JP2005349867A - Negative pressure booster - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable the output to reach a double force critical point in an earlier stage and to retain it at the time of emergency braking while eliminating the delay of the atmospheric air introduction to a working chamber regardless of the time of normal braking or emergency braking in a negative pressure booster. <P>SOLUTION: For this negative pressure booster, a reaction force mechanism 24 is inserted between a valve cylinder 10 which is integrally connected with a booster piston 4, and an input rod 20 and an output rod 25. In the negative pressure booster, a valve piston 33 is fitted on an input piston 18 of the reaction force mechanism 24 being connected with the input rod 20 in such a manner that the valve piston 33 may be slidable forward from a specified retracted position R to the input piston 18. At the same time, the valve piston 33 is urged by a spring in the retracting direction. A fastening means 56 which holds an atmospheric air introduction valve seat 31 under an opened state by engaging the valve piston 33 with a supporting cylinder 54 at the time of emergency braking in which the input piston 18 precedes and advances more than a specified stroke ahead of the valve cylinder 10 is provided in a space between the valve piston 33 and the supporting cylinder 54 which is an separate body and is attached to the valve cylinder 10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 according to the longitudinal movement of the input rod are provided. An atmospheric introduction valve seat formed on the valve piston that is linked to the movement, a negative pressure introduction valve seat that is connected to the valve cylinder so as to be linked to the longitudinal movement, and the atmospheric introduction valve seat and the negative pressure introduction valve seat Springs in the seating direction of the The communication with both the air and negative pressure chambers is shut off. When the air introduction valve seat is opened as the input rod moves forward, the working chamber is communicated with the atmosphere, and when the negative pressure introduction valve seat is opened when the input rod moves backward. The working chamber is composed of a valve body that communicates with the negative pressure chamber. Between the valve cylinder and the input rod and the output rod that is slidably supported by the booster shell, the operation input to the input rod, the working chamber, The reaction force mechanism that transmits the resultant force of the booster piston thrust due to the pressure difference between the negative pressure chambers to the output rod is connected to the input piston connected to the input rod and the booster piston. An operating piston arranged to surround the input piston, an output piston connected to the output rod, and an elastic reaction force piston interposed between the rear end surface of the output piston and the input piston and the front end surface of the operating piston; Of negative pressure booster composed of About the good.

Conventionally, in such a negative pressure booster, as disclosed in Patent Documents 1 and 2, at the time of emergency braking, the air introduction valve is greatly opened to quickly introduce a large amount of air into the working chamber and to increase the output power. A device that is designed to exert its output is known.
JP 2001-63551 A JP 2001-341632 A

  By the way, what was disclosed by patent document 1 can slide a valve piston to the input piston which connects between an input rod and reaction force mechanism, and this can slide between the retreat position and the advance position along an axial direction with respect to an input piston. And an atmospheric introduction valve seat formed at the rear end of the valve piston, a negative pressure introduction valve seat formed on the valve cylinder and surrounding the atmospheric introduction valve seat, the atmospheric introduction valve seat and the negative A cylindrical valve body that is mounted on the inner peripheral surface of the valve cylinder and has a common valve section that can be seated on the pressure introduction valve seat at the front end, and the valve section is an air introduction valve seat and a negative pressure introduction valve seat And a valve spring energized in the seating direction to form a control valve. The valve cylinder communicates with the negative pressure chamber and opens to the outer periphery of the negative pressure introducing valve seat, and communicates with the working chamber. A second port that opens between the air introduction valve seat and the negative pressure introduction valve seat, while the inside of the valve body communicates with the atmosphere, The piston biases the return spring to the retracted position with a smaller set load than the valve spring, and a delay that delays the retract from the forward position due to the biasing force of the return spring of the valve piston between the valve piston and the input piston. According to this configuration, during emergency braking in which the input rod is rapidly advanced, the valve piston receives the delay action of the delay means and moves forward with the input piston while maintaining the substantially forward position. A large amount of air is introduced into the working chamber by opening the valve piston air introduction valve seat far away from the valve part of the valve body at the same time as the input rod advances, and a negative pressure chamber and working chamber are introduced into the booster piston. A large forward thrust due to a large pressure difference between them can be immediately applied, and the output of the output rod can be quickly and greatly increased to cope with emergency braking. In addition, since an expensive solenoid device or emergency brake sensor is not required, the cost can be reduced.

  However, in this negative pressure booster, since the valve piston closes the air introduction valve seat while occupying a predetermined advance position with respect to the input piston at the time of rest, the valve piston is not connected to the input piston when the input piston moves forward. As long as the valve is not moved to the reverse position, the air introduction valve seat cannot be opened. Therefore, the forward stroke of the input piston until the valve piston is moved from the forward position to the reverse position becomes an invalid stroke, and Atmospheric introduction will be delayed somewhat. The thing of patent document 2 also has the same fault.

  The present invention has been made in view of such circumstances, and at the time of emergency braking, the output can be boosted more quickly during emergency braking while eliminating the delay in the introduction of air into the working chamber, whether during normal braking or emergency braking. The purpose of the present invention is to provide a negative pressure booster with a simple structure and good responsiveness that can reach and hold the point.

  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 a negative pressure chamber and the atmosphere in response to the longitudinal movement of the rod is provided, and this control valve is an atmospheric introduction valve formed on the valve piston that is linked to the longitudinal movement of the input rod. A negative pressure introduction valve seat connected to the seat and the valve cylinder so as to be interlocked with the longitudinal movement thereof, and the air introduction valve seat and the negative pressure introduction valve seat are spring-biased in the seating direction. When the seat is seated, the communication between the working chamber and the atmosphere and the negative pressure chamber is interrupted, and the input rod moves forward. When the air introduction valve seat is opened, the working chamber is connected to the atmosphere, and when the negative pressure introduction valve seat is opened due to the reverse of the input rod, the working chamber is composed of a valve body that communicates with the negative pressure chamber. Between the operation input to the input rod and the booster piston thrust due to the pressure difference between the working chamber and the negative pressure chamber to the output rod. The reaction force mechanism includes an input piston connected to the input rod, an actuating piston connected to the booster piston and surrounding the input piston, and an output piston connected to the output rod. , In the negative pressure booster composed of the rear end surface of this output piston and the elastic reaction force piston interposed between the input piston and the front end surface of the working piston, a support cylinder which is separately molded and attached to the valve cylinder ,this A valve piston is fitted to an input piston slidably fitted to the inner periphery of the holding cylinder so that the valve piston can slide forward from a predetermined retracted position with respect to the input piston. A set spring is provided between the valve pistons to urge the valve pistons toward the retracted position, and between the support cylinder and the valve pistons, during an emergency brake in which the input piston advances ahead of the valve cylinder by more than a predetermined stroke, A first feature is that a locking means for locking the valve piston, which has advanced together with the input piston, to the support cylinder and holding the atmosphere introduction valve seat in an open state is provided.

  According to the present invention, in addition to the first feature, the valve cylinder is provided with a through-hole penetrating the central portion thereof, and a recess opening in the front surface thereof and continuing to the through-hole via a step portion. A mounting cylinder formed on the front end of the support cylinder is fitted into the recess, and the front end of the support cylinder having the mounting flange and the valve cylinder are formed so as to surround the recess. A second feature is that an operating piston of the reaction force mechanism is constituted by the annular portion, and the fitting portion of the annular portion and the support cylinder is sealed by an elastic reaction force piston that is in close contact with the front end surface of the operating piston.

  Furthermore, in addition to the first or the second feature, the present invention provides a locking protrusion formed on the outer periphery of a support cylinder connected to the valve cylinder, and a locking spring mounted on the support cylinder. The locking spring has an elastic engagement portion that contracts in the radial direction of the support cylinder, and the elastic engagement portion passes through a slit formed in the side wall of the support cylinder, and the outer peripheral surface of the support cylinder. It faces the inside of the valve piston so that it does not come into contact with the valve, and is positioned behind the locking projection. During the emergency braking, the elastic engagement portion overcomes the locking projection and engages the front surface of the locking projection. The third feature is what has been done.

  The elastic engagement portion corresponds to a leg portion 63b in an embodiment of the present invention described later.

  Furthermore, in addition to any one of the first to third features, the present invention relates to the engagement between the valve piston and the support cylinder by the engagement means by the retraction force of the input return spring of the input rod. The fourth feature is that the stop is released.

  According to the first feature of the present invention, in the case of emergency braking in which the input rod is rapidly advanced, the input piston moves forward by a predetermined stroke or more with respect to the valve cylinder so that the locking means attaches the valve piston to the valve cylinder. The atmospheric introduction valve seat is held in an open state by engaging with the support cylinder. Therefore, even if the valve cylinder moves forward so as to follow the advance of the input rod, the valve piston moves forward together with the support cylinder, so that the fully open state of the air introduction valve seat is maintained. A large amount of air is introduced into the working chamber at once, and the output of the booster piston can immediately reach the boost limit point where the pressure difference between the negative pressure chamber and the working chamber is maximum, and the emergency brake can be quickly Can respond. In addition, since it is not necessary to use expensive solenoid devices and emergency brake sensors, they can be provided at low cost.

  Also, during normal braking and emergency braking, the valve piston with the air introduction valve seat can advance simultaneously with the initial movement of the input rod, so there is no delay in opening the air introduction valve seat, and the booster piston operating response Can increase the sex.

  Furthermore, since the support cylinder for locking the valve piston is formed separately from the valve cylinder, even if it has a special shape such as an annular locking protrusion for locking the valve piston, This can be easily formed without any interference with the valve cylinder. On the other hand, the internal shape of the valve cylinder has been simplified by separating the support cylinder, making it easy to mold, reducing the overall axial dimension of the valve cylinder, and thus making the negative pressure booster compact. Can be achieved.

  According to the second feature of the present invention, the support cylinder is disposed so as to pass through the through hole in the central portion of the valve cylinder, and the mounting flange at the front end portion of the support cylinder is provided with a recess in the front end face of the valve cylinder. The elastic piston of the reaction force mechanism is configured by the front end of the support cylinder and the annular part formed in the valve cylinder so as to surround the recess, and is in close contact with the front end surface of the operation piston Since the annular portion and the fitting portion of the support cylinder are sealed by this, the support cylinder can be easily connected to the valve cylinder without using a special fixing member for connecting the support cylinder to the valve cylinder. Since the elastic reaction force piston also serves as a seal member that seals between the annular portion and the support cylinder, a special seal member is not required and the structure can be simplified.

  Further, according to the third feature of the present invention, the locking means can be configured with a simple structure, and the elastic engagement portion of the locking spring is usually provided by a slit in the side wall of the valve piston. Since it is held in a non-contact state without applying pressure to the outer peripheral surface, it does not come into strong frictional contact with the outer peripheral surface of the support cylinder unless it rides on the locking projection on the outer peripheral surface of the support cylinder. Does not occur. Therefore, it is possible to improve the operational feeling during normal braking, in which the relative displacement between the valve cylinder and the support cylinder is very small.

  Further, according to the fourth feature of the present invention, if the input rod is released after emergency braking, the input rod is retracted by the biasing force of the input return spring, so that the operation of the locking means is released, and the valve The piston can be returned to a predetermined retracted position on the valve piston by the biasing force of the set spring.

  Embodiments of the present invention will be described based on preferred embodiments of the present invention shown in the accompanying drawings. 1 is a longitudinal cross-sectional view of a negative pressure booster according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of two parts of FIG. 1 (resting state), FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. Fig. 5 is a diagram illustrating the operation of the negative pressure booster during normal braking, Fig. 5 is a diagram illustrating the operation of the negative pressure booster during emergency braking, Fig. 6 is a diagram illustrating the operation when the emergency brake is released, and Fig. 7 is a diagram illustrating the same negative pressure booster. It is a diagram which shows the output characteristic of a pressure booster.

  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, and the rear shell half 1b is a vehicle compartment. The cylinder body Ma of the brake master cylinder M operated by the booster B is fixed to the front shell half 1a by a bolt 8a.

  The booster shell 1 has a booster piston 4 housed 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 the 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 bearing member 11 and a seal member 13 on a guide cylinder portion 12 projecting rearward from the center portion of the rear shell half 1b.

  In the valve cylinder 10, an input piston 18, an input rod 20 connected to the input piston 18, and a control valve that switches the working chamber 3 to the negative pressure chamber 2 and the atmosphere in response to the back and forth movement of the input rod 20. 38 is disposed.

  A synthetic resin support cylinder 54 molded separately from the cylinder 10 is attached to the valve cylinder 10 as follows. That is, the valve cylinder 10 is formed with a through hole 60 penetrating through the central portion thereof, and a circular recess 61 that is continuous with the through hole 60 via a stepped portion and opens at the front end surface of the valve cylinder 10. The support tube 54 has a mounting flange 54 a on the outer periphery of the front end, and is disposed in the through hole 60 while fitting the mounting flange 54 a into the recess 61. The support cylinder 54 has a small-diameter cylinder hole 16 opened at a front end surface thereof, and a large-diameter guide hole 62 connected to the small-diameter cylinder hole 16 via a stepped portion at a rear end surface thereof.

  The input piston 18 is connected to the input piston rear portion 18r, the front end of the input piston rear portion 18r, the input piston intermediate portion 18m having a smaller diameter, and the input piston intermediate portion 18m connected to the front end of the input piston rear portion 18r. An input piston front portion 18f having a smaller diameter, a neck portion 18b is formed between the input piston front portion and the intermediate portions 18f, 18m, and an annular spring retaining groove opened at the rear end surface of the input piston rear portion 18r. 18c is formed. The input piston front portion 18f is slidably fitted into the small diameter cylinder hole 16 of the support cylinder 54, and the input piston intermediate portion 18m is slidably fitted into the guide hole 62. The spherical shape of the input rod 20 is formed inside the connecting cylinder portion 18a. The front end portion 20a is fitted, and a part of the connecting tube portion 18a is caulked to prevent the front end portion 20a from coming off. Thus, the input rod 20 is connected to the input piston 18 so as to be able to swing. A brake pedal P is connected to the rear end of the input rod 20 to move it forward.

  A seal member 49 is mounted on the outer peripheral surface of the input piston rear portion 18r, and a cylindrical valve piston 33 is disposed between the reverse position R (see FIG. 2) and the forward position F (see FIG. 6) on the outer peripheral surface. The retracted position R is slidably fitted, and is defined by the rear end surface of the valve piston 33 being received by a retaining ring 50 locked to the outer periphery of the rear end portion of the connecting cylinder portion 18a. The forward position F of the valve piston 33 is defined by the annular shoulder 33a formed on the inner periphery of the rear end of the valve piston 33 coming into contact with the rear end surface of the input piston 18. Between the input piston 18 and the valve piston 33, a set spring 51 for biasing the valve piston 33 toward the retracted position R is contracted, and at this time, the front half of the set spring 51 is connected to the spring holding groove 18c. It is stored in.

  An air introduction valve seat 31 is formed at the rear end of the valve piston 33, and an annular negative pressure introduction valve seat 30 that is concentrically disposed so as to surround the air introduction valve seat 31 is formed in the valve cylinder 10.

  A single common valve element 34 that cooperates with the air introduction valve seat 31 and the negative pressure introduction valve seat 30 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. An annular seal lip 37 bent rearward is integrally formed on the outer periphery of the valve portion 34a.

  The mounting bead portion 34b is airtightly sandwiched between a pair of front and rear valve holders 35A and 35B that contact the rear end of the annular raised portion 10a integrally formed on the inner peripheral side of the valve cylinder 10 together with the negative pressure introducing valve seat 30. The A seal member 43 such as an O-ring that is in close contact with the inner peripheral surface of the valve cylinder 10 is attached to the rear valve holder 35B.

  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 atmospheric introduction valve seat 31, the valve body 34 and the valve spring 36 constitute a control valve 38.

  An input return spring 41 is provided between the rear valve holder 35B and the input rod 20, so that the front and rear valve holders 35A and 35B are in contact with and held by the rear end of the annular raised portion 10a of the valve cylinder 10. , The input rod 20 is urged in the backward direction.

  A front annular chamber 45A surrounding the negative pressure introducing valve seat 30 is formed in the annular raised portion 10a on the inner periphery of the valve cylinder 10, and the front surface of the valve portion 34a faces the chamber 45A. The inner peripheral surface on the radially outer side of the front annular chamber 45A extends rearward from the negative pressure introducing valve seat 30, and the seal lip 37 on the outer periphery of the valve portion 34a is slidably in close contact with the inner peripheral surface. Accordingly, the front annular chamber 45A is closed when the valve portion 34a is seated on the negative pressure introducing valve seat 30.

  Further, on the inner side of the annular raised portion 10a, a rear annular chamber 45B with the back surface of the valve portion 34a facing is defined by a valve portion 34a with a seal lip 37.

  The valve cylinder 10 is provided with first and second ports 28 and 29. The first port 28 is formed such that one end opens into the negative pressure chamber 2 and the other end opens into the front annular chamber 45A. The second port 29 has one end at the working chamber 3 and the other end at the negative pressure introduction valve. It is formed so as to open between the seat 30 and the air introduction valve seat 31. The second port 29 also communicates with the rear annular chamber 45B through a communication hole 47 formed at the base of the annular ridge 10a and parallel to the axis of the valve cylinder 10.

  Both ends of a telescopic boot 40 covering the valve cylinder 10 are attached to the rear end of the guide cylinder 12 of the rear shell half 1b and the input rod 20, and the valve body is attached to the rear end 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.

  Further, from the valve cylinder 10 to the support cylinder 54, a key 32 for defining the backward limit of the booster piston 4 and the input piston 18 is attached so as to be axially movable within a certain distance. The key 32 has a fork portion 32b straddling the neck portion 18b of the input piston 18 at the inner end, and an outer end 32a on the front surface of the stopper wall 19 provided in the guide tube portion 12 of the rear shell half 1b. It arrange | positions so that it may oppose. Thus, when the key 32 abuts against the stopper wall 19, the backward limit of the booster piston 4 and the valve cylinder 10 is defined, and when the front end surface of the neck portion 18 b of the input piston 18 abuts against the key 32, the input piston 18 and the retreat limit of the input rod 20 are defined. The axial length of the neck portion 18b is set to be larger than the thickness of the key 32, so that the input piston 18 and the key 32 can be slightly moved relative to each other.

  An annular locking projection 57 is formed on the outer peripheral surface of the rear end portion of the support cylinder 54 so as to be slidably fitted to the inner periphery of the front end portion of the valve piston 33. A locking spring 63 cooperates therewith. Is attached to the valve piston 33.

  As shown in FIGS. 2 and 3, the locking spring 63 is formed, for example, by bending a single wire rod into a substantially U shape, and has an arcuate portion 63a and tangent lines from both ends of the arcuate portion 63a. A pair of leg portions 63b and 63b that extend along the opposite sides of each other and are opposed to each other, and a certain elastic force is applied to the locking spring 63 in a contraction direction that brings the both leg portions 63b and 63b close to each other. A pair of slits 64, 64 extending along the tangent line and reaching the inside of the valve piston 33 are provided on both diametrical sides of the front end portion of the valve piston 33, and both legs of the locking spring 63 are provided in the slits 64, 64. The locking spring 63 is mounted on the valve piston 33 so that the arcuate portion 63a fits the outer peripheral surface of the valve piston 33 while the portions 63b and 63b are engaged with each other, and can be moved back and forth together with the valve piston 33. . The both leg portions 63b and 63b of the locking spring 63 are arranged in the middle of the valve piston 33 from the slits 64 and 64 by the mutual contraction due to the elastic force being restricted by the bottom surfaces 64a and 64a of the slits 64 and 64. The portion is held in a non-contact state in which no pressure is applied to the outer peripheral surface of the support tube 54. The both leg portions 63b, 63b occupy a rear position close to the locking projection 57 when the valve piston 33 is in the retracted position R. When the valve piston 33 equipped with the locking spring 63 is inserted into the valve cylinder 10, the inner peripheral surface of the valve cylinder 10 comes close to the outer peripheral surface of the arcuate portion 63 a of the locking spring 63, and the valve of the locking spring 63 Detachment from the piston 33 is prevented. Therefore, a special detachment preventing member for the locking spring 63 is not necessary.

  The locking projection 57 is formed in an isosceles triangle or semicircle, or a cross-sectional shape similar to them, and during an emergency brake in which the input piston 18 advances ahead of the valve cylinder 10 by a predetermined stroke or more, the input piston 18 The both leg portions 63b and 63b of the locking spring 63 that advances together with the locking projections 57 are extended outward by the locking projections 57, get over the locking projections 57 and engage with the front surfaces thereof, and the atmospheric introduction valve seat 31 is fully opened. Thus, the valve piston 33 is locked to the support cylinder 54 against the set load of the set spring 51. Accordingly, the locking spring 63 and the locking protrusion 57 are locking means 56 for locking the valve piston 33 that moves forward together with the input piston 18 to the valve cylinder 10 and holding the atmospheric introduction valve seat 31 in a fully opened state during emergency braking. Configure.

  Even when both the leg portions 63b and 63b are engaged with the front surface of the locking projection 57, when a retracting force greater than a predetermined value larger than the set load is applied to the valve piston 33, the locking projection 57 is again moved. It gets over and returns to the rear side of the locking projection 57.

  Referring again to FIG. 2, an annular portion 15 a surrounding the mounting flange 54 a of the support cylinder 54 is formed on the front end surface of the valve cylinder 10, and the operating piston 15 is connected to the annular portion 15 a and the front end portion of the support cylinder 54. Composed. A cup-shaped output piston 21 is slidably fitted on the outer periphery of the operating piston 15, and a flat elastic force is provided between the output piston 21 and the axially opposed surfaces of the operating piston 15 and the input piston front portion 18f. A reaction force piston 22 is interposed.

  At that time, the elastic reaction force piston 22 is in close contact with both the front end surfaces of the annular portion 15a and the support tube 54. As a result, the support cylinder 54 is connected to the valve cylinder 10, and the space between the annular portion 15 a and the mounting flange 54 a is sealed by the elastic reaction force piston 22. Further, a constant gap g is formed between the input piston front portion 18f and the elastic reaction force piston 22 when the negative pressure booster B is not operated.

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

  In the above, the working piston 15, the input piston 18, the elastic reaction force piston 22, and the output piston 21 are the inputs of the input rod 20 and the thrust of the booster piston 4 due to the pressure difference between the working chamber 3 and the negative pressure chamber 2. A reaction force mechanism 24 that transmits the resultant force to the output rod 25 is configured.

  A retainer 26 is disposed so as to contact the output piston 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 embodiment will be described.
[Suspension of negative pressure booster]
When the negative pressure booster B is in a rest state, as shown in FIGS. 1 and 2, the key 32 attached to the support cylinder 54 of the valve cylinder 10 contacts the front surface of the stopper wall 19 of the rear shell half 1b. Since the front end surface of the neck portion 18b of the input piston 18 contacts the booster piston 4 and the input rod 20 are positioned at the respective backward limits. At this time, the valve piston 33 is held at the retracted position R in contact with the retaining ring 50 on the input piston 18 by the urging force of the set spring 51, and the air introduction valve seat 31 at the rear end of the valve piston 33 is the valve element 34. While seated on the valve portion 34a, the valve portion 34a is pressed to be slightly separated from the negative pressure introducing valve seat 30. As a result, the communication between the air introduction port 39 and the second port 29 is interrupted, while the communication between the first and second ports 28 and 29 is established. Since the pressure is transmitted to the chamber 3 and the chambers 2 and 3 have the same pressure, 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.
[Normal brake]
If the brake pedal P is depressed at a normal speed to brake the vehicle and the input rod 20 and the input piston 18 are advanced, the input piston 18 is accompanied by the valve piston 33 held at the reverse position R from the beginning. And move forward. Therefore, immediately after the urging force of the valve spring 36 extends the telescopic cylinder portion 34c, the valve portion 34a is seated on the negative pressure introduction valve seat 30, and at the same time, the atmosphere introduction valve seat 31 is separated from the valve body 34, thereby the first and The communication between the second ports 28 and 29 is blocked, and the second port 29 is communicated with the atmosphere 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 second port 29, so that the working chamber 3 has a higher pressure than the negative pressure chamber 2. Therefore, by obtaining a forward thrust based on the pressure difference between them, the booster piston 4 is subjected to the force of the booster return spring 27 with the valve cylinder 10, the operating piston 15, the elastic reaction force piston 22, the output piston 21 and the output rod 25. The vehicle moves forward, and the piston Mb of the brake master cylinder M is pushed forward by the output rod 25, and the corresponding wheel brake is operated by the output hydraulic pressure. As described above, the air introduction valve seat 31 moves forward simultaneously with the advancement of the input rod 20 and is separated from the valve portion 34a, whereby the responsiveness of the booster piston 4 can be enhanced.

  Even if the atmosphere introduction valve seat 31 is opened until the input piston front portion 18f is moved forward and until the input piston front portion 18f is in contact with the elastic reaction force piston 22, the input rod 20 receives the reaction force from the reaction mechanism 24. Therefore, the output of the output 25 shows a jumping characteristic that rises rapidly as shown by line ab in FIG.

  Further, during the forward operation of the input rod 20, negative pressure transmitted from the first port 28 to the front annular chamber 45A acts on the front surface of the valve portion 34a facing the front annular chamber 45A of the valve cylinder 10. Since the atmospheric pressure transmitted from the second port 29 to the rear annular chamber 45B through the communication hole 47 acts on the back surface of the valve portion 34a facing the rear annular chamber 45B of the valve cylinder 10, the valve portion 34a In addition to the set load of the spring 36, it is also urged in the seating direction with the negative pressure introduction valve seat 30 by the pressure difference between the front and rear annular chambers 45A, 45B. Accordingly, it is possible to reduce the set load of the valve spring 36 by the biasing force due to the pressure difference, and accordingly, it is possible to reduce the set load of the input return spring 41 that biases the input rod 20 in the backward direction. As a result, jumping characteristics can be obtained with a relatively small initial operation input, so that the invalid strokes of the brake master cylinder M and each wheel brake can be quickly eliminated, and the responsiveness of each wheel brake can be enhanced.

  Further, in this state, the seal lip 37 on the outer periphery of the valve portion 34a is bent rearward and is in close contact with the inner peripheral surface of the valve cylinder 10. Therefore, due to the pressure difference between the front and rear annular chambers 45A and 45B, The close contact force to the inner peripheral surface is increased, and the airtightness between the two annular chambers 45A and 45B can be ensured.

  After the front part 18f of the input piston comes into contact with the elastic reaction force piston 22, a part of the reaction force of the output rod 25 is fed back to the input rod 20 via the elastic reaction force piston 22. A person can perceive the magnitude of the output of the output rod 25.

  If the forward movement of the input rod 20 is stopped when the desired output is obtained, the forward movement of the booster piston 4 causes the valve portion 34a of the valve body 34 to be seated on the atmospheric introduction valve seat 31 again, so that the negative pressure of the atmosphere beyond that is increased. It stops by preventing the introduction into the chamber 3 (see FIG. 4). Therefore, the valve cylinder 10 and the booster piston 4 advance in accordance with the advance of the input rod 20.

  By the way, during normal braking where the forward speed of the input rod 20 is relatively low, the follow-up delay of the booster piston 4 and the valve cylinder 10 with respect to the input rod 20 is relatively small, so that the relative displacement of the input rod 20 and the valve cylinder 10 is also small. The relative displacement between the valve piston 33 that moves forward together with the input piston 18 connected to the input rod 20 and the support cylinder 54 connected to the valve cylinder 10 is also small. Therefore, both the leg portions 63 b and 63 b of the locking spring 63 that moves back and forth together with the valve piston 33 rides on the locking projection 57 only by slightly moving on the outer peripheral surface of the support cylinder 54 behind the locking projection 57. There is nothing.

  The output of the output rod 25 increases as shown by the line bc in FIG. 7 with a boost ratio determined by the ratio of the pressure receiving area of the working piston 15 contacting the elastic reaction force piston 22 and the input piston front portion 18f. .

After reaching the boost limit point c at which the pressure difference between the negative pressure chamber 2 and the working chamber 3 reaches the maximum, the output of the output rod 25 is the pressure difference of the booster piston 4 as shown by the line cd. Is the sum of the maximum thrust by and the operation input to the input rod 20.
[Emergency brake]
During emergency braking in which the brake pedal P is depressed rapidly, the forward speed of the input piston 18 is fast. Therefore, before the booster piston 4 and the valve cylinder 10 start to advance, the elastic reaction force piston 22 is compressed by the input piston front portion 18f. The input piston 18 and the valve piston 33 are greatly advanced. Then, as shown in FIG. 5, both legs 63b and 63b of the locking spring 63 of the valve piston 33 get over the locking projection 55 of the support cylinder 54 and engage the front surface of the locking projection 55. The stop spring 63 is engaged with the support cylinder 54 connected to the valve cylinder 10 against the urging force of the set spring 51, and the atmospheric introduction valve seat 31 is fully opened from the valve portion 34 a of the valve body 34. Hold on.

  In this way, when the valve piston 33 is locked to the support cylinder 54 in the fully open state of the air introduction valve seat 31, even if the booster piston 4 and the valve cylinder 10 slightly advance so as to follow the advance of the input rod 20, the valve piston 33 Since 33 moves forward together with the valve cylinder 10, the fully open state of the air introduction valve seat 31 is maintained. As a result, a large amount of air is introduced into the negative pressure chamber 3 at once, and the boost limit point at which the pressure difference between the negative pressure chamber 2 and the working chamber 3 becomes maximum, as indicated by the line aec in FIG. c can be reached immediately, and the piston Ma of the master cylinder M can be pressed strongly to cope with emergency braking. When emergency braking is performed in the middle of normal braking, the boost limit point c is reached immediately as indicated by the line fe'-c in FIG. 7, and emergency braking can be handled.

  Even during this emergency braking, the air introduction valve seat 31 can be moved forward simultaneously with the advancement of the input rod 20, and can be separated from the valve portion 34a, so that the response of the booster piston 4 can be enhanced.

  By the way, during this emergency braking, the locking means 55 for locking the valve piston 33 to the support cylinder 54 when the atmospheric introduction valve seat 31 is fully opened is mounted in a pair of slits 64, 64 on both sides of the valve piston 33. The U-shaped locking spring 63 and an annular locking projection 57 formed on the outer peripheral surface of the support cylinder 54 are configured such that the legs 63b and 63b of the locking spring 63 are mutually contracted by their elastic force. By being regulated by the bottom surfaces 64 a and 64 a of the slits 64 and 64, the intermediate portion that has entered the valve piston 33 from the slits 64 and 64 is maintained in a non-contact state in which no pressure is applied to the outer peripheral surface of the support cylinder 54. Therefore, both the leg portions 63b and 63b of the locking spring 63 do not come into strong frictional contact with the outer peripheral surface of the support cylinder 54 unless they ride on the locking projections 57 on the outer peripheral surface of the support cylinder 54, and slide. Resistance Not. Therefore, it is possible to improve the operational feeling during normal braking where the relative displacement between the valve cylinder 10 and the support cylinder 54 is very small.

  Further, since the support cylinder 54 is molded separately from the valve cylinder 10, the support cylinder 54 is formed in the valve cylinder 10 in spite of a complicated shape including an annular locking projection 57 and a mounting flange 54a on the outer periphery. It can be easily molded without any interference. On the other hand, the internal shape of the valve cylinder 10 is simplified by the separation of the support cylinder 54, and the molding thereof is facilitated. Overall, the axial dimension of the valve cylinder 10 is shortened, and consequently the negative pressure booster. B can be made compact.

In addition, the support cylinder 54 is disposed so as to penetrate a through hole 60 provided in the center of the valve cylinder 10, and a mounting flange 54 a on the outer periphery of the front end portion of the support cylinder 54 is formed on the front end surface of the valve cylinder 10. The operating piston 15 of the reaction force mechanism 24 is constituted by the front end portion of the support cylinder 54 and the annular portion 15a of the valve cylinder 10 surrounding the support cylinder 54, which are fitted into the formed recess 61, and the support cylinder 54 and Since the elastic reaction force piston 22 is brought into close contact with the front end surface of the annular portion 15a, the support cylinder 54 can be easily connected to the valve cylinder 10 without using a special fixing member for connecting the support cylinder 54 to the valve cylinder 10. In addition, since the elastic reaction force piston 22 functions as a seal member that seals between the annular portion 15a and the support cylinder 54, a special seal member is unnecessary.
[Release from emergency braking]
When the pedal force is released from the brake pedal P in order to release the emergency brake state, first, the input rod 20 and the input piston 18 are moved backward by the force of the input return spring 41. When the input piston 18 starts to move backward, as shown in FIG. 6, the rear end surface of the input piston 18 comes into contact with the annular shoulder 33a on the inner periphery of the rear end of the valve piston 33, and pulls it back. Both legs 63b and 63b of the spring 63 ride over the locking projection 55 of the support tube 54 rearward and release the locked state with respect to the support tube 54. Thereafter, the valve piston 33 immediately returns to the retracted position R in contact with the retaining ring 50 of the input piston 18 by the biasing force of the set spring 51, and the air introduction valve seat 31 is seated on the valve portion 34a of the valve body 34. Since the valve portion 34a is pushed rearward and separated from the negative pressure introducing valve seat 30, the working chamber 3 communicates with the negative pressure chamber 2 via the second port 29 and the first port 28, and the working chamber 3 However, since 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 between them is eliminated, the booster piston 4 is also elastic of the booster return spring 27. Retreating with force, the operation of the master cylinder M is released.

  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 U-shaped locking spring 63 is replaced with an annular spring having a reduced diameter made of a coil spring, and when the U-shaped locking spring 63 is attached to the valve piston 33, the portion that enters the slit 64 is the portion of the support cylinder 54. An elastic engagement portion that can engage with the locking protrusion 57 can be provided. Furthermore, this annular spring can be replaced with an annular rubber spring.

The longitudinal cross-sectional view of the negative pressure booster which concerns on the Example of this invention. 2 is an enlarged sectional view of part 2 in FIG. 1 (resting state). FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. The operation explanatory view at the time of normal brake of the same negative pressure booster. The operation explanatory view at the time of emergency braking of the negative pressure booster. Action | operation explanatory drawing at the time of cancellation | release from the said emergency brake state. The diagram which shows the output characteristic of the same negative pressure booster.

Explanation of symbols

B ... Negative pressure booster R ... Reverse position V of valve piston ... Negative pressure source 1 ... Booster shell 2 ... Negative pressure chamber 3 ... Working chamber 4 ... ... Booster piston 10 ... Valve 15 ... Operating piston 15a ... Ring 18 ... Input piston 20 ... Input rod 21 ... Output piston 22 ... Elastic reaction force piston 24 ... ..Reaction force mechanism 25 ... output rod 30 ... negative pressure introduction valve seat 31 ... atmospheric introduction valve seat 33 ... valve piston 34 ... valve element 38 ... control valve 41 ... Input return spring 51... Set spring 52... Locking projection 54... Support cylinder 54 a .. mounting flange 56. · Recess 63 ··· Locking spring 63b · · Leg 64 · · · slit

Claims (4)

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). A control valve (38) for switching communication, and this control valve (38) is connected to an air introduction valve seat (31) formed on a valve piston (33) interlocking with the longitudinal movement of the input rod (20). , A negative pressure introduction valve seat (30) connected to the valve cylinder (10) so as to interlock with the longitudinal movement thereof, and these atmospheric introduction valve seats (31) And the negative pressure introduction valve seat (30) is spring-biased in the seating direction, and when seated with both valve seats (30, 31), the working chamber (3) communicates with either the atmosphere or the negative pressure chamber (2). When the atmosphere introduction valve seat (31) is opened as the input rod (20) moves forward, the working chamber (3) communicates with the atmosphere, and the negative pressure introduction valve seat ( 30) is opened, the working chamber (3) is constituted by a valve body (34) communicating with the negative pressure chamber (2), and is slid onto the valve cylinder (10), the input rod (20), and the booster shell (1). Between the output rod (25) supported movably, the operation input to the input rod (20) and the booster piston (4) due to the pressure difference between the working chamber (3) and the negative pressure chamber (2) The reaction force mechanism (24) that transmits the resultant force with the thrust to the output rod (25) is interposed, and this reaction force mechanism (24) is connected to the input rod (20). A piston (18), an operating piston (15) connected to the booster piston (4) and arranged to surround the input piston (18), an output piston (21) connected to the output rod (25), In the negative pressure booster composed of the rear end surface of the output piston (21) and the elastic reaction force piston (22) interposed between the input piston (18) and the front end surface of the working piston (15),
A valve cylinder (10) is molded separately from the support cylinder (54), and the valve piston (33) is fitted to the input piston (18) slidably fitted to the inner periphery of the cylinder (54). The valve piston (33) is fitted to the input piston (18) so as to be able to slide forward from a predetermined retracted position (R), and between the input piston (18) and the valve piston (33). , A set spring (51) for urging the valve piston (33) toward the retracted position (R) is provided, and an input piston (18) is provided between the support cylinder (54) and the valve piston (33). At the time of emergency braking that has advanced forward by a predetermined stroke or more with respect to (10), the valve piston (33) that has advanced together with the input piston (18) is locked to the support cylinder (54) and the air introduction valve seat (31) is opened. Locking means (56) for holding Only wherein the the negative pressure booster. The negative pressure booster according to claim 1,
The valve cylinder (10) is provided with a through hole (60) that penetrates through the central portion thereof, and a recess (61) that opens in the front surface and continues to the through hole (60) via a step portion. 60), a support cylinder (54) is disposed, and a mounting flange (54a) formed at the front end of the support cylinder (54) is fitted in the recess (61), and the support flange (54a) is provided. The front end of the tube (54) and the annular portion (15a) formed in the valve tube (10) so as to surround the recess (61) constitute an operating piston (15) of the reaction force mechanism (24), A negative pressure booster, wherein the fitting portion of the annular portion (15a) and the support tube (54) is sealed by an elastic reaction force piston (22) in close contact with the front end surface of the operating piston (15). The negative pressure booster according to claim 1 or 2,
The locking means (56) includes a locking projection (57) formed on the outer periphery of a support cylinder (54) provided continuously with the valve cylinder (10), and a locking spring ( 63), and this locking spring (63) has an elastic engagement portion (63b) that contracts in the radial direction of the support tube (54), and this elastic engagement portion (63b) Through the slit (64) formed in the side wall of the support cylinder (54), it faces the valve piston (33) so as not to contact the outer peripheral surface of the support cylinder (54) and is positioned behind the locking projection (57). The negative pressure booster is characterized in that, during the emergency braking, the elastic engagement portion (63b) is moved over the locking projection (57) and engaged with the front surface of the locking projection (57). The negative pressure booster according to any one of claims 1 to 3,
The locking means (56) is locked between the valve piston (33) and the support cylinder (54) by the locking means (56) by the retreating force of the input return spring (41) of the input rod (20). A negative pressure booster that is configured to be released.

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