JP2003063379A - Negative pressure type booster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative type booster contriving reduction of working sound in emergency braking operation. SOLUTION: In the case that an amount of relative movement in the forward direction is a prescribed value or larger to a power piston 22 of a plunger 37, engagement of a holding member 48 and a valve seat member 40 is released to retreat the valve seat member 40, even when a key member 32 is moved rearward, elastic members 32a, 32b are disposed in the inside of the valve seat member 40 between a frontward end face 35a of a second flange part 35 of the plunger 37 and a rearward face 32c of the key member 32, and working sound is reduced by both contact between the frontward end face 35a of the second flange part 35 and the rearward face 32c of the key member 32 due to deformation of the elastic members 32a, 32b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a negative pressure type booster for a vehicle, and more particularly to a negative pressure type booster for compensating for insufficient brake pedal depression force during emergency braking.

[0002]

2. Description of the Related Art When an obstacle suddenly appears on the path of a vehicle while the vehicle is running, the pedaling force applied to the brake pedal by the driver during an emergency braking operation in which the driver depresses the brake pedal in a hurry It has been reported that the brake performance of the vehicle is not fully exerted, because it is smaller than the pedaling force that generates a brake fluid pressure that is large enough to lock the vehicle.

Therefore, in recent years, the brake fluid pressure is locked at the time of emergency braking based on whether the brake pedal is a normal brake, which is operated normally during braking, or an emergency brake which is an emergency braking operation, based on the stepping speed of the brake pedal. A device for raising the size to reach the above has been proposed and is being put to practical use.

As a device for assisting such an emergency braking operation, for example, WO 01/32488 A1
The one described in Japanese Patent Publication is known. The device disclosed in this publication has a housing in which at least one pressure chamber is formed, and is installed inside the housing so as to be able to move forward and backward with respect to the housing, and the pressure chamber is divided into a constant pressure chamber and a variable pressure chamber. Movable wall, a power piston coupled to the movable wall, an input rod installed inside the power piston so as to be able to move forward and backward with respect to the power piston, and a front-back direction with respect to the power piston connected to the input rod. A plunger with a rear end that is slidably inserted into the power piston and an atmospheric valve seat, an output member that outputs the propulsive force of the power piston due to the movement of the movable wall to the outside of the device, and A first negative pressure valve seat that is disposed and faces rearward, and a valve seat that can move forward and backward with respect to the power piston and that is substantially concentric with the first negative pressure valve seat. A valve mechanism having a second negative pressure valve seat formed on the material, a movable part facing the first negative pressure valve seat, and a fixed part airtightly fixed to the power piston, and the amount of advance of the plunger relative to the power piston is predetermined. Drive means for moving the valve seat member toward the movable part by a predetermined amount when the value is equal to or more than the value, and holding for holding the valve seat member at the predetermined position in the power piston when the advance amount of the plunger with respect to the power piston is smaller than the predetermined value Means, a locking member that is fixed to the power piston and that locks the holding means to the power piston, and a key member that is inserted into the radial hole of the power piston and that regulates the amount of forward and backward movement of the plunger with respect to the power piston. And a plunger formed on a rear side of the first flange portion fitted into a through hole formed in the valve seat member. And a second flange portion is provided to be fitted to the inner peripheral surface of the word piston, the key member is disposed between the first flange portion and the second flange portion.

In this structure, when the driver hurriedly depresses the brake pedal and the forward speed of the plunger is higher than the forward speed of the power piston, that is, the amount of relative movement of the plunger forward with respect to the power piston becomes a predetermined value or more. In this case, the engagement between the holding member and the valve seat member is released, the valve seat member retracts, and the distance between the rear end surface of the reaction member (reaction disc) and the front end surface of the valve seal portion of the valve mechanism is increased. By doing so, the so-called jumping amount is increased to obtain the emergency braking characteristic.

That is, at the time of emergency braking, the input-output characteristic of the negative pressure type booster is switched from the characteristic for normal braking to the characteristic for emergency braking so that the braking characteristic becomes the same as when the driver strongly depresses the brake pedal. I am trying to become.

[0007]

In the negative pressure type booster disclosed in this publication, the amount of forward relative movement of the plunger with respect to the power piston becomes a predetermined value or more due to the operation during emergency braking, and the holding member and the valve are not moved. When the engagement with the seat member is released, the valve seat member moves in the backward direction (rearward). Along with that, the key member inserted into the slit of the valve seat member is pushed by the front groove wall of the slit of the valve seat member to move rearward, and the key member pushed backward is located on the front end face of the plunger. Abut. At this time, for example, when both the key member and the plunger are made of a hard material such as a metal member, an operating noise may occur between them and the quality may deteriorate.

The present new technology addresses the above problems.
It is an object of the present invention to provide a negative pressure type booster that reduces operating noise during emergency braking.

[0009]

[Means for Solving the Problems] Means for achieving the above object are as follows: a housing in which a pressure chamber is formed; and a housing which is arranged so as to be able to move forward and backward. A movable wall that divides the pressure chamber into a constant pressure chamber and a variable pressure chamber, a first negative pressure valve seat and a radial hole, a power piston that is integrated with the movable wall, and the power piston inside the power piston. An input rod arranged so as to be able to move forward and backward with respect to the power piston, a first flange portion and a second flange portion, and connected to the input rod,
The thrust force of the power piston, which is inserted into the power piston so as to be slidable in the front-rear direction with respect to the power piston and has an atmospheric valve seat, and the driving force of the power piston accompanying the movement of the movable wall is output to the outside of the device. A second output member for
A valve seat member having a negative pressure valve seat, capable of advancing and retreating with respect to the power piston, and substantially concentric with the first negative pressure valve seat, and disposed in the power piston, and in the first negative pressure valve seat. A valve mechanism having a movable portion facing each other and a fixed portion arranged concentrically with the movable portion, and directing the valve seat member toward the movable portion when the amount of advance of the plunger with respect to the power piston is a predetermined value or more. Drive means for moving a predetermined amount by
Holding means for holding the valve seat member at a predetermined position in the power piston when the amount of advance of the plunger with respect to the power piston is smaller than a predetermined value, and a locking member for locking the holding means to the power piston. , The first hole of the plunger being inserted into the radial hole.
A negative pressure type booster comprising: a key member that moves between a flange portion and the second flange portion in the front-rear direction to regulate the amount of movement of the plunger in the front-rear direction with respect to the power piston. The elastic member is disposed between the front end surface of the portion and the rear surface of the key member.

According to the above-mentioned means, when the relative amount of forward movement of the plunger with respect to the power piston exceeds a predetermined value, the engagement between the holding member and the valve seat member is released and the valve seat member retracts. To do. However, even if the key member moves rearward, the elastic member is arranged between the front end surface of the second flange portion and the rear surface of the key member. The operation noise due to the contact between the front end surface of the two flange portions and the rear surface of the key member is reduced.

In this case, if the protrusion is formed on the elastic member, the forward movement amount (relative movement amount) of the plunger with respect to the power piston becomes a predetermined value or more, and the key member moves backward. With this movement, the projection is crushed first and the projection is deformed, so that the thrust force for moving the key member to the rear is absorbed. Therefore, the operating noise between the front end surface of the second flange portion and the rear surface of the key member is further reduced.

The term "rear" means the brake pedal side or the vehicle rear side of the negative pressure type booster, and the term "front" means the master cylinder side or the vehicle front side of the negative pressure type booster. means.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the new technology will be described below with reference to the drawings. 1 and 2
FIG. 4 is a sectional view of a negative pressure type booster according to an embodiment of the new technology.

In FIG. 1, a negative pressure type booster 10 is composed of a front shell 11, a rear shell 12 and a movable wall 20. The inside of the constant pressure chamber 23 is formed by a disk-shaped movable wall 20.
The housing 14 is divided into a transformer chamber 24 and a transformer chamber 24. The movable wall 20 in the housing 14 is composed of a metal plate 18 and a diaphragm 19 made of rubber, and is disposed so as to be movable in the front-rear direction with respect to the housing 14.

The bead portion on the outer peripheral edge of the diaphragm 19 is
The folded-back portion provided on the outer peripheral edge of the rear shell 12 and the front shell 11 are hermetically sandwiched. Further, the bead portion on the inner peripheral edge of the diaphragm 19 is airtightly fixed together with the plate 18 in a groove provided in front of the outer periphery of the front flange portion of the power piston 22.

The constant pressure chamber 23 is connected to an intake manifold (not shown) of the engine, which is a negative pressure source, and is always kept at a negative pressure while the engine is operating. The variable pressure chamber 24 is connected to the constant pressure chamber 2 through the passage 60 and the valve mechanism 36.
3 is communicated / interrupted with 3 and is also communicated / interrupted with the atmosphere via the valve mechanism 36.

As shown in FIGS. 1 and 2, the cylindrical power piston 22 has a front portion inside thereof (in FIGS. 1 and 2,
A first space 22a located on the left side) and communicating with the constant pressure chamber,
A second space 22b located rearward (rightward in FIGS. 1 and 2) and communicating with the atmosphere, a first space 22a and a second space 22b.
And an intermediate portion 221 interposed therebetween. The intermediate portion 221 extends in the front-rear direction of the power piston 22 in parallel with the outer diameter, and communicates with the intermediate portion 221 a first space 22a located at the front and a second space 22b located at the rear. A third space 22c is formed, and a passage 60 that connects the first space 22a and the second space 22b is formed in the power piston separately from the third space 22c.

Inside the power piston 22, an input rod 28 and a plunger 37, which constitute an input member 27, are provided at a first position.
The first space 22a, the second space 22b, and the third space 22c are penetrated so as to be movable in the front-rear direction with respect to the power piston 22. Further, the input rod 28 and the plunger 37 are integrally joined by being caulked from the outer diameter of the plunger 37 in the joint portion 80 located in the intermediate portion 221 in the radial direction. This input rod 2
A brake pedal (not shown) is connected to the rear of the brake pedal 8.

An annular groove is formed in the front-rear direction at the front end of the power piston 22, and an output member 55 is fitted in the groove so that the front of the power piston 22 is a concave surface and the output. A reaction force member 54 made of an elastic member such as rubber is disposed between the member 55 and the member 55. Further, there is a space between the reaction force member 54 and the front end of the plunger 37, and the contact member 70 is arranged at the front end of the plunger 37. The abutting member 70 is provided inside the locking member 50 that is integrally formed with the power piston 22 and has a concave shape at the front so as to be movable in the front-rear direction.

Plunger 3 for power piston 22
In order to regulate the movement amount of the input rod 28 and the input rod 28, a key member 32 having a substantially U-shape with one forked in a radial hole 33 formed in the intermediate portion 221 of the power piston 22 in the radial direction. Is inserted. The thickness of the key member 32 in the front-rear direction is set to be smaller than the size of the radial hole 33 in the front-rear direction, and the key member 32 can move in the front-rear direction by the distance C shown in FIG. It has become.

The key member 32 is the power piston 2
The rearward step of the rear shell 12 covering the front outer periphery of the rear shell 2 restricts the rearward movement. That is, the housing 1
The rearward movement limit of the power piston 22 with respect to 4 is
As shown in FIG. 2, the front wall 33a of the radial hole 33 abuts on the front surface 32d of the key member 32, and the rear surfaces 32c at both ends of the key member 32 are moved rearward by the rear end step of the rear shell 12. Movement is restricted. The center of the key member 32 is
A first flange portion 34 formed in the center of the plunger 37
Rear end surface 34b of the second flange portion 35 and the front end surface 35 of the second flange portion 35.
It is arranged between a and a. Therefore, the power piston 2
The rearward movement limit of the plunger 37 with respect to 2 is the position where the rear end surface 34b contacts the front surface 32d of the key member 32 and the rear surface 32c of the key member 32 contacts the rear wall 33b of the radial hole 33. Also, power piston 2
The forward movement limit of the plunger 37 with respect to 2 is a position where the front end surface 35a abuts on the rear surface 32c of the key member 32 and the front surface 32d of the key member 32 abuts on the front wall 33a of the radial hole 33.

Inside the power piston 22, the variable pressure chamber 24 is communicated with the constant pressure chamber 23 in response to the forward / backward movement of the plunger 37 with respect to the power piston 22, while the variable pressure chamber 24 is shut off from the atmosphere. Is the constant pressure chamber 2
3 and the output holding action state in which the variable pressure chamber 24 is shut off from the atmosphere and the output increasing action state in which the variable pressure chamber 24 is shut off from the constant pressure chamber 23 and communicates with the atmosphere.

The valve mechanism 36 includes an atmosphere valve seat 37a integrally formed on a rear end surface of a rear end portion of the plunger 37, which has a flange shape in the radial direction, and a front and rear direction of an intermediate portion 221 of the power piston 22. A first negative pressure valve seat 38 integrally formed at the extending rear end portion and a second negative pressure valve seat 39 integrally formed at the rear end portion of the tubular valve seat member 40.
And a movable portion 41 having valve seal portions 41a and 41b, which are arranged to face the first negative pressure valve seat 38 and the atmosphere valve seat 37a, respectively, and seal the first negative pressure valve seat 38 and the atmosphere valve seat 37a, respectively. The power piston 2 is provided by the retainer 42 which is disposed behind the movable portion 41 and whose forward movement is restricted by the inner step portion located behind the power piston 22.
The fixing portion 43 that hermetically fixes the second space 22b in the second
The movable portion 41 mainly includes a tubular member 45 made of an elastic member that is urged forward by a spring 44 arranged between the valve mechanism 36 and the retainer 42.

FIG. 3 shows the outer shape of the valve member 40. The valve seat member 40 has the plunger 37 inserted therein, and the slit 40b into which the second flange portion 35 protruding in the radial direction of the plunger 37 protrudes, and the through hole 40e penetrating in the front-rear direction.
Equipped with. The annular portion 40 is provided in front of the slit 40b.
and the annular front groove wall 4 is provided in front of the slit 40b.
0f, and an annular rear groove wall 40g having a larger diameter than the front groove wall 40f is provided on the rear side.
It is connected to and integrated with g by two arms 40a, and the two arms 40a are formed on a straight line with respect to a straight line passing through the center of the valve seat member 40. The forked key member 32 is inserted into the slit 40b of the valve seat member 40 from both sides of the arm 40a in the radial direction. The valve seat member 40 is disposed in the third space 22c of the intermediate portion 221, and is movable in the front-rear direction with respect to the power piston 22.

The first flange portion 34 of the plunger 37 is inserted into the through hole 40e of the valve seat member 40, and the second flange portion 35 projects from the slit 40b to the outside of the valve seat member 40. When the plunger 37 provided with the valve seat member 40 is disposed in the power piston 22, the second flange portion 35 abuts the inner peripheral surface 221a of the intermediate portion 221, and the plunger 3
7, the second flange portion 35 is the inner peripheral surface 22 of the intermediate portion 221.
It is slidably supported in the front-rear direction along 1a.

On the other hand, the valve seat member 40 is located between the outer periphery of the plunger 37 and the inner periphery of the intermediate portion 221 of the power piston 22, and has a rear end portion in the shape of a flange that swells in the radial direction. Even at the rear end portion where the second negative pressure valve seat 39 is formed, the inner peripheral surface of the intermediate portion 221 slidably abuts at two positions in the front-rear direction. That is, the power piston 22 includes the intermediate portion 221 having a function of holding the valve seat member 40 slidably rearward. An annular recess is formed on the outer peripheral surface of the rear end portion of the valve seat member 40 fitted and inserted in the intermediate portion 221 to ensure airtightness between the rear end portion of the valve seat member 40 and the inner peripheral surface of the intermediate portion 221. A retaining annular sealing member 46 is mounted in this recess.

A retainer 58 locked by a step portion formed on the input rod 28 integrally connected to the plunger 37 by a coupling portion 80, and an inner diameter step portion of the power piston 22 disposed in front of the retainer 58. A spring 59 is arranged between the retainer 42 and the retainer 42. This spring 59 urges the input rod 28 rearward,
When the brake pedal is not depressed, the atmosphere valve seat 3
7a is brought into contact with the valve seal portion 41b provided on the movable portion 41 of the valve mechanism 36, and the distance between the valve seal portion 41a provided on the movable portion 41 and the first negative pressure valve seat valve seat 38 is reduced by the distance A. Hold in a separated state.

The passage 60 formed in the front-rear direction and communicating with the intermediate portion 221 and the first space 22a connect the valve mechanism 36 and the constant pressure chamber 23, and the third space 22c connects the valve mechanism 36 and the variable pressure chamber. To contact.

Inside the intermediate portion 221 of the power piston 22, four substantially J-shaped groove portions are formed at predetermined intervals in the circumferential direction, and a driving means for propelling the valve seat member 40 rearward is provided therein. Is provided. This drive means is composed of a spring 47 that is locked to a flange formed on the rear side of the valve seat member 40 and biases the valve seat member 40 rearward, and the key member 32 described above.

The first located in front of the power piston 22
A holding means 48 is arranged in the space 22a. The holding means 48 has a holding member 52 having an engaging portion 52b on the rear side that engages with an engaged portion 40c formed in a flange shape on the front side of the valve seat member 40, and a holding member 52 in the direction of reducing the diameter of the holding member 52. The retaining portion 52c of the holding member 52 is fitted into the retaining groove 50a of the retaining member 50 fixed to the front portion of the power piston 22. As a result, the holding member 52 cannot move in the front-rear direction, and the expansion / contraction movement in the radial direction around the locking portion 52c is allowed. As shown in FIG. 4, the holding member 52 has a three-section hollow truncated cone shape in which a hollow truncated cone is cut along three planes passing through the central axis of the holding member 52. It is attached to 22.

In this embodiment, during the emergency braking operation, the plunger 37 advances with respect to the power piston 22, the front end surface 35a of the second flange portion 35 abuts on the rear surface of the key member 32, and the key member 32 The front surface 32d of 32 abuts on the front wall 33a of the radial hole 33 of the power piston 22. That is, the plunger 37 can move forward by the distance E with respect to the power piston 22.

Next, the structure of the key member 32 of this new technology will be described with reference to FIG. As shown in FIG. 6A, the key member 32 is made of a metal member having a substantially U-shape, one of which is bifurcated, and has a function of restricting the movement of the plunger 37 in the front-rear direction. The bifurcated outer shape is provided with notches 32e at four positions above and below. The notch 32e allows the power piston 22 to move in the front-rear direction but cannot move in the radial direction, and is fitted into the radial hole 33 formed in the radial direction of the power piston 22. It is supposed to be done. As shown in FIG. 6B, in the key member 32, the front surface 32d is flat, but the rear surface 32c is provided with two elastic members 32a integrally with the key member 32 at two central portions of the flat surface. ing.
The elastic member 32 is formed on the key member by vulcanizing rubber and baking the key member 32. The outer shape of the elastic member 32a is a semicircular shape having an arc surface on the outside. Further, the elastic member 32a is provided inside the valve seat member 40, and prevents the front end surface 35a of the plunger 37 from directly contacting the key member 32. The left and right elastic members 32a, which are bifurcated, are each provided with two trapezoidal projections 32b in the vertical direction (radial direction), and the projections 32b are arranged so as to face the front end surface 35a of the plunger 37. .

Next, the operation of the negative pressure type booster 10 of this new technology will be described. Since the operation as the booster in the normal operating state is known, the description thereof is omitted here.
The operation during emergency braking will be mainly described.

The emergency braking characteristic of the negative pressure type booster 10 of this new technology is obtained by changing the jumping characteristic described above.
This is achieved by applying a larger propulsive force to the output member than during normal braking. In order to change the jumping characteristic, the gap D between the contact member 70 and the reaction member 54 in FIG. 2 may be increased. The expansion of the gap D is
This is the same as increasing the distance between the contact surface 22d of the power piston 22 against the reaction force member 54 and the valve seal portion 41b. That is, by moving the valve seal portion 41b rearward, the gap D is enlarged and the contact member 70 is moved by the reaction member 54.
The output is increased until the reaction force is received, and the output in the so-called jumping state where the ratio of the output to the input is infinite is made larger than in the normal state.

The actual operation during the emergency braking operation will be described below.

If the relative movement amount between the plunger 37 and the power piston 22 becomes larger than a predetermined value B during an emergency brake operation in which the driver hurriedly depresses the brake pedal due to the appearance of an obstacle while the vehicle is traveling, the plunger 37 moves. The inclined surface 37b abuts the tapered portion 52a of the holding member 52, and radially expands the holding member 52, which is biased by the ring-shaped elastic body 53 in the direction of reducing the diameter.

Thereafter, the minimum inner diameter portion 52aa protruding inward of the taper portion 52a rides on the first flange portion 34 of the plunger 37, and becomes the engaged portion 40c of the valve seat member 40 and the engaging portion 52b of the holding member 52. Is released. When the engagement is released in this way, the valve seat member 40 has the spring 47 arranged between the substantially J-shaped groove portion inside the power piston and the front end of the rear flange portion of the valve seat member 40. Is urged backwards. Therefore, the engaged portion 40
When the engagement of c is released, the valve seat 40 is instantaneously moved rearward by the biasing force of the spring 47.

In this case, since the key member 32 is fitted and inserted with the two arms 40a sandwiched by the rearward movement of the valve seat member 40, when the valve seat member 40 moves rearward, the front groove wall 40f. As a result, the front surface 32d of the key member 32 is pushed rearward, and as a result, the key member 32 and the valve seat portion 40 move integrally rearward. The key member 32 is movable by a distance E, and hits the front end face 35a of the second flange portion 35 of the plunger 37 during the movement, but in the present embodiment, the elastic member 32a, the elastic member 32a,
Since 32b is provided, when the key member 32 is moved rearward, the front end surface 35a is defined by the trapezoidal protrusion 32.
b abuts first. The protrusion 32b is gradually deformed by the rearward moving force (thrust) of the key member 32, and thereafter,
The force is attenuated and the force that is not absorbed by the protrusion 32b is eventually transmitted to the elastic member 32a, so that the force at the time of contact can be absorbed by the elastic member 32a including the protrusion 32b. As a result, the power piston 2 of the plunger 37
When the amount of relative movement to the front with respect to 2 exceeds a predetermined value, the engagement between the holding member 48 and the valve seat member 40 is released, the valve seat member 40 retracts, and the key member moves rearward. Also the front end surface 35a of the second flange portion 35 and the key member 3
The thrust is absorbed by the deformation of the elastic member 32a including the projection 32b arranged between the rear surface 32c of the second flange portion 35 and the rear surface 32 of the key member 32.
It is possible to reduce the operating noise due to the contact between the two and c. In this case, since the force is first received by the small area of the trapezoidal shape, the above-described operating noise can be further reduced by the deformation of the protrusion 32b compared with the case where it is received by a large area at once.

In this way, when the valve seat member 40 moves rearward, the second negative pressure valve seat 39 of the valve seat member 40 abuts on the valve seal portion 41a constituting the movable portion 41 of the valve mechanism 36, and the constant pressure chamber. The communication between 23 and the transformer room 24 is cut off. At this time, the plunger 37 is moving forward together with the input rod 28, and the valve seat member 40 pushes back the movable portion 41 of the valve mechanism 36 to the rear.
a and the valve seal portion 41 that constitutes the movable portion 41 of the valve mechanism 36.
b is rapidly separated, and the variable pressure chamber 24 communicates with the atmosphere. As a result, compared with the normal braking operation, the communication between the constant pressure chamber 23 and the variable pressure chamber 24 is interrupted and the variable pressure chamber 24 is rapidly communicated with the atmosphere, and substantially, the reaction force member 54 of the power piston 22 to the reaction force member 54 is substantially reduced. Since the distance between the contact surface 22d and the valve seal portion 41b is increased, the output in the jumping state can be made larger than that in the normal state.

FIG. 7 shows the normal brake characteristic and the emergency brake characteristic. In FIG. 5, the jumping in the normal brake can obtain only the output of F ₀₁ , but the jumping in the emergency braking is increased to F ₀₁₁ and the brake fluid pressure is sufficient with a small pedal effort. Can be generated.

When the brake operation is completed and the brake pedal is returned, the plunger 37 moves rearward while the rear end surface 34b of the first flange portion 34 contacts the front surface of the key member 32. When the rear surface of the key member 32 contacts the rear shell 12, the front surface of the key member 32 contacts the front groove wall 40f of the valve seat member 40, and the power piston 2
The rearward movement of the valve seat member 40 that has retracted integrally with the valve 2 is restricted. At this time, since the power piston 22 still retracts, the engaging portion 52b of the holding member 52 that retracts integrally with the power piston 22 abuts the rear shell 12 via the key member 32 and remains stationary. The engaging member 40c of the seat member 40 is engaged, and the retaining member 52 and the valve seat member 40 disengaged by the emergency braking operation.
And will be re-engaged to prepare for the next emergency braking operation.

[0042]

According to the new technology, when the relative amount of forward movement of the plunger with respect to the power piston exceeds a predetermined value, the engagement between the holding member and the valve seat member is released, and the valve seat member is released. Even if the key member moves backward and the key member moves rearward at that time, the elastic member is arranged between the front end surface of the second flange portion and the rear surface of the key member. By the deformation, the operating noise due to the contact between the front end surface of the second flange portion and the rear surface of the key member can be reduced, and the product quality of the negative pressure booster can be improved.

In this case, if the projection is formed on the elastic member, the relative amount of forward movement of the plunger with respect to the power piston becomes a predetermined value or more, and when the key member moves rearward, the movement thereof. Accordingly, the protrusion is crushed and deformed, so that the thrust force when the key member is moved rearward can be absorbed. Therefore, the operating noise between the front end surface of the second flange portion and the rear surface of the key member can be further reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a negative pressure type booster according to an embodiment of the new technology.

FIG. 2 is a partial enlarged view of a main part showing details inside the power piston shown in FIG.

FIG. 3 is a perspective view showing an outer shape of the valve seat member shown in FIG.

FIG. 4 is a perspective view showing one outer shape of the holding member shown in FIG.

FIG. 5 is a characteristic diagram showing the relationship between the force (input) applied to the input rod of the negative pressure type booster and the propulsive force (output) of the output member 55 in the embodiment of the new technology.

6 is a diagram showing the shape of the key member shown in FIG.
(A) is a front view, (b) is a side view, and (c) is a partial enlarged view of a part where an elastic member is provided.

[Explanation of symbols]

10 Negative pressure type booster 14 housing 20 movable walls 22 Power Piston 23 Constant pressure chamber 24 transformer room 28 Input rod 32 key members 32a elastic member 32b protrusion (elastic member) 33 radial holes 34 First flange part 34a front end face 35 Second flange part 35a front end face 36 valve mechanism 37 Plunger 37a Atmospheric valve seat 38 First negative pressure valve seat 39 Second negative pressure valve seat 40 valve seat member 40e through hole 41 Moving part 43 Fixed part 47 spring (drive means) 48 holding means 50 locking member 50b rear end 55 Output member

Claims (2)

[Claims] 1. A housing having a pressure chamber formed therein, a movable wall disposed inside the housing such that the pressure chamber can be moved forward and backward, and dividing the pressure chamber into a constant pressure chamber and a variable pressure chamber. A power piston having a first negative pressure valve seat and a radial hole and integrated with the movable wall; and an input rod arranged inside the power piston so as to be able to move forward and backward with respect to the power piston. Having a first flange portion and a second flange portion, connected to the input rod, and fitted into the power piston so as to be slidable in the front-rear direction with respect to the power piston,
A plunger having an atmosphere valve seat, an output member for outputting the propulsive force of the power piston accompanying the movement of the movable wall to the outside of the device, a second negative pressure valve seat, and a forward and backward movement with respect to the power piston. A valve seat member that can be retracted and is substantially concentric with the first negative pressure valve seat, a movable portion that is disposed in the power piston and faces the first negative pressure valve seat, and is disposed concentrically with the movable portion. A valve mechanism having a fixed portion; drive means for moving the valve seat member toward the movable portion by a predetermined amount when the amount of advance of the plunger with respect to the power piston is greater than or equal to a predetermined value; and the power piston of the plunger. Holding means for holding the valve seat member at a predetermined position in the power piston when the amount of advance relative to the power piston is smaller than a predetermined value; a locking member for locking the holding means to the power piston; A key member that is inserted into the radial hole and that moves in the front-rear direction between the first flange portion and the second flange portion of the plunger, and that regulates the front-rear movement amount of the plunger with respect to the power piston; In the negative pressure type booster including: a negative pressure type booster, wherein an elastic member is disposed between a front end surface of the second flange portion and a rear surface of the key member. 2. The negative pressure type booster according to claim 1, wherein a protrusion is formed on the elastic member.