JP2006312897A - Inner tube structure for internal combustion engine double tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inner tube structure for an internal combustion engine double tube, eliminating the possibility of forming a gap between inner and outer shaft ends even when adopting the construction of radially superimposing the shaft ends of tubular members each section-shaped with a flat portion and a curved portion combined. <P>SOLUTION: The inner tube structure for the internal combustion engine double tube comprises the plurality of tubular members 2 joined together in the tube-axial direction. In a joint portion 3 between the tubular members 2, the shaft end 2c of one tubular member 2 is fitted to the inside of the shaft end 2d of the other tubular member 2 and the shaft ends 2c, 2d are each section-shaped with the flat portion 2a and the curved portion 2b combined. As a restricting means for restricting the deformation of one tubular member 2 to the inside of the flat portion 2a, a reinforcing member 4 is provided on the joint portion 3 for contacting the flat portion 2a of one tubular member 2 at its inside to support the flat portion 2a in the radial direction of the tubular member 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inner pipe structure of a double pipe for an internal combustion engine having a cross-sectional shape combining a flat part and a curved part.

As an exhaust pipe of an internal combustion engine, an exhaust pipe in which a part of the cross-sectional shape is set to be elliptical is known (for example, see Patent Document 1). For the purpose of improving heat insulation, an exhaust manifold having a double pipe structure in which a plurality of tubular members are joined in the tube axis direction to form an inner tube and the inner tube is covered with an outer tube is also provided. As an inner tube structure used for this type of double tube, the shaft end of one tubular member is fitted inside the shaft end of the other tubular member at the joint of the tubular members, and these shaft ends are connected to the tube. An inner tube structure that is slidable in the axial direction is also known (see Patent Document 2, for example).
JP-A-7-324621 Japanese Patent Laid-Open No. 11-93658

  However, in the above-described double tube structure, the axial end of the tubular member fitted inside the joint is more likely to be heated than the axial end of the outer tubular member, so the thermal elongation of the inner axial end is outside. It is limited by the shaft end. For this reason, when the axial end of the tubular member is formed in a cross-sectional shape combining a flat portion and a curved portion, such as an elliptical shape or a racetrack shape, However, there is a possibility that thermal stress is generated in the flat portion having low rigidity, the flat portion is deformed inward, and a gap is generated between the shaft end portions. If such a gap is generated, the exhaust gas leaks from the joint portion of the inner tube, and thereby the outer tube is vibrated and abnormal noise is generated, or the heat insulation property is deteriorated.

  Therefore, the present invention may cause a gap between the inner and outer shaft end portions even in a structure in which the shaft end portions of the tubular member having a cross-sectional shape combining the flat portion and the curved portion are overlapped in the radial direction. It is an object of the present invention to provide an internal pipe structure of a double pipe for an internal combustion engine that can be eliminated.

  In the present invention, a plurality of tubular members are joined in the tube axis direction, and at the joint portion between the tubular members, the shaft end portion of one tubular member is fitted inside the shaft end portion of the other tubular member, and An inner pipe structure of a double pipe for an internal combustion engine in which each shaft end portion has a cross-sectional shape combining a flat portion and a curved portion, and the deformation of the one tubular member to the inside of the flat portion The above-described problem is solved by using an inner tube structure in which a suppressing means for suppressing the above is provided in the joint portion (claim 1).

  According to the inner tube structure of the present invention, since the means for suppressing the inward deformation of the flat portion of the tubular member disposed inside at the joint is provided, the shaft end of the inner tubular member at the joint Even when heated, the deformation to the inside of the shaft end portion is limited, thereby eliminating the possibility that a gap is generated between the shaft end portions of the inner and outer tubular members. Accordingly, it is possible to suppress the occurrence of inconveniences such as gas leakage occurring at the joint portion, abnormal noise caused by vibrating the outer tube, or deterioration of the heat insulation of the double tube.

  In one form of the present invention, the joining portion may be provided with a reinforcing member that is in contact with the flat portion of the one tubular member from the inside and supports the flat portion in the radial direction of the tubular member as the suppressing means. Good (claim 2). According to this form, the deformation | transformation to the inner side of a flat part can be suppressed by supporting a flat part from an inner side with a supporting member. Thereby, the possibility that a gap is generated between the shaft end portions of the inner and outer tubular members can be eliminated.

  In one form of the present invention, in the joint portion, the thickness of the flat portion of the one tubular member is set to be larger than the thickness of the curved portion of the one tubular member, whereby the suppression means is It may be configured (claim 3). According to this embodiment, the rigidity of the inner flat portion is relatively increased as compared with the case where the wall thickness of the shaft end portion of the tubular member disposed on the inner side in the joint portion is set constant over the entire circumference. . Thereby, the deformation | transformation to the inner side of a flat part can be suppressed and the possibility that a clearance gap may arise between the axial edge parts of an inner and outer tubular member can be excluded.

  In one form of the present invention, in the joint portion, the thickness of the flat portion of the other tubular member is set to be smaller than the thickness of the curved portion of the other tubular member. It may be configured (claim 4). According to this embodiment, the rigidity of the outer flat portion is relatively reduced as compared with the case where the wall thickness of the shaft end portion of the tubular member disposed outside in the joint portion is set constant over the entire circumference. To do. For this reason, the flat part of the inner shaft end part is easily deformed to the outside, and as a result, the deformation of the flat part provided on the inner tubular member is suppressed to the inner side, and the inner and outer tubular members are spaced from each other. It is possible to eliminate the possibility that a gap is formed in the surface.

  As described above, according to the inner tube structure of the double tube of the present invention, it is possible to suppress the deformation of the tubular member disposed inside on the inner side at the joint portion between the tubular members. Therefore, the possibility that a gap is generated between the shaft end portions of the inner and outer tubular members is eliminated, the occurrence of gas leakage at the joint portion, the generation of abnormal noise due to the vibration of the outer tube, or the deterioration of the heat insulation of the double tube. The occurrence of inconvenience can be suppressed.

(First form)
FIG. 1 shows an inner pipe structure of a double pipe for an internal combustion engine according to the first embodiment of the present invention. FIG. 2 is a sectional view taken along line II-II in FIG. The double pipe is used as an exhaust pipe for an internal combustion engine. The double pipe includes an inner pipe 1 and an outer pipe (not shown) that covers the inner pipe 1 from the outside. The inner tube 1 is configured by joining a plurality of tubular members 2 in the tube axis direction (left-right direction in FIG. 1). The tubular member 2 has an elliptical cross-sectional shape over the entire length thereof in which a curved portion 2b having a larger curvature than the flat portion 2a is combined between both ends of the pair of flat portions 2a. However, the tubular member 2 should just have the cross-sectional shape which combined the flat part 2a and the curved part 2b in the axial edge part 2c, 2d of both sides at least. The cross-sectional shape of the tubular member 2 is not limited to an elliptical shape, and may be, for example, a racetrack shape. The wall thickness of the tubular member 2 is set uniformly. The tubular member 2 is formed of a metal having heat resistance, for example, stainless steel. One shaft end portion (hereinafter referred to as one end portion) 2c of each tubular member 2 has a diameter smaller than that of the other portion. One end portion 2 c of each tubular member 2 is fitted inside the other shaft end portion (hereinafter referred to as the other end portion) 2 d of the adjacent tubular member 2, thereby connecting the joint portion 3 between the tubular members 2. Is formed. Further, in the joint portion 3, the one end portion 2 c and the other end portion 2 d are fitted so as to be slidable in the tube axis direction, that is, relative to each other. In the following description, the left tubular member 2 in FIG. 1 may be referred to as an inner tube 2A, and the right tubular member as an outer tube 2B. In FIG. 1, the inner tube 2A corresponds to one tubular member, and the outer tube 2B corresponds to the other tubular member.

  In the joint portion 3, a reinforcing member 4 as a suppressing means is provided inside the one end portion 2 c of the inner tube 2 </ b> A. The reinforcing member 4 is supported between the flat portions 2a from the radially inner side by being spanned between the flat portions 2a so as to be in contact with the pair of flat portions 2a from the inner surface side thereof. The reinforcing member 4 is formed of a material having heat resistance and high rigidity, for example, stainless steel. The width W1 in the radial direction, the width W2 in the tube axis direction, and the shape of the reinforcing member 4 can be appropriately determined as long as the flat portion 2a of the inner tube 2A is not deformed inward. At least a part of the reinforcing member 4 may be welded to the inner tube 2A.

  According to the above inner tube structure, even if the one end portion 2c of the inner tube 2A is heated and a thermal stress is generated, each flat portion 2a is supported from the inner side by the reinforcing member 4, so that the inner side of the flat portion 2a The deformation to is suppressed. This eliminates the possibility that a gap is formed between the inner tube 2A and the outer tube 2B at the joint portion 3, and leaks exhaust gas from the joint portion 3, vibration of the outer tube due to gas leakage, and abnormal noise. The occurrence of inconvenience such as occurrence can be suppressed.

(Second form)
Next, an inner tube structure according to the second embodiment of the present invention will be described with reference to FIG. In the following description, the same reference numerals are assigned to portions common to the first embodiment and the description, and description thereof is omitted.

  In this embodiment, the reinforcing member 4 described above is omitted. Instead, at the one end portion 2c of the inner tube 2A, the thickness t1 of the flat portion 2a is set larger than the wall thickness t2 of the curved portion 2b at the one end portion 2c of the inner tube 2A. Yes. The wall thickness of the other end 2d of the outer tube 2B is set uniformly over the entire circumference. The thickness of the portion other than the one end 2c may be determined as appropriate, and may be uniform over the entire circumference, for example.

  According to the present embodiment, the rigidity of the flat portion 2a is relatively higher than that in the case where the thickness of the one end portion 2c of the inner tube 2A is uniformly formed over the entire circumference. Thereby, the deformation | transformation to the inner side of the flat part 2a is suppressed, and there can exist an effect similar to a 1st form.

(Third form)
Next, an inner tube structure according to a third embodiment of the present invention will be described with reference to FIG. Note that portions common to the first or second embodiment are denoted by the same reference numerals and description thereof is omitted.

  In this embodiment, the thickness of the one end portion 2c of the inner tube 2A is uniform over the entire circumference, and the reinforcing member 4 is also omitted in the joint portion 3. Instead of this, at the other end 2d of the outer tube 2B, the thickness t3 of the flat portion 2a is set smaller than the wall thickness t4 of the curved portion 2b at the other end 2d of the outer tube 2B. It is configured. The thickness of the portion other than the other end 2d of the outer tube 2B may be determined as appropriate, and may be uniform over the entire circumference, for example.

  According to this embodiment, the rigidity of the flat portion 2a is relatively low as compared with the case where the thickness of the other end 2d of the outer tube 2B is uniformly formed over the entire circumference. Therefore, when one end 2c of the inner tube 2A is heated and thermal stress is generated, the flat portion 2a of the inner tube 2A is likely to be thermally deformed to the outside, whereby the inner portion 2a of the inner tube 2A enters the inside of the flat portion 2a. Deformation is suppressed and the same effect as the first embodiment can be obtained.

  Next, a method for manufacturing the tubular member 2 having a different thickness between the flat portion 2a and the curved portion 2b will be described. FIG. 5 shows a sectional view of an outer mold for forming the tubular member 2. The outer mold 12 is provided with a cavity 13 for molding the tubular member 2. The cross-sectional shape of the cavity 13 is set to the same shape as the elliptical cross-sectional shape to be given to the tubular member 2. A material tube 14 having a circular cross section and a constant wall thickness is inserted into the hollow portion 13, and a pressurized liquid is introduced into the material tube 14 to introduce a material tube into the material tube 14. The tubular member 2 is formed by plastic deformation so that 14 is spread from the inside. Since the material pipe 14 is deformed more in the major axis direction than in the minor axis direction (vertical direction in FIG. 5) of the cavity 13, the thickness of the flat portion 2a of the obtained tubular member 2 is larger than that of the curved portion 2b. Become. The inner tube 2A of the second form is obtained by drawing one end portion 2c of the tubular member 2 obtained by such a manufacturing method.

  FIG. 6 shows another method for forming the tubular member 2. 7 is a cross-sectional view taken along line VII-VII in FIG. In this example, the outer mold 16 is provided with a cavity 17 penetrating from one end 16a to the other end 16b. The cross-sectional shape of the cavity 17 is circular at one end 16a and is elliptical at the other end 16b. The cross-sectional shape at the other end 16 b matches the outer peripheral cross-sectional shape to be given to the tubular member 2. Between the one end 16a and the other end 16b, the cross-sectional shape gradually changes from a circular shape to an elliptical shape. Further, the outer mold 16 is formed with slits 18 that connect both side surfaces 16 c and the cavity 17 over the entire length of the outer mold 16. The position of the slit 18 coincides with the apex position of the cavity 17 in the long axis direction.

  In order to form the tubular member 2 with the outer mold 16 as described above, a material tube 13 similar to that shown in FIG. 5 is inserted into the cavity portion 17 from the one end 16 a side of the outer mold 16. Then, heat is applied to the material tube 13 through the slit 18 while gradually moving the material tube 13 toward the other end 16b. The heating method may be appropriately selected. For example, hot air may be introduced into the slit 18, or a heater may be embedded in the slit 18 for heating. By such processing, the material pipe 13 is gradually plastically deformed into an elliptical cross-sectional shape, and the tubular member 2 having an elliptical cross-section is obtained from the other end 16b. In the deformation process of the material pipe 13, the vicinity of the apex in the major axis direction of the cavity 17 is heated, so that the curved portion 2b of the tubular member 2 is thermally deformed more greatly, so that the thickness of the flat portion 2a becomes the curved portion 2b. Bigger than that. The inner tube 2A of the second form is obtained by drawing one end portion 2c of the tubular member 2 obtained by such a manufacturing method.

  In the manufacturing method shown in FIGS. 6 and 7, the thickness of the flat portion 2a is increased as in the third embodiment by arranging the slit 18 near the apex in the short axis direction of the cavity 17 and heating the material tube 13. Can be set smaller than that of the curved portion 2b. In this case, by performing heating only when the other end portion 2d and its vicinity are formed, the flat portion 2a and the curved portion 2b have the same thickness at the one end portion 2a, so that the tubular member of the third form 2 can be obtained. Note that the position and width W3 of the slit 18 may be appropriately determined according to the position where the thickness is changed and the range thereof.

  This invention is not limited to the form mentioned above, It can implement with a various form. You may form an inner pipe | tube combining the 2nd form and 3rd form which were mentioned above. Furthermore, the reinforcing member of the first form may be further provided in the inner tube of the second or third form. Instead of the configuration in which one end portion of the tubular member is reduced in diameter, the other end portion may be expanded in diameter to join the respective tubular members.

The figure which shows a part of inner tube | pipe structure which concerns on the 1st form of this invention. Sectional drawing in the II-II line of FIG. The figure which shows the cross section in the junction part of the inner tube | pipe structure which concerns on the 2nd form of this invention. The figure which shows the cross section in the junction part of the inner tube | pipe structure which concerns on this invention 3rd form. The figure which shows the shaping | molding method of the tubular member which has nonuniform thickness. The figure which shows the other shaping | molding method of the tubular member which has nonuniform thickness. Sectional drawing in the VII-VII line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner pipe 2 Tubular member 2a Flat part 2b Curved part 2c One end part 2d Other end part 3 Joint part 4 Reinforcement member

Claims (4)

  A plurality of tubular members are joined in the tube axis direction, and at the joint portion between the tubular members, the shaft end portion of one tubular member is fitted inside the shaft end portion of the other tubular member, and each shaft end The inner tube structure of a double pipe for an internal combustion engine having a cross-sectional shape combining a flat portion and a curved portion, and suppressing the deformation of the one tubular member to the inside of the flat portion An inner pipe structure of a double pipe for an internal combustion engine, characterized in that means are provided at the joint.   The reinforcing portion, which is in contact with the flat portion of the one tubular member from the inside and supports the flat portion in the radial direction of the tubular member, is provided as the restraining means in the joint portion. 1. The inner tube structure according to 1.   In the joint portion, the suppression means is configured by setting the thickness of the flat portion of the one tubular member to be larger than the thickness of the curved portion of the one tubular member. The inner pipe structure according to claim 1 or 2. In the joint portion, the suppression means is configured by setting the thickness of the flat portion of the other tubular member to be smaller than the thickness of the curved portion of the other tubular member. The inner pipe structure according to any one of claims 1 to 3.

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