JP5780808B2 - Cylinder head structure and cone entrance structure - Google Patents

Description

  TECHNICAL FIELD The present invention relates to the structure of an engine cylinder head and an exhaust manifold, and in particular, a cylinder head in which a collecting portion in which exhaust ports are gathered is provided in the cylinder head, and an exhaust manifold having a catalyst outside the cylinder head is bolted. The shape of the exhaust port and the shape of the connection port of the exhaust manifold connected to the exhaust port.

  In recent years, a cylinder head of a multi-cylinder engine includes a type of engine in which exhaust ports are gathered inside the cylinder head, and exhaust gas is gathered by an exhaust manifold provided outside the cylinder head. This is intended to reduce the size of the engine, and in many cases, an exhaust manifold and a combustion catalyst carrier are connected downstream of the cylinder head outlet (exhaust port) through a pipe that changes its direction immediately.

  In Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-052546), an overhanging portion that protrudes outward from the side surface of the cylinder block is provided, and an exhaust collecting portion that collects exhaust ports from each cylinder is provided inside the overhanging portion. An invention is disclosed in which the dead space between the lower surface of the overhang portion and the side surface of the cylinder block is effectively used to reduce the size of the entire engine.

  FIG. 7 shows the outer surface shape of the cylinder head of Patent Document 1. An exhaust outlet 148 is formed on the side surface of the cylinder head 112. In addition to the spark plug insertion cylinder 121, a reinforcing wall 161 and a lead-out portion 149 are also formed on this surface. In the present invention, the cylinder head 112 is formed so that the height in the vertical direction is also reduced (as a whole is a flat shape), and the exhaust outlet 148 formed on the outer surface of the cylinder head 112 is also in the shape of a track (semicircles are linearly connected to each other). Connected to form a track).

  The exhaust outlet 148 is provided with a substantially cylindrical exhaust gas purification catalyst (not shown) following the exhaust pipe bent downward by 90 °. Further, an exhaust manifold is attached to the exhaust outlet 148 by fastening bolts. Boss portions 158a to 158c for that purpose are formed.

JP 2004-052546 A

  In order to reduce the size of the engine, it is necessary to reduce the size of the cylinder head and to handle the exhaust pipe as close to the engine as possible. However, turning the exhaust pipe near the engine means that the exhaust pipe is bent at a steep angle. On the other hand, since the exhaust gas is a high-temperature and high-speed gas, when it flows in the bent pipe, it tends to pass through the path with the highest speed.

  In particular, the exhaust gas immediately after coming out of the cylinder head has a high flow velocity. Therefore, in piping that bends greatly at the outlet of the cylinder head, the exhaust gas tends to have a difference in speed between the outside and inside of the bend. That is, the flow velocity of the exhaust gas passing through the path outside the bend with a large curvature radius is fast, and the flow velocity of the exhaust gas passing through the path inside the bend with a small curvature radius is slow. Then, the exhaust gas purification catalyst disposed immediately after the exhaust pipe bent greatly from the cylinder head outlet enters exhaust gas having a high flow velocity into a portion corresponding to the outside of the bend.

  The exhaust gas purification catalyst is activated in a predetermined temperature range. Accordingly, the activity of the catalyst is nonuniform between the portion where the exhaust gas is strongly hit and the portion where the exhaust gas is weak. Further, if exhaust gas continues to strike only a portion of the catalyst, only that portion becomes too hot and the catalyst function may be deactivated. That is, when trying to reduce the size of the cylinder head, it is necessary to ensure uniformity per gas to the exhaust gas purification catalyst.

  On the other hand, if the exhaust outlet of the cylinder head is made large in order to make the exhaust gas contact with the exhaust gas purification catalyst uniform, the sealing performance cannot be maintained in the attachment with the exhaust pipe. For example, in Patent Document 1, three bolt fastening bosses are provided, but the exhaust outlet 148 has a portion 200 protruding from the line connecting the boss portions. In such a state, the cylinder head and the exhaust pipe cannot be fastened with sufficient force. That is, if the line connecting the boss and the exhaust outlet overlap, the axial force of the bolt is not uniform and the sealing performance is lowered.

  The present invention has been conceived in view of the above-described problems, and improves the uniformity of the exhaust gas hitting the exhaust gas purification catalyst connected to the bent exhaust pipe immediately after the cylinder head. It is an object of the present invention to provide a cylinder head structure capable of firmly fastening an exhaust pipe. An exhaust manifold structure connected to the cylinder head is also provided.

More specifically, the cylinder head structure of the present invention is:
An outer shell having an exhaust outlet formed on the outer surface;
A collecting portion that aggregates downstream portions of exhaust ports from a plurality of cylinders is provided inside the outer shell, and an outlet of the collecting portion is communicated with the exhaust outlet inside the outer shell,
An engine cylinder head structure in which an exhaust gas purification catalyst is connected to the exhaust outlet on the downstream side, and a cone portion bent at a substantially right angle is bolted at a plurality of fastening points provided around the exhaust outlet on the outer surface. ,
When the shape of the exhaust outlet is the longitudinal direction of the crankshaft direction, it is formed in an oval shape that is long in the longitudinal direction,
The ellipse shape has a curvature radius on the upper side of the longest diameter in the longitudinal direction smaller than the curvature radius on the lower side,
The oval shape is located inside a line connecting the fastening points.

Moreover, the entrance structure of the cone part of the present invention is
An exhaust outlet of the cylinder head and an inlet structure of a cone portion arranged between the exhaust gas purifying catalyst which is arranged at right angles to the lower side as soon as it exits the exhaust outlet and is subsequently arranged,
A flange bolted to the exhaust outlet at a plurality of fastening points;
Entrance front Symbol cone portion forms a crankshaft direction of the engine when the longitudinal direction, a long oval shape in the longitudinal direction,
The ellipse shape has a curvature radius on the upper side of the longest diameter in the longitudinal direction smaller than the curvature radius on the lower side,
The oval shape is located inside a line connecting the fastening points.

  In the cylinder head structure of the present invention, the exhaust outlet formed in the outer shell of the cylinder head is a horizontally long ellipse, and the upper radius of curvature of the longest diameter is smaller than the lower radius of curvature. Since the lower exhaust gas flow rate can be made relatively faster than the upper exhaust gas flow rate, compared to the case where the upper and lower curvature radii are the same, the per-gas per catalyst gas Uniformity is improved.

  Moreover, since the exhaust outlet is located inside the line connecting the bolt fastening points of the cone portion, no overhang occurs. Therefore, the sealing performance of the fastening portion between the cylinder head and the cone portion can be kept highly airtight.

  The shape of the inlet of the exhaust manifold connected to the cylinder head structure is the same shape as the exhaust outlet of the cylinder head. Specifically, it is a horizontally long ellipse, and the upper radius of curvature of the longest diameter is made smaller than the lower radius of curvature. Accordingly, the flow rate of the exhaust gas on the lower side of the exhaust outlet can be made relatively faster than the flow rate of the upper exhaust gas, so that the upper and lower curvature radii are equal to the catalyst. The same effect as the cylinder head structure of the present invention that the uniformity per gas is improved.

It is a figure which shows the external appearance of the cylinder head structure of this invention. It is a figure which shows the AA cross section in FIG. It is the front (FIG. 3 (a)) and sectional drawing (FIG.3 (b)) of an exhaust outlet. It is a figure which shows the example of the exhaust outlet shape which is not applied to this invention. It is a figure which shows a mode that an ellipse is approximated by a circular arc. It is a figure which shows the fastening point around an exhaust outlet. It is a figure which shows the external appearance of the conventional cylinder head.

  The present invention will be described below with reference to the drawings. The following description exemplifies an embodiment of the present invention, and the following embodiment may be modified without departing from the gist of the present invention.

  FIG. 1 shows a perspective view of a cylinder head structure of the present invention. The cylinder head structure 1 of the present invention includes a cylinder head 10, a cone portion 12, and an exhaust gas purification catalyst (converter: hereinafter also simply referred to as “catalyst”) 14. The cylinder head 10 has an outer shell 10f, and the upper side and the lower side have a connecting surface 10c. The outer shell 10 f is the outer surface of the cylinder head 10.

  This is because the cylinder head 10 is airtightly connected to an upper portion of a cylinder block (not shown), and a head cover (or a rocker cover: not shown) is also airtightly fixed to the upper portion of the cylinder head 10. The height of the cylinder head 10 is represented by reference numeral 10h. Further, the cone portion 12 is provided with a flange 12f around the entrance 12i and is fastened to the cylinder head 10 with a bolt.

  The cylinder head 10 includes a water jacket (not shown) inside. The water jacket is a passage for flowing cooling water for cooling each part of the cylinder head 10, and has a cooling water intake port (not shown) and a cooling water outlet port 10w.

  FIG. 2 is a schematic diagram of the AA cross section of FIG. Referring to FIG. 2, the cylinder head 10 has an assembly portion 16 in which exhaust ports 15 a to 15 f (collectively referred to as “exhaust ports 15”) from each cylinder are gathered. Conventionally, the gathering portion 16 where the exhaust ports 15 gather is formed outside the cylinder head 10. However, the collecting portion 16 is formed inside the cylinder head 10 in order to reduce the size of the engine. In this embodiment, the case of three cylinders (17a to 17c) will be described, but the number of cylinders is not limited to three. Further, since the collecting portion 16 is formed as shown in FIG. 2, the crankshaft is arranged in a direction parallel to the arrow 18.

  Referring to FIG. 1 again, an exhaust outlet 20 is formed in the cylinder head 10. The exhaust outlet 20 is a through hole formed in the outer shell (side surface) 10 f of the cylinder head 10. The outlet of the collecting portion 16 of the exhaust port 15 is connected to the inside of the exhaust outlet 20. Therefore, when the exhaust outlet 20 is viewed from the outside, the inside of the collective portion 16 of the exhaust port 15 can be seen. A cone portion 12 also serving as an exhaust manifold is fastened to the outside of the exhaust outlet 20.

Co over down portion 12 has a substantially 90 ° bend structure downward as soon as it exits the exhaust outlet 20. An exhaust gas purification catalyst 14 is attached to the outlet 12 o of the cone portion 12. The outlet 12o of the cone portion 12 and the exhaust gas purification catalyst 14 are preferably joined by welding. This is because airtightness is necessary so that the exhaust gas does not leak, and because the portion is exposed to vibration, a strong connection is required.

  FIG. 3A shows the exhaust outlet 20 when the cylinder head 10 is viewed from the front. The exhaust outlet 20 has an oval shape. Here, the oval shape is a round shape that is formed by a smooth curve and has one maximum diameter axis in the horizontal direction along the outer shell of the cylinder head 10 and in the vertical direction that is the height direction of the cylinder head 10. The horizontal maximum diameter (hereinafter referred to as “horizontal maximum diameter 22”) is larger than the vertical maximum diameter (hereinafter referred to as “vertical maximum diameter 23”). The lateral direction coincides with the crankshaft direction 18.

  In addition, the inlet 12i of the cone part 12 connected with the exhaust outlet 20 has the same shape within a manufacturing tolerance range. This is because if the shapes of the exhaust outlet 20 of the cylinder head 10 and the inlet 12i of the cone portion 12 are different, the flow of exhaust gas does not flow smoothly and the effects of the present invention cannot be achieved.

  More specifically, it is divided into an upper shape 24 and a lower shape 26 with the lateral maximum diameter 22 as a boundary, and the upper shape 24 and the lower shape 26 are both elliptical. Since the overall shape is an ellipse, these upper and lower ellipses are combinations of ellipses having the same major axis (which coincides with the maximum horizontal diameter 22) and different flatness ratios. Here, the ellipse may include a shape that approximates the ellipse by a combination of arcs. This is because in the actual manufacture of the cylinder head, it may be difficult to manufacture a through hole having a shape in which accurate ellipses are combined.

  Further, the flatness of the upper shape 24 is smaller than that of the lower shape 26. The flatness is expressed by “1-b / a” where the major axis of the ellipse is a and the minor axis is b, “0” for a perfect circle, and “1” as it is crushed vertically. is there. Accordingly, the fact that the flatness of the upper shape 24 is smaller than that of the lower shape 26 means that the lower shape 26 is an ellipse crushed in the vertical direction. In other words, the short axis length (or ½ of the short axis length) in the ellipse of the lower shape 26 is shorter than the short axis length (or ½ of the short axis length) in the ellipse of the upper shape 22. A two-dot chain line 28 f drawn under the lower shape 26 in FIG. 3A shows an ellipse having the same short axis length as the upper shape 24.

  In FIG.3 (b), the conceptual diagram of the BB cross section of Fig.3 (a) is shown. An alternate long and two short dashes line 28s is the same as the two-dot chain line 28f in FIG. FIG. 3B shows the flow of exhaust gas from the cylinder head 10 to the converter 14. The cone portion 12 has a shape that continuously changes from an inlet 12 i having the same shape as the exhaust outlet 20 of the cylinder head 10 to an outlet 12 o connected to the exhaust gas purification catalyst 14. However, there may be a protrusion or a recess that controls the flow of the exhaust gas.

  If the upper shape 24 and the lower shape 26 of the exhaust outlet 20 are composed of the same ellipse (in the case of the two-dot chain line in FIG. 3B), in FIG. 3B, the lower end 20bb of the exhaust outlet 20 is The radius of curvature increases. On the other hand, when the lower shape 26 of the exhaust outlet 20 is composed of an ellipse having a large flatness (a more collapsed ellipse) (in the case of the solid line in FIG. 3B), in FIG. The radius of curvature at the lower end 20ab is reduced.

  Here, if the radius of curvature at the lower end 20bb of the exhaust outlet 20 is large as indicated by a two-dot chain line, the flow velocity of the exhaust gas 30bb flowing through this portion becomes slow, and the exhaust gas 30t passing through the upper end 20t of the exhaust outlet 20 is slow. The difference with the flow rate becomes large. In other words, from the viewpoint of hitting the gas to the catalyst 14, the catalyst 14 o far from the cylinder head 10 has a strong gas hit and the catalyst 14 i near the cylinder head 10 has a weak hit per gas. That is, the uniformity per gas deteriorates.

  On the other hand, the amount of exhaust gas flowing from the exhaust port 15 to the collecting portion 16 tends to decrease. Therefore, by reducing the radius of curvature at the lower end 20ab of the exhaust outlet 20, the flow velocity of the exhaust gas 30ab flowing through this portion is increased. That is, the cone portion 12 is bent and hits the catalyst 14 in a state where the difference from the flow velocity of the exhaust gas 30t flowing near the upper end 20t of the exhaust outlet 20 is small, and the uniformity per gas to the catalyst 14 is improved.

  In other words, when the exhaust pipe connected to the cylinder head 10 is arranged to bend approximately 90 degrees immediately after, the shape of the exhaust outlet 20 of the cylinder head 10 is an arc whose lower radius of curvature is larger than the upper radius of curvature. If it forms in (4), the flow velocity of the exhaust gas in the pipe cross section after bending can be rectified to a nearly uniform state.

  FIG. 4A shows a case where the exhaust outlet has a track shape 40. The track shape is a shape in which one circle is divided at the center and left and right semicircles 41a and 41b are connected by straight lines 42a and 42b. If the exhaust outlet 20 has the track shape 40, the outlet of the collecting portion 16 of the exhaust port 15 is also formed in the track shape 40. That is, the upper and lower walls of the collecting portion 16 are also flat at the center near the exit. In such a shape, a large amount of exhaust gas spreads to the left and right in the vicinity of the upper wall 40u, so that the exhaust gas flow velocity differs between the center and the left and right ends of the exhaust outlet. Therefore, the flow rate of the exhaust gas hitting the catalyst 14 cannot be made uniform.

  FIG. 4B shows an extreme example of FIG. The upper shape 24 is a semicircle 45 and the lower shape 26 is a straight line. When the exhaust outlet 20 has such a shape, a square shape 45c is generated at the corner. Since the cylinder head 10 is exposed to a strong heat cycle, such a square shape 45c causes stress concentration, which may cause a problem in durability of the cylinder head 10 itself.

  Referring to FIG. 3A again, as described above, in order to improve the uniformity per gas to the catalyst 14, the lower shape 26 of the exhaust outlet 20 is flattened vertically compared to the upper shape 24. Use an ellipse. The shape of the exhaust outlet 20 is defined by the ratio of the height of the upper shape 24 and the lower shape 26 to the maximum lateral diameter 22 of the exhaust outlet 20. This is because the ratio of the longitudinal maximum diameter 23 to the lateral maximum diameter 22 is important because the oval exhaust outlet 20 is provided in order to reduce the height 10h (see FIG. 1) of the cylinder head 10.

  Specifically, if the length of the lateral maximum diameter 22 is L, the height 24h of the upper shape 24 is preferably 0.3L to 0.4L, and the height 24h of the upper shape 24 and the height of the lower shape 26 The ratio of 26h is preferably between 1.5 and 2.0. Here, “height (24h and 26h)” means the distance from the long axis (lateral maximum diameter 22) that coincides with the upper shape 24 and the lower shape 26 to the farthest point, and the upper shape 24 and the lower shape 26 are In the case of an ellipse, it is half of each short axis length. When the height 24h of the upper shape 24 approaches 0.5L, it approaches a perfect circle (half), and the height 10h of the cylinder head 10 is increased to ensure a sufficient exhaust outlet area. As a result, the engine itself cannot be downsized. On the other hand, if the height of the upper shape 24 is smaller than 0.3 L, the exhaust outlet 20 itself becomes too flat, and the resistance to the flow of exhaust gas increases.

  Further, when the ratio of the height of the upper shape 24 and the lower shape 26 is increased, the flatness of the lower ellipse is increased, so that FIG. 4B is approached. On the other hand, when the height ratio approaches 1, the exhaust outlet approaches a perfect circle or a vertically symmetrical ellipse, and the exhaust gas uniformity deteriorates.

  The elliptical shape can be approximated by an arc. FIG. 5 shows how the ellipse of the upper shape 24 is approximated by an arc. The elliptical shape is approximated by the upper arc 24a and the upper arcs 24b on both sides. The rest of each arc is represented by a dotted line. Although not shown, the same can be applied to the ellipse of the lower shape 26, and the corresponding portions are a lower arc 26a and a lower arc 26b, respectively. That is, the shape of the exhaust outlet 20 in the present invention can be approximated by four arcs of an upper arc 24a, an upper arc 24b, a lower arc 26a, and a lower arc 26b. Each arc has a radius of curvature of R24a, R24b, R26a, and R26b, respectively.

  For example, assuming that the length of the lateral maximum diameter 22 is L, R24a is 0.8L, R24b is 0.3L, R26a is 1.5L, and R26b is 0.2L, one preferred embodiment of the exhaust outlet 20 is formed. be able to. Each value may be changed within a range of ± 0.05L.

  Here, the radius of curvature R24 at the position farthest from the lateral maximum diameter 22 in the upper shape 24 is referred to as the “curvature radius of the upper shape”. When the ellipse of the upper shape 24 is approximated by the above arc, the radius (R24a) of the upper arc 24a is the radius of curvature of the upper shape 24. Similarly, the curvature radius R26 at the position farthest from the lateral maximum diameter 22 in the lower shape 26 is referred to as a “curvature radius of the lower shape”. When the lower shape 26 is approximated by the arc, the radius (R26a) of the lower arc 26a is the radius of curvature of the lower shape 26.

  Further, even if the exhaust outlet 20 has a perfect elliptical shape, the curvature radii at the same point as above are referred to as “curvature radius of the upper shape” and “curvature radius of the lower shape”. It can be said that the shape of the exhaust outlet 20 in the cylinder head structure of the present invention is such that the curvature radius of the upper shape 24 is smaller than the curvature radius of the lower shape 26.

  The shape of the exhaust outlet 20 as described above also has an effect of improving the sealing performance with the cylinder head 10 when the cone portion 12 is attached. FIG. 6A shows bolt fastening points (50 a to 50 d) formed around the exhaust outlet 20. The exhaust outlet 20 of the cylinder head 10 also serves as an exhaust manifold, and is connected with a cone portion 12 that changes its direction substantially vertically downward immediately after exiting the exhaust outlet 20. Since the exhaust gas discharged from the exhaust outlet 20 is high temperature and high pressure, the cone portion 12 needs to be in close contact with the exhaust outlet 20 and firmly fixed.

  The fastening points (50a to 50d) are bolt holes into which bolts for fastening the cone portion 12 to the cylinder head 10 are screwed. The larger the number of bolts, the more firmly the bolts can be attached. However, the larger the number, the greater the number of work steps and the higher the cost.

  It is preferable that the cone portion 12 to be bolted to the oval exhaust outlet 20 is provided with a flange 12f around the opening and bolted with the flange 12f (see FIG. 1). However, since the cone portion 12 is bent downward immediately after exiting the cylinder head 10, even if the flange 12 f is arranged around the entire opening of the cone portion 12, the bolt in the shaded portion of the cone portion 12. It cannot be stopped. Therefore, it is necessary to perform fastening with the cylinder head 10 above and on the side of the exhaust outlet 20.

  The fastening bolts (that is, the fastening points) should be as close as possible, but the exhaust outlet protrudes from the line connecting the fastening point 50c and the fastening point 50d as shown by a two-dot chain line 28f in FIG. (This is referred to as an overhang state) is not sufficient in sealing performance in the bolt fastening between the cone portion 12 and the cylinder head 10, and the exhaust gas may leak.

  In this respect, since the shape of the exhaust outlet 20 of the cylinder head structure 1 of the present invention has a large radius of curvature R26 of the lower shape 26, the distance 52 between the upper fastening points (50a and 50b) and the lower fastening points (50c and 50d). There is no need to increase the size. That is, even with the cylinder head 10 having a short length (low in height 10 h), the cone portion 12 can be fastened without overhang. In other words, it can be said that the rigidity of the cone portion 12 fastened to the cylinder head 10 is improved because the curvature radius on the upper side of the cone portion 12 with a large amount of gas is increased. Therefore, the effect of reducing the radiated sound due to the gas can also be obtained.

  Further, as shown in FIG. 6 (b) taken along the line CC in FIG. 6 (b), the cylinder head structure 1 of the present invention is closer to the outer shell 10f than the bottom 53 of the screw hole at the fastening point 50 (50d). The tip 55t of the water jacket 55 is extended to the point. This is to alleviate the heat shock of the fastening bolt and prevent the screw from coming off. More specifically, the water jacket 55 is disposed at at least one of the fastening points 50.

  Here, “arranged on one side” means that a water jacket is arranged on either the upper, lower, left or right side of the fastening point. In other words, when viewed from the front of the cylinder head 10, the water jacket 55 does not need to be disposed on the entire circumference of the fastening point 50. Further, assuming that the diameter of the fastening point is RR, the tip 55t of the water jacket 55 is disposed close to a position closer to at least 3RR. This is because the fastening bolt cannot be cooled if it is installed away from the fastening point 50.

  The tip 55t of the water jacket 55 is disposed closer to the outer shell 10f of the cylinder head 10 than at least the bottom 53 of the fastening point 50. This is for cooling the fastening bolt. As described above, in the cylinder head structure 1 of the present invention, the water jacket 55 is disposed at least one of the fastening points 50 of the exhaust outlet 20 from the bottom 53 of the fastening point 50 to the outer shell 10f side. Since it is not exposed to a heat cycle with a large difference, problems such as bolt loosening are less likely to occur.

  As described above, in the cylinder head structure 1 of the present invention, the shape of the exhaust outlet 20 is an elliptical combination having different flatness ratios, so that the uniformity of the exhaust gas hitting the catalyst 14 is improved. The sealing performance can be maintained when the 12 is attached. Moreover, since the upper curvature radius R24 with a large amount of gas is increased, the rigidity of the exhaust manifold (cone portion 12) is improved, and the effect of reducing the emission sound due to the gas can be obtained. In addition, since the water jacket 55 of the cylinder head 10 is disposed up to the vicinity of the fastening point 50, screw unscrewing due to heat cycle hardly occurs. Further, the exhaust manifold inlet that is bolted to the cylinder head of the present invention also has the same structure as the exhaust outlet 20, so that the uniformity of the exhaust gas can be improved.

  The cylinder head structure of the present invention can be suitably used for a cylinder head of an internal combustion engine.

DESCRIPTION OF SYMBOLS 1 Cylinder head structure 10 Cylinder head 10f Outer shell 10h Height of cylinder head 12 Cone part 14 Exhaust gas purification catalyst (converter or catalyst)
DESCRIPTION OF SYMBOLS 15 Exhaust port 16 Collecting part 17 Cylinder 18 Crankshaft direction 20 Exhaust outlet 22 Horizontal maximum diameter 23 Vertical maximum diameter 24 Upper shape 24h Upper shape height 24a Upper arc 24b Upper part arc 26 Lower shape 26a Lower arc 26b Lower part arc 26h Lower shape height 30 Exhaust gas 40 Track shape 41a, 41b Semicircle 42a, 42b Straight line 45 Semicircular shape 50 Fastening point 52 Fastening point distance 53 Fastening point bottom 55 Water jacket R24 Upper shape radius of curvature R24a Upper arc Radius of curvature R24b radius of curvature of the upper arc

Claims (2)

An outer shell having an exhaust outlet formed on the outer surface;
A collecting portion that aggregates downstream portions of exhaust ports from a plurality of cylinders is provided inside the outer shell, and an outlet of the collecting portion is communicated with the exhaust outlet inside the outer shell,
The engine has a cylinder head structure in which an exhaust gas purification catalyst is connected to the exhaust outlet on the downstream side, and a cone portion bent at a substantially right angle is bolted at a plurality of fastening points provided around the exhaust outlet on the outer surface. And
When the shape of the exhaust outlet is the longitudinal direction of the crankshaft direction, it is formed in an oval shape that is long in the longitudinal direction,
The ellipse shape has a curvature radius on the upper side of the longest diameter in the longitudinal direction smaller than the curvature radius on the lower side,
The cylinder head structure, wherein the oval shape is located inside a line connecting the fastening points. An exhaust outlet of the cylinder head and an inlet structure of a cone portion arranged between the exhaust gas purifying catalyst which is arranged at right angles to the lower side as soon as it exits the exhaust outlet and is subsequently arranged ,
And a flange which is bolted in the plurality of fastening points before Sharing, ABS care outlet,
Entrance front Symbol cone portion forms a crankshaft direction of the engine when the longitudinal direction, a long oval shape in the longitudinal direction,
The ellipse shape has a curvature radius on the upper side of the longest diameter in the longitudinal direction smaller than the curvature radius on the lower side,
The entrance structure of a cone part, wherein the oval shape is located inside a line connecting the fastening points.