KR100303603B1 - Method and device for producing bellows - Google Patents

Abstract

In order to produce a metal bellows of length " Ls " for use in a high temperature environment, the following steps are performed. First, a blank of a bellows, which is a metal tube having a plurality of bulges formed around it, is prepared. The blank has a length L longer than the length Ls. Later, the blanks are compressed by a length 'a' in the axial direction so that the compressed blank has a length 'L-a' of less than length 'Ls'. Later, the compressed blank is expanded in the axial direction such that the expanded blank has a length " L-a + b " Later, the force applied to the blank is removed, and the treated blank is placed at room temperature until the treated blank due to the spring-back phenomenon has a length of 'Ls'.

Description

METHOD AND DEVICE FOR PRODUCING BELLOWS FIELD OF THE INVENTION [0001]

The present invention relates to a method and apparatus for manufacturing or reforming bellows, and more particularly to a method and apparatus for manufacturing or reforming bellows in an automotive internal combustion engine to compensate for the relative displacement between two parts of the exhaust line, To a method and apparatus for manufacturing or remolding a metal bellows installed in a flexible tube disposed in an exhaust pipe.

In order to clarify the task of the present invention, a conventional flexible tube to which a bellows is actually applied will be briefly described with reference to Figs. 5 and 6 of the accompanying drawings. The conventional flexible tube shown in Figs. 5 and 6 is described in detail in Japanese Utility Model No. 1 < / RTI > Provisional Application No. 61-187916.

In Figure 6, a flexible tube, indicated generally at 100, is shown. As can be seen from the figure, the flexible tube 100 is adapted to absorb the vibration of the exhaust line or to compensate for the relative displacement between the two pipes "UP" and "DP" And a downstream exhaust pipe 'DP'.

The flexible tube 100 has an upstream end sealingly disposed on the downstream side end of the upstream side exhaust pipe UP and a downstream end sealingly disposed on the upstream side end of the downstream side exhaust pipe DP . A cover 104 of braided metal wire is disposed sealingly disposed on the downstream end of the bellows 102 and an upstream end sealingly disposed on the upstream end of the bellows 102, Thereby covering or surrounding the bellows 102 having the downstream end portion. In order to sealably mount the upstream and downstream ends of the bellows 102 and the cover 104 on the upstream exhaust pipe UP and the downstream exhaust pipe DP, each metal collar 106, And is disposed sealingly on the upstream and downstream ends of the cover 104 as shown. The bellows 102 can absorb vibration transmitted from the internal combustion engine (not shown) through the upstream side exhaust pipe UP. That is, when receiving the vibration, the bellows 102 undergoes a certain elastic deformation due to the characteristics of the bellows which absorbs the vibration and corrects the relative displacement between the upstream exhaust pipe UP and the downstream exhaust pipe DP do.

The cover 104 limits the excessive extension of the bellows 2 and serves to protect the bellows 102 from being hit by small stones or similar flying objects from the road. That is, by a predetermined length, the cover 104 composed of the braided metal wire can be expanded in the axial direction in accordance with the extension of the bellows 102. Thus, when the extension of the bellows 102 reaches a predetermined length, the cover 104 functions to stop further extension of the bellows 102. [ That is, due to the provision of the cover 104, the bellows 102 can be protected from excessive elongation. That is, the bellows 102 can be expanded axially within the cover 104 by a predetermined length.

In order to assemble the flexible tube 100, the metal bellows 102 is reshaped before being placed in the cover 104. That is, the metal bellows 102 undergoes a so-called " single compression process " to achieve the dimensional stability of the treatment bellows 102 and the appropriate axial flexibility of the treatment bellows 102. 5, in this compression process, the blank 102X of the bellows 102 is once compressed to a length L-a shorter than the normal length Ls of the bellows 102 . This compression process is actively performed because of the 'spring-back phenomenon' of the compressed bellows 102Y that inevitably occurs. In fact, after compression due to this spring-back phenomenon, the excessively compressed bellows 102Y is gradually expanded to have a normal length 'Ls'. Moreover, due to this compression, the pitch of the bulges of the process bellows 102 is reduced, and each bulge has a generally Ω-shaped cross-section that causes an appropriate axial flexibility or resilient deformation of the bellows 102.

It has been found, however, that the single compression of the bellows 102X described above leaves a kind of stress (or residual stress) in the bellows 102 that causes the bellows 102 to expand axially when heated.

Therefore, when the flexible tube 100 having the bellows 102 described above installed therein is actually used, that is, when it is used in the exhaust pipe line of the engine, the overall length 'Ls' Tends to increase due to the release of the residual stress due to heat of the gas. However, an increase in the overall length " Ls " of the bellows 102 means a reduction by a predetermined length that the bellows 102 can expand axially in the cover 104. [ That is, the so-called " elongational flexibility " of the bellows 102 is reduced or decreased when the flexible tube 100 is actually used.

The expansion / contraction of the bellows 102 is interrupted by the cover 104 and is performed. The cover 104 has a structure for reducing the diameter when it is expanded in the axial direction. Thus, the extension of the bellows 102 caused by the application of exhaust gas heat causes the cover 104 to stretch, thus reducing the diameter of the cover. A reduction in the diameter of the cover 104 that causes obstacles to the stretch flexibility of the bellows 102 narrows the annular space formed between the bellows 102 and the cover 104. This fact will be understood from the graph of FIG.

The graph of FIG. 4 shows the relationship between the elongation "E" of the bellows and the force "F" required for the elongation of the bellows. In the graph, the solid curve indicates the elongation flexibility of the normal-sized bellows 102A installed in the cover 104 having the normal length 'Ls' and the critical elongation 'S'. As can be seen from these graphs, in the bellows 102A of normal dimensions, the elongation 'E' of the bellows 102A in the region of the critical elongation 'S' is the tensile force applied to the bellows 102A ' F '.≪ / RTI > When the elongation 'E' extends beyond the critical elongation 'S', the tensile force 'F' increases abruptly, thus reducing the elongation flexibility of the bellows 102. Dotted curves represent the great length 'Ls _1' and 'S' less than the critical height 'S1' has a somewhat expanded bell due to the applied heat the exhaust gas rose (102B) having an elongation flexibility than 'Ls'. As can be seen from the graph, in this bellows 102B, a sudden increase in tensile force 'F' due to a decrease in critical elongation occurs at an early stage of elongation 'E'. This means that the stretch flexibility of bellows 102B is poorer than the stretch flexibility of bellows 102A. The one-dot chain curve has elongation flexibility of 102 ° C, which is slightly shorter than the bellows (102 A) due to excessive compression applied with a threshold elongation 'S2' greater than 'Ls ₂ ' and 'S' . The short initial length 'Ls ₂ ' of the bellows 102C may cause difficulty when the bellows 102C is installed in the cover 104, although this bellows 102C may provide sufficient extension during actual use. do. That is, in this case, the assembled flexible tube 100 can not have a normal-sized structure.

Following the tests performed by the inventors, the following facts were additionally shown. That is, when the bellows is about 300 mm long and undergoing a single compression process at room temperature, the bellows is expanded or stretched by about 2 mm. When the bellows is actually used or heated by the exhaust gas from the engine, the bellows is expanded or stretched by about 6 to 8 mm. This means that even if the bellows undergoes a single compression process, the predetermined stress (residual stress) that causes the bellows to expand axially, especially when heated, remains in the bellows. The inventor further noted that the stresses in the bellows are sufficiently removed when the bellows is annealed at 600 ° C for about 2 minutes. However, in this case, the addition of the annealing heat treatment process complicates the manufacturing process, thus increasing the cost of the flexible tube.

Accordingly, it is an object of the present invention to provide a method for producing a bellows which does not have the above disadvantages.

Another object of the present invention is to provide a manufacturing apparatus in which the method of the present invention can be practically carried out.

According to a first aspect of the present invention there is provided a method for producing a metal bellows of length " Ls " for use in a high temperature environment. (B) providing a blanket of bellows having a length "L" greater than the length "Ls"; (b) Axially compressing the blank by a length "a" to have a shorter length "L-a"; and (c) compressing the blank so that the expanded blank has a length "L-a + (D) removing the force applied thereto to inflate the blank, and (e) when the treated blank has a length of 'Ls' due to the spring-back phenomenon, To room temperature.

According to a second aspect of the present invention, there is provided an apparatus for reshaping a bellows for use in a high temperature environment. The bellows is a metal tube having a plurality of bulges formed around it. The apparatus comprises a base member, a first clamping mechanism fixedly mounted on the base member and having a first hydraulically actuated clamping means for clamping a tubular one end of the bellows when actuated, and a second clamping mechanism fixedly mounted on the base member A second clamping mechanism having a second hydraulic actuating clamping means for clamping the other end of the tubular bellows when actuated, and a second clamping mechanism for clamping the other end of the first hydraulic actuating clamping means and the second hydraulic actuating clamping means A hydraulic power source for operating with hydraulic pressure, and an electric transfer mechanism for moving the second clamping mechanism toward and away from the first clamping mechanism when electrically excited.

Other objects and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a bellows manufacturing or reshaping step employed in the process according to the invention.

2 is a front partial cross-sectional view of a bellows making or remoulding device that actually performs the method of the present invention;

3 is an enlarged view of a portion indicated by reference symbol A in Fig.

4 is a graph showing the characteristics of three bellows in relation to the relationship between the height of the bellows and the force required for the bellows's elongation.

Fig. 5 is a diagram showing steps of bellows manufacture or reshaping employed in the conventional method; Fig.

6 is a front partial cross-sectional view of a flexible tube applied with a bellows manufactured or reformed by a conventional method;

Description of the Related Art

2: Bellows

2X, 2Y, 2Z: blank

12, 14, 16, 18: stand

20, 36: Actuator

22, 38: Clamp mechanism

26: Screw shaft

28: Servo motor

50: Bellows manufacturing device

Hereinafter, the method of the present invention in which the bellows 2 is manufactured or reformed will be described in detail with reference to FIGS. 1 to 3 of the accompanying drawings. The shape of the bellows 2 produced by the method of the present invention is substantially the same as the shape of the bellows 102 employed in the conventional flexible tube 100 of Fig. For ease of explanation, the term " manufacture " and its corresponding terminology will be used hereinafter to describe the method of the present invention.

In order to manufacture the bellows 2, the following manufacturing steps shown in Fig. 1 are performed.

First, the blank 2X of the bellows 2 is prepared. The blank 2X is a double-layer stainless steel pipe having a plurality of bulges formed around it. A known hydraulic bulge forming process is used to produce the blank 2X. That is, in order to perform such a process, a straight double-layer stainless steel pipe is placed in a split mold having a plurality of annular grooves formed on the inner surface thereof, and then a predetermined hydraulic pressure is applied to the inner surface of the pipe to expand the pipe radially outward. As a result, the groove of the metal mold comes into contact with the inner surface of the recess, thereby forming a plurality of bulges on the periphery, that is, the blank 2X having the length 'L'.

The blank 2X is then axially compressed by the length "a" against the reaction force generated by the blank 2X when compressed, so that the compressed blank 2Y is pressed against the normal length of the bellows 2 L-a 'shorter than' Ls'.

Thereafter, the compressed blank 2Y expands in the axial direction by a length 'b' against the reaction force generated by the blank 2Y when inflated, so that the expanded blank 2Z is longer than 'Ls' L-a + b 'shorter than L'.

Thereafter, the force for expanding the blank 2Z is removed. At this time, the expanded blank 2Z is contracted to have a predetermined length that is slightly longer than the normal length 'Ls'. Thereafter, the blank 2Z is left at room temperature for a few seconds. Thus, due to the spring-back phenomenon of the blank 2Z, the blank 2Z has the normal length 'Ls'. That is, the bellows 2 is manufactured.

As will be described later in detail, the bellows 2 produced in this manner exhibits excellent performance.

Referring to Fig. 2, a bellows making apparatus 50 is shown through which the bellows making step is actually carried out.

The bellows manufacturing apparatus 50 includes a base member 10. On the base member 10, first, second, third and fourth stands 12, 14, 16, 18 are mounted. The first stand 12 supports the first hydraulic actuator 20 and the first clamping mechanism 22. The actuator 20 has a plunger 20a that can protrude toward the center of the first clamping mechanism 22. [ The details of the clamping mechanism 22 will become apparent hereinafter. The second stand 14 supports the guide 24 for the blank 2X. The second stand (14) rotatably supports the front end of the screw shaft (26). The third stand 16 rotatably supports the rear end of the screw shaft 26. The fourth stand 18 supports the servo motor 28 having an output shaft connected to the rear end of the screw shaft 26 through the coupling 30. [ Thus, when the servo motor 28 is operated, the screw shaft 26 is rotated about the axis. A slider 32 having a threaded bore through which the screw shaft 26 engages is disposed on the screw shaft 26. A slider guide portion for restricting the rotation of the slider 32 about the axis of the screw shaft 26 and guiding the axial movement of the slider 32 is disposed on the base member 10 although not shown in the figure. The slider 32 moves forward and backward on the screw shaft 26 when the servo motor 28 is operated and the screw shaft 26 is rotated about the axis. The slider 32 supports the fifth stand 34. The fifth stand 34 supports the second hydraulic actuator 36 and the second clamp mechanism 38 that move together with the slider 32. The actuator 36 has an output plunger 36a which can be projected toward the center of the second clamping mechanism 38. [ As shown, the first and second clamp mechanisms 22 and 38 are arranged to face each other. The first and second hydraulic actuators 20, 36 are connected to the pressurized fluid source 42 through the flexible fluid tube 40. Although not shown in the drawing, an on / off valve for controlling the first and second hydraulic actuators 20, 36 is provided in the fluid source 42 by supplying fluid pressure from the fluid source 42.

The details of the second clamping mechanism 38 will be described with reference to Fig. Since the first clamping mechanism 22 is substantially the same as the second clamping mechanism 38, the description of the first clamping mechanism 22 will be omitted.

As shown in Fig. 3, the second clamping mechanism 38 includes a tubular housing 38a in which the output plunger 36a of the second hydraulic actuator 36 is movably accommodated in the axial direction. As shown, the plunger 36a has a tapered leading end. Within the tubular housing 38a, a plurality of clamp pieces 38b (i.e., three in the illustrated embodiment) arranged so as to surround the axis of the tubular housing 38a are movably arranged. Each clamp piece 38b is formed with a tapered inner surface that can engage with the tapered end of the plunger 36a. An annular groove is formed in the clamp piece 38b to receive the O-shaped ring 38c. The clamp piece 38b is supported by a support member 38d surrounding the main portion of the plunger 36a. The circular cap 38e is placed on the clamp piece 38b. As shown, the right tubular end of the blank 2X generally extends between the tubular housing 38e with a cylindrical unit consisting of a plunger 36a, a clamp piece 38b, a support member 38d and a circular cap 38e And is received in the formed annular clearance. When the plunger 36a is moved to the left side (i.e., in the direction of the arrow M ') by a predetermined angle due to the operation of the second hydraulic actuator 36, the tapered end of the plunger 36a is clamped by the clamp piece 38b So that the O-shaped ring presses the right tubular end of the blank 2X against the tubular housing 38a. As a result, the right tubular end of the blank 2X is tightly clamped by the second clamping mechanism 38. It should be noted that the left tubular end of the blank 2X is clamped by the first clamping mechanism 22 substantially the same as the clamping mechanism in the second clamping mechanism 38.

Hereinafter, the operation of the bellows manufacturing apparatus 50 will be described with reference to Figs. 2 and 3. Fig.

First, by operating the servo motor 28 to rotate in one direction, the second clamping mechanism 38 is moved away from the first clamping mechanism 22 to a predetermined position. The blanks 2X of the bellows 2 having the left tubular end guided into the annular clearance of the first clamping mechanism 22 are placed in the guide portion 24. By actuating the servomotor 28 to rotate in the other direction, the second clamping mechanism 38 is moved toward the first clamping mechanism 22, receiving the right tubular end of the blank 2X within the annular clearance. When the left and right tubular ends of the blank 2X are properly accommodated in the respective annular clearances of the first and second clamp mechanisms 22 and 38, the servo motor 28 is deactivated. The pressurized fluid of the fluid source 42 is guided to the first and second hydraulic actuators 20 and 36 by operating the on / off valve of the fluid source 42 thereafter. The plungers 20a and 36a are moved to actuate the clamp pieces 38b so that the left and right tubular ends of the blank 2X are held in contact with the first and second clamp mechanisms 22 and 38, Lt; / RTI > In this state, it should be noted that the blank 2X has an axial length 'L' (see FIG. 1).

Thereafter, by operating the servo motor 28, the second clamp mechanism 38 is moved toward the fixed first clamp mechanism 22 to compress the blank 2X. When the blank 2X is compressed to have a length of "L-a" (see FIG. 1), the operation of the servo motor 28 is reversed to expand the compressed blank 2Y. When the stroke of the blank 2Y becomes "L-a + b" due to expansion, the servo motor 28 is deactivated. The on / off valve is deactivated to release the right and left tubular ends of the expanded blank 2Z from the first and second clamping mechanisms 22,38. The second clamping mechanism 38 moves away from the first clamping mechanism 22 to separate the blank 2Z from the first and second clamping mechanisms 22 and 38 by operating the servo motor 28 do.

The bellows 2 made in this way and remoulded is used to assemble the flexible tube as shown in Fig.

The bellows 2 produced in this manner has excellent dimensional stability compared to the bellows 102 (see Fig. 5) manufactured in the conventional manner. That is, even when the bellows 2 is actually used as a part of the flexible tube in the exhaust pipe line of the internal combustion engine, the overall length 'Ls' remains substantially unchanged regardless of the temperature change of the exhaust pipe line. In fact, a very small contraction occurs in the bellows 2. This can be attributed to the kind of residual stress that causes the bellows 2 to contract in the axial direction when heated. It should be noted, however, that the reduction of the length of the bellows 2 means an increase by a predetermined length that allows the bellows 2 to expand axially in the cover of the flexible tube. That is, the stretch flexibility of the bellows 2 is increased when the flexible tube is actually used.

Japanese Patent Application No. 9-327735 (filed on November 28, 1997) is incorporated herein by reference in its entirety.

While the present invention has been described with reference to certain embodiments of the invention, it is to be understood that the invention is not limited to the embodiments described above. It will be apparent to those skilled in the art from the foregoing teachings that modifications and variations of the embodiments described above may be accomplished.

The bellows produced by the method of the present invention have excellent dimensional stability compared to the bellows produced by the conventional method. That is, even when the bellows is actually used in the exhaust line of the internal combustion engine as part of the flexible tube, the overall length 'Ls' remains substantially unchanged regardless of the temperature change of the exhaust line.

Claims (11)

A method for producing a metal bellows of length " Ls " for use in a high temperature environment, (A) preparing a blank of a bellows having a plurality of bulges formed around it and having a length L longer than the length Ls, (B) axially compressing the blank by a length 'a' such that the compressed blank has a length L-a 'that is less than the length' Ls' (C) axially expanding the compressed blank such that the expanded blank has a length " L-a + b " (D) removing the applied force to inflate the blank, (E) placing the treated blank at room temperature until it has a length " Ls " due to a spring-back phenomenon. The method of claim 1, wherein the blank prepared in step (a) is a double-layer stainless steel pipe having a plurality of bulges formed around it. 3. The method of claim 2, wherein the blank prepared in step (a) is produced through a hydraulic bulge processing process. The method of claim 1, wherein step (b) is performed against a reaction force generated when the blank is compressed. 5. The method of claim 4, wherein step (c) is performed against a reaction force generated when the blank is expanded. The method according to claim 1, wherein steps (b) and (c) are characterized in that the kind of stress causing the bellows to contract slightly in the axial direction when heated is controlled to remain in the treated blank prepared in step (e) Lt; / RTI > 2. The method of claim 1, wherein steps (b) and (c) are characterized in that the type of stress causing the bellows to have a fixed axial length even if heated is controlled to remain in the treated blank prepared in step (e) Lt; / RTI > 1. An apparatus for re-forming a bellows made of a metal tube having a plurality of bulges formed on a circumference for use in a high temperature environment, A base member, A first clamping mechanism fixedly mounted on the base member and having a first hydraulically actuated clamping means for clamping the tubular one end of the bellows when actuated, A second clamping mechanism fixedly mounted on the base member and having a second hydraulic actuating clamping means for clamping the other end of the bellows when operated, A hydraulic power source for operating the first hydraulic actuating clamping means and the second hydraulic actuating clamping means in an on state with hydraulic pressure; And an electro-moving mechanism for moving the second clamping mechanism toward and away from the first clamping mechanism when electrically excited. 9. The apparatus of claim 8, wherein each of the first hydraulically actuated clamping means and the second hydraulically actuated clamping means comprises: A hydraulic actuator having an output plunger with a tapered leading end, A tubular housing having an output plunger movably received in the axial direction, A plurality of clamp pieces each having a tapered inner surface mounted in the tubular housing in a manner surrounding the tapered leading end of the output plunger and engageable with the tapered end of the plunger, An O-shaped ring accommodated in an annular groove formed in the clamp piece, Support members which are provided in the tubular housing in such a manner as to surround a main portion of the output plunger and each support one end of the corresponding clamp piece, And a circular cap mounted on the tubular housing and resting on the clamp piece. The electrophotographic apparatus according to claim 8, A slider having a threaded bore which is mounted so as to move the second clamping mechanism, A screw shaft passing through the screw bores of the slider for providing engagement, A support device for rotatably supporting the screw shaft on the base member, And a servo motor for rotating the screw shaft when electrically operated. 11. A device according to claim 10, characterized in that the support device supports a guiding part for supporting and guiding the bellows.