JP2011236870A - Exhaust device in internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce flow resistance of exhaust gas in an exhaust port, in an internal combustion engine configured to: be integrally provided with a boss 9 which projects inward at a portion where a valve shaft 7a of an exhaust valve 7 on the inner surface of the exhaust port 5 from a combustion chamber 4 penetrates; and support the valve shaft at the boss.SOLUTION: The device includes a passage cross section-reducing part 11 at a portion which is further on the upstream side than the boss 9 on the inner surface of the exhaust port 5. The passage cross section-reducing part reduces a passage cross section at the portion on the upstream side to: be substantially equal to a passage cross section at the boss; or be smaller than the passage cross section at the boss.

Description

  The present invention relates to an exhaust device for exhausting exhaust gas after combustion in each cylinder in an internal combustion engine.

  In general, as shown in FIG. 7, an exhaust device in an internal combustion engine is provided with an exhaust port 25 extending from a combustion chamber 24 on the lower surface of a cylinder head 23 that closes the top of a cylinder bore 22 in a cylinder block 21. Exhaust gas after combustion is exhausted by opening and closing a valve seat opening 26 to the combustion chamber 24 by an exhaust valve 27 provided in the valve seat opening 26.

  In this type of exhaust device, as is well known, a boss portion 29 projects inwardly into a portion of the inner surface of the exhaust port 25 through which the valve shaft 27a of the exhaust valve 27 passes. The exhaust valve 27 has improved durability by supporting the valve bush 30 that is slidably fitted to the valve shaft 27a of the exhaust valve 27 by the boss portion 29. In addition, the overall height of the internal combustion engine is reduced (for example, see Patent Document 1).

JP 09-105330 A

  However, in the conventional exhaust device, the passage cross-sectional area in the exhaust port 25 is temporarily increased from the valve seat opening 26 to the combustion chamber 24 toward the outlet 28 or is substantially equalized. Since a boss portion 29 for supporting the valve shaft 27a is integrally projected at a portion of the inner surface of the port 25 through which the valve shaft 27a of the exhaust valve 27 passes, As shown in FIG. 8, the passage cross-sectional area at each location along the axial direction becomes the smallest passage cross-sectional area Sx at the boss portion 29, and the upstream and downstream portions of the boss portion 29 The shape is such that it is larger than the minimum passage cross-sectional area Sx, and the passage cross-sectional area is locally sharply narrowed (constricted) at the boss portion 29. , The throttle resistance will occur.

  This throttle resistance is relatively large due to a local change in the cross-sectional area of the passage, and this throttle resistance is directly added to the exhaust gas flow resistance in the exhaust port, so that the exhaust gas flow resistance is reduced. Since it greatly increases, there has been a problem that exhaust efficiency is lowered, and output and fuel consumption are greatly reduced.

  An object of the present invention is to provide an exhaust device that can reduce the flow resistance of exhaust gas.

In order to achieve this technical problem, claim 1
“The cylinder head that closes the top of the cylinder bore is provided with an exhaust port extending from the combustion chamber on its lower surface, and an exhaust valve that opens and closes the valve seat opening is provided at the valve seat opening of the exhaust port to the combustion chamber. Further, a boss portion projecting inward is integrally provided at a portion of the inner surface of the exhaust port through which the valve shaft of the exhaust valve passes, and the valve shaft is supported by the boss portion. In an internal combustion engine,
Reducing the passage cross-sectional area of the upstream portion of the inner surface of the exhaust port to be substantially equal to the passage cross-sectional area of the boss portion; or A passage cross-sectional area reduction portion is provided that reduces the passage cross-sectional area to be smaller than the passage cross-sectional area at the boss portion. "
It is characterized by that.

Claim 2
“The valve seat opening of the exhaust port according to claim 1, wherein the valve seat opening of the exhaust port is located at a portion eccentric from the center of the cylinder bore when viewed from the axial direction of the cylinder bore, Is provided at a location adjacent to the inner peripheral surface of the cylinder bore as viewed from the axial direction of the cylinder bore.
It is characterized by that.

Furthermore, claim 3
“In the first aspect of the present invention, two exhaust ports are provided for one combustion chamber, and the valve seat opening of each exhaust port is viewed from the axial direction of the cylinder bore, and the cylinder bore The passage cross-sectional area reduction portion in each exhaust port is shaped to reduce the passage cross-sectional area in a part of the exhaust port in the circumferential direction, and the axis of the cylinder bore Provided at a location adjacent to the inner peripheral surface of the cylinder bore as viewed from the direction. "
It is characterized by that.

  According to claim 1, the passage cross-sectional area in each part of the exhaust port along the axial direction thereof is substantially the same as the minimum passage cross-sectional area in the part of the boss part. It is possible to avoid the occurrence of a portion in which the passage cross-sectional area is abruptly narrowed (constricted) locally at the location of the boss portion 7 because they are equal or smaller.

  As a result, the flow rate of the exhaust gas in the exhaust port is higher in the portion upstream of the boss projecting into the exhaust port than in the conventional case, but the location of the boss in the exhaust port. Therefore, it is ensured that a large throttle resistance is added to the exhaust gas flow resistance in the exhaust port by eliminating the local constricted (constricted) portion as in the conventional case. Since it can be avoided, the flow resistance of the exhaust gas can be reduced, and the exhaust efficiency can be improved. As a result, the output and fuel consumption can be improved.

  According to the second aspect of the present invention, the passage cross-section reduction by the passage cross-sectional area reduction portion in the exhaust port is performed at a location adjacent to the inner peripheral surface of the cylinder bore in the exhaust port when viewed from the axial direction of the cylinder bore. As a result, the passage cross section in the upstream portion of the exhaust port from the boss portion is widened near the center of the cylinder bore and narrowed near the inner peripheral surface of the cylinder bore. Thus, the exhaust gas can flow smoothly into the exhaust port at the central portion of the cylinder bore, and the flow resistance of the exhaust gas can be further reduced.

  Furthermore, according to claim 3, when the exhaust port is configured in two for one combustion chamber, the exhaust gas flows out into each exhaust port in the central portion of the cylinder bore more smoothly. be able to.

It is a vertical front view of the principal part which shows 1st Embodiment. FIG. 2 is a sectional view taken along the line II-II in FIG. 1. FIG. 3 is a sectional view taken along line III-III in FIG. 1. FIG. 4 is a sectional view taken along line IV-IV in FIG. 1. It is a figure which shows the change of the passage sectional area in an exhaust port in the said 1st Embodiment. It is a plane sectional view showing a 1st embodiment. It is a vertical front view of the principal part which shows the conventional example. It is a figure which shows the change of the passage sectional area in an exhaust port in the conventional example.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  1 to 5 show a first embodiment.

  In this figure, reference numeral 1 denotes a cylinder block having a cylinder bore 2, and reference numeral 3 denotes a cylinder head fastened so as to close the cylinder bore 2 on the upper surface of the cylinder block 1.

  The cylinder head 3 is formed with an exhaust port 5 extending from the combustion chamber 4 in addition to a recess formed in the lower surface of the cylinder head 3.

  The valve seat opening 6 to the combustion chamber 4 in the exhaust port 5 is eccentric outward from the center 2a of the cylinder bore 2 in the radial direction as seen from the axial direction of the cylinder bore 2 as shown in FIG. The valve seat opening 6 is provided with a poppet type exhaust valve 7 for opening and closing the valve seat opening 6, while the outlet 8 of the exhaust port 5 It opens to the side surface 3 a of the cylinder head 3.

  A portion of the inner surface of the exhaust port 5 through which the valve shaft 7a of the exhaust valve 7 penetrates is integrally provided with a boss portion 9 projecting inward, and the boss portion 9 slides on the valve shaft 7a. The valve bush 10 that is freely fitted is supported.

  Further, a portion of the inner surface of the exhaust port 5 on the upstream side of the boss portion 9, more precisely, a portion between the boss portion 9 and the valve seat opening 6, has a passage cut-off in the portion. A passage cross-sectional area reduction portion 11 is provided that reduces the area so as to be substantially equal to the passage cross-sectional area Sx at the boss portion 9.

  As shown in FIGS. 2 and 4, the passage cross-sectional area reducing portion 11 has a shape that reduces the cross-sectional area of the passage in a part of the exhaust port 5 in the circumferential direction as seen from the axial direction of the cylinder bore 2. , A portion adjacent to the inner peripheral surface of the cylinder bore 2, that is, an inner portion of the curved portion in a portion in which the exhaust port 5 is bent from the downward direction toward the valve seat opening 6 to the outlet portion 8. .

  According to this configuration, the passage cross-sectional area of each portion of the exhaust port 5 along the axial direction of the exhaust port 5 is entirely the upstream portion of the boss portion 9 as shown in FIG. It is substantially equal to the minimum passage cross-sectional area Sx at the location, and it is possible to avoid the formation of a portion where the passage cross-sectional area is sharply narrowed (constricted) locally at the location of the boss portion 9.

  As a result, the flow rate of the exhaust gas in the exhaust port 5 is faster than the conventional case in the portion upstream of the boss portion 9 protruding into the exhaust port 5. As the boss portion 9 does not have a locally constricted (constricted) portion as in the conventional case, a large throttle resistance is added to the exhaust gas flow resistance in the exhaust port 5. It can be avoided reliably.

  In another embodiment, a portion of the inner surface of the exhaust port 5 on the upstream side of the boss portion 9, more precisely, between the boss portion 9 and the valve seat opening 6. The passage cross-sectional area in the portion is reduced by the passage cross-sectional area reducing portion 11 to be smaller than the minimum passage cross-sectional area Sx at the location of the boss portion 7 as shown by a two-dot chain line A in FIG. be able to.

  Also in this configuration, the exhaust gas flow velocity in the exhaust port 5 is faster in the upstream portion than the boss portion 9 protruding into the exhaust port 5 as compared with the conventional case. In the port 5, there is no locally restricted (narrowed) portion at the boss portion 9 as in the conventional case, and the exhaust gas flow resistance in the exhaust port 5 is large. It is possible to reliably avoid adding the aperture resistance.

  In the first embodiment, the valve seat opening 6 of the exhaust port 5 is located at a position eccentric from the center 2a of the cylinder bore 2 when viewed from the axial direction of the cylinder bore 2, while the exhaust port 5 The passage cross-sectional area reducing portion 11 in the port 5 is shaped to reduce the passage cross-sectional area in a part of the exhaust port 5 in the circumferential direction so that the inner periphery of the cylinder bore 2 can be seen from the axial direction of the cylinder bore 2. It is provided at a location adjacent to the surface.

  With this configuration, the reduction of the passage cross section by the passage cross-sectional area reducing portion 11 in the exhaust port 5 is a portion adjacent to the inner peripheral surface of the cylinder bore 2 in the exhaust port 5 when viewed from the axial direction of the cylinder bore 2. As a result, the passage cross section in the portion of the exhaust port 5 upstream of the boss portion 9 becomes wider near the center of the cylinder bore 2 and narrower near the inner peripheral surface of the cylinder bore 2 in the passage cross section. As a result, the exhaust gas can flow smoothly into the exhaust port at the central portion of the cylinder bore 2.

  Next, FIG. 6 shows a second embodiment.

  The second embodiment is a case where one cylinder bore 2 (combustion chamber 4) is constituted by two exhaust ports 5 ', 5 ". In this case as well, each of the exhaust ports 5', 5" is provided. As in the first embodiment, the exhaust ports 5 ′ and 5 ″ are located on the downstream side of the boss portion 9, more precisely, the boss portion 9 and the valve seat opening 6. The passage cross-sectional area reducing portions 11 ′ and 11 ″ are respectively provided in the portion between the boss portion 9 and the passage cross-sectional area is reduced so as to be substantially equal to the passage cross-sectional area at the boss portion 9 or The boss portion 9 is reduced so as to be smaller than the passage sectional area.

  In addition to this, the valve seat openings 6 ', 6 "of the exhaust ports 5', 5" are arranged side by side at a position eccentric from the center 2a of the cylinder bore 2 when viewed from the axial direction of the cylinder bore 2. On the other hand, the passage cross-sectional area reducing portions 11 ', 11 "in the exhaust ports 5', 5" are shaped so as to reduce the passage cross-sectional area in a part of the exhaust ports 5 ', 5 "in the circumferential direction. As seen from the axial direction of the cylinder bore 2, the cylinder bore 2 is provided at a location adjacent to the inner peripheral surface.

  Note that the exhaust ports 5 ′ and 5 ″ in the second embodiment merge with one outlet portion 8 ′ at the outlet on the side surface 3 a of the cylinder head 3.

  According to this configuration, when the exhaust port is configured to be two for one combustion chamber, the exhaust gas flows into the exhaust ports 5 ′ and 5 ″ at the central portion in the cylinder bore 2 more smoothly. Can be.

1 Cylinder block 2 Cylinder bore 3 Cylinder head 4 Combustion chamber 5, 5 ', 5 "Exhaust port 6, 6', 6" Exhaust port valve seat opening 7 Exhaust valve 7a Exhaust valve valve shaft 8, 8 'Exhaust port Outlet part 9 Boss part 10 Valve bushing 11, 11 ', 11 "Passage cross-sectional area reduction part

Claims (3)

A cylinder head that closes the top of the cylinder bore is provided with an exhaust port extending from the combustion chamber on the lower surface thereof, and an exhaust valve that opens and closes the valve seat opening is provided at the valve seat opening of the exhaust port to the combustion chamber. , An internal surface of the exhaust port in which the valve shaft of the exhaust valve passes is integrally provided with an inwardly protruding boss portion, and the boss portion is configured to support the valve shaft. In the institution
Reducing the passage cross-sectional area of the upstream portion of the inner surface of the exhaust port to be substantially equal to the passage cross-sectional area of the boss portion; or An exhaust system for an internal combustion engine, characterized in that a passage cross-sectional area reducing portion that reduces so as to be smaller than a passage cross-sectional area at the boss portion is provided.   The valve seat opening of the exhaust port according to claim 1, wherein the valve seat opening of the exhaust port is located at a portion eccentric from the center of the cylinder bore when viewed from the axial direction of the cylinder bore, An internal combustion engine having a shape that reduces the cross-sectional area of the passage in a part of the exhaust port in the circumferential direction, and is provided at a location adjacent to the inner peripheral surface of the cylinder bore as seen from the axial direction of the cylinder bore Exhaust system.   In the first aspect of the present invention, two exhaust ports are configured for one combustion chamber, and the valve seat opening of each exhaust port is viewed from the axial direction of the cylinder bore. The passage cross-sectional area reduction portion in each exhaust port is arranged side by side in an eccentric position from the center, and the passage cross-sectional area is reduced in part in the circumferential direction of the exhaust port, so that the axial direction of the cylinder bore And an exhaust device for an internal combustion engine, which is provided at a location adjacent to the inner peripheral surface of the cylinder bore.

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