Exhaust system of internal combustion engine

Abstract

To provide an exhaust device of an internal combustion engine, which can seal gaps between assembled components of the internal combustion engine to prevent exhaust gas leakage even if manufacturing tolerances occur in the components.SOLUTION: As means for sealing the gap between a housing and a shaft of an internal combustion engine, there are provided: a fixed plate of a fixed member that is press-fitted into a through hole in the housing and rotatably supports the shaft; a sliding plate of a sliding member that is press-fitted into the axial direction of the shaft and slidably abuts against the fixed plate; and a spring or the like of an elastic member that urges the sliding plate in a direction of pressing it against the fixed plate. The sliding plate and fixed plate have mutually abutting surfaces that are in complementary conical or curved shapes, and are fitted together with the entire circumference abutting at at least one point.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to exhaust systems for internal combustion engines. [Background technology]

[0002] Conventionally, in exhaust systems for internal combustion engines, a seal structure has been proposed that seals the gap between a bearing press-fitted into a housing of a valve that opens and closes the exhaust gas passage and a shaft that serves as the rotating axis of the valve and is supported by the bearing, in order to prevent exhaust gas from leaking from the exhaust gas passage through the gap between the bearing press-fitted into the housing and the shaft. This seal structure that reduces exhaust gas leakage maintains the concentricity of the shaft, improves the efficiency of the sealing method, and reduces exhaust gas leakage by adding a complementary pair of truncated spheres, cones, or other shapes to the mating surfaces of the shaft and its bearing (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2013-530337 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the exhaust device for an internal combustion engine disclosed in Patent Document 1, by adding a complementary pair of truncated spheres, cones or other shapes to the joint surface of a shaft and its bearing, the concentricity of the shaft is maintained by the shape in question and the gap at the joint surface is reduced; however, it is unavoidable that slight tilt occurs due to manufacturing tolerances in assembled parts such as the housing and shaft of the internal combustion engine, and it is difficult to completely eliminate the gap between the shaft and its bearing, and there is a concern that exhaust gas may leak through the minute gap that occurs.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an exhaust device for an internal combustion engine that can seal gaps between assembled parts such as the housing and shaft of the internal combustion engine to prevent exhaust gas leakage, even if manufacturing tolerances occur in these parts. [Means for solving the problem]

[0006] The exhaust system for an internal combustion engine according to the present disclosure comprises: The exhaust gas purifier includes a pipe through which exhaust gas flows, a housing having a through-hole therein connected to one radial end of the pipe, a valve that opens and closes the pipe to control the flow rate of the exhaust gas, and a shaft that is disposed in the through-hole of the housing and serves as a rotation axis of the valve, a fixing member that is press-fitted into a through hole of the housing and rotatably supports the shaft; a sliding member that is press-fitted into the shaft in the axial direction and slidably contacts the fixed member; an elastic member is provided to bias the sliding member in a direction to press the sliding member against the fixed member; The sliding member and the fixed member are characterized in that the surfaces that come into contact with each other have complementary conical or curved shapes, and are fitted together with the entire circumference abutting at least one point. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to obtain an exhaust device for an internal combustion engine that can seal gaps between assembled parts such as the housing and shaft of the internal combustion engine to prevent exhaust gas leakage, even if manufacturing tolerances occur in these parts. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing the configuration of an internal combustion engine according to a first embodiment. [Figure 2] 1 is a cross-sectional perspective view showing the configuration of an internal combustion engine according to a first embodiment. [Figure 3] FIG. 2 is a perspective view showing a sliding plate and a fixed plate according to the first embodiment. [Figure 4]FIG. 2 is a cross-sectional view showing a sliding plate and a fixed plate according to the first embodiment. [Figure 5] FIG. 10 is a cross-sectional view showing a sliding plate and a fixed plate according to a second embodiment. [Figure 6] FIG. 11 is a cross-sectional perspective view showing a sliding plate and a fixed plate according to a third embodiment. [Figure 7] FIG. 10 is a cross-sectional view showing a sliding plate and a fixed plate according to a third embodiment. [Figure 8] FIG. 10 is a cross-sectional view showing a sliding plate and a fixed plate according to a fourth embodiment. [Figure 9] FIG. 11 is a cross-sectional view showing a sliding plate and a fixed plate according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the present embodiment will be described with reference to the drawings. In each drawing, the same reference numerals indicate the same or corresponding parts. Furthermore, FIGS. 1 to 9 relate to one embodiment, and the present disclosure is not limited to these drawings. In this disclosure, unless otherwise specified, when referring to "upper", "lower", "above", or "below", the "upper" or "upper" refers to one side in the radial direction of the pipe and in the axial direction of the shaft, and the other side in the axial direction as viewed from the "upper" or "above" refers to the "lower" or "belower".

[0010] Embodiment 1 FIG. 1 is a cross-sectional view of an exhaust device 100 for an internal combustion engine according to a first embodiment, and FIG. 2 is a cross-sectional perspective view of the exhaust device 100 for an internal combustion engine according to the first embodiment. A lower portion indicated by a wavy line in FIG. 2 is omitted. In FIGS. 1 and 2, the exhaust device 100 for an internal combustion engine includes a pipe 1 through which exhaust gas flows, a housing 2 that is continuous with the pipe 1 and has a through-hole therein that connects to an upper portion of the pipe 1, a valve 3 that opens and closes the pipe 1 to control the flow rate of the exhaust gas, a shaft 4 that is disposed in the through-hole of the housing 2 and serves as a rotation axis of the valve 3, a fixed plate 5 that is press-fitted into the through-hole of the housing 2 and serves as a fixed member that rotatably supports the shaft 4, a sliding plate 6 that is press-fitted into the axial upper portion of the shaft 4 and serves as a sliding member that slidably abuts against the fixed plate 5, and a spring holder 7 and a spring 8 that serve as elastic members that urge the sliding plate 6 in a direction that presses it against the fixed plate 5 above.

[0011] Furthermore, the exhaust device 100 for an internal combustion engine includes a press-fit pin 9 that fixes the valve 3 to the center of the shaft 4, a bearing 10 that supports the shaft 4 at the bottom of the piping 1, and a bushing 11 that is positioned below the fixed plate 5 and the sliding plate 6 and is press-fit into a through hole in the housing 2 to facilitate rotation of the shaft 4, and the shaft 4 passes through the fixed plate 5 and protrudes upward from the housing 2, and the end of the shaft 4 is welded to a spring holder 7 that is positioned above the through hole in the housing 2. The spring holder 7 is provided on the outer periphery of the through hole of the housing 2 and welded to the spring 8, and the shaft 4, spring holder 7 and spring 8 are integrated by this welding.

[0012] The spring 8 exerts an elastic force in a direction pushing up the spring holder 7, urging the spring holder 7 in a direction protruding from the housing 2. The spring force of this spring 8 pushes up the spring holder 7, which is welded to the spring 8. As a result, the shaft 4 is pulled upward, and the fixed plate 5 press-fitted into the housing 2 and the sliding plate 6 press-fitted onto the shaft 4 come into slidable contact with each other. Here, the through hole of the housing 2 is cylindrical and has a stepped structure with two stages of different diameters, with the fixed plate 5 pressed into the first stage and the sliding plate 6 placed on the second stage, which has a smaller diameter than the first stage.

[0013] The following describes the structure of the sliding plate 6 and the fixed plate 5 as means for sealing the gap between the housing 2 and the shaft 4. Fig. 3 is a perspective view showing the sliding plate 6 and the fixed plate 5 fitted together in the first embodiment, and Fig. 4 is a cross-sectional view showing the sliding plate 6 and the fixed plate 5. In Figure 4, the sliding plate 6 and the fixed plate 5 have complementary conical surfaces that abut against each other, and the slope angle A with respect to the central axis of the tapered portion of the sliding plate 6 and the draft angle B with respect to the central axis of the tapered portion of the fixed plate 5 are each within the range of 20° to 40°. The rotation axis of the shaft 4 is the central axis of the sliding plate 6 and the fixed plate 5. In addition, the sliding plate 6 is cylindrical from the tapered portion downwards, and the shaft 4 is press-fitted inside, and the fixed plate 5 is shaped like a cylinder with the conical shape of the sliding plate 6 hollowed out.

[0014] Here, the slope angle A of the sliding plate 6 and the draft angle B of the fixed plate 5 are set within a range of 20° or more and 40° or less to allow slidable contact and maintain engagement, but the slope angle A of the sliding plate 6 is set to be approximately 1° to 5° smaller than the draft angle B of the fixed plate 5. As shown in FIG. 4, the tip portion of the sliding plate 6 is shaped to extend from the contacting surfaces to the inside of the fixed plate 5 along the tapered portion, and the tip portion of the sliding plate 6 is fitted into the fixed plate 5. At this time, even if manufacturing tolerances occur in assembled parts such as the housing 2 and shaft 4 and the shaft 4 is positioned at a slight tilt, the tip of the sliding plate 6 fits inside the fixed plate 5, so the gap between the contacting surfaces is completely sealed. The fixed plate 5 may be a bearing, and may have a shape complementary to the surface of the sliding plate 6 that comes into contact with it.

[0015] Furthermore, by selecting the materials for the sliding plate 6 press-fitted onto the shaft 4 and the fixed plate 5 press-fitted into the housing 2 according to the temperature conditions of the exhaust gas, it is possible to prevent exhaust gas leakage without any problems even at high temperatures of 200 to 800 degrees. Possible materials include carbon, metal, ceramic, etc., but stainless steel is preferable for both the sliding plate 6 and the fixed plate 5 in the case of high-temperature gas, and carbon may be used at low temperatures. Furthermore, by applying a metal coating to the surface treatment of the contact surface between the sliding plate 6 and the fixed plate 5, it is possible to suppress wear on the contact surface between the sliding plate 6 and the fixed plate 5. For example, by using materials with the same or similar hardness for the sliding plate 6 and the fixed plate 5 and applying a surface treatment such as nickel plating, nickel chrome, or nitriding to the contact surface between the sliding plate 6 and the fixed plate 5, it is possible to reduce wear.

[0016] According to the exhaust device 100 for an internal combustion engine of embodiment 1, as means for sealing the gap between the housing 2 and the shaft 4, there are provided a fixed plate 5 that is press-fitted into the housing 2 and supports the shaft 4, a sliding plate 6 that is press-fitted in the axial direction of the shaft 4 and slidably abuts against the fixed plate 5, and a spring 8 that biases the sliding plate 6 in a direction pressing it against the fixed plate 5, etc. Therefore, even if manufacturing tolerances occur in the assembled parts of the internal combustion engine, such as the housing 2 and shaft 4, the gap between these parts can be sealed and exhaust gas leakage can be prevented. In particular, the surfaces of the sliding plate 6 and the fixed plate 5 that come into contact with each other are made to have complementary conical shapes, and the tip of the sliding plate 6 fits into the inside of the fixed plate 5 along the tapered portion of the latter. Therefore, even if the shaft 4 is positioned at a slight tilt due to manufacturing tolerances, the gap between the surfaces that come into contact with each other is completely sealed, preventing exhaust gas leakage.

[0017] Embodiment 2 The second embodiment will be described with reference to Fig. 5, focusing on the differences from the first embodiment as a means for sealing the gap between the housing 2 and the shaft 4. Fig. 5 is a cross-sectional view showing the sliding plate 6 and the fixed plate 5 of the second embodiment, in which the shapes of the surfaces where the sliding plate 6 and the fixed plate 5 come into contact with each other are changed from the configuration of the first embodiment.

[0018] In Figure 5, the surfaces of the sliding plate 6 and the fixed plate 5 that abut against each other have complementary curved shapes, for example, bowl shapes, and the radius of curvature C, which is the inner diameter of the curved surface of the sliding plate 6, is smaller than the radius of curvature D, which is the inner diameter of the curved surface of the fixed plate 5. In the second embodiment, as in the first embodiment, the sliding plate 6 has a cylindrical shape below the curved surface, and the shaft 4 is pressed into the inside, and the fixed plate 5 has a shape such that the curved shape of the sliding plate 6 has been carved out of the cylindrical shape. The curved shape of the contacting surfaces is not limited to a bowl shape, but may be a spherical shape or an elliptical shape.

[0019] According to the exhaust device 100 for an internal combustion engine of embodiment 2, as a means for sealing the gap between the housing 2 and the shaft 4, in particular, the mutually abutting surfaces of the sliding plate 6 and the fixed plate 5 are made to have complementary curved shapes, and are configured so that the curved surface of the sliding plate 6 is included in the curved surface of the fixed plate 5 and fits together. Therefore, even if manufacturing tolerances occur in assembled parts such as the housing 2 and shaft 4 of the internal combustion engine and the shaft 4 is positioned at a slight tilt, the gap between the mutually abutting surfaces is completely sealed and exhaust gas leakage can be prevented.

[0020] Embodiment 3 Embodiment 3 will be described with reference to Figures 6 and 7, focusing on the differences from Embodiment 1 in terms of the means for sealing the gap between the housing 2 and the shaft 4. Figure 6 is a cross-sectional perspective view showing the sliding plate 6 and fixed plate 5 of Embodiment 3, and Figure 7 is a cross-sectional view showing the sliding plate 6 and fixed plate 5 in Figure 6. In this case, the sliding plate 6 and fixed plate 5 are different from the configuration in Embodiment 1 in that they have complementary steps in the axial direction of the shaft 4 from their mutual contact surfaces.

[0021] 7, the sliding plate 6 and the fixed plate 5 have complementary conical surfaces that come into contact with each other, and the sliding plate 6 has a convex step from this contact surface in the axial direction of the shaft 4, forming a two-step structure consisting of a tapered cone-shaped portion and a stepped convex portion. The fixed plate 5 also has a two-step structure with a recessed portion that is complementary to the stepped convex portion, and is configured so that the stepped concave and convex portions fit together. Here, the step portion between the sliding plate 6 and the fixed plate 5 is cylindrical, and the inner diameter E of the step portion of the fixed plate 5 is larger than the outer diameter F of the step portion of the sliding plate 6, so that even if the shaft 4 is tilted slightly, the corner of the step portion of the sliding plate 6 will abut against the wall surface of the step portion of the fixed plate 5. The gradient angle A of the tapered portion of the sliding plate 6 and the draft angle B of the tapered portion of the fixed plate 5 are in the range of 20° to 40°, similarly to the first embodiment.

[0022] According to the exhaust device 100 for an internal combustion engine relating to embodiment 3, as a means for sealing the gap between the housing 2 and the shaft 4, in particular, the sliding plate 6 and the fixed plate 5 have a two-stage structure consisting of a tapered portion and a stepped portion. Therefore, even if manufacturing tolerances occur in assembled parts such as the housing 2 and shaft 4 of the internal combustion engine and the shaft 4 is positioned at a slight tilt, the gap can be reduced by the corner of the convex-shaped step abutting against the wall surface of the concave-shaped step, thereby reducing the leakage of exhaust gas.

[0023] Embodiment 4 The fourth embodiment will be described with reference to Fig. 8, focusing on the differences from the first embodiment as a means for sealing the gap between the housing 2 and the shaft 4. Fig. 8 is a cross-sectional view showing the sliding plate 6 and the fixed plate 5 of the fourth embodiment, and is different from the configuration of the first embodiment in that a disc spring 12 is disposed between the mutually abutting surfaces of the sliding plate 6 and the fixed plate 5.

[0024] In Figure 8, the sliding plate 6 and the fixed plate 5 have complementary conical surfaces that abut against each other, and a conical disc spring 12 is arranged around the entire circumference between the abutting surfaces of the sliding plate 6 and the fixed plate 5, with the tapered surface of the disc spring 12 abutting against the tapered portion of the sliding plate 6 and the back surface of the disc spring 12 abutting against the tapered portion of the fixed plate 5, thereby fitting the sliding plate 6 and the fixed plate 5 together. With the tapered portion of the disc spring 12 in contact with the tapered portion of the sliding plate 6, the sliding plate 6 is pressed against the fixed plate 5 by an elastic member such as the spring 8 shown in FIG. 1, and the back surface of the disc spring 12 comes into contact with the tapered portion of the fixed plate 5, and the gap between the sliding plate 6 and the fixed plate 5 is sealed by the spring force of the disc spring 12 itself. The angle of the taper of the disc spring 12 is not specified, but similar to the angle of the gradient angle A of the tapered portion of the sliding plate 6, it is preferably within the range of 20° or more and 40° or less.

[0025] According to the exhaust device 100 for an internal combustion engine of embodiment 4, as a means for sealing the gap between the housing 2 and the shaft 4, a disc spring 12 is arranged between the sliding plate 6 and the fixed plate 5, and the tapered portion of the disc spring 12 is configured to abut and fit against the tapered portion of the sliding plate 6. Therefore, even if manufacturing tolerances occur in the assembled parts of the internal combustion engine, such as the housing 2 and shaft 4, and the shaft 4 is positioned at a slight tilt, the spring force of the disc spring 12 itself will seal the gap between the sliding plate 6 and the fixed plate 5, preventing exhaust gas leakage.

[0026] Embodiment 5 The fifth embodiment will be described with reference to Fig. 9, focusing on the differences from the first embodiment as a means for sealing the gap between the housing 2 and the shaft 4. Fig. 9 is a cross-sectional view showing the sliding plate 6 and fixed plate 5 of the fifth embodiment, and is different from the configuration of the first embodiment in that a cylindrical oil seal 13 is disposed between the fixed plate 5 and the shaft 4.

[0027] In Figure 9, a cylindrical oil seal 13 is arranged between a fixed plate 5 and the shaft 4 shown in Figures 1 and 2, and an inner surface 14 of the oil seal 13 and the shaft 4 abut over the entire circumference at at least two points, and an outer surface 15 of the oil seal 13 and the fixed plate 5 are in surface contact over the entire circumference at at least one point, so that the shaft 4 is supported by the fixed plate 5. The oil seal 13 is made of a metal material, and a lubricant such as oil containing grease is applied between the oil seal 13 and the shaft 4 to facilitate rotation of the shaft 4. The material of the oil seal 13 may be any metal that can withstand high temperatures of around 450 degrees.

[0028] Here, the oil seal 13 is fitted between the tip end portion of the sliding plate 6 and the ceiling portion of the fixed plate 5 in the axial direction of the shaft 4. The ceiling portion of the fixed plate 5 has a stepped structure so that the oil seal 13 does not slip out upward. The surfaces of the sliding plate 6 and the fixed plate 5 that come into contact with each other may have any of the shapes in Embodiments 1 to 4, as long as they have a stepped structure that allows the oil seal 13 to be placed between the tip end portion of the sliding plate 6 and the ceiling portion of the fixed plate 5. Furthermore, after the oil seal 13 is placed on the fixed plate 5, the shaft 4 passes through the oil seal 13, and due to the spring force of the oil seal 13, the inner surface 14 of the oil seal 13 abuts against the shaft 4 at least two points, and the outer surface 15 of the oil seal 13 comes into surface contact with the fixed plate 5 at least one point.

[0029] According to the exhaust device 100 for an internal combustion engine of embodiment 5, a cylindrical oil seal 13 is arranged between the fixed plate 5 and the shaft 4 as a means for sealing the gap between the housing 2 and the shaft 4, and the oil seal 13 and the shaft 4 are configured so that they abut over their entire circumference at at least two points, and the oil seal 13 and the fixed plate 5 are in surface contact over their entire circumference at at least one point.Therefore, even if manufacturing tolerances occur in assembled parts such as the housing 2 and shaft 4 of the internal combustion engine and the shaft 4 is positioned at a slight tilt, the spring force of the oil seal 13 will seal the gap between the fixed plate 5 and the shaft 4 that sandwich the oil seal 13, preventing exhaust gas leakage.

[0030] Although the present disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not exemplified are conceivable within the scope of the technology disclosed in this specification, including, for example, cases where at least one component is modified, added, or omitted, and cases where at least one component is extracted and combined with components of another embodiment. Various aspects of the present disclosure are summarized below as appendices.

[0031] (Appendix 1) An exhaust system for an internal combustion engine, comprising: a pipe through which exhaust gas flows; a housing having a through-hole therein connected to one radial end of the pipe; a valve that opens and closes the pipe to control the flow rate of the exhaust gas; and a shaft that is disposed in the through-hole of the housing and serves as a rotation axis of the valve, a fixing member press-fitted into the through hole of the housing and rotatably supporting the shaft; a sliding member that is press-fitted in the axial direction of the shaft and slidably contacts the fixed member; an elastic member that biases the sliding member in a direction pressing the sliding member against the fixed member; The sliding member and the fixed member have mutually contacting surfaces which have complementary conical or curved shapes, and are fitted together with their entire circumferences contacting at least one point. (Appendix 2) The exhaust device for an internal combustion engine described in Appendix 1, characterized in that the through hole of the housing has a cylindrical shape with two stages of different diameters, the fixed member is press-fitted into the first stage, and the sliding member is disposed in the second stage having a diameter smaller than that of the first stage. (Appendix 3) 3. The exhaust system for an internal combustion engine according to claim 1, wherein the sliding member and the fixed member are a pair of sliding and fixed plates made of carbon, stainless steel, or ceramic material. (Appendix 4) 4. The exhaust system for an internal combustion engine according to claim 3, wherein the surfaces of the sliding member and the fixed member that come into contact with each other are coated with a metal such as nickel plating, nickel chrome, or nitriding. (Appendix 5) The exhaust device for an internal combustion engine according to any one of Supplementary Note 1 to Supplementary Note 4, characterized in that the elastic member includes a spring holder fixed to an end of the shaft that penetrates the fixed member and protrudes from the housing, and a spring that is provided on the outer periphery of the housing and urges the spring holder in a direction that protrudes from the housing, and the sliding member abuts against the fixed member when the shaft is pulled in the axial direction. (Appendix 6) 6. The exhaust device for an internal combustion engine according to any one of Supplementary notes 1 to 5, wherein the sliding member and the fixed member have mutually contacting surfaces that have complementary conical shapes, and an inclination angle of the tapered portion of the sliding member relative to the axis of the shaft and a draft angle of the tapered portion of the fixed member relative to the axis of the shaft are each within a range of 20° to 40°, and the inclination angle is smaller than the draft angle. (Appendix 7) 7. The exhaust device for an internal combustion engine according to claim 6, wherein a tip portion of the sliding member has a shape that extends from a surface where the sliding member and the fixed member abut against each other to the inside of the fixed member along a taper of the front fixed member, and the sliding member is fitted in a state where the tip portion of the sliding member extends into the inside of the fixed member. (Appendix 8) 6. The exhaust device for an internal combustion engine according to any one of claims 1 to 5, wherein the sliding member and the fixed member have mutually contacting surfaces that have complementary curved shapes, and the radius of curvature of the curvature of the sliding member is smaller than the radius of curvature of the curvature of the fixed member. (Appendix 9) The exhaust device for an internal combustion engine according to any one of Supplementary Note 1 to Supplementary Note 8, wherein the sliding member has a convex-shaped step provided in the axial direction of the shaft from a surface that abuts against the fixed member, the fixed member has a concave-shaped step that is complementary to the convex-shaped step, and the stepped portion of the sliding member is fitted into the stepped portion of the fixed member. (Appendix 10) 10. The exhaust device for an internal combustion engine according to claim 9, wherein a step portion between the sliding member and the fixed member has a cylindrical shape, and an inner diameter of the step portion of the fixed member is larger than an outer diameter of the step portion of the sliding member. (Appendix 11) 11. The exhaust device for an internal combustion engine according to any one of claims 1 to 10, further comprising a conical disc spring disposed around the entire circumference between the mutually abutting surfaces of the sliding member and the fixed member, wherein the sliding member and the fixed member are fitted together with a tapered front surface of the disc spring abutting against the sliding member and a back surface of the disc spring abutting against the fixed member. (Appendix 12) 12. The exhaust system for an internal combustion engine according to claim 1, further comprising a cylindrical oil seal disposed between the fixed member and the shaft, wherein the oil seal and the shaft abut over their entire circumferences at at least two points, and the shaft is supported by the fixed member in a state in which the oil seal and the fixed member abut over their entire circumferences at at least one point. (Appendix 13) 13. The exhaust system for an internal combustion engine according to claim 12, wherein the oil seal is made of a metal material, and a lubricant is applied between the oil seal and the shaft. (Appendix 14) 13. The exhaust system for an internal combustion engine according to claim 12, wherein the oil seal is fitted between a tip end portion of the sliding member and a ceiling portion of the fixed member in the axial direction of the shaft. [Explanation of symbols]

[0032] 100: exhaust system for internal combustion engine, 1: piping, 2: housing, 3: valve, 4: shaft, 5: fixed plate, 6: sliding plate, 7: spring holder, 8: spring, 9: press-fit pin, 10: bearing, 11: bushing, 12: disc spring, 13: oil seal.

Claims

1. An exhaust system for an internal combustion engine, comprising: a pipe through which exhaust gas flows; a housing having a through-hole therein connected to one radial end of the pipe; a valve that opens and closes the pipe to control the flow rate of the exhaust gas; and a shaft that is disposed in the through-hole of the housing and serves as a rotation axis of the valve, a fixing member press-fitted into the through hole of the housing and rotatably supporting the shaft; a sliding member that is press-fitted in the axial direction of the shaft and slidably contacts the fixed member; an elastic member that biases the sliding member in a direction pressing the sliding member against the fixed member; The sliding member and the fixed member have mutually contacting surfaces which are complementary in shape to each other and have a conical or curved shape, and are fitted together with their entire circumferences contacting at least one point.

2. 2. The exhaust device for an internal combustion engine according to claim 1, wherein the through hole of the housing has a cylindrical shape with two stages of different diameters, the fixing member is press-fitted into the first stage, and the sliding member is disposed in the second stage having a diameter smaller than that of the first stage.

3. 2. The exhaust system for an internal combustion engine according to claim 1, wherein the sliding member and the fixed member are a pair of sliding and fixed plates made of carbon, stainless steel, or ceramic material.

4. 4. The exhaust system for an internal combustion engine according to claim 3, wherein the surfaces of the sliding member and the fixed member that come into contact with each other are coated with a metal such as nickel plating, nickel chrome, or nitriding.

5. 2. The exhaust device for an internal combustion engine according to claim 1, wherein the elastic member has a spring holder fixed to the end of the shaft that penetrates the fixed member and protrudes from the housing, and a spring that is provided on the outer periphery of the housing and urges the spring holder in the direction of protruding from the housing, and the sliding member abuts against the fixed member when the shaft is pulled in the axial direction.

6. 2. The exhaust device for an internal combustion engine according to claim 1, wherein the sliding member and the fixed member have mutually contacting surfaces that have complementary conical shapes, and an inclination angle of the tapered portion of the sliding member relative to the axis of the shaft and a draft angle of the tapered portion of the fixed member relative to the axis of the shaft are each within a range of 20° to 40°, and the inclination angle is smaller than the draft angle.

7. 7. The exhaust device for an internal combustion engine according to claim 6, wherein a tip portion of the sliding member has a shape that extends inward from a surface where the sliding member and the fixed member abut against each other along a tapered portion of the front fixed member, and the sliding member is fitted in a state where the tip portion of the sliding member extends inside the fixed member.

8. 2. The exhaust device for an internal combustion engine according to claim 1, wherein the sliding member and the fixed member have mutually contacting surfaces that have complementary curved shapes, and the radius of curvature of the curve of the sliding member is smaller than the radius of curvature of the curve of the fixed member.

9. 2. The exhaust device for an internal combustion engine according to claim 1, wherein the sliding member has a convex-shaped step provided in the axial direction of the shaft from a surface that abuts against the fixed member, the fixed member has a concave-shaped step that is complementary to the convex-shaped step, and the stepped portion of the sliding member is fitted into the stepped portion of the fixed member.

10. 10. The exhaust device for an internal combustion engine according to claim 9, wherein the step portion between the sliding member and the fixed member is cylindrical, and the inner diameter of the step portion of the fixed member is larger than the outer diameter of the step portion of the sliding member.

11. 2. The exhaust device for an internal combustion engine according to claim 1, further comprising a conical disc spring disposed around the entire circumference between the mutually abutting surfaces of the sliding member and the fixed member, wherein the sliding member and the fixed member are fitted together with a tapered surface of the disc spring abutting against the sliding member and a back surface of the disc spring abutting against the fixed member.

12. 2. The exhaust device for an internal combustion engine according to claim 1, further comprising a cylindrical oil seal disposed between the fixed member and the shaft, wherein the oil seal and the shaft abut on their entire circumference at at least two points, and the shaft is supported by the fixed member in a state in which the oil seal and the fixed member abut on their entire circumference at at least one point.

13. 13. The exhaust system for an internal combustion engine according to claim 12, wherein the oil seal is made of a metal material, and a lubricant is applied between the oil seal and the shaft.

14. 13. The exhaust system for an internal combustion engine according to claim 12, wherein the oil seal is fitted between the tip end portion of the sliding member and the ceiling portion of the fixed member in the axial direction of the shaft.

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