JP2011126383A - Negative pressure booster and method for manufacturing the same - Google Patents

Abstract

Disclosed is a negative pressure booster that is easy to process and has a simple structure.
A valve cylinder 10 slidably supported on a rear wall of a booster shell 1 and a reaction force mechanism 24 between an input rod 20 and an output rod 25 disposed in the valve cylinder 10 are provided. In a negative pressure booster in which a master cylinder M having a master piston Mb driven forward by an output rod 25 is attached to the front wall of the booster shell 1, the output rod 25 is bottomed at the front end. An output rod main body 50 having a hollow cylindrical portion 50a and having a rear end connected to the reaction force mechanism 24, a fitting shaft portion 51a fitted into the hollow cylindrical portion 50a, and the fitting shaft portion 51a The end piece 51 is integrally connected to the front end via a forward stepped portion 51c. The hollow cylindrical portion 50a is opposed to the stepped portion 51c to prevent the fitting shaft portion 51a from being detached from the hollow cylindrical portion 50a. The stopper portion 53 is formed by caulking.
[Selection] Figure 2

Description

  The present invention relates to a negative pressure booster used for boosting operation of a brake master cylinder of an automobile, and more particularly, to a booster shell and a front negative pressure chamber connected to a negative pressure source and a rear working chamber. The booster piston to be partitioned is accommodated, and a valve cylinder that is slidably supported on the rear wall of the booster shell is connected to the booster piston. A control valve that switches the working chamber to the negative pressure chamber and the atmosphere according to the longitudinal movement of the valve is arranged, and between the valve cylinder and the input rod and the output rod that is slidably supported by the valve barrel. , A reaction mechanism that transmits the resultant force of the operation input to the input rod and the booster piston thrust due to the pressure difference between the working chamber and the negative pressure chamber to the output rod, and on the front wall of the booster shell, A mass having a master piston driven forward by an output rod An improvement of vacuum booster and a manufacturing method thereof cylinder is attached.

  Such a negative pressure booster is already known as disclosed in Patent Document 1.

JP 2005-349867 A

  In such a negative pressure booster, the output rod must be kept in contact with the rear end of the master piston at all times, and the forward movement of the output rod must be transmitted to the master piston without loss. Therefore, conventionally, an adjustment bolt is screwed so as to be adjustable so that it abuts on the rear end portion of the master piston in consideration of manufacturing errors of each portion, at the front end portion of the output rod. However, in such a case, troublesome screw hole processing is required for the output rod, and in addition to the adjusting bolt, a lock nut for preventing the rotation is necessary, which contributes to the high cost. .

  The present invention has been made in view of such circumstances, and an object thereof is to provide a negative pressure booster that is easy to process and has a simple structure, and a method for manufacturing the same.

  In order to achieve the above object, the present invention accommodates a booster piston that divides the inside thereof into a front negative pressure chamber and a rear working chamber connected to a negative pressure source. A valve cylinder that is slidably supported on the rear wall of the booster shell is connected in series, and an input rod that can be moved back and forth in the valve barrel, and a working chamber that is connected to the negative pressure chamber according to the forward and backward movement of the input rod. A control valve that communicates with the atmosphere, and an operation input to the input rod, a working chamber, and a negative pressure between the valve barrel and the input rod and an output rod that is slidably supported by the valve barrel. A master cylinder that is equipped with a reaction force mechanism that transmits the resultant force with the booster piston thrust due to the pressure difference between the chambers to the output rod, and that has a master piston that is driven forward by the output rod on the front wall of the booster shell In the negative pressure booster to which An output rod body having a bottomed hollow cylindrical portion at the front end portion and a rear end portion connected to the reaction force mechanism, a fitting shaft portion detachably fitted into the hollow cylindrical portion, and The fitting shaft portion is composed of an end piece composed of a pressing shaft portion that is integrally connected to a front end ending in the hollow cylindrical portion via a forward stepped portion and substantially abuts on a rear end portion of the master piston. A first feature is that the hollow cylindrical portion is formed with a stopper portion that opposes the stepped portion and prevents the fitting shaft portion from being detached from the cylindrical portion.

  Further, in addition to the first feature, the present invention has a second feature in that a thin portion thinner than the rear portion is provided at the front end portion of the hollow cylindrical portion, and the stopper portion is caulked and formed on the thin portion. To do.

  Furthermore, the present invention provides a step of preparing a plurality of end pieces having different lengths and assembling a negative pressure booster except for the master cylinder and the end piece in manufacturing the negative pressure booster having the first feature. Measuring the distance between the front end face of the booster shell in the negative pressure booster and the bottom face of the hollow cylindrical portion of the output rod body, and corresponding to the distance from the prepared plurality of end pieces Select one end piece and fit it until the fitting shaft part bottoms into the hollow cylindrical part of the output rod body, and set the distance between the front end of the end piece and the front end face of the booster shell. A third feature is that a step of setting to a predetermined value and a step of forming the stopper portion by caulking the front end portion of the hollow cylindrical portion radially inward are performed.

  In addition to the third feature of the present invention, when the step of forming the stopper portion is executed, the input rod is advanced so that the output rod main body is moved outward from the opening of the front wall of the booster shell. A fourth feature is that the hollow cylindrical portion is exposed together with the end piece, and the stopper portion is formed in the exposed state.

  According to the first feature of the present invention, the output rod can be composed of two parts, ie, the output rod main body and the end piece, both of which are simple in shape and easy to process, which contributes to the cost reduction of the negative pressure booster. obtain. Moreover, since the end piece is prevented from coming out of the hollow cylindrical portion by the stopper portion that is caulked to the hollow cylindrical portion of the output rod main body, its retaining structure is simple and can contribute to further cost reduction. . In addition, the substantial contact setting between the end piece pressing shaft and the rear end of the master piston can be selected from multiple end pieces with different lengths, and the length can be adjusted by processing the end face of the end piece. Can be performed.

  According to the second feature of the present invention, the thin cylindrical portion is provided at the front end portion of the hollow cylindrical portion from the rear portion, and the stopper portion is caulked and formed on the thin portion, so that the stopper portion has a relatively small caulking force. Can be easily formed, and it is possible to avoid applying unnecessary distortion to the portion other than the thin wall portion and the end piece of the hollow cylindrical portion.

  According to the third feature of the present invention, the output rod can be configured with two parts of the output rod main body and the end piece, both of which are simple in shape and easy to process, and the front end position of the output rod is set by the booster. Based on the measurement of the distance between the front end surface of the shell and the bottom surface of the hollow cylindrical portion of the output rod body, one of the end pieces of different lengths prepared in advance is selected and the output rod body This is done by fitting into the hollow cylindrical portion, so that the front end position of the output rod can be set easily and quickly.

  According to the fourth aspect of the present invention, the caulking of the stopper portion can be easily performed without being disturbed by the booster shell.

The longitudinal cross-sectional view of the negative pressure booster which concerns on one Example of this invention. The principal part longitudinal cross-sectional enlarged view of FIG. FIG. 3 is an enlarged sectional view taken along line 3-3 in FIG. 2. The side view of the several end piece from which the length prepared as a component of the said output rod differs. Explanatory drawing of the process of measuring the distance between the rear-end surface of a cylinder body in a brake master cylinder, and the connection recessed part bottom face of a master piston. Explanatory drawing of the process of measuring the distance between the front end surface of the booster shell in a negative pressure booster, and the bottom face of the hollow cylindrical part of an output rod main body. Explanatory drawing of the process of setting the front end of an end piece, the front end surface of a booster shell, and distance within tolerance. Explanatory drawing of the process of forming a stopper part by caulking the front end part of the hollow cylindrical part of an output rod main body to radial inside. FIG. 9 is an enlarged cross-sectional view taken along the line 9-9 in FIG.

  Embodiments of the present invention will be described based on preferred embodiments of the present invention shown in the accompanying drawings.

  1 and 2, the booster shell 1 of the negative pressure booster B is composed of a pair of front and rear shell halves 1a and 1b that connect opposite ends to each other, and is attached to the front wall of the front shell half 1a. The cylinder body Ma of the brake master cylinder M is fixed by a plurality of bolts 6, and the rear shell half 1 b is fixed by a bolt 7 to the front wall F of the automobile interior.

  The inside of the booster shell 1 includes a booster piston 4 accommodated therein so as to be capable of reciprocating back and forth, and a diaphragm 5 attached to the rear surface of the booster shell 1 and sandwiched between both shell halves 1a and 1b. Are divided into a negative pressure chamber 2 and a rear working chamber 3. The negative pressure chamber 2 is connected to a negative pressure source V (for example, inside the intake manifold of the internal combustion engine) via a negative pressure introduction pipe 14.

  The booster piston 4 is formed in an annular shape from a steel plate, and a synthetic resin valve cylinder 10 is integrally coupled to the central portions of the booster piston 4 and the diaphragm 5. The valve cylinder 10 is slidably supported via a bearing member 9 and a seal member 13 on a support cylinder part 12 protruding rearward from the center part of the rear shell half 1b.

  In the valve cylinder 10, there is a valve piston 18, an input rod 20 connected to the valve piston 18, and a control valve for switching the working chamber 3 between the negative pressure chamber 2 and the atmosphere in accordance with the longitudinal movement of the input rod 20. 38 is disposed. A brake pedal P for operating the input rod 20 is connected to the rear end of the input rod 20.

  The valve piston 18 is slidably fitted in a guide hole 11 provided in the valve cylinder 10, and a reaction force piston 17 is provided at the front end via a neck portion 18b, and a flange shape is provided at the rear end. Each of the air introduction valve seats 31 is formed. An annular negative pressure introduction valve seat 30 that is concentrically arranged so as to surround the atmosphere introduction valve seat 31 is formed in the valve cylinder 10.

  The valve piston 18 is provided with a connecting hole 18a that opens at the rear end surface of the air introduction valve seat 31, and a ball joint 20a formed at the front end of the input rod 20 is fitted into the connecting hole 18a, and the valve joint 18a is removed. A part of the valve piston 18 is caulked for stopping. In this way, the input rod 20 is connected to the valve piston 18 so as to be swingable.

  An expandable and contractible cylindrical valve body 34 having an annular valve portion 34 a that cooperates with the negative pressure introduction valve seat 30 and the atmospheric introduction valve seat 31 is attached to the valve cylinder 10 by a valve holder 35. The entire valve body 34 is formed of an elastic material such as rubber, and an annular reinforcing plate 44 is embedded in the valve portion 34a from the inner peripheral side thereof. An annular seal lip 37 bent rearward is integrally formed on the outer periphery of the valve portion 34a.

  The valve portion 34a is disposed so as to face the atmosphere introduction valve seat 31 and the negative pressure introduction valve seat 30 so as to be seated. Between the reinforcing plate 44 of the valve portion 34a and the input rod 20, a valve spring 36 that urges the valve portion 34a in the seating direction with the valve seats 30 and 31 is contracted. Thus, the negative pressure introduction valve seat 30, the atmospheric introduction valve seat 31, the valve body 34 and the valve spring 36 constitute a control valve 38.

  An input return spring 41 is contracted between the valve holder 35 and the input rod 20, whereby the input rod 20 is biased in the backward direction, while the valve holder 35 is held at a fixed position in the valve cylinder 10. The

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

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

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

  Both ends of a stretchable boot 40 covering the valve cylinder 10 are attached to the rear end of the support cylinder portion 12 and the input rod 20, and the rear end of the boot 40 communicates with the inside of the valve body 34. An air introduction port 39 is provided. A filter 42 for filtering the air flowing into the atmosphere introduction port 39 is interposed between the outer peripheral surface of the input rod 20 and the inner peripheral surface of the valve cylinder 10. This filter 42 has flexibility so as not to hinder the relative movement of the input rod 20 and the valve cylinder 10.

  Furthermore, a key 32 that defines the backward limit of the booster piston 4 and the valve piston 18 is attached to the valve cylinder 10 so as to be movable in the axial direction within a certain distance. The key 32 has a fork portion 32b straddling the neck portion 18b between the valve piston 18 and the reaction force piston 17 at the inner end, and an outer end portion 32a provided on the support cylinder portion 12 of the rear shell half 1b. The stopper wall 19 is disposed so as to face the front surface. Thus, when the key 32 comes into contact with the stopper wall 19, the backward limit of the valve cylinder 10 is defined, and when the rear end surface of the reaction force piston 17 comes into contact with the key 32, the valve piston 18 and the input rod 20 move backward. Limits are defined. The axial length of the neck portion 18b is set to be larger than the plate thickness of the key 32 so that the valve piston 18 and the key 32 can be slightly moved relative to each other.

  Further, the valve cylinder 10 is provided with an operating piston 15 that protrudes forward and a small-diameter cylinder hole 16 that penetrates the center of the operating piston 15, and the reaction-force piston 17 slides in the small-diameter cylinder hole 16. Fits freely. A cup body 21 is slidably fitted on the outer periphery of the working piston 15, and the cup body 21 is filled with a flat elastic piston 22 that faces the working piston 15 and the reaction force piston 17. At that time, a constant gap is formed between the reaction force piston 17 and the elastic piston 22 when the negative pressure booster B is not operated.

  An output rod 25 is connected to the front surface of the cup body 21. Therefore, the output rod 25 is slidably supported by the valve cylinder 10 via the cup body 21. The output rod 25 is connected to the rear end portion of the master piston Mb of the brake master cylinder M that passes through an opening 33 provided at the center of the front shell half 1a.

  In the above, the operation piston 15, the reaction force piston 17, the elastic piston 22, and the cup body 21 constitute a reaction force mechanism 24 that feeds back a part of the output of the output rod 25 to the input rod 20.

  A retainer 26 is disposed so as to contact the cup body 21 and the front end face of the valve cylinder 10, and the booster piston 4 and the valve cylinder 10 are urged in the backward direction between the retainer 26 and the front wall of the booster shell 1. The booster return spring 27 is contracted.

  As clearly shown in FIGS. 2 and 3, the output rod 25 is composed of an output rod main body 50 that is integrally projected at the center of the front surface of the cup body 21, and an end piece 51 that is coupled to the front end portion thereof. Is done. The output rod main body 50 has a hollow cylindrical portion 50a with a bottom at the front end portion, and the end piece 51 has a fitting shaft portion 51a fitted into the hollow cylindrical portion 50a so as to be detachable, The fitting shaft portion 51a is formed of a pressing shaft portion 51b having a smaller diameter than the fitting shaft portion 51a, which is integrally connected to the front end of the fitting shaft portion 51a through the annular step portion 51c facing forward. A thin portion 50at having a thickness smaller than that of the rear portion is formed at the front end portion of the hollow cylindrical portion 50a, and the hollow portion of the fitting shaft portion 51a is opposed to the step portion 51c of the end piece 51 in the thin portion 50at. A plurality of stopper portions 53 for preventing separation from the cylindrical portion 50a are formed by caulking.

  The front end portion of the pressing shaft portion 51b has a hemispherical shape, and the front end portion is formed on the hemispherical bottom surface of the connecting concave portion 52 formed on the rear end surface of the master piston Mb when the brake master cylinder M is in a resting state. They are arranged opposite each other with almost no gap. That is, the pressing shaft portion 51b is disposed in a substantially abutting state with the bottom surface of the connecting recess 52 of the master piston Mb. In order to obtain such an arrangement, the length of the end piece 51 is preset.

  Next, the operation of this embodiment will be described.

  In the resting state of the negative pressure booster B, the key 32 attached to the valve cylinder 10 contacts the front surface of the stopper wall 19 of the rear shell half 1b, and the rear end surface of the reaction force piston 17 contacts the key 32, The booster piston 4 and the input rod 20 are located at the backward limit. At this time, while the air introduction valve seat 31 is in close contact with the valve portion 34 a of the valve body 34, the valve portion 34 a is pressed and slightly separated from the negative pressure introduction valve seat 30. As a result, the communication between the air introduction port 39 and the second port 29 is cut off, while the communication between the first and second ports 28 and 29 is established, so that the negative pressure in the negative pressure chamber 2 operates through both the ports 28 and 29. Since the pressure is transmitted to the chamber 3 and the chambers 2 and 3 have the same pressure, the booster piston 4 and the valve cylinder 10 are held in the retracted position by the urging force of the booster return spring 27.

  Now, when the input rod 20 is advanced together with the valve piston 18 against the set load of the input return spring 41 by depressing the brake pedal P to brake the vehicle, the urging force of the valve spring 36 causes the valve portion 34a to be negative. At the same time that the pressure introduction valve seat 30 is seated, the atmosphere introduction valve seat 31 is separated from the valve body 34, thereby disconnecting the communication between the first and second ports 28 and 29, and the second port 29 is connected to the valve body. 34 is communicated with the air inlet 39 through the inside.

  As a result, the atmosphere flowing into the valve cylinder 10 from the atmosphere introduction port 39 passes through the atmosphere introduction valve seat 31 and is introduced into the working chamber 3 through the second port 29, so that the working chamber 3 has a higher pressure than the negative pressure chamber 2. Therefore, by obtaining a forward thrust based on the pressure difference between them, the booster piston 4 resists the force of the booster return spring 27 with the valve cylinder 10, the operating piston 15, the elastic piston 22, the cup body 21 and the output rod 25. And move forward.

  By the way, the front end portion of the pressing shaft portion 51b of the end piece 51 that constitutes a part of the output rod 25 is substantially the same as the bottom surface of the connecting recess 52 on the rear end surface of the master piston Mb when the brake master cylinder M is in a resting state. Therefore, the end piece 51 drives the master piston Mb forward almost simultaneously with the advancement of the booster piston 4. The elastic piston 22 is compressed by the reaction force generated by this driving and a part of the elastic piston 22 bulges into the small-diameter cylinder hole 16. The reaction force until the bulging portion abuts against the front surface of the reaction force piston 17. Is not transmitted to the input rod 20, the output of the output rod 25 exhibits a jumping characteristic that rises rapidly.

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

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

  After the elastic piston 22 contacts the reaction force piston 17, a part of the reaction force of the output rod 25 is fed back to the input rod 20 via the elastic piston 22, so that the operator can output the output rod 25. The size of the output can be perceived. The output of the output rod 25 increases with a boost ratio determined by the ratio of the pressure receiving areas of the working piston 15 and the reaction force piston 17 that are in contact with the elastic piston 22.

  After reaching the boost limit point at which the pressure difference between the negative pressure chamber 2 and the working chamber 3 reaches the maximum, the output of the output rod 25 is the maximum thrust generated by the booster piston 4 due to the pressure difference and the input to the input rod 20. This is the sum of the operation input.

  When the pedaling force is released from the brake pedal P in order to release the braking state of the vehicle, first, the input rod 20 and the valve piston 18 are moved backward by the force of the input return spring 41. Accordingly, the valve piston 18 largely separates the valve body 34 from the negative pressure introduction valve seat 30 while seating the air introduction valve seat 31 on the valve body 34, so that the working chamber 3 is connected to the second port 29 and the second port 29. The negative pressure chamber 2 communicates with the first port 28. As a result, the introduction of the atmosphere into the working chamber 3 is prevented, while the air in the working chamber 3 is sucked into the negative pressure limit V through the negative pressure chamber 2 and the pressure difference therebetween is eliminated. With the elastic force of the booster return spring 27, the master cylinder M is released from operation. Then, the booster piston 4 and the input rod 20 return to the resting state again.

  By the way, the output rod 25 is composed of an output rod main body 50 projecting integrally at the center of the front surface of the cup body, and an end piece 51 connected to the front end portion thereof. The hollow cylinder portion 50a is hollow and has a bottom, and the end piece 51 includes a fitting shaft portion 51a that is detachably fitted into the hollow cylinder portion 50a, and a hollow cylinder of the fitting shaft portion 51a. The front end ending in the portion 50a is composed of a pressing shaft portion 51b having a smaller diameter than the fitting shaft portion 51a integrally connected through a forward stepped portion 51c. The hollow cylindrical portion 50a includes a step portion 51c of the end piece 51. Since the stopper portion 53 that prevents the fitting shaft portion 51a from being detached from the hollow cylindrical portion 50a is formed by caulking, the two parts of the output rod main body 50 and the end piece 51 that are both simple in shape and easy to process. To configure output 杆 25 And it is able to, can contribute to a reduction in cost of the vacuum booster B. Moreover, since the end piece 51 is prevented from coming out of the hollow cylindrical portion 50a by the stopper portion 53 formed by caulking on the hollow cylindrical portion 50a of the output rod main body 50, its retaining structure is simple and the cost is further increased. It can contribute to reduction. Further, since the caulking of the stopper portion 53 is performed at the thin portion 50at at the front end portion of the hollow cylindrical portion 50a, not only the stopper portion 53 can be easily formed with a relatively small caulking force but also the hollow cylindrical portion 50a. It is possible to avoid applying unnecessary distortion to the parts other than the thin part 50at and the end piece 51. Thus, during the handling of the negative pressure booster B before the brake master cylinder M is attached, it is possible to prevent the end piece 51 from falling off the output rod main body 50.

  The stopper portion 53 is merely for preventing the end piece 51 from coming out of the hollow cylindrical portion 50a, and does not hold the end piece 51 in a bottom-up state with respect to the bottom surface in the hollow cylindrical portion 50a. On the contrary, in order to allow the end piece 51 to freely slide within a limited range within the hollow cylindrical portion 50a without giving unnecessary distortion to the end piece 51, the stopper portion 53 is arranged on the outer peripheral surface of the pressing shaft portion 51b. It is desirable not to make it come into strong contact with. The bottom pushing state of the end piece 51 with respect to the bottom surface in the hollow cylindrical portion 50a is held by the retreating force of the master piston Mb.

  Next, a method for manufacturing the negative pressure booster B will be described with reference to FIGS.

  First, as shown in FIG. 4, as the end piece 51, a plurality of pieces (five pieces in the illustrated example) whose lengths are different by a predetermined dimension S are prepared.

  On the other hand, in the brake master cylinder M, as shown in FIG. 5, the distance between the rear end surface of the cylinder body Ma superimposed on the front end surface of the booster shell 1 and the bottom surface of the connecting recess 52 of the master piston Mb at a predetermined retracted position. Measure L1.

  Next, as shown in FIG. 6, the negative pressure booster B is assembled except for the end piece 51, and the front end surface of the booster shell 1 and the bottom surface of the hollow cylindrical portion 50a of the output rod main body 50 at a predetermined retracted position. The distance L2 between them is measured.

  Next, the distance L2−the distance L1 = L3 is calculated, and an end piece 51 having a length that falls within a range in which a predetermined tolerance α is taken into consideration for L3 is selected from the plurality of end pieces 51, and the selected The fitting shaft portion 51a of the end piece 51 (hereinafter referred to as a selected end piece) is fitted into the hollow cylindrical portion 50a of the output rod main body 50 as shown in FIG. Thus, the distance L4 between the front end of the selected end piece 51 and the front end face of the booster shell 1 is measured in a state where the fitting shaft portion 51a is fitted into the hollow cylindrical portion 50a of the output rod main body 50. For example, the distance L4≈the distance L1, and (L4−L1) falls within the tolerance α.

  Next, as shown in FIG. 8, the input rod 20 is advanced against the urging force of the booster return spring 27, and the hollow cylindrical portion 50 a of the output rod main body 50 is moved together with the selected end piece 51 to the front end wall of the booster shell 1. The front end of the hollow cylindrical portion 50a is caulked from four surroundings by a pair of L-shaped caulking tools T and T as shown in FIG. Four stopper portions 53 are formed so as to face the annular step portion 51c of the piece 51, and these stopper portions 53 abut against the annular step portion 51c, thereby preventing the selected end piece 51 from being detached from the hollow cylindrical portion 50a. can do. Thus, the output rod 25 is completed.

  If the forward pressing force is released from the input rod 20 after caulking of the stopper portion 53, the output rod 25 is returned into the booster shell 1 by the urging force of the booster return spring 27. Thereafter, as shown in FIG. The master cylinder M is attached to the front end wall of the booster shell 1 while the front end of the selected end piece 51 is accommodated in the Mb coupling recess 52.

  Thus, the tip end portion of the selection end piece 51 of the output rod 25 can be placed in a state of substantially contacting the bottom surface of the connecting recess 52 of the master piston Mb.

  According to such a manufacturing method of the negative pressure booster B, the output rod 25 can be constituted by the two components of the output rod main body 50 and the end piece 51 which are both simple in shape and easy to process. The front end position is set based on the measurement of the distance L2 between the front end surface of the booster shell 1 and the bottom surface of the hollow cylindrical portion 50a of the output rod main body 50. Since one piece is selected from the pieces 51 and fitted into the hollow cylindrical portion 50a of the output rod main body 50, the front end position of the output rod 25 can be easily and quickly set.

  Further, when the stopper portion 53 for preventing the end piece 51 from coming off from the hollow cylindrical portion 50a is caulked and formed on the hollow cylindrical portion 50a, the hollow cylindrical portion 50a is moved together with the end piece 51 by the forward pressing of the input rod 20. Since the shell 1 is exposed to the front, the caulking of the stopper portion 53 can be easily performed without being obstructed by the booster shell 1.

  The present invention is not limited to the above embodiments, and various design changes can be made without departing from the scope of the invention. For example, in the end piece 51, the pressing shaft portion 51b is formed to have the same diameter as the fitting shaft portion 51a, the outer peripheral portion of the pressing shaft portion 51b is partially cut away, and the gap between the pressing shaft portion 51b and the fitting shaft portion 51a. It is also possible to form a forward-facing step 51c. Further, the number of the stopper portions 53 may be one.

B ... Negative pressure booster M ... Master cylinder (brake master cylinder)
Mb: master piston V ... negative pressure source 1 ... booster shell 2 ... negative pressure chamber 3 ... working chamber 4 ... booster piston 10 ... valve cylinder 20 ... Input rod 24 ... Reaction force mechanism 25 ... Output rod 33 ... Opening portion 38 ... Control valve 50 ... Output rod main body 50a ... Hollow cylindrical portion 50at ... Thin portion 51 ... End piece 51a ... Fitting shaft 51b ... Pressing shaft 51c ... Step

Claims (4)

The booster shell (1) accommodates a booster piston (4) which is divided into a front negative pressure chamber (2) and a rear working chamber (3) connected to the negative pressure source (V). A valve cylinder (10) that is slidably supported on the rear wall of the booster shell (1) is connected to the piston (4), and an input rod (20) that can move back and forth in the valve cylinder (10). And a control valve (38) for switching the working chamber (3) to the negative pressure chamber (2) and the atmosphere in response to the longitudinal movement of the input rod (20). Between the input rod (20) and the output rod (25) slidably supported by the valve cylinder (10), the operation input to the input rod (20), the working chamber (3) and the negative pressure chamber ( 2) It is equipped with a reaction force mechanism (24) that transmits the resultant force with the thrust of the booster piston (4) due to the pressure difference between the two to the output rod (25). The front wall of Tasheru (1), in the vacuum booster to a master cylinder (M) is attached with a master piston that is driven forward (Mb) by the output rod (25),
The output rod (25) has a bottomed hollow cylindrical portion (50a) at the front end and an output rod main body (50) whose rear end is connected to the reaction force mechanism (24), and the hollow cylinder A fitting shaft portion (51a) that is removably fitted into the portion (50a), and a forward stepped portion (51c) at the front end of the fitting shaft portion (51a) ending in the hollow cylindrical portion (50a) ) And an end piece (51) comprising a pressing shaft portion (51b) that substantially contacts the rear end portion of the master piston (Mb), and the hollow cylindrical portion (50a ) Is characterized in that a stopper portion (53) is formed by caulking against the step portion (51c) to prevent the fitting shaft portion (51a) from being detached from the hollow cylindrical portion (50a). Negative pressure booster. The negative pressure booster according to claim 1,
A negative pressure booster characterized in that a thin-walled portion (50 at) thinner than a rear portion is provided at a front end portion of the hollow cylindrical portion (50a), and the stopper portion (53) is caulked and formed on the thin-walled portion (50 at). . In manufacturing the negative pressure booster according to claim 1,
Preparing a plurality of end pieces (51) having different lengths, assembling a negative pressure booster (B) excluding the master cylinder (M) and the end piece (51), and negative pressure thereof Measuring the distance (L2) between the front end face of the booster shell (1) in the booster (B) and the bottom face of the hollow cylindrical part (50a) of the output rod main body (50); One end piece (51) corresponding to the distance (L2) is selected from the end piece (51), and its fitting shaft portion (51a) is used as the hollow cylindrical portion (50a) of the output rod main body (50). Fitting until it bottoms in, and setting the distance (L4) between the front end of the end piece (51) and the front end face of the booster shell (1) to a predetermined value; 50a) The front end part is radially inward Method for producing a negative pressure booster, characterized in that to perform the step of forming the stopper portion in Rukoto (53). In the manufacturing method of the negative pressure booster according to claim 3,
When executing the step of forming the stopper portion (53), the input rod (20) is advanced, and the output rod main body (50) is moved outward from the opening (33) of the front wall of the booster shell (1). The hollow hollow cylindrical part (50a) is exposed together with the end piece (51), and the stopper part (53) is formed in the exposed state.

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