JP4512032B2 - Negative pressure booster - Google Patents

Description

  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 and a front negative pressure chamber connected to a negative pressure source and a rear working chamber. The booster piston to be partitioned is accommodated, and a valve cylinder that is slidably supported on the rear wall of the booster shell is connected to the booster piston. An input return spring that urges the valve in the reverse direction and a control valve that switches the working chamber to the negative pressure chamber and the atmosphere in response to the longitudinal movement of the input rod are provided. An air introduction valve seat that is connected in a swingable manner and slides back and forth through the guide hole of the valve cylinder, and is connected to the rear end of the valve piston via a small diameter part, and the valve cylinder is linked to its longitudinal movement. Negative pressure introduction valve seats connected to the air, these atmospheric introduction valve seats and negative pressure introduction valves The valve cylinder is spring-biased in the seating direction, and when the valve body opens the atmosphere introduction valve seat as the input rod advances, the atmosphere is introduced into the working chamber through the atmosphere introduction valve seat. And a negative pressure introduction path for introducing the negative pressure of the negative pressure chamber into the working chamber through the negative pressure introduction valve seat when the valve body opens the negative pressure introduction valve seat as the input rod moves backward, A plurality of axial grooves formed on the inner peripheral surface of the guide hole in which the valve piston is slidably fitted to the atmosphere introduction path, and a valve cylinder for communicating the front end of these axial grooves with the working chamber It is related with the improvement of the negative pressure booster comprised with the horizontal hole provided in.

Such a negative pressure booster is already known as disclosed in Patent Document 1.
Japanese Patent No. 2963422

  The valve piston in such a negative pressure booster has an input rod connected to the valve piston in a swingable manner between a piston portion slidably fitted in the guide hole of the valve cylinder and the air introduction valve seat. Since the small diameter part for connecting the front end part is formed, when the atmosphere introduction valve seat is opened by the forward operation of the input rod, immediately after the atmosphere passes through the atmosphere introduction valve seat, an annular ring around the small diameter part of the valve piston is formed. The present inventors have determined that eddy currents are generated in the space, and this is one of the causes of the introduction of atmospheric air.

  Therefore, an object of the present invention is to provide the negative pressure booster that can effectively silence the above-described atmosphere introduction sound.

In order to achieve the above object, the present invention accommodates a booster piston that divides the inside thereof into a front negative pressure chamber and a rear working chamber connected to a negative pressure source. A valve cylinder that is slidably supported on the rear wall of the booster shell is connected, and an input rod that can be moved back and forth in the valve barrel, an input return spring that biases the input rod in the backward direction, and an input A control valve that switches the working chamber to the negative pressure chamber and the atmosphere according to the back-and-forth movement of the rod is provided, and this control valve is connected to the input rod so that it can swing, and the guide hole of the valve cylinder is An air introduction valve seat that is connected to the rear end of the valve piston that slides through a small diameter portion, a negative pressure introduction valve seat that is connected to the valve cylinder so as to be linked to its longitudinal movement, and The valve body is spring-biased in the seating direction of the air introduction valve seat and the negative pressure introduction valve seat. When the valve body opens the air introduction valve seat as the soot advances, the air introduction path introduces air into the working chamber through the air introduction valve seat, and the valve body opens the negative pressure introduction valve seat as the input soot moves backward A negative pressure introduction passage for introducing the negative pressure of the negative pressure chamber into the working chamber through the negative pressure introduction valve seat, and the atmosphere introduction passage is slidably fitted to the inner peripheral surface of the guide hole in which the valve piston is slidably fitted A negative pressure booster comprising a plurality of axial grooves formed in the cylinder and a lateral hole provided in the valve cylinder so as to communicate the front end portion of the axial grooves with the working chamber. The partition wall is extended so that its rear end crosses the periphery of the small diameter portion and reaches the atmosphere introduction valve seat, and the atmosphere passing through the atmosphere introduction valve seat is guided to the axial groove around the valve piston. configure the baffle wall, the front Symbol atmosphere introduction valve seat formed in a larger diameter than the valve piston These valves piston and the baffle wall in the air introducing valve seats, and that the height is formed stepwise decreasing stepwise toward the air introducing valve seat side first feature.

In addition to the first feature, the second feature of the present invention is that the rectifying wall is formed in a tapered shape so that the lateral width thereof decreases toward the atmosphere introduction valve seat.

  Furthermore, in addition to the first or second feature, the present invention provides a key member that restricts the backward limit of the valve cylinder and the input rod by attaching the lateral hole to the valve cylinder across the neck of the valve piston. The third feature is that it is used for the mounting hole.

  According to the first aspect of the present invention, when the atmosphere introduction valve seat is opened by the forward operation of the input rod, if the atmosphere passes through the atmosphere introduction valve seat, the atmosphere is formed by a plurality of rectifying walls formed in the valve cylinder. It is guided to the axial groove around the valve piston, which can suppress the generation of atmospheric vortex in the annular space around the small diameter part of the valve piston and effectively prevent the air introduction sound caused by the vortex. Or can be significantly reduced.

In addition, the opening of the air introduction valve seat is small at the time of weak braking with a small forward operation amount of the input rod or at the beginning of slow braking, and the air introduction valve seat is located in the middle of the low part of the rectifying wall. In this state, there is a small annular space behind the air introduction valve seat, so a part of the atmosphere that has passed through the atmosphere introduction valve seat spreads to the annular small space side. Therefore, the flow velocity can be reduced, thereby suppressing the generation of atmospheric introduction sound called “flute”.

  Also, during forced movement or sudden braking that greatly advances the input rod, the opening of the air introduction valve seat is large and the air introduction valve seat is close to the high part of the rectifying wall. Passes through the air introduction valve seat and is smoothly guided to the multiple axial grooves around the valve piston while being immediately rectified by the second part of the high rectifying wall, thus suppressing the generation of air introduction noise. However, it is possible to increase the operating response of the booster piston by flowing a large amount of air through the air introduction path.

According to the second feature of the present invention, when the atmosphere introduction valve seat is opened, the rectification function of the rectification wall for guiding the atmosphere to the axial groove is enhanced to more effectively suppress the generation of the atmosphere introduction sound. Can do.

  According to the third aspect of the present invention, the lateral hole that communicates a plurality of axial grooves with the working chamber is used as a mounting hole for the key member, so that the structure can be simplified and the cost can be reduced. .

Embodiments of the present invention will be described based on reference examples and preferred examples of the present invention shown in the accompanying drawings.

1 is a longitudinal sectional view of a negative pressure booster according to a reference example of the present invention, FIG. 2 is an enlarged sectional view of part 2 of FIG. 1 (sectional view taken along line 2-2 of FIG. 3), and FIG. 4 is a sectional view taken along line 4-4 of FIG. 3, FIG. 5 is a longitudinal sectional view of the valve cylinder alone, FIG. 6 is an explanatory view of the action when the air introduction valve seat is opened, and FIG. FIG. 8 is a diagram corresponding to FIG. 6 showing a first embodiment, and FIG. 8 is a diagram corresponding to FIG. 5 showing a second embodiment of the present invention in correspondence with a reference example .

First, the description starts with the description of the reference example of the present invention shown in FIGS. 1 and 2, the booster shell 1 of the negative pressure booster B is composed of a pair of front and rear shell halves 1a and 1b that connect opposite ends to each other. The cylinder body Ma of the brake master cylinder M is attached to the front wall of the front shell half 1a via a plurality of mounting bolts 6, and the rear shell half 1b is connected to the automobile via a plurality of support bolts 7. To the front wall F of the passenger compartment.

  The inside of the booster shell 1 includes a booster piston 4 accommodated therein so as to be capable of reciprocating back and forth, and a diaphragm 5 attached to the rear surface of the booster shell 1 and sandwiched between both shell halves 1a and 1b. Are divided into a negative pressure chamber 2 and a rear working chamber 3. The negative pressure chamber 2 is connected to a negative pressure source V (for example, inside the intake manifold of the internal combustion engine) via a negative pressure introduction pipe 14.

  The booster piston 4 is formed in an annular shape from a steel plate, and a synthetic resin valve cylinder 10 is integrally coupled to the central portions of the booster piston 4 and the diaphragm 5. The valve cylinder 10 is slidably supported via a seal member 13 on a support cylinder part 12 protruding rearward from the center part of the rear shell half 1b. When an annular support plate 8 that is insert-coupled to the seal member 13 is fitted to the support cylinder portion 12, a lock ring 9 that fixes the support plate 8 is locked.

  In the valve cylinder 10, a valve piston 18, an input rod 20 connected to the valve piston 18, and a control for switching the working chamber 3 between the negative pressure chamber 2 and the atmosphere according to the back and forth movement of the input rod 20 are controlled. A valve 38 is provided.

  The valve piston 18 has a piston portion 18a that is slidably fitted in a guide hole 11 provided in the valve cylinder 10, and a small-diameter portion 18b having a smaller diameter that is connected to the rear end of the piston portion 18a. A reaction force piston 17 is integrally connected to the front end of the piston portion 18a via the neck portion 19, and a flange-like air introduction valve seat 31 is integrally connected to the rear end of the small diameter portion 18b. An annular negative pressure introduction valve seat 30 that is concentrically arranged so as to surround the atmosphere introduction valve seat 31 is formed in the valve cylinder 10.

  The valve piston 18 is provided with a bottomed connecting hole 18c that opens at the rear end surface of the air introduction valve seat 31, and the ball joint portion 20a of the input rod 20 is rotatably fitted in the connecting hole 18c. The small-diameter portion 18b of the valve piston 18 is caulked and joined to prevent it from coming off. In this way, the input rod 20 is connected to the valve piston 18 so as to be swingable.

  Further, a common valve body 34 that cooperates with the negative pressure introduction valve seat 30 and the atmospheric introduction valve seat 31 is attached to the valve cylinder 10. The valve body 34 is entirely formed of an elastic material such as rubber, and includes an annular attachment bead portion 34b, an expansion / contraction cylinder portion 34c extending forward from the attachment bead portion 34b, and a front end of the expansion / contraction cylinder portion 34c. A flange-shaped valve portion 34a projecting outward in the radial direction is formed, and an annular reinforcing plate 44 is inserted into the valve portion 34a from the inner peripheral side thereof and is mold-coupled.

  The mounting bead portion 34b is sandwiched and fixed between the inner peripheral surface of the valve cylinder 10 and the front end portion of the valve holder 35 fitted to the inner peripheral surface of the valve cylinder 10 behind the negative pressure introducing valve seat 30. Is done. The valve holder 35 has a front end abutted against a rearward annular step 45 on the inner peripheral surface of the valve cylinder 10, and an input return spring 41 is contracted between the valve holder 35 and the input rod 20. As a result, the valve holder 35 is held in a contact position with the annular step 45 and the input rod 20 is urged in the backward direction.

  Further, the valve portion 34a is disposed so as to face the atmosphere introduction valve seat 31 and the negative pressure introduction valve seat 30 so as to be seated. Between the reinforcing plate 44 of the valve portion 34a and the input rod 20, a valve spring 36 that urges the valve portion 34a in the seating direction with the valve seats 30 and 31 is contracted. Thus, the negative pressure introduction valve seat 30, the atmosphere introduction valve seat 31, the valve body 34 and the valve spring 36 constitute the control valve 38.

  Both ends of an extendable boot 40 covering the valve cylinder 10 are attached to the rear end of the support cylinder portion 12 of the rear shell half 1b and the input rod 20, and the valve body is attached to the rear end portion of the boot 40. An air introduction port 39 that communicates with the inside of 34 is provided. A filter 42 for filtering the air flowing into the atmosphere introduction port 39 is interposed between the outer peripheral surface of the input rod 20 and the inner peripheral surface of the valve cylinder 10. This filter 42 has flexibility so as not to hinder the relative movement of the input rod 20 and the valve cylinder 10.

  2 and 3, the valve cylinder 10 includes an air introduction passage 29 for introducing the air taken in from the air introduction port 39 into the working chamber 3 through the control valve 38, and a negative pressure in the negative pressure chamber 2. A negative pressure introduction path 28 is provided for introduction into the working chamber 3 via 38. The air introduction passage 29 communicates the plurality of axial grooves 29 a, 29 a... Formed in the inner periphery of the guide hole 11 of the valve cylinder 10 and the front ends of these axial grooves 29 a, 29 a. Thus, it is comprised by the flat horizontal hole 29b which crosses the valve cylinder 10 along a diameter line.

  4 and 5, the plurality of axial grooves 29a, 29a,... On the inner peripheral surface of the guide hole 11 are formed so that a partition wall is formed between the axial grooves 29a, 29a,. Are arranged at equal intervals in the circumferential direction. Each of the partition walls is configured as a rectifying wall 47, 47... By extending the rear end of the valve piston 18 across the small diameter portion 18 b of the valve piston 18 until reaching the periphery of the atmosphere introduction valve seat 31. The air that has passed 31 is guided to the axial grooves 29a, 29a,... Around the piston portion 18a.

  As shown in FIGS. 3 and 4, on the other hand, the negative pressure introduction path 28 extends in the axial direction outside the guide hole 11 in the radial direction, and the rear end opens to the outer peripheral portion of the negative pressure introduction valve seat 30. A plurality of axial holes 28a, 28a ... formed in the valve cylinder 10, and a plurality of funnel-shaped holes 28b that open to the negative pressure chamber 2 while expanding forward from the front ends of the axial holes 28a, 28a ... , 28b...

  As shown in FIGS. 2 and 4, the valve cylinder 10 further includes a key member 50 that extends through the lateral hole 29b and straddles the neck portion 19 between the valve piston 18 and the reaction force piston 17 within a certain distance. It is attached so that it can move in the direction. Both ends of the key member 50 (corresponding to the upper and lower ends in FIG. 3) protrude outward from the outer peripheral surface of the valve cylinder 10 by a predetermined length, and both ends of the key member 50 are front surfaces of the locking ring 9. , The retracting limit of the booster piston 4 is defined, and the retracting limit of the valve piston 18 with respect to the valve cylinder 10 is defined by the key member 50 receiving the stopper surface 19a at the front end of the neck portion 19. It has become.

  The width of the lateral hole 29b along the axial direction of the valve cylinder 10 is set to be larger than the plate thickness of the key member 50, so that the valve cylinder 10 and the key member 50 can be relatively moved relative to each other. Further, the axial length of the neck portion 19 is set to be larger than the plate thickness of the key member 50, so that the valve piston 18 and the key member 50 can move slightly relative to each other.

  Further, the valve cylinder 10 is provided with an operating piston 15 that protrudes forward and a small-diameter cylinder hole 16 that penetrates the center of the operating piston 15, and the reaction-force piston 17 slides in the small-diameter cylinder hole 16. Fits freely. A cup body 21 is slidably fitted on the outer periphery of the working piston 15, and the cup body 21 is filled with a flat elastic piston 22 that faces the working piston 15 and the reaction force piston 17. At this time, a constant gap is formed between the reaction force piston 17 and the elastic piston 22 when the negative pressure booster B is not operated.

  An output rod 25 projects from the front surface of the cup body 21, and this output rod 25 is connected to the piston Mb of the brake master cylinder M.

  In the above, the operation piston 15, the reaction force piston 17, the elastic piston 22, and the cup body 21 constitute a reaction force mechanism 24 that feeds back a part of the output of the output rod 25 to the input rod 20.

  A retainer 26 is disposed so as to abut the cup body 21 and the front end face of the valve cylinder 10, and the booster piston 4 and the valve cylinder 10 are urged in the backward direction between the retainer 26 and the front wall of the booster shell 1. The booster return spring 27 is contracted.

Next, the operation of this reference example will be described.

  In the rest state of the negative pressure booster B, as shown in FIGS. 2 and 4, the key member 50 attached to the valve cylinder 10 contacts the front surface of the locking ring 9 of the rear shell half 1 b, thereby booster piston 4. The key member 50 receives the stopper surface 19a connected to the front end of the neck portion 19 to hold the valve piston 18 in the backward limit. At this time, the air introduction valve seat 31 presses the valve portion 34 a and is slightly separated from the negative pressure introduction valve seat 30 while being in close contact with the valve portion 34 a of the valve body 34. As a result, the communication between the air introduction port 39 and the air introduction path 29 is cut off, while the communication between the negative pressure introduction path 28 and the air introduction path 29 is established, so that the negative pressure in the negative pressure chamber 2 is reduced to the negative pressure introduction path 28 and The booster piston 4 and the valve cylinder 10 are held in the retracted position by the urging force of the booster return spring 27 because the pressure is transmitted to the working chamber 3 through the atmosphere introduction passage 29 and the chambers 2 and 3 are at the same pressure.

  Now, when the input rod 20 is advanced together with the valve piston 18 against the set load of the input return spring 41 by depressing the brake pedal P to brake the vehicle, the urging force of the valve spring 36 causes the telescopic cylinder portion 34c to move. The valve portion 34a is seated on the negative pressure introduction valve seat 30 while extending, and at the same time, the atmosphere introduction valve seat 31 is separated from the valve body 34, thereby disconnecting the communication between the atmosphere introduction passage 29 and the negative pressure introduction passage 28. The air introduction path 29 is communicated with the air introduction port 39 through the inside of the valve body 34.

  As a result, the atmosphere flowing into the valve cylinder 10 from the atmosphere introduction port 39 passes through the atmosphere introduction valve seat 31 and is introduced into the working chamber 3 through the atmosphere introduction passage 29, and the working chamber 3 is set to a pressure higher than that of the negative pressure chamber 2. Therefore, by obtaining a forward thrust based on the pressure difference between them, the booster piston 4 resists the force of the booster return spring 27 with the valve cylinder 10, the operating piston 15, the elastic piston 22, the cup body 21 and the output rod 25. The piston Mb of the brake master cylinder M is driven by the output rod 25. The elastic piston 22 is compressed by the reaction force generated by the driving, and a part of the elastic piston 22 is expanded into the small-diameter cylinder hole 16, and the front surface of the reaction force piston 17 is brought into contact with the expanded portion. A part of the reaction force is fed back to the input rod 20 via the elastic piston 22, so that the operator can feel the magnitude of the output of the output rod 25. The output of the output rod 25 increases with a boost ratio determined by the ratio of the pressure receiving areas of the working piston 15 and the reaction force piston 17 that are in contact with the elastic piston 22.

  By the way, the upstream side of the air introduction path 29 is constituted by a plurality of axial grooves 29a, 29a,... On the inner peripheral surface of the guide hole 11 of the valve cylinder 10 into which the valve piston 18 is slidably fitted. The partition walls between the direction grooves 29a, 29a,... Are configured to extend to the atmosphere introduction valve seat 31 so as to cross the periphery of the small diameter portion 18b of the valve piston 18 and are formed into the rectifying walls 47, 47, etc. Passes through the atmosphere introduction valve seat 31, and the atmosphere is immediately guided to the axial grooves 29a, 29a,... Around the piston portion 18a by the plurality of rectifying walls 47, 47,. Generation of atmospheric eddy currents in the space can be suppressed, and air introduction sound due to the eddy currents can be effectively prevented or significantly reduced.

  Further, the downstream side of the air introduction path 29 is constituted by a flat lateral hole 29b that traverses the valve cylinder 10 along the diameter line so that the front ends of the plurality of axial grooves 29a, 29a, ... communicate with the working chamber 3. In addition, since the key member 50 is attached to the valve cylinder 10 using the lateral hole 29b, the lateral hole 29b serves both as a configuration on the downstream side of the air introduction path 29 and a mounting hole for the key member 50. Therefore, the structure can be simplified and the cost can be reduced.

  When the pedaling force is released from the brake pedal P in order to release the braking state of the vehicle, first, the input rod 20 and the valve piston 18 are moved backward by the force of the input return spring 41. Accordingly, the valve piston 18 largely separates the valve body 34 from the negative pressure introduction valve seat 30 while seating the atmosphere introduction valve seat 31 on the valve body 34, so that the working chamber 3 is connected to the atmosphere introduction path 29 and the negative pressure passage 29. The negative pressure chamber 2 communicates with the pressure introduction path 28. As a result, the introduction of the atmosphere into the working chamber 3 is prevented, while the air in the working chamber 3 is sucked into the negative pressure limit V through the negative pressure chamber 2 and the pressure difference therebetween is eliminated. With the elastic force of the booster return spring 27, the master cylinder M is released from operation. Then, the booster piston 4 and the input rod 20 return to the resting state shown in FIGS.

Next, a first embodiment of the present invention shown in FIG. 7 will be described.

In the first embodiment, the air introduction valve seat 31 is formed with a larger diameter than the valve piston 18. Further, between the valve piston 18 and the atmosphere introduction valve seat 31, the flow regulating walls 47, 47... Are formed in a stepped shape whose height gradually decreases toward the atmosphere introduction valve seat 31 side. Specifically, the rectifying walls 47, 47... Correspond to a region where the atmosphere introduction valve seat 31 moves, and the first portion 47a having a low height and the outer peripheral surface of the valve piston 18 connected to the rear end of the first portion 47a. And a second portion 47b having a height corresponding to.

The other configuration is the same as the reference example, in FIG. 7, the parts corresponding to reference example are denoted by the same reference numerals, and overlapping description is omitted.

According to the first embodiment, at the time of weak braking with a small forward operation amount of the input rod 20 or at the early stage of advancement of the input rod 20 in the slow braking, the air introduction valve seat 31 has the height of the rectifying walls 47, 47. It occupies a small opening position A corresponding to an intermediate portion of the first portion 47a having a small height. In this state, an annular small space S exists between the atmosphere introduction valve seat 31 and the second portions 47b of the rectifying walls 47, 47. By spreading the flow toward the annular small space S, the flow velocity can be reduced, thereby suppressing the generation of atmospheric introduction sound called “flute”.

  When the input rod 20 is forcibly moved forward or suddenly braked, the air introduction valve seat 31 occupies a large opening position B close to the second portion 47b of the rectifying walls 47, 47. . In this state, a large amount of air passes through the air introduction valve seat 31 and is immediately rectified by the second portion 47b having the high rectifying walls 47, 47. 29a..., 29a..., 29a..., 29a.

In the second embodiment of the present invention shown in correspondence with the reference example in FIG. 8, except that the respective rectifying walls 47, 47... Are tapered so that the lateral width decreases toward the air introduction valve seat 31. if omitted, the same as the reference example, in FIG. 8, the parts corresponding to reference example are denoted by the same reference numerals, and redundant description.

According to the second embodiment, when the air introduction valve seat 31 is opened, the rectifying function of guiding the air to the axial grooves 29a, 29a,... Suppression can be performed more effectively. The configuration of the second embodiment, that apply to the first embodiment.

  The present invention is not limited to the above embodiments, and various design changes can be made without departing from the scope of the invention. For example, the negative pressure booster B can be configured as a tandem type in which a pair of front and rear booster pistons are coupled to the same valve cylinder.

It is a longitudinal cross-sectional view of the negative pressure booster which concerns on the reference example of this invention. FIG. 2 is an enlarged cross-sectional view of part 2 of FIG. 1 (cross-sectional view taken along line 2-2 of FIG. 3). FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. It is a longitudinal cross-sectional view of a single valve cylinder. It is operation | movement explanatory drawing at the time of open | release of an air introduction valve seat. 1 shows a first embodiment of the present invention. FIG. 6 is a diagram corresponding to FIG. 5 and illustrating the second embodiment of the present invention in correspondence with the reference example .

B ... Negative pressure booster V ... Negative pressure source 1 ... Booster shell 2 ... Negative pressure chamber 3 ... Working chamber 4 ... Booster piston 10 ... Valve Tube 11 ... Guide hole 18 ... Valve piston 18a ... Piston part 18b ... Small diameter part 20 ... Input rod 28 ... Negative pressure introduction passage 29 ... Air introduction passage 29a ... Axial groove 29b .. Horizontal hole 30 ... Negative pressure introduction passage 31 ... Atmospheric introduction passage 38 ... Control valve 41 ... Input return spring 47 ... Rectification wall 50 ... Key member

Claims (3)

The booster shell (1) accommodates a booster piston (4) which is divided into a front negative pressure chamber (2) and a rear working chamber (3) connected to the negative pressure source (V). A valve cylinder (10) that is slidably supported on the rear wall of the booster shell (1) is connected to the piston (4), and an input rod (20) that can move back and forth in the valve cylinder (10). And an input return spring (41) for urging the input rod (20) in the backward direction, and the working chamber (3) into the negative pressure chamber (2) and the atmosphere according to the longitudinal movement of the input rod (20). And a control valve (38) for switching communication. The control valve (38) is slidably moved back and forth through the guide hole (11) of the valve cylinder (10) by connecting the input rod (20) so as to swing. An air introduction valve seat (31) connected to a rear end portion of the moving valve piston (18) via a small diameter portion (18b) and a valve cylinder (10) A negative pressure introduction valve seat (30) arranged to be interlocked with the longitudinal movement, and a valve body that is spring-biased in the seating direction of the atmospheric introduction valve seat (31) and the negative pressure introduction valve seat (30) (34), and the valve cylinder (10) has the atmosphere introduced into the atmosphere introduction valve seat (31) when the valve element (34) opens the atmosphere introduction valve seat (31) as the input rod (20) advances. ) Through the air introduction path (29) to be introduced into the working chamber (3), and when the valve element (34) opens the negative pressure introduction valve seat (30) as the input rod (20) moves backward, the negative pressure chamber (2 ) Is introduced into the working chamber (3) through the negative pressure introduction valve seat (30), and the valve piston (18) slides in the atmosphere introduction passage (29). A plurality of axial grooves (29a) formed on the inner peripheral surface of the guide hole (11) to be freely fitted, and front end portions of these axial grooves (29a) In the negative pressure booster constructed out with horizontal hole provided in the valve cylinder to pass communicating (10) the working chamber (3) (29 b),
The partition between each of the plurality of axial grooves (29a) is extended so that the rear end thereof crosses the periphery of the small diameter portion (18b) and reaches the periphery of the atmosphere introduction valve seat (31). A flow straightening wall (47) for guiding the air that has passed through the introduction valve seat (31) to the axial groove (29a) around the valve piston (18) ;
The atmosphere introduction valve seat (31) is formed to have a larger diameter than the valve piston (18), and the height of the flow straightening wall (47) between the valve piston (18) and the atmosphere introduction valve seat (31) is increased. A negative pressure booster characterized by being formed in a stepped shape that decreases stepwise toward the atmosphere introduction valve seat (31) side . The negative pressure booster according to claim 1,
A negative pressure booster characterized in that the flow straightening wall (47) is formed in a tapered shape so that its lateral width decreases toward the atmosphere introduction valve seat (31) . The negative pressure booster according to claim 1 or 2,
The lateral hole (29b) is a key that is attached to the valve cylinder (10) so as to straddle the neck (19) of the valve piston (18) and regulates the backward limit of the valve cylinder (10) and the input rod (20). A negative pressure booster characterized in that it is used for a mounting hole of a member (50).

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