JP2003182560A - Shell structure of negative pressure booster - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the strength of the whole end wall part while reducing a weight of the end wall part without using a reinforcing member beyond necessity in a shell structure of a negative pressure booster provided with the end wall part in which a diameter of a front shell half body constituting a part of a booster shell is reduced toward a cylindrical part and forward basically and which is continuous to a front end of the cylindrical part and a flat mounting part provided at a front end of the end wall part so as to be tightened to a flange of a master cylinder in a pair of tightening sections arranged on a virtual straight line crossing an axial line of the master cylinder orthogonally. <P>SOLUTION: A cross sectional shape of the end wall part 41 along a plane crossing a virtual straight line orthogonally and passing an axial line of the front shell half body 6 is formed into substantially straight line by connecting an outer fringe of the mounting part 42 with a front end fringe of the cylindrical part 40. A cross sectional shape of the end wall part 41 along a plane passing a virtual straight line and a straight line of the front shell half body 6 is formed in such a way that the cross sectional shape is constituted by a plurality of straight lines forming an angle mutually so as to connect the outer fringe of the mounting part 42 with the front end fringe of the cylindrical part 40. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shell structure of a negative pressure booster, and more particularly, to a front shell half constituting a booster shell in cooperation with a rear shell half. A master having a cylindrical portion to which the rear end is joined to the rear shell half, an end wall basically formed so as to have a smaller diameter toward the front and continuing to the front end of the cylindrical portion, and a flange at the rear portion. And a flat mounting portion provided at a front end of the end wall portion so as to be fastened to the flange at a pair of fastening locations arranged on a virtual straight line orthogonal to the axis of the cylinder. Regarding improvement. Conventionally, such a shell structure is disclosed in, for example, Japanese Patent Application Laid-Open No. 7-205798 and Japanese Utility Model Application Laid-Open No. 56-152.
It is already known in, for example, Japanese Patent Publication No. 760. [0003] When the negative pressure booster and the master cylinder are operated, hydraulic pressure generated in the hydraulic chamber of the master cylinder is applied to the end wall of the front shell half body. In order to sufficiently withstand the load, the reinforcing member is fixed to the inner surface of the end wall in order to sufficiently withstand the load. However, if the reinforcing member is used indiscriminately, the size of the negative pressure booster increases and the weight of the negative pressure booster increases. In order to sufficiently increase the rigidity of the end wall of the front shell half, the end wall is formed so as to linearly connect the outer edge of the mounting portion and the front edge of the cylindrical portion. desirable. However, since the load acting on the end wall portion from the master cylinder side is largest on a straight line where the fastening portion of the flange and the mounting portion is arranged, that is, on a virtual straight line orthogonal to the axis line of the master cylinder, as described above, When the end wall portion is formed over the entire circumference so as to linearly connect the outer edge of the portion and the front end edge of the cylindrical portion, stress concentrates on the connecting portion between the end wall portion and the cylindrical portion near the virtual straight line. The present invention has been made in view of such circumstances, and has been made to increase the overall strength of the end wall portion of the front shell half while reducing the weight without using an unnecessary reinforcing member. It is an object to provide a shell structure of a negative pressure booster. SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a front shell half which forms a booster shell in cooperation with a rear shell half. A imaginary axis perpendicular to the axis of the master cylinder having a cylindrical portion to which the rear end is joined, an end wall basically formed so as to have a smaller diameter toward the front and continuing to the front end of the cylindrical portion, and a flange at the rear portion. In a shell structure of a negative pressure booster including a flat mounting portion provided at a front end of the end wall portion so as to be fastened to the flange at a pair of fastening points arranged on a straight line, the shell structure is orthogonal to the virtual straight line. The cross-sectional shape of the end wall along a plane passing through the axis of the front shell half
The cross-sectional shape of the end wall portion is formed in a substantially straight line connecting the outer edge of the attachment portion and the front end edge of the cylindrical portion, and is along a plane passing through the virtual straight line and the straight line of the front shell half.
It is characterized by being constituted by a plurality of straight lines which are mutually angled and formed so as to connect between the outer edge of the mounting portion and the front end edge of the cylindrical portion. [0007] According to such a configuration, at the point where the load acting on the end wall portion by the hydraulic pressure generated by the master cylinder becomes the largest, that is, on the imaginary straight line where the fastening point of the flange and the mounting portion is arranged, they are mutually angled. The end wall portion is formed so as to connect between the outer edge of the mounting portion and the front end edge of the cylindrical portion. By alleviating the stress, it is possible to prevent the occurrence of stress concentration at the connecting portion between the end wall portion and the cylindrical portion. On the other hand, in a portion orthogonal to the virtual straight line, sufficient rigidity can be obtained by forming the end wall portion so as to connect the outer edge of the attachment portion and the front end edge of the cylindrical portion in a substantially straight line. Therefore, it is possible to improve the strength of the entire end wall while reducing the weight of the end wall without using an unnecessary reinforcing member. An embodiment of the present invention will be described below with reference to an embodiment of the present invention shown in the accompanying drawings. 1 to 3 show an embodiment of the present invention. FIG. 1 is a longitudinal side view of a negative pressure booster, FIG. 2 is a front view of a front shell half, and FIG. FIG. 3 is a sectional view taken along line 3-3. Referring to FIG. 1, a booster shell 5 of a negative pressure booster B is formed by mutually connecting a front shell half 6 and a rear shell half 7 to each other.
Inside, a booster piston 8 is housed so as to be able to reciprocate back and forth. A diaphragm 9 is superimposed on the rear surface of the booster piston 8, and an outer peripheral bead 9a of the diaphragm 9 is bonded to an abutting portion of the front and rear shell halves 6,7. Inside the booster shell 5, a booster piston 8 and a diaphragm 9 provide a front-side negative pressure chamber 10 facing the front surface of the booster shell 5, and a diaphragm 9.
And a working chamber 11 facing the rear surface of the working chamber 11. [0013] Booster piston 8 and diaphragm 9
A synthetic resin valve cylinder 12 is coupled to the center of the valve. The valve cylinder 12 is slidably supported via a bearing member 52 on a support cylinder 7a protruding from the center of the rear wall of the rear shell half 7, and the bearing member 52 is engaged with the support cylinder 7a. It is held between the locking ring 13 to be stopped and the support cylinder 7a. Further, a negative pressure introducing pipe 51 is continuously provided on the front wall of the booster shell 5,
The negative pressure chamber 10 is connected to a negative pressure source (not shown, for example, an intake manifold of an engine) via a negative pressure introducing pipe 51. The valve cylinder 12 is provided with a valve piston 14, a part of an input rod 15 connected to the valve piston 14, and a working chamber 11 in accordance with the forward and backward movement of the input rod 15.
And a control valve 16 for switching communication with the atmosphere. The valve piston 14 is slidably fitted in a guide hole 17 provided in the valve cylinder 12. The reaction piston 1 is provided at the front end of the valve piston 14 via a neck 18.
9 are connected in series. The input rod 15, which is connected to the brake pedal 20 and moves back and forth, has a spherical portion at the tip, and the spherical portion is swingably connected to the rear portion of the valve piston 14. The control valve 16 comprises a negative pressure introduction valve seat 21, an atmosphere introduction valve seat 22, a valve element 23 and a valve spring 24. The atmosphere introduction valve seat 22 is formed at the rear end of the valve piston 14. The annular negative pressure introducing valve seat 21 is
Is formed in the valve cylinder 12 so as to surround the Valve cylinder 12
A valve holder 25 is fitted and fixed to the rear of the valve holder 25. A valve body 23 made of an elastic material such as rubber is commonly used for the air introduction valve seat 22 and the negative pressure introduction valve seat 21. Is held. Further, the valve spring 24 is connected to the negative pressure introduction valve seat 2.
1 and between the valve body 23 and the input rod 15 so as to exert a spring force for urging the valve body 23 to be seated on the air introduction valve seat 22. In the valve cylinder 12, a front annular chamber 26 surrounding the valve piston 14 at the front side of the valve body 23 and communicating with the negative pressure chamber 10; A rear annular chamber 27 leading to 11 is formed. At the rear end of the support cylinder portion of the rear shell half 7 and on the input rod 15, both ends of an extendable boot 28 that covers the valve cylinder 12 are attached. An air introduction port 29 communicating with the inside of 23 is provided. A filter 30 for purifying air flowing through the air inlet 29 is provided between the input rod 15 and the valve holder 25.
Is interposed. A key member 31 for defining the retreat limit of the booster piston 8 and the valve piston 14 is attached to the valve cylinder 12 so as to be movable within a certain distance in a direction along one diameter line of the valve cylinder 12. . Thus, when the booster piston 8 is retracted, the key member 3 projecting from the outer periphery of the valve cylinder 12
The retraction limit of the booster piston 8 is regulated by the end of the rod 1 being in contact with the locking ring 13, and the retraction limit of the valve piston 14 is regulated by the key member 31 receiving the reaction force piston 19. An operating piston 32 projecting forward is integrally provided at the front end of the valve cylinder 12.
The reaction force piston 19 is slidably fitted to the piston.
A cup body 33 is fitted around the outer periphery of the working piston 32 so as to be relatively slidable, and an elastic piston 34 facing the working piston 32 and the reaction force piston 19 is connected to the cup body 3.
3 is filled. A retainer 35 is in contact with the front surface of the cup body 33, and a return spring 36 is contracted between the front shell half 6 and the retainer 35. An output rod 37 is provided on the front surface of the cup body 33.
And the output rod 37 is connected to the piston 38 of the master cylinder M. In the rest state of the negative pressure booster B, the booster piston 8 and the valve piston 14 are held at the retreat limit by the key member 31, and the valve body 23 is seated on the air introduction valve seat 22 but the air introduction valve seat 21 slightly away. Thereby, the communication between the air inlet 29 and the working chamber 11 is cut off, and the negative pressure chamber 10 and the working chamber 1 are disconnected.
1 are in communication with each other, and both chambers 10 and 11 have the same pressure.
Is held at the retracted position by the urging force of When the brake operation is performed by depressing the brake pedal 20, the valve body 23 is seated on the negative pressure introducing valve seat 21 and is separated from the atmosphere introducing valve seat 22. The communication between them is cut off, and the working chamber 11 communicates with the atmospheric pressure inlet 29, so that the pressure of the working chamber 11 becomes higher than that of the negative pressure chamber 10. As a result, the booster piston 8 obtains a forward thrust according to the pressure difference between the two chambers 10 and 11, and moves forward with the valve cylinder 12, the working piston 32, the elastic piston 34, the cup body 33 and the output rod 37. The piston 38 of the master cylinder M is pressed and driven by the output rod 37. At this time, the elastic piston 34 is compressed by the reaction force and the reaction piston 1
Although the bulges toward the ninth side, the reactive force is not transmitted to the input rod 15 until the bulged portion comes into contact with the reaction force piston 19, and the output of the output rod 37 shows a jumping characteristic that rises rapidly. After the elastic piston 34 comes into contact with the reaction force piston 19, a part of the operation reaction force of the output rod 37 is fed back to the input rod 15 via the elastic piston 34. Can sense the magnitude of the output of the output rod 37. Thus,
The output of the output rod 37 increases with a boosting ratio determined by the ratio between the pressure receiving areas of the working piston 32 and the reaction force piston 19 that are in contact with the elastic piston 34. The output of the output rod 37 after reaching the boosting point at which the pressure difference between the negative pressure chamber 10 and the working chamber 11 is maximized is the maximum thrust of the booster piston 8 due to the pressure difference and the input rod 15 And the operation input to 2 and 3, the front shell half 6 has a cylindrical portion 40 having a rear end joined to the rear shell half 7, and has a smaller diameter basically as it goes forward. End wall portion 4 formed so as to be continuous with the front end of cylindrical portion 40
1, a flat mounting portion 42 provided at the front end of the end wall portion 41 so that the master cylinder M is fastened to a flange 45 provided at the rear portion, and a central portion of the mounting portion 42 connected to the booster shell 5 side. A small-diameter cylindrical part 43 immersed;
An inward flange 44 provided at the inner end of the small-diameter cylindrical portion 43 is integrally provided. The rear end of the master cylinder M is fitted to the small-diameter cylindrical portion 43 with a sealing member 46 interposed between the master cylinder M and the inward flange 44, and is attached to the mounting portion 42 and the mounting portion 42 from the front. The flange 45 in contact is fastened. The flange 45 and the mounting portion 42 are formed so as to be long in a direction along an imaginary straight line L orthogonal to the axis of the master cylinder M based on a rhombus having four rounded corners as a basic shape. It is fastened at a pair of fastening points P, P arranged on L. That is, the heads 48a of the bolts 48 that are respectively inserted into the insertion holes 47 provided in the fastening portions P are fixed to the inner surface of the mounting portion 42, and the bolts 48 that penetrate the flange 45 are screwed. By tightening the nuts 49 to be combined, the flange 45 and the mounting portion 42 are fastened. The end wall 41 has a tapered portion 41a having a larger diameter toward the rear, and a pair of steps 41b, 41 formed between the tapered portion 41a and the mounting portion 42.
b, and a pair of flat portions 41c, 41c arranged between the tapered portion 41a and the cylindrical portion 40. The tapered portion 41a is formed so as to linearly connect the outer edge of the mounting portion 42 and the front edge of the cylindrical portion 40 on a straight line passing through the axis of the front shell half 6 perpendicular to the virtual straight line L. However, since the mounting portion 42 is formed to be long in the direction along the virtual straight line L, the taper is formed at a position deviated from a straight line passing through the axis of the front shell half 6 orthogonally to the virtual straight line L. As a result, a step is generated between the outer edge of the portion 41a and the outer edge of the mounting portion 42, and both step portions 41b, 41b
Is formed so as to connect between the outer edges of the tapered portion 41a and the mounting portion 42 at a position shifted from a straight line passing through the axis of the front shell half 6 orthogonally to the virtual straight line L. The large-diameter end of the tapered portion 41a is located at a position inwardly spaced from the front end edge of the cylindrical portion 40 at a position orthogonal to the virtual straight line L and deviated from a straight line passing through the axis of the front shell half 6. The two flat portions 41c, 41c
Is formed so as to connect between the front end of the cylindrical portion 40 and the large-diameter end of the tapered portion 41a at a position spaced inward from the front end of the cylindrical portion 49. The front shell half 6 is attached to the large-diameter end of the tapered portion 41a at 45 degrees on both sides from the virtual straight line L.
Are formed in a radially inward side of the groove 50 in a circular arc shape, and a negative pressure introducing pipe 51 is disposed in one of the concave portions 50. In such an end wall portion 41, the cross-sectional shape of the end wall portion 41 along a plane orthogonal to the virtual straight line L and passing through the axis of the front shell half 6 is the outer edge of the mounting portion 42 and the cylindrical portion 40. Are formed in a substantially straight line by connecting the front end edges thereof, and the cross-sectional shapes of the end wall portions 41 along a plane passing through the imaginary straight line L and the straight line of the front shell half 6 are mutually angled. It is constituted by a plurality of straight lines, and is formed so as to connect between the outer edge of the attachment portion 42 and the front end edge of the cylindrical portion 40. Next, the operation of this embodiment will be described. A place where the load acting on the end wall portion 41 of the front shell half 6 due to the hydraulic pressure generated by the master cylinder M becomes the largest, that is, the flange 45 and the mounting portion 42 On an imaginary straight line L on which the fastening points P and P are arranged, an end wall portion 41 is formed by a plurality of straight lines making an angle with each other and connecting the outer edge of the mounting portion 42 and the front edge of the cylindrical portion 40. Have been. Therefore, on the imaginary straight line L, the end wall 41 is sufficiently bent to relieve the stress, so that it is possible to prevent the concentration of stress from occurring at the connection between the end wall 41 and the cylindrical portion 40. On the other hand, the sectional shape of the end wall portion 41 along a plane orthogonal to the virtual straight line L and passing through the axis of the front shell half 6 is as follows:
Since the outer edge of the attachment portion 42 and the front end edge of the cylindrical portion 40 are connected to form a substantially straight line, sufficient rigidity can be obtained. As a result, the strength of the end wall portion 41, that is, the entire front shell half 6, is improved while reducing the weight of the end wall portion 41, ie, the front shell half 6, without using an unnecessary reinforcing member. be able to. Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the appended claims. It is possible. As described above, according to the present invention, the strength of the entire end wall can be improved while reducing the weight of the end wall without using an unnecessary reinforcing member.

[Brief description of the drawings] FIG. 1 is a vertical sectional side view of a negative pressure booster. FIG. 2 is a front view of a front shell half. FIG. 3 is a sectional view taken along line 3-3 of FIG. 2; [Explanation of symbols] 5 ・ ・ ・ Booster shell 6: Front shell half 7 Rear half shell 40 ・ ・ ・ Cylindrical part 41 ・ ・ ・ End wall 42 ・ ・ ・ Mounting part 45 ・ ・ ・ Flange B: Negative pressure booster L: virtual straight line M: Master cylinder P ... fastening point

Claims (1)

Claims 1. A front shell half (6), which forms a booster shell (5) in cooperation with a rear shell half (7), is rearwardly attached to the rear shell half (7). Cylindrical part (40) to which the ends are joined
Basically, the end wall portion (4) formed so as to have a smaller diameter toward the front and connected to the front end of the cylindrical portion (40).
1) and a pair of fastening points (P) arranged on an imaginary straight line (L) orthogonal to the axis of the master cylinder (M) having a flange (45) at the rear portion so as to be fastened to the flange (45). And a flat mounting portion (42) provided at the front end of the end wall portion (41) in a shell structure of a negative pressure booster, wherein the front shell half (6) is orthogonal to the virtual straight line (L). The cross-sectional shape of the end wall portion (41) along a plane passing through the axis of is substantially linearly formed by connecting the outer edge of the mounting portion (42) and the front end edge of the cylindrical portion (40). The cross-sectional shape of the end wall portion (41) along a plane passing through the straight line (L) and the straight line of the front shell half (6) is constituted by a plurality of straight lines that are mutually angled, and the mounting portion (42) is formed. Between the outer edge of the cylindrical portion and the front edge of the cylindrical portion (40). Shell structure of the vacuum booster, characterized in that it is made.