JP2007055397A - Negative pressure type booster - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smoothly flex a bellows of a boot to follow a valve piston even at a rapid actuation time of a brake. <P>SOLUTION: A boot 26 is provided to which a bellows 26b shrinkable in an axial direction for covering a valve piston 8 is formed, and one end of the boot is engaged with a booster shell 1. The other end of the boot is fitted with an annular groove 23a formed on an input member 20, and a ventilation hole 26c for introducing the atomosphere to an atmosphere valve 31b is formed at a plane part 26a of the boot fitted with the annular groove so as to heighten the rigidity of a plane part of the boot and a bending part 26b1 bent in the direction of the bellows from the plane part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a negative pressure type booster for a vehicle, and more particularly to a negative pressure type booster equipped with a boot excellent in expansion / contraction followability during braking operation.

  Generally, in a negative pressure type booster, when a brake pedal is depressed and a plunger is moved forward relative to a valve piston by an input rod, the negative pressure valve abuts on the negative pressure valve seat and the variable pressure chamber and the constant pressure chamber. And the atmosphere valve seat and the atmosphere valve are separated, and the atmosphere is introduced from the outside air into the variable pressure chamber. As a result, the valve piston is moved forward following the forward movement of the input rod and the plunger due to the pressure difference between the variable pressure chamber and the constant pressure chamber, the master piston is pushed, and the brake hydraulic pressure corresponding to the pedal effort of the brake pedal is increased. Generated in the master cylinder.

  The valve piston elastically deforms the reaction force member with the operating force corresponding to the pressure difference between the variable pressure chamber and the constant pressure chamber and pushes the master piston. Therefore, the reaction force member causes the plunger to move backward due to the elastic deformation of the reaction force member. Press. As a result, the plunger is retracted, and the atmospheric valve seat is seated on the atmospheric valve to cut off the communication between the atmosphere and the variable pressure chamber, thereby maintaining a desired brake hydraulic pressure.

By the way, in the case of emergency braking when the brake pedal is depressed rapidly, a negative pressure booster equipped with an emergency brake function that changes the jumping characteristics so that a larger braking force than that during normal braking can be output, for example, is patented. Known as described in Document 1.
JP 2005-170383 A (paragraphs 0035 to 0037, FIG. 2)

  However, in the negative pressure type booster having an emergency brake function as described in Patent Document 1 described above, as shown in FIG. 6, when the valve piston moves forward with rapid depression of the brake pedal, 1 of the bellows portion 1b does not bend smoothly, and only the flat portion 1a of the boot 1 fitted to the fitting portion 2a of the input rod 2 is bent so as to be inclined in a conical shape. In the worst case, the flat portion 1a of the boot 1 is bent. May be detached from the fitting portion 2a of the input rod 2. When the flat surface portion 1a of the boot 1 is detached from the fitting portion 2a of the input rod 2, a silencer 4 made of a silencing felt disposed at the opening of the valve piston 3 is caused to float to the outside. This will cause a problem that the sound deadening function by the air pressure decreases and the air intake sound increases when the brake is operated.

  Such a problem hardly occurs in a negative pressure booster having a normal brake function, but tends to occur in a negative pressure booster having an emergency brake function. This is because, in a negative pressure type booster equipped with an emergency brake function, the emergency brake function parts must be installed in a limited space. For this reason, when the flat part of the boot is bent as described above, the flat part of the boot is easily detached from the fitting part of the input rod with the help of the pushing action by the silencer. It is.

  The present invention has been made to solve the conventional problems, and provides a negative pressure type booster device in which the bellows portion of the boot smoothly bends following the stroke of the valve piston even when the brake is suddenly operated. It is intended to do.

  In order to solve the above problems, the structural feature of the invention according to claim 1 is that a booster shell is partitioned into a variable pressure chamber and a constant pressure chamber by a partition member, and a proximal end portion of the valve piston is fixed to the partition member. The output of the partition member based on the pressure difference between the variable pressure chamber and the constant pressure chamber is transmitted from the valve piston to the output rod via a reaction member, and by a plunger and a brake pedal that operate in cooperation with the reaction member. An input rod that is axially coupled is used as an input member, and a negative pressure valve seat and an atmospheric valve seat are formed on the valve piston and the plunger, and the variable pressure chamber is made to contact and separate from the negative pressure valve seat and the atmospheric valve seat. A negative pressure type booster provided with a negative pressure valve and an atmospheric valve that communicates with and shuts off the constant pressure chamber and the atmosphere, and includes a boot having a bellows portion that extends in the axial direction and covers the valve piston. One end of the boot is engaged with the booster shell, the other end of the boot is fitted into an annular groove formed in the input member, and the atmosphere valve is connected to the atmospheric valve on the flat portion of the boot fitted into the annular groove. Ventilation holes are formed, and the rigidity of the flat portion of the boot and the bent portion that bends in the direction of the bellows portion from the flat portion is increased.

  The structural feature of the invention according to claim 2 is the negative pressure booster according to claim 1, wherein the thickness of the flat portion and the bent portion of the boot is increased.

  The structural feature of the invention according to claim 3 is that, in claim 1, a plurality of circumferential ribs (126a, 126b1) are formed on the flat portion and the bent portion of the boot, respectively. It is.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the bent portion is constituted by at least one mountain of the bellows portion.

  According to the first aspect of the present invention configured as described above, the rigidity of the flat portion of the boot covering the valve piston and the bent portion that bends in the direction of the bellows portion from the flat portion is increased. When the piston is moved forward following the forward movement of the input rod and the plunger, the flat surface portion and the bent portion function as a rigid body, and the bellows portion is smoothly expanded and contracted. Therefore, even during a sudden operation, the flat portion does not tilt, so that the flat portion does not slip out of the annular groove of the input rod, the silencer can be prevented from being raised, and the silencing function by the silencer does not deteriorate.

  According to the invention according to claim 2 configured as described above, the flat portion and the bent portion of the boot can be obtained by a simple configuration in which the thickness of the flat portion and the bent portion of the boot is made larger than the thickness of the other bellows portion. The rigidity of the part can be increased.

  According to the invention according to claim 3 configured as described above, the rigidity of the flat portion and the bent portion of the boot can be increased by a simple configuration in which a plurality of circumferential ribs are formed on the flat portion and the bent portion of the boot. Can be increased.

  According to the invention according to claim 4 configured as described above, since the bent portion is configured by at least one mountain of the bellows portion, the flat surface portion of the boot and at least one mountain bellows portion can function as a rigid body. The bellows part can be expanded and contracted smoothly.

  Embodiments of a negative pressure booster according to the present invention will be described below with reference to the drawings. As shown in FIG. 1, the booster shell 1 is composed of a front shell 2 and a rear shell 3, and a flexible diaphragm 4 as a partition member is hermetically sandwiched between the shells 2 and 3 by a bead at the outer peripheral edge. The booster shell 1 is partitioned into a constant pressure chamber 5 and a variable pressure chamber 6. A disk-like plate 7 is superposed on the diaphragm 4 on the constant pressure chamber 5 side. The outer peripheral surface of the base end portion 8 a of the cylindrical valve piston 8 is airtightly fixed to the diaphragm 4 and the plate 7, and the front end surface of the base end portion 8 a is exposed to the constant pressure chamber 5. A negative pressure introduction pipe 10 is attached to the front shell 2, and the constant pressure chamber 5 is communicated with the intake manifold of the engine via the negative pressure introduction pipe 10 so that the negative pressure is always maintained during engine operation.

  As shown in FIG. 2, the center portion of the rear shell 3 is bent outward, a cylindrical projecting portion 3 a is projected rearward, and a through hole 3 b is formed on the axis. The valve piston 8 is provided with a sliding cylindrical portion 8b protruding rearward from the base end portion 8a, and the sliding cylindrical portion 8b passes through the through hole 3b and protrudes rearward from the protruding portion 3a of the rear shell 3. A seal 9 is interposed between the inner peripheral surface of the through-hole 3b and the outer peripheral surface of the sliding cylindrical portion 8b to block the variable pressure chamber 6 from the atmosphere.

  As shown in FIG. 1, the master cylinder 11 has a rear end portion 11a penetrating through a center hole formed in the front shell 2 and projecting airtightly into the constant pressure chamber 5, and a flange portion 11b It is in contact with the front surface of the shell 2. The front shell 2 and the rear shell 3 are joined by a plurality of, for example, two tie rods 12 extending in parallel with the axis at a substantially intermediate position between the axis and the outer periphery of the booster shell 1 constituted by both shells. 11 is fixed. Each tie rod 12 is fitted with a sliding hole in each seal portion provided in the diaphragm 4 so as to be slidable while maintaining airtightness, and maintains an airtight partition between the constant pressure chamber 5 and the variable pressure chamber 6. Yes.

  A master piston 13 fitted to the master cylinder 11 so as to be slidable in the front-rear direction protrudes from the rear end portion of the master cylinder 11 into the constant pressure chamber 5 and extends to the vicinity of the front end surface of the valve piston 8. An output rod 14 is interposed between the valve piston 8 and the master piston 13. The valve piston 8 transmits the output of the diaphragm 4 based on the pressure difference between the constant pressure chamber 5 and the variable pressure chamber 6 to the output rod 14 via the reaction member 17, and the output rod 14 pushes the master piston 13 forward. A return spring 16 is interposed between the front shell 2 and the front end face of the valve piston 8 to urge the valve piston 8 rearward.

  As shown in FIG. 2, the valve piston 8 has a reaction force chamber hole 8c from the front end surface toward the rear end surface, a locking member storage hole 8d having a smaller diameter than the reaction force chamber hole 8c, a plunger storage hole 8e, and a plunger storage hole 8e. Larger-diameter valve body storage holes 8f are sequentially drilled on the axis. At the step portion 8g between the reaction force chamber hole 8c and the locking member storage hole 8d, a flanged cylinder 18 is fixed with the bottom surface of the flange being flush with the step portion 8g, and an annular concave groove 8n is formed at the cylinder 18. It is formed in the axial direction surrounding the ridge. An annular protrusion 14a formed at the rear end of the output rod 14 is fitted into the annular groove 8n so as to be relatively movable in the axial direction, and is opposite between the output rod 14, the bottom surface of the cylindrical body 18, and the step portion 8g. A force chamber 15 is formed, and a disk-shaped reaction force member 17 formed of an elastic material is accommodated in the reaction force chamber 15.

  A plunger 21 is housed in the plunger housing hole 8e so as to be movable in the front-rear direction. A distal end shaft portion 21a is slidably fitted to the rear wall of the tubular body 18 and is formed in the tubular body 18. The front end surface is in contact with the rear end surface of the contact member 19 that extends into the force hole 18a and is slidably fitted in the reaction force hole 18a. An atmospheric valve seat 21 b is formed on the rear end surface of the plunger 21.

  Reference numeral 22 denotes an H-shaped key member, and the relative movement amount of the plunger 21 with respect to the valve piston 8 is regulated by the key member 22. The insides of the linear portions on both sides of the key member 22 enter into an annular engagement groove 21c formed in the plunger 21 so as to be able to move relative to each other by a predetermined amount in the front-rear direction. A rectangular hole 8i drilled in the radial direction between the two is slidably in contact with the outer surface of both linear portions and extends to the outside. The wall thickness dimension of the key member 22 in the front-rear direction is smaller than the dimension of the rectangular hole 8 i in the front-rear direction, and the key member 22 can move relative to the valve piston 8 by a predetermined amount in the front-rear direction. Further, the key member 22 can be brought into contact with the end surface of the protruding portion 3 a of the rear shell 3 at both ends protruding to the outer peripheral side of the valve piston 8. Thus, the valve piston 8 and the plunger 21 are relatively moved in the axial direction by a distance obtained by subtracting a distance obtained by adding twice the thickness of the key member 22 from a distance obtained by adding the widths of the rectangular hole 8i and the engagement groove 21c. Can do.

  An input rod 23 is rotatably connected to the rear end of the plunger 21, and the input rod 23 passes through a filter 24 for preventing passage of dust and the like and a silencer 27 made of felt having a sound absorbing function, and slides a cylindrical portion 8b. It extends further rearward and is connected to a brake pedal 25 (see FIG. 1). The filter 24 and the silencer 27 are attached to the rear end portion (open end of the sliding cylindrical portion 8b) of the valve body housing hole 8f of the valve piston 8. The plunger 21 and the input rod 23 constitute the input member 20 that is axially moved by the brake pedal 25.

  A boot 26 that covers the valve piston 8 is provided between the protrusion 3 a of the rear shell 3 and the input rod 23. The boot 26 has a bottomed cylindrical shape with an opening at the front, and the rear bottom constitutes a flat portion 26 a that is orthogonal to the axis of the input rod 23. The front opening portion of the boot 26 is engaged with the protruding portion 3a of the rear shell 3, and the inner end (center portion) of the flat portion 26a is formed on the outer periphery of the input rod 23 so as to close the rear opening portion of the valve piston 8. It is fitted in the annular groove 23a. A bellows portion 26b composed of a plurality of peaks that can be expanded and contracted in the axial direction is formed in a cylindrical portion that is bent and extends forward from the flat portion 26a of the boot 26. A plurality of circumferentially vent holes 26c are opened in the flat portion 26a of the boot 26, and outside air is introduced into the valve piston 8 through the silencer 27 and the filter 24 from the vent holes 26c.

  One or two crests of the flat portion 26a of the boot 26 and the bellows portion 26b connected to the flat portion 26a (hereinafter, referred to as at least one bellows portion 26b1) is more rigid than the other bellows portions 26b2. In addition, when the axial force is applied to the flat portion 26a of the boot 26 by the axial movement of the input rod 23, the flat portion 26a and at least one bellows portion 26b1 are formed. The heel also functions as a rigid body, and the other bellows portion 26b2 is configured to be smoothly expanded and contracted. The bent portion in the claims is constituted by the at least one accordion portion 26b1.

  A valve mechanism 30 that communicates by switching the variable pressure chamber 6 to the constant pressure chamber 5 or the atmosphere is housed in the valve body housing hole 8 f of the valve piston 8. The valve mechanism 30 includes a cylindrical valve body 31 that is loosely fitted in the valve body housing hole 8f, and a first negative formed at a front end of the valve body 31 at a connection portion between the plunger housing hole 8e and the valve body housing hole 8f. A negative pressure valve 31a is provided to connect and block the variable pressure chamber 6 and the constant pressure chamber 5 in contact with and away from the pressure valve seat 8k. A passage 8m that passes through the side wall of the valve piston 8 and opens to the constant pressure chamber 5 is formed around the first negative pressure valve seat 8k, and the inside is always in communication with the variable pressure chamber 6. The rear end portion of the plunger 21 is inserted into the valve body 31, and the atmospheric valve seat 21 b is formed at the rear end thereof so as to contact and separate from the atmospheric valve 31 b provided on the valve body 31 to communicate and block the variable pressure chamber 6 and the atmosphere. ing.

  The rear end of the valve body 31 is connected to an annular holding body 35 via a bellows 34 that allows the valve body 31 to move in the axial direction. The holding body 35 is fitted to the inner periphery of the valve body storage hole 8f, and the spring force of the compression spring 38 interposed between the retainer 37 locked to the center portion of the input rod 23 causes the valve body storage hole 8f to move. It is pressed against the shoulder.

  A compression spring 39 is interposed between the rear end surface of the valve body 31 and the retainer 37 to urge the valve body 31 forward against the valve piston 8. As a result, during normal operation (when the brake is not in operation), the atmospheric valve 31b is brought into contact with the atmospheric valve seat 21b, and the negative pressure valve 31a is held at a position slightly separated from the first negative pressure valve seat 8k. The chamber 6 and the constant pressure chamber 5 communicate with each other.

  Reference numeral 40 denotes a valve seat member that surrounds the plunger 21. The valve seat member 40 is hermetically sealed by a seal 41 on the inner peripheral surface of the plunger housing hole 8e of the valve piston 8 and is slidably fitted in the axial direction. Yes. A second negative pressure valve seat 40b is provided at the rear end of the valve seat member 40 so as to correspond to the inside of the first negative pressure valve seat 8k, and the second negative pressure valve seat 40b is more than the first negative pressure valve seat 8k in a normal state. It is located slightly forward and is farther away than the negative pressure valve 31a. A compression spring 43 that urges the valve seat member 40 rearward is interposed between an annular protrusion 40h projecting from the outer periphery of the valve seat member 40 and an annular step 8h formed on the inner peripheral surface of the plunger housing hole 8e. Has been.

  The valve seat member 40 is provided with an annular engagement portion 40d slidably fitted to the large diameter portion of the distal end shaft portion 21a of the plunger 21, and the engagement portion 40d and the rear end portion (deletion: cylindrical). The part 40a) is connected by two connecting parts 40e. The two connecting portions 40e are sandwiched between both straight portions of the H-shaped key member 22 on both sides of the distal end shaft portion 21a, and the horizontal bar portion of the key member 22 contacts the outer periphery of one connecting portion 40e. A locking portion formed on the inner side surface of the second engaging portion engages with the outer periphery of the other connecting portion 40e to prevent it from coming off. As a result, the valve seat member 40 is prevented from rotating by the key member 22. The two connecting portions 40e pass through a notch portion provided in the annular step portion 8h and a communication groove provided in the axial direction in the fitting portion of the plunger 21 fitted in the annular step portion 8h. To a rectangular hole 8i.

  The locking means 44 that locks the valve seat member 40 in the normal position against the spring force of the compression spring 43 so that the second negative pressure valve seat 40b is further away from the valve body 31 than the first negative pressure valve seat 8k. The claw portion 45a projecting radially inward from the rear end portion of the locking member 45 engages with an annular engagement projection 40f projecting from the outer peripheral surface of the engagement portion 40d, so that the valve seat member 40 is normally operated. Locked in position. The locking member 45 has a shape in which the hollow frustum is divided in half by a plane passing through the central axis, and the two locking members 45 in the shape of the hollow hollow frustum shape surround the outer peripheral surface of the cylindrical body 18. The recess 45b stored in the locking member storage hole 8d and engraved on the inner peripheral surface of the base of the locking member 45 is engaged with the convex portion 18b protruding from the outer peripheral surface of the cylindrical body 18. A spacer 46 is interposed between the outer periphery of the base of the locking member 45 and the inner peripheral surface of the locking member storage hole 8d, and when the locking member 45 rotates, the spacer 45 moves outward and the concave portion 45b becomes the convex portion 18b. To prevent it from lifting up. An annular garter spring 47 is fitted in an annular groove carved on the outer peripheral surface of the two engaging members 45, and the engaging member 45 is moved inward so that the claw portion 45a engages with the annular engaging projection 40f. Energized.

  The locking means 44 includes release means 48 that releases the valve seat member 40 when the plunger 21 advances relative to the valve piston 8 by a predetermined amount or more. A taper surface 21e is formed at the distal end of the large diameter portion of the distal end shaft portion 21a of the plunger 21 as the releasing means 48, and a protrusion 45c having a cam surface is formed in the circumferential direction in the central inner peripheral surface of the locking member 45. When the plunger 21 advances relative to the valve piston 8 by a predetermined amount or more, the taper surface 21e engages with the cam surface of the protrusion 45c, rotates the locking member 45, and moves the claw portion 45a to the annular engagement protrusion 40f. Break away from.

  When the valve seat member 40 is moved forward relative to the valve piston 8 in a state where the plunger 21 is not moved forward relative to the valve piston 8 by a predetermined amount or more, the locking means 44 moves the claw portion 45a. A return means 49 is provided that engages with the annular engagement protrusion 40f to lock the valve seat member 40 in the normal position. In a state where the rear end of the engaging portion 40d of the valve seat member 40 is in contact with the key member 22, the valve piston 8 is returned to the return spring 16 after the key member 22 contacts the inner surface of the step portion of the protruding portion 3a of the rear shell 3. The valve seat member 40 is moved forward relative to the valve piston 8, and a tapered surface 40g formed on the front end surface of the annular engagement projection 40f is formed on the end surface of the claw portion 45a. The claw portion 45a is pushed and widened against the spring force of the garter spring 47 by engaging with the inclined surface, and the annular engagement projection 40f is engaged with the claw portion 45a to allow the valve seat member 40 to be normally moved. Lock in position.

  Next, the operation of the negative pressure booster according to the above-described embodiment will be described. During normal operation of the brake pedal 25, when the brake pedal 25 is stepped on and the plunger 21 is moved forward together with the input rod 23 against the spring force of the compression spring 38, the valve body 31 is a spring of the compression spring 39. The negative pressure valve 31a is brought into contact with the first negative pressure valve seat 8k and cuts off the communication between the variable pressure chamber 6 and the constant pressure chamber 5 by the force. When the plunger 21 is further advanced, the atmospheric valve seat 21b is separated from the atmospheric valve 31b, and the variable pressure chamber 6 is communicated with the atmosphere via the silencer 27 and the filter 24. As a result, the atmosphere is introduced into the valve piston 8, and the introduced atmosphere flows into the variable pressure chamber 6 via the atmosphere valve 31b.

  When air is introduced into the variable pressure chamber 6, a pressure difference is generated between the variable pressure chamber 6 and the low pressure chamber 5, and the diaphragm 4, the plate 7, and the valve piston 8 are moved forward by this pressure difference, and the output rod 14. Is advanced through the reaction force member 17. Accordingly, the master piston 13 is pushed by the output rod 14, and a brake hydraulic pressure corresponding to the depression force of the brake pedal 25 is generated in the master cylinder 11.

  During normal operation of the brake pedal 25 described above, the relative movement of the input member 20 with respect to the valve piston 8 is small, so that the valve seat member 40 and the locking member 45 are maintained in the engaged state shown in FIG. The second negative pressure valve seat 40 b is separated from the valve body 31.

  The valve piston 8 elastically deforms the reaction member 17 with an operating force corresponding to the pressure difference between the two chambers 5 and 6 acting on the diaphragm 4 and pushes the master piston 13 through the output rod 14. Due to the elastic deformation of the reaction force member 17, the reaction force member 17 flows into the reaction force hole 8 d and presses the distal end portion of the distal end shaft portion 21 a of the plunger 21 backward via the contact member 19. For this reason, the plunger 21 is retracted, the atmospheric valve seat 21b is seated on the atmospheric valve 31b, the communication between the atmosphere and the variable pressure chamber 6 is cut off, and the desired brake hydraulic pressure is maintained. At this time, the force of stepping on the brake pedal 25 is transmitted from the tip shaft portion 21a of the plunger 21 to the reaction force member 17 via the input rod 23, and the reaction force member 17 is elastically deformed according to the depression force. You can feel the reaction force.

  When the brake pedal 25 is released after the brake operation, the plunger 21 is moved rearward with respect to the valve piston 8 together with the input rod 23 by the spring force of the compression spring 38, so that the atmospheric valve seat 21b contacts the atmospheric valve 31b. In contact therewith, the valve body 31 is moved rearward relative to the valve piston 8, and the negative pressure valve 31a is separated from the first negative pressure valve seat 8k. Thereby, the negative pressure in the constant pressure chamber 5 is introduced into the variable pressure chamber 6 through the passage 8m, and the pressure difference between the variable pressure chamber 6 and the constant pressure chamber 5 is eliminated. Accordingly, the valve piston 8, the plate 7 and the diaphragm 4 are moved rearward by the spring force of the return spring 16, and the master piston 13 is moved rearward and the hydraulic pressure in the master cylinder 11 is lost.

  The plunger 21 stops at the same time as the key member 22 contacts the inner surface of the step portion of the protrusion 3 a of the rear shell 3, and the valve piston 8 stops by contacting the key member 22. As a result, when the brake is not operated, the negative pressure valve 31a is very close to the first negative pressure valve seat 8k, and when the brake is applied, the negative pressure valve 31a quickly moves to the first negative pressure valve seat 8k due to the forward movement of the valve body 31. Can abut.

  Next, the operation at the time of emergency braking in which the driver depresses the brake pedal 25 rapidly will be described. The emergency braking characteristic is achieved by changing the jumping characteristic and applying a larger driving force to the output member 14 than during normal braking. In order to change the jumping characteristics, the gap between the contact member 19 and the reaction member 17 may be increased. That is, by moving the atmospheric valve 31b rearward, the gap is enlarged, the output until the contact member 19 receives the reaction force from the reaction force member 17 is increased, and the ratio of the output to the input becomes infinite. The output in the so-called jumping state is made larger than that in the normal state.

  The jumping characteristic in which the ratio of output to input is infinite is that the negative pressure valve 31a comes into contact with the first negative pressure valve seat 8k, and the contact member 19 starts to be separated from the atmospheric valve seat 21b. It depends on the advance distance of the plunger 21 until it comes into contact. At the time of emergency braking, the second negative pressure valve seat 40b contacts the negative pressure valve 31a formed on the valve body 31 and moves the valve body 31 rearward, so that the atmospheric valve 31b contacts after the air valve seat 21b starts to open. The advance distance of the plunger 21 until the member 19 abuts against the reaction force member 17 becomes larger than that during normal braking, and the distance during which the atmospheric valve 31b is separated from the atmospheric valve seat 21b is increased during that time, and the variable pressure chamber 6 is rapidly opened. Further, it is forcibly communicated with the atmosphere, and a thrust larger than that during normal braking is output to the output member 14 to improve the jumping characteristic.

  During emergency braking in which the driver depresses the brake pedal 25 rapidly, as described above, the plunger 21 is relatively advanced with respect to the valve piston 8 by a predetermined amount or more, so that the tapered surface 21e of the plunger 21 protrudes from the locking member 45. The cam surface of 45c is pressed. Accordingly, the locking member 45 is rotated against the spring force of the garter spring 47 so that the claw portion 45a is detached from the engagement protrusion 40f, and the locking means 44 releases the valve seat member 40. Accordingly, the valve seat member 40 is rapidly retracted with respect to the valve piston 8 by the spring force of the compression spring 43.

  Thus, when the valve seat member 40 moves rearward, the second negative pressure valve seat 40b of the valve seat member 40 contacts the negative pressure valve 31a to retract the valve body 31, and the atmospheric valve 31b is opened from the atmospheric valve seat 21b. Let go. The backward movement of the valve seat member 40 with respect to the valve piston 8 is restricted by the rear end of the engaging portion 40d coming into contact with the key member 22 in contact with the rear end surface of the rectangular hole 8i.

  As a result, the variable pressure chamber 6 is rapidly and forcibly communicated with the atmosphere, a thrust larger than that during normal braking is output to the output member 14, and a large hydraulic pressure is sent from the master cylinder. When the output is increased, the reaction force member 17 flows into the reaction force hole 18a and pushes back the plunger 21 via the contact member 19, so that the atmospheric valve seat 21b contacts the atmospheric valve 31b and the atmospheric flow in. The output during emergency braking is determined.

  When the brake pedal 25 is released, the plunger 21 is moved rearward relative to the valve piston 8 and the valve body 31 by the spring force of the compression spring 36, and the negative pressure valve 31a is separated from the second negative pressure valve seat 40b. As a result, the variable pressure chamber 6 and the constant pressure chamber 5 communicate with each other, so that the output decreases, and the valve piston 8 is moved backward by the return spring 16. When the valve piston 8 is retracted by the spring force of the return spring 16 after the key member 22 abuts on the inner surface of the protrusion 3a of the rear shell 3, it abuts on the key member 22 at the rear end of the engaging portion 40d. The valve seat member 40 that has been moved forward relative to the valve piston 8. As a result, the engagement member 45 resists the spring force of the garter spring 47 by engaging the tapered engagement surface 40g formed at the tip of the annular engagement protrusion 40f with the inclined surface formed at the end surface of the claw portion 45a. Then, after passing through the claw portion 45a, the locking member 45 is returned by the spring force of the garter spring 47, and the claw portion 45a engages with the annular engagement protrusion 40f, so that the valve seat member 40 is moved to the normal position. Lock to.

  By the way, when the valve piston 8 is moved forward following the forward movement of the input rod 23 and the plunger 21 during the emergency brake operation, the boot 26 is bent to a state shown in the lower half of the state shown in the upper half of FIG. However, in the present embodiment, since the flat surface portion 26a of the boot 26 and at least one bellows portion 26b1 are thicker than the other bellows portions 26b2 to increase rigidity, the flat surface portion 26a and at least The one bellows portion 26b1 functions as a rigid body, and the other bellows portion 26b2 is smoothly expanded and contracted. Therefore, the flat portion does not tilt conically as in the prior art (see FIG. 6), and the flat portion 26a of the boot 26 does not come out of the annular groove 23a of the input rod 23 even during a sudden operation. Therefore, the silencer 27 can be prevented from being raised, and the silencer function of the silencer 27 is not lowered.

  4 and 5 show a second embodiment of the present invention. The rigidity of the flat portion 26a of the boot 26 and at least one bellows portion 26b1 is different from that of the first embodiment described above. It is intended to be enhanced by configuration.

  In the second embodiment, as shown in FIGS. 4 and 5, the thickness of the flat portion 26 a and the bellows portion 26 b of the boot 26 is made uniform over the entire length, and the flat portion 26 a of the boot 26 and at least one mountain are formed. By forming a plurality of circumferential ribs 126a and 126b1 at the bellows portion 26b1 (bent portion), the rigidity of the flat portion 26a of the boot 26 and at least one bellows portion 26b1 is made higher than the rigidity of the other bellows portions. It is an enhanced one. Since other configurations are the same as those in the first embodiment, the same reference numerals are given, and descriptions thereof are omitted.

  The boot 26 which constitutes the main part of the present invention is effective when applied to a negative pressure booster having an emergency brake function capable of changing the jumping characteristic during emergency braking and outputting a larger braking force than during normal braking. The present invention can also be applied to a negative pressure booster having no emergency brake function.

  In the embodiment described above, the thickness of the flat portion 26a and at least one bellows portion 26b1 (bending portion) of the boot 26 is increased, or the flat portion 26a and at least one mountain bellows portion 26b1 (bending portion) are increased. By forming the ribs 126a and 126b1, the rigidity of a part of the boot 26 is increased. However, the bent portion does not necessarily have to be a bellows portion, and a portion bent from the flat portion 26a toward the bellows portion 26b. A cylindrical portion may be provided, and the thickness of the cylindrical portion may be increased, or a rib may be formed on the cylindrical portion.

It is sectional drawing of the negative pressure type booster which shows the 1st Embodiment of this invention. It is an expanded sectional view of the valve mechanism part which looked at the arrow along the AA line of FIG. It is a figure which shows the operation state of FIG. It is a figure which shows the 2nd Embodiment of this invention. It is a B arrow view of FIG. It is a figure which shows the behavior of the boot at the time of the conventional brake action.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Booster shell, 2 ... Front shell, 3 ... Rear shell, 4 ... Partition member (diaphragm), 5 ... Constant pressure chamber, 6 ... Variable pressure chamber, 8 ... Valve piston, 8b ... Sliding cylindrical part, 8k ... 1st negative pressure valve Seat, 11 ... Master cylinder, 13 ... Master piston, 14 ... Output rod, 15 ... Reaction force chamber, 16 ... Return spring, 17 ... Reaction force member, 20 ... Input member, 21 ... Plunger, 21b ... Air valve seat , 22 ... key member, 23 ... input rod, 23a ... annular groove, 24 ... filter, 25 ... brake pedal, 27 ... silencer, 26 ... boot, 26a ... flat part, 26b ... bellows part, 26b1 ... at least one bellows Part (bending part), 26b2 ... other bellows part, 126a, 126b1 ... rib, 30 ... valve mechanism, 31 ... valve body, 31a ... negative pressure valve, 31b ... atmospheric valve, 35 ... holding body, 38, 9 ... spring, 40 ... valve seat member, 40b ... second negative pressure valve seat, 44 ... locking means, 45 ... engaging member, 48 ... release means, 49 ... return means.

Claims (4)

The booster shell (1) is partitioned into a variable pressure chamber (6) and a constant pressure chamber (5) by a partition member (4), and a base end portion (8a) of the valve piston (8) is fixed to the partition member, A plunger that transmits the output of the partition member based on the pressure difference between the chamber and the constant pressure chamber from the valve piston to the output rod (14) via the reaction force member (17) and acts in cooperation with the reaction force member ( 21) and the input rod (23) pivoted by the brake pedal (25) are connected to form an input member (20), and the negative pressure valve seat (8k) and the atmospheric valve seat (21b) are the valve piston and the plunger. And a negative pressure type booster provided with a negative pressure valve (31a) and an atmospheric valve (31b) that are connected to and separated from the negative pressure valve seat and the atmospheric valve seat to communicate and block the variable pressure chamber to and from the constant pressure chamber and the atmosphere. In the valve A boot (26) having a bellows part (26b) that can extend and contract in the axial direction covering the piston is provided, one end of the boot is engaged with the booster shell, and the other end of the boot is formed on the input member A vent hole (26c) for introducing the atmosphere into the atmospheric valve is formed in the flat portion (26a) of the boot that fits into the groove (23a) and fits in the annular groove, and the flat portion of the boot and the flat surface A negative pressure booster characterized in that the rigidity of the bent portion (26b1) bent in the direction of the bellows portion from the portion is increased. 2. The negative pressure booster according to claim 1, wherein the thickness of the flat portion and the bent portion of the boot is increased. The negative pressure type booster according to claim 1, wherein a plurality of circumferential ribs (126a, 126b1) are formed on the flat portion and the bent portion of the boot, respectively. 4. The negative pressure booster according to claim 1, wherein the bent portion is constituted by at least one mountain of the bellows portion.

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