JP4716100B2 - Pneumatic booster - Google Patents

Description

  The present invention relates to a pneumatic booster mounted on a brake device of a vehicle such as an automobile.

  In general, a brake device for an automobile is equipped with a pneumatic booster to increase the braking force. As a pneumatic booster, the inside of the housing is divided into a constant pressure chamber (which is always maintained at a negative pressure by the engine intake negative pressure) and a variable pressure chamber by a power piston, and in a valve body connected to the power piston. By moving the provided plunger by the input rod, the atmosphere (positive pressure) is introduced into the variable pressure chamber, and a pressure difference is generated between the constant pressure chamber and the variable pressure chamber. This pressure difference causes the power piston. It is known that thrust is applied to an output rod via a reaction member, and a part of the reaction force applied to the reaction member from the output rod is fed back to the input rod.

  In general, the relationship between the input (brake pedal operating force) and output (braking force) of this type of pneumatic booster is controlled by the jump-in output due to the gap between the plunger and the reaction member in the initial stage of braking. After starting up the power, the output reaches the full load in linear proportion to the input.

  However, the characteristic that the brake pedal operating force and the braking force are linearly proportional as in the conventional pneumatic booster described above naturally requires a large operating force when generating a large braking force in an emergency. Become. Thus, a pneumatic booster equipped with a so-called brake assist mechanism is desired to reduce the brake pedal operating force when a large braking force is required in an emergency. A pneumatic booster equipped with a brake assist mechanism can be expected to significantly improve braking force in an emergency, coupled with an anti-lock brake device that prevents a wheel from being locked during braking.

The present applicant has proposed a pneumatic booster equipped with a brake assist mechanism as shown in FIG. 7 (see, for example, FIG. 28 of Patent Document 1). FIG. 7 shows the inside of the valve body 1 of the pneumatic booster. A brake assist mechanism 6 is provided between a plunger 3 connected to the input rod 2 and a reaction disk 5 attached to the output rod 4. It is intervened.
JP 2004-51078 A

  In the brake assist mechanism 6, a holder 7 that contacts the plunger 3 and a piston 8 that contacts the reaction disk 5 are connected and coupled by a stem 10 with an elastic member 9 interposed therebetween. A cylindrical sleeve 11 is slidably fitted. The stem 10 is slidably inserted into the holder 7, and the brake assist mechanism 6 can be compressed in the axial direction by the elasticity of the elastic member 9.

An inner circumferential groove 12 is formed in the sleeve 11. A spring 13 is interposed between the holder 7 and the sleeve 11, and the sleeve 11 is urged toward the output rod 4 by the spring force of the spring 13 and is in contact with the flange portion 14 of the piston 8. . In this state, the inner peripheral surface of the sleeve 11 is in contact with the elastic member 9, and the inner peripheral groove 12 of the sleeve 11 faces the elastic member 9 when the sleeve 11 moves to the input rod 2 side. ing. The piston 8, the holder 7, the elastic member 9, and the spring 13 can be sub-assembled by connecting the piston 8 and the holder 7 with the stem 10.

  With this configuration, the shape of the elastic member 9 is held by the inner peripheral surface of the cylindrical portion of the sleeve 11 during normal braking, so that the brake assist mechanism 6 is hardly compressed in the axial direction. As with the booster, an output that is substantially proportional to the input is generated.

During sudden braking, the input speed (the speed at which the brake pedal is stepped on) is high, so that the sleeve 11 abuts against the pressure receiving member 15 fixed to the valve body 1 and retreats with respect to the piston 8 so that the inner circumference The groove 12 moves on the elastic member 9. In this state, when the elastic member 9 is compressed in the axial direction, the elastic member 9 is easily compressed in the axial direction by being pushed into the inner circumferential groove 12 and expanding in diameter. As a result, the plunger 3 is greatly displaced with respect to the valve body 1 , the boost ratio is increased, and a large braking force can be generated quickly.

  However, the pneumatic booster equipped with the conventional brake assist mechanism shown in FIG. 7 has the following problems. In order to make the brake assist mechanism 6 into a sub-assembly, a stem 10 for connecting the piston 8 and the holder 7 is necessary, and the number of parts is large. When the stem 10 is press-fitted into the piston 8, a precise axial dimension is required. Management is required and assembly is not good.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a pneumatic booster equipped with a brake assist mechanism that has a simple structure and excellent assemblability.

In order to solve the above-mentioned problems, the present invention defines the inside of a housing as a constant pressure chamber and a variable pressure chamber by a power piston, and moves a plunger disposed in a valve body connected to the power piston by an input rod. Thus, the valve means is opened to introduce the working gas into the variable pressure chamber to generate a pressure difference between the constant pressure chamber and the variable pressure chamber, and the thrust generated in the power piston due to this pressure difference via the reaction member In the pneumatic booster configured to act on the output rod and to transmit a part of the reaction force acting on the reaction member from the output rod to the input rod,
A piston opposed to the reaction member; an elastic member interposed between the piston and the plunger; and a slidably fitted to the outer periphery of the piston, the elastic member, and the plunger, and A stepped sleeve having a small-diameter cylindrical portion that restricts expansion and a large-diameter cylindrical portion that allows expansion of the elastic member, an attachment portion that engages with the end surface of the piston on the reaction member side, and the attachment portion A spring holder having a plurality of arm portions extending to the plunger side through the outer peripheral side of the stepped sleeve, and a claw portion projecting radially inward from a distal end portion of the arm portion; and a step portion of the stepped sleeve and a spring for biasing the stepped sleeve is interposed between the claw portion to said reaction member, the stepped sleeve, usually, the biasing force of the spring The small-diameter cylindrical portion is in a position that limits the expansion of the elastic member, and when the speed or movement amount of the plunger with respect to the valve body reaches a predetermined value, it moves against the biasing force of the spring. A brake assist mechanism is provided in which the large-diameter cylindrical portion allows the elastic member to expand in diameter.

  According to the pneumatic booster according to the invention, the stepped sleeve is fitted to the outer periphery of the piston and the elastic member, the attachment portion of the spring holder is engaged with the piston, and the claw portion of the arm portion of the spring holder is stepped. The brake assist mechanism can be sub-assembled by interposing a spring between the step portion of the sleeve. As a result, the conventional stem can be eliminated, so that the number of parts can be reduced, and precise assembly of dimensions can be improved without requiring precise axial dimension management.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
As shown in FIGS. 1 and 3, a pneumatic booster 16 according to this embodiment is a tandem pneumatic booster, and the inside of a shell 17 (housing) is separated from a front chamber 19 and a rear by a partition wall 18. The room 20 is divided into two rooms. The front chamber 19 and the rear chamber 20 are defined by constant pressure chambers 19A and 20A and variable pressure chambers 19B and 20B by power pistons 21 and 22, respectively. The constant pressure chambers 19A and 20A and the variable pressure chambers 19B and 20B communicate with each other through passages 23 and 24, respectively. A substantially cylindrical valve body 25 is connected to the power pistons 21, 22, and the valve body 25 is slidably and airtightly inserted into the partition wall 18 and the rear wall 26 of the shell 17. Is extended from the rear wall 26 to the outside. An output rod 28 is connected to the front portion of the valve body 25 via a reaction disk 27 (reaction member), and a tip portion of the output rod 28 is a master cylinder (not shown) attached to the front wall of the shell 17. ).

  A brake assist mechanism 29, a plunger 30, a poppet seal 31 (valve means), and an input rod 32 are provided in the valve body 25. A brake assist mechanism 29 is interposed between one end of the plunger 30 and the reaction disk 27, and one end of the input rod 32 is connected to the other end of the plunger 30. The other end of the input rod 32 is inserted through a breathable dust seal 33 attached to the rear end of the valve body 25 and extends to the outside. A brake pedal (not shown) is connected to the tip of the input rod 32. Is done. The poppet seal 31 is seated on the seat portion 34 of the valve body 25 and the seat portion 35 of the plunger 30, and communicates with the passage 36 communicating with the constant pressure chambers 19 </ b> A and 20 </ b> A and the variable pressure chambers 19 </ b> B and 20 </ b> B as the plunger 30 moves. It opens and closes between the passage 37 and between the passage 35 and the atmosphere.

  A stop key 38 is inserted into the passage 37 of the valve body 25, and the stop key 38 engages with a stopper 39 of the shell 17, so that the retracted position of the valve body 25 and the relative position between the plunger 30 and the valve body 25. Is stipulated. 1 and 3, reference numeral 40 denotes a negative pressure introduction port that is connected to a negative pressure source such as an intake pipe of the engine and introduces negative pressure into the constant pressure chamber 19A, 41 denotes a return spring of the input rod 32, and 42 denotes A valve spring 43 for biasing the poppet seal 31 and a return spring of the valve body 25 are shown.

Next, the brake assist mechanism 29, which is a main part of the present embodiment, will be described with reference to FIG.
The brake assist mechanism 29 includes a piston 44 that contacts the reaction disk 27, an elastic member 45 that contacts the plunger 30, a stepped sleeve 46 attached to the outer periphery thereof, a spring 47, and a spring holder 48. Yes.

  The piston 44 has a stepped circle in which a small-diameter portion 49 that abuts the reaction disk 27 protrudes on one end side, and a contact portion 50 that has a diameter reduced to the same diameter as the elastic member 45 protrudes on the other end side. It is formed in a column shape. A cylindrical ratio ring 51 is slidably fitted to the small diameter portion 49. The ratio ring 51 is slidably inserted into an annular pressure receiving member 52 attached to the front end of the valve body 25. Then, the stepped portion 53 formed on the outer periphery of the ratio ring 51 abuts on the stepped portion 54 formed on the inner periphery of the pressure receiving member 52, whereby the retracted position of the ratio ring 51 is defined. In the non-braking position shown in FIG. 1, a predetermined gap C (jump-in clearance) is provided between the small diameter portion 49 of the piston 44 and the tip of the ratio ring 51 and the reaction disk 27.

  The elastic member 45 is a columnar member made of an elastic body such as rubber interposed between the plunger 30 and the piston 44, and the tip of the plunger 30, the contact portion 50 of the piston 44, and the elastic member 45 Have the same diameter.

  The stepped sleeve 46 is slidably fitted to the outer periphery of the large-diameter cylindrical portion 55 that is slidably fitted to the outer periphery of the piston 44, and the contact portion 50 of the piston 44, the elastic member 45, and the distal end portion of the plunger 30. 1 and 4, a stepped portion 57 is formed between the large diameter cylindrical portion 55 and the small diameter cylindrical portion 56. As shown in FIGS. 2 and 4, a rectangular notch 58 is provided at the end of the side wall of the large-diameter cylindrical portion 55, and the three notches 58 are equally spaced along the circumferential direction. Has been placed.

  As shown in FIGS. 1 and 5, the spring holder 48 includes a ring-shaped attachment portion 59 that fits into an annular recess 44 </ b> A formed on the outer peripheral portion of the end surface from which the small diameter portion 49 of the piston 44 projects, and an attachment portion. And three arm portions 60 that extend radially outward from 59 and bend along the axial direction of the attachment portion 59. Three arm portions 60 are arranged at equal intervals along the circumferential direction of the attachment portion 59 and can be respectively inserted into the three notch portions 58 of the stepped sleeve 46. A claw portion 61 that protrudes radially inward is formed at the tip of the arm portion 60.

  The spring 47 is provided between the stepped portion 57 of the stepped sleeve 46 fitted to the piston 44 and the elastic member 45 and the claw portion 61 of the spring holder 48 in which the mounting portion 59 is fitted to the concave portion 44 </ b> A of the piston 44. The stepped portion 57 of the stepped sleeve 46 is always pressed against the end surface from which the contact portion 50 of the piston 44 protrudes. In this state, the tip end portion of the large diameter cylindrical portion 55 of the stepped sleeve 46 protrudes from the end surface from which the small diameter portion 49 of the piston 44 protrudes.

Next, the operation of the present embodiment configured as described above will be described.
In the non-braking state shown in FIG. 1, the poppet seal 31 is seated on the seat portions 34, 35, the variable pressure chambers 19B, 20B are cut off from the atmosphere and the constant pressure chambers 19A, 20A (negative pressure), and the constant pressure chambers 19A, 19A, 20A and the pressure change chambers 19B and 20B are in balance with each other, and no thrust is generated in the power pistons 21 and 22.

  In a normal brake operation in which the depression speed of the brake pedal is low, when the plunger 30 is advanced by the input rod 32, the seat portion 35 is separated from the poppet seal 31, and the atmosphere is introduced into the variable pressure chambers 19B and 20B, and the constant pressure is maintained. A pressure difference is generated between the chambers 19A and 20A (negative pressure). Due to this pressure difference, a thrust (servo force) is generated in the power pistons 21 and 22, and the valve body 25 moves forward and presses the output rod 28 via the reaction disk 27. When the poppet seal 31 is seated on the seat portion 35 by the advancement of the valve body 25, the introduction of the atmosphere is stopped, and the pressure difference between the constant pressure chambers 19A, 20A and the variable pressure chambers 19B, 20B is maintained. At this time, part of the reaction force acting on the reaction disk 27 from the output rod 28 is fed back to the plunger 30 and the input rod 32 via the brake assist mechanism 29.

  At this time, in the brake assist mechanism 29, an axial compressive force acts on the elastic member 45 by the reaction force from the reaction disk 27. Since the elastic member 45 is in a sealed space surrounded by the contact portion 50 of the piston 44, the distal end portion of the plunger 30, and the small diameter cylindrical portion 56 of the stepped sleeve 46, the axial compression depends on its volume elasticity. However, since the elastic modulus is sufficiently large, it is hardly compressed. Therefore, since the brake assist mechanism 29 is hardly shortened in the axial direction, the reaction force from the reaction disk 27 is transmitted to the plunger 30 side as it is.

In this case, in the initial stage of braking, the plunger 30 can move forward without receiving a reaction force from the reaction disk 27 due to the gap C between the small-diameter portion 49 of the piston 44 and the reaction disk 27. It can be launched quickly (jump-in action). Thereafter, the reaction force from the reaction disk 27 is fed back to the plunger 30 and the input rod 32 through the ratio ring 51 and the small diameter portion 49 of the piston 44, so that a braking force corresponding to the brake pedal depression force can be generated. . Then, after the stepped portion 53 of the ratio ring 51 abuts on the stepped portion 54 of the pressure receiving member 52, the pressure receiving area with respect to the reaction force from the reaction disk 27 decreases and the boost ratio increases.

  When the input to the input rod 32 is released, the input rod 32 and the plunger 30 are retracted by the spring force of the return spring 41, the seat portion 35 of the plunger 30 presses the poppet seal 31, and the seat portion 34 of the valve body 25. Separate from. As a result, the constant pressure chambers 19A, 20A and the variable pressure chambers 19B, 20B are communicated with each other, the pressure difference between them is eliminated, the thrust of the power pistons 21, 22 disappears, and the valve body 25 by the return spring 43 is provided. Reverses and braking is released.

  During sudden braking, that is, when the depression speed of the brake pedal is large, the follow-up operation of the valve body 25 by the thrust of the power pistons 21 and 22 is delayed with respect to the movement of the plunger 30. As a result, the tip end portion of the large diameter cylindrical portion 55 of the stepped sleeve 46 contacts the pressure receiving member 52, the stepped sleeve 46 moves backward with respect to the piston 44, and the large diameter cylindrical portion 55 overlaps the elastic member 45. Move to. In this state, as shown in FIG. 6, the elastic member 45 compressed in the axial direction is allowed to be deformed in the diameter-expanding direction and is pushed into the space formed by the large-diameter cylindrical portion 55. The modulus of elasticity for directional compression is sufficiently small. Thereby, the brake assist mechanism 29 is compressed in the axial direction by the input to the plunger 30 and the reaction force from the reaction disk 27. As a result, the plunger 30 can be moved forward without increasing the reaction force from the reaction disk 27 and the seat portion 35 can be separated from the poppet seal 31, and the atmosphere is introduced into the variable pressure chambers 19B and 20B to obtain a large servo. Can generate power. In this way, by operating the brake assist mechanism 29 in an emergency and allowing the compression of the elastic member 45 in the axial direction, it is possible to reduce the operating force of the brake pedal and quickly start up a large braking force. .

  The brake assist mechanism 29 has a stepped sleeve 46 with a piston 44 fitted into a large diameter cylindrical portion, a small diameter cylindrical portion 56 fitted with an elastic member 45, and a spring holder 48 with a stepped portion while expanding the arm portion 60. The fitting portion 59 is fitted onto the sleeve 46 and the mounting portion 59 is fitted into the concave portion 44 </ b> A of the piston 44, and the spring 47 is expanded to the step portion 57 of the stepped sleeve 46 and the claw portion 61 of the spring holder 48 while the arm portion 60 is expanded. Can be easily sub-assembled. This eliminates the need for a stem for connecting the conventional piston and the holder, thereby reducing the number of components and improving the assembling property. In addition, the structure of each member is simple and the manufacturing cost is low.

  In the above embodiment, three cutout portions 58 of the stepped sleeve 46 and three arm portions 60 of the spring holder 48 are provided, but the number thereof may be two or more, and is selected as appropriate. be able to.

It is a longitudinal cross-sectional view which expands and shows the principal part in the non-braking state of the pneumatic booster which concerns on one Embodiment of this invention. It is an expanded sectional view by the AA line of the brake assist mechanism of the pneumatic booster shown in FIG. It is a longitudinal cross-sectional view of the pneumatic booster shown in FIG. FIG. 2 is an end view and a longitudinal sectional view of a stepped sleeve of a brake assist mechanism of the pneumatic booster shown in FIG. 1. It is the end view and longitudinal cross-sectional view of the spring holder of the brake assist mechanism of the pneumatic booster shown in FIG. FIG. 2 is a longitudinal sectional view showing an enlarged main part in a braking state in which a brake assist mechanism is operated in the pneumatic booster shown in FIG. 1. It is a vertical sectional view which expands and shows the principal part of the pneumatic booster provided with the conventional brake assist mechanism.

Explanation of symbols

16 atmospheric pressure booster, 17 shell (housing), 19A, 20A constant pressure chamber, 19B, 20B variable pressure chamber, 21, 22 power piston, 25 valve body, 27 reaction disc (reaction member), 28 output rod, 29 brake assist Mechanism, 30 Plunger, 31 Poppet seal (valve means), 32 Input rod, 44 Piston, 45 Elastic member, 46 Stepped sleeve, 47 Spring, 48 Spring holder, 55 Large diameter cylindrical part, 56 Small diameter cylindrical part, 57 Step part , 59 Mounting part, 60 Arm part, 61 Claw part

Claims (1)

The inside of the housing is defined as a constant pressure chamber and a variable pressure chamber by a power piston, and a plunger disposed in a valve body connected to the power piston is moved by an input rod, thereby opening valve means and operating gas in the variable pressure chamber. And a pressure difference is generated between the constant pressure chamber and the variable pressure chamber, and a thrust generated in the power piston due to the pressure difference is applied to the output rod via a reaction member, and the reaction from the output rod is performed. In a pneumatic booster configured to transmit a part of the reaction force acting on the member to the input rod,
A piston opposed to the reaction member; an elastic member interposed between the piston and the plunger; and a slidably fitted to the outer periphery of the piston, the elastic member, and the plunger, and A stepped sleeve having a small-diameter cylindrical portion that restricts expansion and a large-diameter cylindrical portion that allows expansion of the elastic member, an attachment portion that engages with the end surface of the piston on the reaction member side, and the attachment portion A spring holder having a plurality of arm portions extending to the plunger side through the outer peripheral side of the stepped sleeve, and a claw portion projecting radially inward from a distal end portion of the arm portion; and a step portion of the stepped sleeve and a spring for biasing the stepped sleeve is interposed between the claw portion to said reaction member, the stepped sleeve, usually, the biasing force of the spring The small-diameter cylindrical portion is in a position that limits the expansion of the elastic member, and when the speed or movement amount of the plunger with respect to the valve body reaches a predetermined value, it moves against the biasing force of the spring. A pneumatic booster characterized in that a brake assist mechanism is provided in which the large-diameter cylindrical portion allows the elastic member to expand in diameter.

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