction force mechanism (24) is connected to the input rod (20). A valve piston (33) is fitted on the outer periphery of the input plunger (18) so that the valve piston (33) can move between the retreat position (R) and the advance position (F) along the axial direction with respect to the input plunger (18). And the valve piston (3
3) is urged toward the retracted position (R) by a return spring (44), and this valve piston (33) is moved to the control valve (38).
When the valve piston (33) has advanced to the advance position (F), the control valve (38) is connected to the working chamber (2b, 2b).
3b) is connected so as to switch to a maximum communication state with the atmosphere, and the valve cylinder (10) and the valve piston (33) move relative to each other in the axial direction while overlapping each other in the radial direction according to their relative movement in the axial direction. A first permanent magnet (51) and a second permanent magnet (52) are provided respectively, and the first and second permanent magnets (51, 52) are attached to the valve piston (3).
3) Retraction position (R) with respect to input plunger (18)
When the forward movement from the valve is less than a predetermined distance (s), a repulsive force is generated which urges the valve piston (33) toward the retreat position (R) by causing the same poles to face each other in the radial direction and the axial direction. , The input plunger (1) of the valve piston (33)
8) When the advance from the retreat position (R) with respect to the retreat position (R) exceeds a predetermined distance (s), the valve piston (33) is moved to the advance position (F) with the opposite poles facing each other in the radial and axial directions. A negative pressure booster characterized by being configured to generate a suction force. 2. The negative pressure booster according to claim 1,
The spherical front end portion (20a) of the input rod (20) is swaged to the input plunger (18) so as to swing, and the swaged connection portion (19a) is connected to the valve piston (3).
3) and an air introduction valve seat (31) formed at the rear end of the valve piston (33), and the valve cylinder so as to surround the air introduction valve seat (31) with an annular passage (32) interposed therebetween. (1
0) and the valve cylinder (1).
0) so as to be able to move back and forth, and the negative pressure introduction valve seat (3)
0) and the valve part (34a) at the front end on the air introduction valve seat (31).
And a valve spring (36) for urging the valve portion (34a) of the valve body (34) in the seating direction of the two valve seats (30, 31). (38), the inside of the valve body (34) communicates with the atmosphere, and the negative pressure introducing valve seat (30) is connected to the negative pressure chambers (2a, 3).
a) a first port (29a) communicating with the working chamber (2b, 3b), and a second port (29b) communicating with the working chamber (2b, 3b). A negative pressure booster characterized in that an outer peripheral surface (32a) of the piston (33) facing the annular passage (32) is formed in a tapered shape having a smaller diameter toward a rear end.