JP2007247432A - Exhaust port liner of internal combustion engine and method of manufacturing cylinder head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deformation and damage by stress of an exhaust port liner 31. <P>SOLUTION: This exhaust port liner 31 arranged in an exhaust port 2 by enveloped casting, is a double tube of combining an inner pipe 36 and an outer pipe 32 so as to have an air layer. Mutually joined upstream side end parts 35 and 39 are formed as the free end displaceable in the axial direction, without being welded to a base material of a cylinder head 1. Downstream end flange parts 33 and 37 on the downstream side are mutually superposed, and sandwiched and fixed by an exhaust manifold 42, to become the fixed end. The inner pipe 36 has an annularly continuing bead part 38 for allowing the expansion in the axial direction. The outer pipe 32 has annularly continuing first bead part 341 and second bead part 342 for allowing the expansion in the axial direction. The first bead part 341 swells to the outer peripheral side, and the second bead part 342 is recessed to the inner peripheral side. Since the upstream side end parts 35 and 39 are the free end, the stress is easily absorbed by the respective bead parts. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust port liner disposed on an inner peripheral surface of an exhaust port in order to suppress a decrease in exhaust temperature at an exhaust port of an internal combustion engine.

  In order to suppress a decrease in the exhaust temperature, it has been conventionally practiced to arrange a cylindrical exhaust port liner made of a material having a lower heat transfer coefficient on the inner peripheral surface of the exhaust port. For example, an aluminum alloy In many cases, an exhaust port liner made of a separate member is attached to the cylinder head by casting, when a cylinder head made of such a casting is cast.

In Patent Document 1, an exhaust port liner having a length almost the entire length of the exhaust port extending from the vicinity of the valve seat to the port opening on the side surface of the cylinder head is cast during cylinder head casting, and one end (upstream end) on the valve seat side. And the other end (downstream end) on the port opening surface side is a free end that is not joined to the base material of the cylinder head by interposing a heat insulating material.
JP 2003-286897 A

  In the above configuration, since the upstream end of the exhaust port liner is provided adjacent to the valve seat, the stress of the exhaust port liner due to thermal expansion is transmitted to the valve seat and the valve seat may be lifted.

  Further, during the operation of the internal combustion engine, the thermal expansion of the base material of the cylinder head is larger than that of the exhaust port liner. Therefore, the upstream side portion of the exhaust port liner having a complicated shape has a fixed valve seat side. Tensile stress is generated between the upstream end, and cracks and breakage are likely to occur.

  An exhaust port liner of an internal combustion engine according to the present invention comprises an inner pipe and an outer pipe formed by joining an upstream end and a downstream end to each other so as to form a double pipe having an air layer therebetween, and a cylinder It is casted downstream from the valve guide of the exhaust port of the head, and its upstream end is configured as a free end that can be displaced in the axial direction with respect to the base material of the cylinder head, and the downstream end is It is characterized by being configured as a fixed end sandwiched and fixed with the exhaust manifold.

  Also, the cylinder head manufacturing method of the present invention is a port liner composed of an inner pipe and an outer pipe formed by joining an upstream end and a downstream end to each other so as to form a double pipe having an air layer therebetween. Is casted at a position downstream of the valve guide of the exhaust port so that it does not weld to the base material of the cylinder head when casting the cylinder head, and its upstream end is axially directed to the base material of the cylinder head. After casting, the exhaust manifold mounting surface of the cylinder head where the downstream end is located is machined after casting, and the flange extending to the outer peripheral side of the downstream end is the exhaust manifold mounting It is characterized by being exposed to the surface.

  That is, in the present invention, for example, the cylinder head is made of an aluminum alloy or the like, and the exhaust port liner is made of a stainless steel plate, but the exhaust port liner disposed in the cylinder head by cast-in when the cylinder head is cast is They are not welded to each other and are held in the base material by physical engagement due to their shapes. Therefore, the upstream end is not a complicated shape that does not engage with the base material, thereby providing a free end that can be displaced in the axial direction with respect to the base material. Thereby, the displacement by a relative thermal expansion difference with a base material is accept | permitted, and excessive stress generation | occurrence | production is avoided. On the other hand, the downstream end is exposed to the exhaust manifold mounting surface of the cylinder head, and is sandwiched between the exhaust manifold fixed to the mounting surface and becomes a fixed end. This avoids unnecessary movement and vibration of the exhaust port liner.

  According to the present invention, relative expansion and contraction of the exhaust port liner with respect to the base material does not affect the valve seat, and cracks and breakage of the exhaust port liner due to excessive stress can be prevented.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a cross section of a cylinder head 1 of an internal combustion engine provided with an exhaust port liner 31 according to the present invention. The cylinder head 1 is integrally cast of a light alloy such as an aluminum alloy, and has a combustion chamber 4 formed in a lower surface, that is, a cylinder block mounting surface 5 and a cross flow type intake port. 3 and an exhaust port 2 are formed. Inside the cylinder head 1, water jackets 11, 12, 13, and 14 are integrally formed by a core so as to surround the combustion chamber 4, the intake port 3, and the exhaust port 2.

  A side surface of the cylinder head 1 on the exhaust valve side is machined as an exhaust manifold mounting surface 23, and the exhaust port 2 has a downstream end opened to the exhaust manifold mounting surface 23. In the exhaust port 2, the downstream portion near the exhaust manifold mounting surface 23 is substantially linear, and the upstream portion close to the combustion chamber 4 is loose toward the combustion chamber 4 from the vicinity where the valve guide 21 is located. Curved to form a letter shape. The exhaust port liner 31 is provided in a downstream portion close to a straight line in the exhaust port 2, particularly in a downstream portion of the exhaust port liner 31 while avoiding the valve guide 21 having a complicated shape.

  FIG. 2 is a cross-sectional view showing the details of the exhaust port liner 31. The exhaust port liner 31 has a substantially cylindrical shape as a whole, and is a double pipe having an air layer therebetween. An inner tube 36 and an outer tube 32 made of a stainless steel plate having a low thermal conductivity are combined. The inner pipe 36 has an inner peripheral surface that is a substantial flow path surface of the exhaust port 2, and the upstream end 39 is straight without bending (in other words, a simple cylindrical shape). It extends. On the other hand, the upstream end 35 of the outer tube 32 has a diameter along the outer peripheral surface of the inner tube 36 via a stepped portion 32D that is bent in a step shape from the central main body portion of the outer tube 32 to the inner peripheral side. The upstream end 35 of the outer tube 32 and the upstream end 39 of the inner tube 36 are joined to each other. Note that the two may be firmly joined together in advance by welding or the like, or may be simply tightly fitted.

  On the other hand, the downstream end portion of the outer pipe 32 located on the exhaust manifold mounting surface 23 is formed as a downstream end flange portion 33 that extends obliquely toward the outer peripheral side. On the other hand, the downstream end portion of the inner pipe 36 has a downstream end flange portion 37 that obliquely expands to the outer peripheral side at the same angle, and these downstream end flange portions 33 and 37 overlap each other. It is joined to. This portion may also be firmly joined by welding or the like, or may be left in a state of being simply fitted. Here, at the downstream end of the inner pipe 36, as shown in FIGS. 5 and 6, relative to the convex portion 51 partially protruding in the axial direction on the inner peripheral side of the downstream end flange portion 37. In particular, there are provided wavy portions 50 that are alternately arranged in the circumferential direction so that concave portions 52 that are recessed in the axial direction form a waveform. The axial front end surface of the convex portion 51 is substantially perpendicular to the center line of the inner tube 36, whereas the axial front end surface of the concave portion 52 is inclined continuously to the downstream end flange portion 37. It has a surface. Therefore, more specifically, the downstream end flange portion 33 of the outer pipe 32 is joined across both a part of the outer peripheral side of the recess 52 and the downstream end flange portion 37 (see FIG. 6). That is, as shown in FIG. 5, the overall radial width of the inclined surface is L1, and the radial width of the inclined surface of the recess 52 therein is L2.

  The inner tube 36 has an annular continuous bead portion 38 for allowing axial expansion and contraction at two axial positions. The bead portion 38 is formed to bulge toward the outer peripheral side so that its cross section is U-shaped or C-shaped, has a relatively narrow axial width, and protrudes into the air layer. The diameter is set so that the maximum outer diameter portion does not contact the inner peripheral surface of the outer tube 32.

  Further, the outer tube 32 includes a first bead portion 341 and a second bead portion 342 that are continuously connected in an annular shape to allow expansion and contraction in the axial direction. These bead portions 341 and 342 are processed so as to have a wider width in the axial direction than the bead portion 38 of the inner tube 36 and have a C-shaped cross section, and are particularly located on the upstream side. The first bead portion 341 bulges toward the outer peripheral side, and the second bead portion 342 located on the downstream side is recessed toward the inner peripheral side. The diameter of the second bead portion 342 is also set so as not to contact the inner tube 36.

  FIG. 2 shows a state in which the exhaust port liner 31 having the above-described configuration is disposed on the cylinder head 1 by casting. That is, the exhaust port liner 31 in which the inner pipe 36 and the outer pipe 32 formed in the above-described shape are integrally assembled is set in a mold together with a core corresponding to the exhaust port 2 and cast with an aluminum alloy or the like. It is. In this state, as a result of the base material of the cylinder head 1 solidifying along the outer shape of the outer pipe 32, the exhaust port liner 31 is physically fixed and held, but the outer surface of the outer pipe 32 and the base of the cylinder head 1 are held. It is not welded to the material surface. Therefore, the upstream end portions 35 and 39 of the exhaust port liner 31 are free ends that can be displaced in the axial direction with respect to the base material of the cylinder head 1. More specifically, since the stepped portion 32D contacts the stepped portion of the base material, it cannot be displaced from the position in FIG. 2 to the extension side (left side in the figure), but can be relatively displaced to the contraction side (right side in the figure). is there.

  On the other hand, the downstream end flange portions 33 and 37 of the exhaust port liner 31 are exposed on the exhaust manifold mounting surface 23, and the mounting flange 41 of the exhaust manifold 42 shown in FIGS. By this, it clamps and fixes between the base materials of the cylinder head 1 located in the back part of the downstream end flange parts 33 and 37. That is, since the downstream end flange portions 33 and 37 extending to the outer peripheral side cannot be displaced to the left in FIG. 2, the fixed end cannot be displaced in the axial direction at all when the exhaust manifold 42 is attached. It becomes.

  Here, the exhaust manifold mounting surface 23 is machined so as to become a plane with a predetermined accuracy after the cylinder head 1 is cast together with the exhaust port liner 31. At this time, the downstream end flange portion 33 is processed. , 37 can also be cut at the same time. Also in this case, since the downstream end flange portions 33 and 37 are inclined obliquely as shown in FIG. 2, the outer peripheral edge is only partly scraped off, and serves as a fixed end for fixing the exhaust port liner 31. The function is never lost.

  According to the exhaust port liner 31 configured as described above, it is made of a stainless steel plate having a low thermal conductivity and has an air layer in the middle, so that a high heat insulating effect is obtained and the exhaust gas temperature is kept high. it can. As a result, for example, early activation of the catalyst in a downstream catalytic converter (not shown) can be achieved, or cooling loss can be suppressed.

  Next, the operation when the temperature of the cylinder head 1 changes will be described.

  FIG. 3 shows a state in which the engine is stopped and the entire cylinder head 1 is at a very low temperature. Under this condition, the thermal contraction of the cylinder head 1 is relatively large with respect to the exhaust port liner 31. Therefore, the step portion 32D of the outer tube 32 is pressed to the right in the drawing by the base material of the cylinder head 1 and compressive stress is generated in the outer tube 32, but the first bead portion 341 bulging to the outer peripheral side is formed. Since it is elastically deformed so as to shrink away from the base material in the axial direction, the stress is absorbed and deformation and breakage of the outer tube 32 are avoided.

  When the downstream end portion of the exhaust port liner 31 is pushed out to the exhaust manifold 42 side due to the thermal contraction of the cylinder head 1, in addition to the downstream end flange portions 33 and 37, the wavy portion 50 (convex portion) 51) abuts against the exhaust manifold 42 (gasket 40) and is reliably restrained, so that its position is reliably held as a fixed end.

  FIG. 4 shows a state when the internal combustion engine is at a high temperature due to high load operation. Under this condition, the thermal expansion of the cylinder head 1 is relative to the exhaust port liner 31 (outer pipe 32). Big. Accordingly, a tensile stress is generated in the outer tube 32. At this time, the second bead portion 342 recessed toward the inner peripheral side can be elastically deformed so as to extend in the axial direction away from the base material. Absorbed and deformation or breakage of the outer tube 32 is avoided. At this time, the upstream end portions 35 and 39 can be displaced in the axial direction, and a slight gap 36H can be formed between the step portion 32D of the outer tube 32 and the base material.

  Further, since only the inner pipe 36 becomes hot due to the high-temperature exhaust gas, compressive stress due to thermal expansion acts on the inner pipe 36, but the stress is similarly absorbed by the bead portion 38 of the inner pipe 36, and the inner pipe 36. Deformation and damage of the are avoided.

1 is a cross-sectional view of an entire cylinder head including an exhaust port liner according to the present invention. Sectional drawing of the exhaust port provided with the exhaust port liner. Sectional drawing which shows the state at the time of low temperature. Sectional drawing which shows the state at the time of high temperature. The front view which looked at the downstream end part of the exhaust port liner from the front. Sectional drawing of the principal part along the AA line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cylinder head 2 ... Exhaust port 31 ... Exhaust port liner 32 ... Outer pipe 36 ... Inner pipe 33, 37 ... Downstream end flange part 35, 39 ... Upstream end part 38 ... Bead part 341 ... First bead part 342 ... Second bead section

Claims (6)

  It consists of an inner pipe and an outer pipe that are joined to each other at the upstream end and the downstream end so as to form a double pipe having an air layer between them, and is located downstream of the valve guide of the exhaust port of the cylinder head. A fixed end that is casted and whose upstream end is configured as a free end that is axially displaceable with respect to the base material of the cylinder head, and whose downstream end is sandwiched and fixed with the exhaust manifold An exhaust port liner for an internal combustion engine, characterized by being configured as follows.   2. The exhaust port liner for an internal combustion engine according to claim 1, wherein the inner pipe is formed with an annular continuous bead portion that allows axial expansion and contraction at one or a plurality of locations in the axial direction. .   The outer tube has a first bead portion and a second bead portion that are annularly continuous to allow expansion and contraction in the axial direction, the first bead portion bulges toward the outer peripheral side, and the first bead portion The exhaust port liner for an internal combustion engine according to claim 1 or 2, wherein the two bead portions are recessed toward the inner peripheral side.   At the downstream end, a downstream end flange portion is formed on each of the inner tube and the outer tube so as to extend obliquely toward the outer peripheral side, and both overlap each other so that the base material of the cylinder head and the exhaust gas are overlapped with each other. The exhaust port liner for an internal combustion engine according to any one of claims 1 to 3, wherein the exhaust port liner is sandwiched between the manifold and the manifold.   At the downstream end portion of the inner pipe, convex portions that partially protrude in the axial direction and concave portions that are relatively recessed in the axial direction are alternately arranged in the circumferential direction on the inner peripheral side of the downstream end flange portion. An exhaust port liner for an internal combustion engine according to any one of claims 1 to 4, further comprising: A port liner composed of an inner pipe and an outer pipe formed by joining an upstream end and a downstream end to each other so as to form a double pipe having an air layer between the cylinder head when the cylinder head is cast. In order to prevent welding with the base material of the exhaust port, it is cast at a position downstream of the valve guide of the exhaust port, and its upstream end is made a free end that can be displaced axially with respect to the base material of the cylinder head, and after casting The exhaust manifold mounting surface of the cylinder head where the downstream end is located is machined, and the flange portion that extends to the outer peripheral side of the downstream end is exposed to the exhaust manifold mounting surface. A method for manufacturing a cylinder head of an internal combustion engine.

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