JP2003040101A - Negative pressure type servo unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative pressure type servo unit having high responsiveness allowing smooth flow-in of atmospheric air into a pressure changing chamber. SOLUTION: A sliding portion 37c of a plunger 37 slidable with a power piston 22 is provided with recesses 37e1, 37e2 permitting flow of fluid in the longitudinal direction, and the distance between bottoms of the recesses 37e1, 37e2 is made smaller than the outer diameter of a body 37g of the plunger 37.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative pressure booster for a vehicle, and more particularly to a negative pressure booster capable of compensating for insufficient brake pedal depression force during emergency braking. The present invention relates to a pressure booster. [0002] When an obstacle suddenly appears on the course of a vehicle and the driver depresses the brake pedal in a hurry, that is, at the time of emergency braking, the driver applies a depressing force to the brake pedal. There is a recent analysis result that the brake force of the vehicle is not sufficiently exerted in many cases, as it is considerably smaller than the pedaling force that generates the brake fluid pressure that reaches the wheel lock. Based on the result of this analysis, a device has been proposed that determines whether the brake is a normal brake or an emergency brake from the stepping speed of the brake pedal, and automatically raises the brake fluid pressure to a level at which the wheel locks during emergency braking, It is being put to practical use. [0003] Various types of devices have been proposed as such devices, for example, those described in WO 01/32488 A1. In this device, a negative pressure valve seat urges a valve seat member formed at a rear end portion rearward by a spring, and a holding member engaged with a locking member integrated with a power piston moves rearward of the valve seat member. It is structured to restrict the movement of Then, when the amount of forward movement of the plunger with respect to the power piston exceeds a predetermined value, in other words, when the driver depresses the brake pedal in a hurry and the forward speed of the plunger is higher than the forward speed of the power piston, the holding is performed. The engagement between the member and the valve seat member is released, the valve seat member retreats, and by increasing the distance between the rear end surface of the reaction disk and the front end surface of the valve seal portion of the valve mechanism, the so-called jumping amount is increased. To obtain emergency braking characteristics. That is, in the case of emergency braking, by switching the input-output characteristic of the vacuum booster from the characteristic for normal braking to the characteristic for emergency braking, the same result as when the driver depresses the brake pedal strongly is obtained. . In this conventional vacuum booster, the air valve seat is separated from the valve seal portion during normal braking and emergency braking to form a gap, so that the air is released. The propulsion force is applied to the movable wall and the power piston by being introduced into the variable pressure chamber. However, since the valve seat member must be arranged coaxially with the power piston, only a small gap formed between the inner peripheral surface of the power piston and the outer peripheral surface of the plunger as an air inflow passage. When the air passes rapidly and in large quantities, such as during emergency braking, this gap acts as a restrictor, preventing the smooth inflow of air into the transformer chamber and resulting in a low-response negative pressure booster. There is a fear. SUMMARY OF THE INVENTION It is an object of the present invention to provide a negative pressure booster having a high responsiveness, in which the air flows into the transformer chamber smoothly. [0007] In order to achieve the above object, a housing having at least one pressure chamber formed therein and a housing formed inside the housing are provided. A movable wall which is installed so as to be able to move forward and backward and divides the pressure chamber into a constant pressure chamber and a variable pressure chamber, a power piston coupled to the movable wall, and a power piston inside the power piston. And an input rod connected to the input rod so as to be slidable in the front-rear direction with respect to the power piston, and an air valve seat is formed at a rear end portion. A plunger, an output member for outputting the propulsive force of the power piston accompanying the movement of the movable wall to the outside of the device, and the power piston. A first negative pressure valve seat facing rearward, and a second negative pressure valve seat formed on a valve seat member capable of moving forward and backward with respect to the power piston and substantially concentric with the first negative pressure valve seat;
A valve mechanism having a movable portion facing the first negative pressure valve seat and a fixed portion hermetically fixed to the power piston; and a drive for moving the valve seat member toward the movable portion by a predetermined amount under predetermined conditions. Means, the plunger includes a rear flange portion on which the atmospheric valve seat is formed, a cylindrical main body portion formed in front of the flange portion, and a front portion of the main body portion. And an intermediate flange portion that slides on the inner peripheral surface of the power piston, and a rear flange portion into which the valve seat member is inserted, and allows fluid flow in the front-rear direction through the intermediate flange portion. In addition, a negative pressure type booster is provided in which a plurality of sets of concave portions facing each other are provided, and a distance between bottom portions of the concave portions facing each other is smaller than an outer diameter of the main body. According to the first aspect of the present invention, the intermediate flange portion, which is a sliding portion of the plunger with the power piston, is provided with a concave portion that allows the flow of fluid in the front-rear direction, and is provided between the opposed concave bottom portions. Is smaller than the outer diameter of the main body, a passage having a sufficiently large cross-sectional area is formed between the power piston and the plunger. Therefore, when the brake valve is operated and the air valve seat separates from the movable part of the valve mechanism and the air flows into the variable pressure chamber, the inflowing air flows into the variable pressure chamber without being throttled, and the responsiveness is improved. And a negative pressure booster with a high pressure can be obtained. In particular, during emergency braking when the air passes rapidly and in large quantities, there is no gap that acts as a throttle, so that the air flows into the transformer chamber smoothly,
Emergency braking with high responsiveness is realized. The term "rearward" means the brake pedal side or the vehicle rear side with respect to the vacuum booster, and the front means the master cylinder side or the vehicle front side with respect to the vacuum booster. Embodiments of the present invention will be described below with reference to the accompanying drawings. FIGS. 1 to 4 are cross-sectional views of a vacuum booster according to a first embodiment of the present invention, and FIG.
It is A sectional drawing. FIG. 3 is a sectional view taken along line B-C-D-E of FIG. 2, and FIG. 4 is a partially detailed view of FIG. Referring to FIG. 1, a negative pressure booster 10 includes a front shell 11, a rear shell 12, and a movable wall 20. The housing is divided into a constant pressure chamber 23 and a variable pressure chamber 24 by the movable wall 20. 14 is provided. The movable wall 20 in the housing 14 includes a metal plate 18 and a rubber diaphragm 19, and is installed so as to be movable in the front-rear direction with respect to the housing 14. The bead portion on the outer peripheral edge of the diaphragm 19
The rear shell 12 is hermetically sandwiched between the folded portion provided on the outer peripheral edge and the front shell 11. The bead portion on the inner peripheral edge of the diaphragm 19 is hermetically fixed together with the plate 18 in a groove provided on the outer periphery of the front flange portion of the power piston 22. The constant pressure chamber 23 is communicated with an engine intake manifold (not shown), which is a negative pressure source, and is always maintained at a negative pressure during operation of the engine. The transformation chamber 24 has a passage 60.
In addition to being communicated with and interrupted from the constant pressure chamber 23 via the valve mechanism 36, the air is communicated with and interrupted from the atmosphere via the valve mechanism 36. As shown in FIGS. 1 to 4, the power piston 22 has a front portion inside thereof (in FIGS. 1, 3 and 4,
A first space 22a located on the left side and communicating with the constant pressure chamber;
A second space 22b which is located rearward (to the right in FIGS. 1, 2 and 4) and communicates with the atmosphere, and an intermediate portion interposed between the first space 22a and the second space 22b. 221. The middle part 221 is a first part at the center of the middle part 221.
Third space 22 communicating between space 22a and second space 22b
c, and a passage 60 communicating the first space 22a and the second space 22b separately from the third space 22c. Inside the power piston 22, an input rod 28 and a plunger 37 constituting an input member 27 are provided.
The power piston 22 is installed so as to penetrate the first space 22 a, the second space 22 b, and the third space 22 c and move in the front-rear direction with respect to the power piston 22. Further, the input rod 28 and the plunger 37 are integrally connected by a connecting portion 80, and the input rod 28 is connected to a brake pedal (not shown) at the rear thereof. An output member 55 is fitted to the front end of the power piston 22, and a reaction member 54 is disposed between the front end of the power piston 22 and the output member 55. Further, a contact member 70 is provided between the reaction force member 54 and the front end of the plunger 37, and the contact member 70
Is a power piston 22 so that it can move in the front-rear direction.
It is installed inside the locking member 50 which is provided integrally with the first member. Plunger 3 for power piston 22
A key member 32 is inserted through a radial hole 33 formed in an intermediate portion 221 of the power piston 22 in order to regulate the amount of movement of the input rod 7 and the input rod 28. The thickness of the key member 32 in the front-rear direction (the left-right direction in FIGS. 1 and 3) is smaller than the front-rear dimension of the radial hole 33, and
2 can move in the front-rear direction with respect to the power piston 22 by a distance C shown in FIG. The key member 32 can contact the rear shell 12 at the rear surfaces of both ends protruding to the outer peripheral side of the power piston 22. The rearward movement limit of the power piston 22 with respect to the housing 14 is shown in FIG. As shown in FIG. 5, the front wall of the radial hole 33 is in contact with the front surface of the key member 32, and the rear surfaces of both ends of the key member 32 are in contact with the rear shell 12. The center of the key member 32 is formed by a pair of flange surfaces 34 and 35 formed at the center of the plunger 37.
The rearward movement limit of the plunger 37 with respect to the power piston 22 is such that the flange surface 34 abuts the front surface of the key member 32 and the rear surface of the key member 32 is the rear wall of the radial hole 33. This is the position where it abuts. The forward movement limit of the plunger 37 with respect to the power piston 22 is such that the flange surface 35 contacts the rear surface of the key member 32 and the front surface of the key member 32 is
This is the position in contact with the front wall. Inside the power piston 22, a power reducing operation state in which the variable pressure chamber 24 is cut off from the atmosphere while communicating with the constant pressure chamber 23 in accordance with the longitudinal movement of the plunger 37 with respect to the power piston 22, and a variable pressure chamber 24 are provided. Constant pressure chamber 23
And the power holding action state and the transformer chamber 24 cut off from the atmosphere
A valve mechanism 36 is provided for switching to a state of increasing the output, which is shut off from the constant pressure chamber 23 and communicated with the atmosphere. The valve mechanism 36 includes an atmospheric valve seat 37a integrally formed with a rear flange portion 37f of the plunger 37.
A first negative pressure valve seat 38 formed integrally with the power piston 22; a second negative pressure valve seat 39 formed integrally with the rear portion of the valve seat member 40; Valve seat 3
7a includes a movable portion 41 having valve seal portions 41a and 41b opposed to each other, and a fixed portion 43 airtightly fixed to the power piston 22 by a retainer 42,
The cylindrical member 45 whose movable portion 41 is urged forward by a spring 44 is a main component. The valve seat member 40 disposed in the third space 22c of the intermediate portion 221 is movable in the front-rear direction with respect to the power piston 22. As shown in a perspective view in FIG.
Is provided with a slit 40b into which a sliding portion 37c protruding in the radial direction is inserted into the outer periphery of the plunger 37, and a through hole 40e penetrating the valve seat member 40 in the front-rear direction. The key member 32 is inserted into the slit 40b. By inserting the front flange portion 37i of the plunger 37 into the through hole 40e of the valve seat member 40,
The sliding portion 37c projects outside the valve seat member 40 via the slit 40b. When the plunger 37 provided with the valve seat member 40 is disposed in the power piston 22, the sliding portion 37c comes into contact with the inner peripheral surface 221a of the intermediate portion 221 and the plunger 37 moves the sliding portion 37c. It is slidably supported on the inner peripheral surface 221a of the intermediate portion 221 through the intermediate portion 221. On the other hand, the valve seat member 40 is located between the outer peripheral portion of the plunger 37 and the inner peripheral portion of the intermediate portion 221 of the power piston 22, and at the rear end where the second negative pressure valve seat 39 is formed. It comes into contact with the inner peripheral surface of the intermediate portion 221 so as to be slidable in the front-back direction. That is, the power piston 2
2 has an intermediate portion 221 as a holding portion for holding the valve seat member 40 slidably rearward. An annular seal member for maintaining airtightness between the rear end of the valve seat member 40 and the inner peripheral surface of the intermediate portion 221 is provided on the outer periphery of the rear end of the valve seat member 40 inserted into the intermediate portion 221. 46
Is installed. Further, the valve seat member 40 includes the valve seat member 4.
It is urged rearward by a spring 47 disposed between the center portion 221 and a flange portion provided on the inner peripheral surface of the intermediate portion 221. A spring 59 disposed between a retainer 58 locked to the input rod 28 integrally connected to the plunger 37 and the coupling portion 80 and a retainer 42 locked to the power piston 22 serves as an input. When the rod 28 is urged backward and the brake pedal is not depressed, the atmospheric valve seat 37a is brought into contact with the movable portion 41 of the valve mechanism 36 and the movable portion 41 is moved from the first negative pressure valve seat valve seat 38. It is kept in a state separated by the distance A. The passage 60 formed in the intermediate portion 221 and the first
The space 22a communicates the valve mechanism 36 with the constant pressure chamber 23,
The third space 22c communicates the valve mechanism 36 with the variable pressure chamber. A driving means for propelling the valve seat member 40 rearward is provided inside the front portion of the power piston 22, that is, in the intermediate portion 221. The driving means includes a spring 47 for urging the valve seat member 40 rearward and the key member 32.
It is composed of A holding means 48 is provided inside the front portion of the power piston 22, that is, in the first space 22a. The holding means 48 includes a holding member 52 having an engaging portion 52b that engages with the engaged portion 40c of the valve seat member 40, and a ring-shaped elastic body 53 that urges the holding member 52 in a direction to reduce the diameter. The locking portion 52c of the holding member 52 is fitted in a locking groove 50a of a locking member 50 fixed to a front portion of the power piston 22. Therefore, the holding member 52
Cannot move in the front-rear direction, but can move in the radial direction around the locking portion 52c. As shown in FIG. 6, the holding member 52 has a truncated hollow truncated cone shape obtained by cutting the truncated hollow cone into three planes passing through the central axis thereof. The power piston 22 is assembled to face the power piston 22. In this embodiment, the power piston 2
The slit 22e is formed in the inner peripheral surface 221a of the intermediate portion 221 in
1, 22e2 are formed, and the plunger 3
The recessed portions 37e1 and 37e2 facing the slits 22e1 and 22e2 are formed in the sliding portion 37c of No. 7. Recess 3
The distance Y between the bottoms of 7e1 and 37e2 is
Are set smaller than the outer diameter X of the main body 37g, and the slits 22e1 and 22e2 and the recesses 37e1 and 37e2 form passages R1 and R2 that communicate the second space 22b and the transformation chamber 24. When the brake operation is performed, the atmosphere valve seat 37a is separated from the valve seal portion 41b by the passages R1 and R2.
The passage through which the atmosphere flows into the transformation chamber 24 through the radial hole 33 of the power piston 22 is a passage formed by the slits 22e1, 22e2 and the recesses 37e1, 37e2, as described above. Recess 3
Since the distance Y between the bottoms of 7e1 and 37e2 is smaller than the outer diameter X of the main body 37g of the plunger 37, a sufficiently large passage cross-sectional area is obtained, and the smooth flow of the atmosphere becomes possible. Next, the operation of the vacuum booster of the present invention will be described.
Since it is generally known, the description thereof will be omitted, and mainly the operation at the time of emergency braking will be described. The emergency braking characteristic of the vacuum booster of the present invention is achieved by changing the above-mentioned jumping characteristic and applying a larger propulsive force to the output member than during normal braking. In order to change the jumping characteristic, the gap D between the contact member 70 and the reaction member 54 may be increased in FIG. The enlargement of the gap D is caused by the contact surface 22 between the power piston 22 and the reaction member 54.
This is the same as increasing the distance between d and the valve seal portion 41b. That is, the gap D is enlarged by moving the valve seal portion 41b backward, so that the contact member 70
The output in the so-called jumping state, in which the ratio of the output to the input is infinite, is increased from that in the normal state by increasing the output from step 4 until receiving the reaction force. Hereinafter, the actual operation will be described. When the relative movement amount between the plunger 37 and the power piston 22 becomes larger than the predetermined value B during an emergency braking in which the driver depresses the brake pedal in a hurry,
The inclined surface 37b of the plunger 37 contacts the tapered portion 52a of the holding member 52, and expands the diameter of the holding member 52 urged in the direction of reducing the diameter by the ring-shaped elastic body 53 in the radial direction. When the minimum inner diameter portion 52aa of the tapered portion 52a rides on the front flange 37i of the plunger 37, the engaged portion 40c of the valve seat member 40 and the engaging portion 5 of the holding member 52
The engagement with 2b is released. Since the valve seat member 40 is urged rearward by the spring 47, the engaged portion 40
Immediately after the engagement of c is released, the spring 47 moves backward by the urging force of the spring 47. When the valve seat member 40 moves backward, the second negative pressure valve seat 39 of the valve seat member 40 is moved by the movable portion 41 of the valve mechanism 36.
And interrupts the communication between the constant-pressure chamber 23 and the variable-pressure chamber 24. At this time, plunger 3
7 is moving forward together with the input rod 28, and the valve seat member 40 pushes back the movable portion 41 of the valve mechanism 36 backward, so that the air valve seat 37a of the plunger 37 and the valve mechanism 36 are movable. The valve seal portion 41b constituting the portion 41 is quickly separated from the pressure sensor, and the variable pressure chamber 24 communicates with the atmosphere. As a result, the communication between the constant pressure chamber 23 and the variable pressure chamber 24 is cut off and the communication between the constant pressure chamber 23 and the atmosphere is performed rapidly, and the reaction force member 5 of the power piston 22 is substantially reduced.
This increases the distance between the contact surface 22d and the valve seal portion 41b, so that the output in the jumping state can be made larger than that in the normal state. FIG. 7 shows the normal brake characteristics and the emergency brake characteristics. 7, Jean emissions ping in normal braking, but only obtained output of the magnitude of F _01, jumping emergency braking, increased to F _011, the brake fluid pressure of sufficient magnitude in small pedaling force Can be generated. When the brake operation is completed and the brake pedal is returned, the plunger 37 moves rearward while the flange surface 34 contacts the key member 32.
When the key member 32 comes into contact with the rear shell 12, the key member 32 comes into contact with the front groove wall 40f of the valve seat member 40, and regulates the rearward movement of the valve seat member 40 which has been retracted integrally with the power piston 22. I do. At this time, since the power piston 22 still retreats, the engaging portion of the holding member 52 that retreats integrally with the power piston 22 abuts on the rear shell 12 via the key member 32 and is stationary. Member 40
The holding member 52 and the valve seat member 40, which have been disengaged by the emergency braking operation, are re-engaged to prepare for the next emergency braking operation. In this embodiment, when the atmosphere valve seat 37a is separated from the valve seal portion 41b and the atmosphere flows into the variable pressure chamber 24 through the radial hole 33 of the power piston 22, the slits 22e1 and 22e2 37e1, 37
Since the air passes through the passages R1 and R2 having a sufficiently large passage cross-sectional area formed by e2 and e2, the air can smoothly flow, and high brake responsiveness can be achieved not only during normal braking but also during emergency braking. can get. According to the present invention, it is possible to provide a negative pressure booster having a high responsiveness and a high response to the air flowing into the transformer chamber.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a negative pressure booster according to an embodiment of the present invention. FIG. 2 is a sectional view taken along line AA of FIG. FIG. 3 is a B-C-D-E sectional view of FIG. 2; FIG. 4 is a partially detailed view of FIG. 3; FIG. 5 is a perspective view of the valve seat member 40 before assembly. FIG. 6 is a perspective view showing a state before the holding member 52 is assembled. FIG. 7 is a diagram showing a relationship between a force (input) applied to the input rod 28 and a propulsion force (output) of the output member 55. DESCRIPTION OF SYMBOLS 10 Negative pressure type booster 14 Housing 20 Movable wall 22 Power piston 23 Constant pressure chamber 24 Transformation chamber 28 Input rod 32 Key member (drive means) 36 Valve mechanism 37 Plunger 37a Atmospheric valve seat 37f Rear flange 37g Main body Part 37h Sliding part (intermediate flange part) 37i Front flange part 37e1, 37e2 Recess 38 First negative pressure valve seat 39 Second negative pressure valve seat 40 Valve seat member 41 Movable part 43 Fixed part 47 Spring (driving means) 55 Output member

Claims (1)

Claims: 1. A housing having at least one pressure chamber formed therein, and a pressure chamber which is installed inside the housing so as to be able to move forward and backward with respect to the housing, and wherein the pressure chamber is a constant pressure chamber. A movable wall divided into a variable pressure chamber, a power piston coupled to the movable wall, an input rod installed inside the power piston so as to be able to move forward and backward with respect to the power piston, and connected to the input rod. A plunger fitted to the power piston so as to be slidable in the front-rear direction with respect to the power piston and having an air valve seat formed at a rear end thereof; and a propulsive force of the power piston accompanying movement of the movable wall. An output member for outputting the power piston outside the apparatus, a first negative pressure valve seat disposed on the power piston and facing rearward, and the power piston A second negative pressure valve seat formed on a valve seat member which is capable of moving forward and backward and is substantially concentric with the first negative pressure valve seat, and a movable portion facing the first negative pressure valve seat and the power piston are hermetically sealed. A negative pressure booster comprising: a valve mechanism having a fixed portion to be fixed; and driving means for moving the valve seat member toward the movable portion by a predetermined amount under a predetermined condition. A rear flange part with a seat formed,
A cylindrical main body formed in front of the flange,
An intermediate flange portion formed in front of the main body portion and sliding on the inner peripheral surface of the power piston, and a rear flange portion into which the valve seat member is inserted. A negative pressure booster, wherein a plurality of sets of concave portions facing each other are provided while permitting fluid flow, and a distance between bottom portions of the concave portions facing each other is smaller than an outer diameter of the main body portion.