JP2017008778A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve cooling efficiency of a common cylinder wall disposed between two bore regions adjacent to each other.SOLUTION: An internal combustion engine is provided with a first cylinder wall passage and a second cylinder wall passage in which a cooling medium flows through a common cylinder wall and a head gasket. The first cylinder wall passage has a crank shaft-side segment communicated to a water jacket, and a first head-side segment communicated to a top face of the head gasket. The second cylinder wall passage has a second head-side segment communicated to the top face of the head gasket and communicated to the first cylinder wall passage at a connection part. The head-side segment having a relatively large angle at an acute angle side to the top face of the head gasket, of the first and second head-side segments, is closed by a stopper.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a multi-cylinder internal combustion engine, and more particularly to an internal combustion engine in which a cooling medium passage is provided in a common cylinder wall provided between two adjacent bore regions.

  In one of the widely adopted structures in a cylinder block of a multi-cylinder internal combustion engine, two adjacent bore wall portions are partially integrated to form a common cylinder wall. With this structure, the interval between the cylinders can be narrowed, and the internal combustion engine can be reduced in size and weight.

  Patent Document 1 discloses a cylinder block in which first and second inclined cooling water passages are provided so as to cross each other through the common cylinder wall in order to cool such a common cylinder wall portion. ing. The first and second inclined cooling water passages have different inclination angles with respect to the deck surface. The lower open end of the first inclined cooling water passage is open to the water jacket below the upper end of the piston at the bottom dead center, so that relatively low-temperature cooling water can be used. Has been.

Japanese Patent Laid-Open No. 7-119541

  However, in the cylinder block of Patent Document 1, when the cooling water flowing into the first and second inclined cooling water passages from the water jacket moves to the cylinder head side from the intersection of both passages, Of the head side segment (that is, the portion closer to the cylinder head than the intersecting portion), more cooling water may flow into the head side segment having a larger acute angle with respect to the deck surface. As a result, sufficient cooling water does not flow to the other head side segment, and the common cylinder wall may be insufficiently cooled.

  An object of the present invention is to improve the cooling efficiency of a region near a combustion chamber in a common cylinder wall.

The first aspect of the present invention is:
An internal combustion engine configured to include a cylinder block, a head gasket, and a cylinder head block,
The cylinder block includes a water jacket, at least one common cylinder wall provided between two adjacent bore regions, and a deck surface on which the head gasket is to be placed,
A first cylinder wall passage and a second cylinder wall passage through which a cooling medium flows are provided inside the at least one common cylinder wall;
The first cylinder wall passage has a crankshaft side segment communicating with the water jacket and a first head side segment communicating with the deck surface, and the crankshaft side segment and the first head side segment are connected to each other. Connected to each other in parts,
The second cylinder wall passage has a second head side segment communicating with the deck surface and communicating with the first cylinder wall passage at the connection portion,
An internal combustion engine configured according to any one of the following (i) to (iii).
(I) Of the first and second head side segments, one head side segment having a relatively large acute angle with respect to the deck surface is closed by a plug.
(Ii) Of the first and second head side segments, the end portion on the deck surface side of one head side segment having a relatively large acute angle with respect to the deck surface is blocked by a blocking element. Has been.
(Iii) Of the first and second head side segments, one head side segment having a relatively large acute angle with respect to the deck surface, and the head so as to communicate with the one head side segment One coupling passage is constituted by one head gasket passage hole provided in the gasket and one cylinder head block communication passage communicating with the one head gasket passage hole and the common passage in the cylinder head block,
Of the first and second head side segments, the other head side segment, the other head gasket through hole provided in the head gasket so as to communicate with the other head side segment, and the other head gasket passage. The other coupling passage is configured by the other cylinder head block communication passage communicating with the hole and the common passage,
The minimum value of the cross-sectional area of the one coupling passage is made smaller than the minimum value of the cross-sectional area of the other coupling passage.

  In this aspect, of the first and second head side segments, one head side segment having a relatively large acute angle with respect to the upper surface of the head gasket is closed, or one of the head side segments is closed. The flow resistance of one coupling passage passing through the head side segment is made larger than the flow resistance of the other coupling passage passing through the other head side segment. Therefore, the circulation of the cooling medium in the other head side segment is promoted. The other head-side segment has a relatively small acute angle with respect to the upper surface of the head gasket, and therefore extends more in the region near the combustion chamber than the one head-side segment. . Accordingly, by promoting the circulation of the cooling medium in the other head side segment, it is possible to promote the cooling of the region in the vicinity of the combustion chamber having a large calorific value in the common cylinder wall. In addition, the cross-sectional area in this invention means the area in the cross section orthogonal to the extension direction (namely, longitudinal direction) of a channel | path.

Another aspect of the present invention provides:
The internal combustion engine is configured according to the above (iii),
The one head side segment is partially blocked by a stopper, so that the minimum cross-sectional area of the one coupling passage is smaller than the minimum cross-sectional area of the other coupling passage. An internal combustion engine characterized by the above.

  In this mode, in addition to the same advantages as the first mode, there is an advantage that the cross-sectional area of the head side segment can be easily controlled. In addition to fitting a plug having a shape corresponding to the head side segment, a plug may be formed inside the cylinder block portion of the head side segment by welding beads or brazing beads. it can.

Another aspect of the present invention provides:
The internal combustion engine is configured according to the above (iii),
The opening in the deck surface of the one head side segment is partially blocked by a blocking element, so that the minimum value of the cross-sectional area of the one coupling passage is the minimum of the cross-sectional area of the other coupling channel. An internal combustion engine characterized by being made smaller than the value.

  In this mode, in addition to the same advantages as the first mode, there is an advantage that the cross-sectional area of the head side segment can be easily controlled on the deck surface. For example, a head gasket, a weld bead, or a brazed bead disposed on the deck surface can be used as the closing element.

Preferably,
When viewed in the axial direction of the two bore regions,
The opening on the deck surface of the one head side segment is disposed on the first side with respect to the narrowed position where the interval between the two adjacent bore regions is the minimum,
The opening on the deck surface of the other head side segment is disposed on a second side opposite to the first side with respect to the narrowed position,
The connecting portion is disposed on the first side.

  In this aspect, since the opening of the other head side segment is disposed on the opposite side of the connection portion across the narrowed position, the vicinity of the combustion chamber is suitably cooled by the other head side segment. can do. In this case, it is particularly preferred that the first side is the intake side and the second side is the exhaust side.

It is a top view which shows the cylinder block in the internal combustion engine which concerns on 1st Embodiment of this invention. It is the sectional view on the AA line of FIG. It is the BB sectional view taken on the line of FIG. It is sectional drawing which shows the cylinder block in the internal combustion engine which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows the cylinder block in the internal combustion engine which concerns on 3rd Embodiment of this invention. It is sectional drawing which shows the principal part of the internal combustion engine of the modification using a closure element. It is sectional drawing which shows the principal part of the internal combustion engine of the modification which uses the lower surface of a cylinder head block as a closure element. It is sectional drawing which shows the principal part of the internal combustion engine of the modification which controls the minimum value of the cross-sectional area of a coupling path.

  Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment]
FIG. 1 is a plan view showing a cylinder block 1 in an internal combustion engine according to a first embodiment of the present invention. In FIG. 1, the cylinder block 1 has four bore regions 2 for accommodating the pistons. The four bore regions 2 are generally cylindrical and are arranged in series, that is, arranged in a row. The present invention is not limited to a four-cylinder engine, and can be applied to an engine having a plurality of arbitrary cylinders.

  The cylinder block 1 includes a bore wall portion 3 and an outer wall portion 5. The bore wall 3 has a shape in which approximately four cylindrical shapes are connected in a row so as to define the four bore regions 2. The outer wall 5 is provided outside the bore wall 3 and defines a water jacket space 4 with the bore wall 3. The bore wall 3 and the outer wall 5 are connected at the bottom of the water jacket space 4 as shown in FIG. 3, and are integrally formed of the same material, for example, by casting using a mold. A cooling water inlet 4 a connected to the water jacket space 4 is provided on one end surface of the cylinder block 1. An iron cylinder liner 6 is fitted on the inner peripheral surface of the bore wall 3 in order to provide wear resistance.

  The water jacket space 4 is generally formed in a shape of four cylinders connected in a row, that is, in a single ring shape surrounding the four bore regions 2 in plan view, and the axial direction of the piston (the vertical direction in FIG. 2). ). The cylinder block 1 has a so-called open deck structure, and the water jacket space 4 opens to the upper surface of the cylinder block 1, that is, the deck surface 7. The deck surface 7 is coupled to a cylinder head (not shown) via a head gasket (not shown). A screw hole 8 is formed outside the water jacket space 4. A head bolt is inserted into the screw hole 8 in order to fix a cylinder head (not shown).

  A common cylinder wall 9 is provided between two bore regions 2 adjacent to each other. The cylinder head 1 of this embodiment has four bore regions 2 and three common cylinder walls 9.

  As shown in FIG. 2, a first cylinder wall passage 11 and a second cylinder wall passage 12 through which the cooling medium flows are provided inside each common cylinder wall 9. The second cylinder wall passage 12 branches from the first cylinder wall passage 11 at the connection portion 13. In other words, the lower end portion of the second cylinder wall passage 12 is connected to the first cylinder wall passage 11 at the connection portion 13. The first cylinder wall passage 11 and the second cylinder wall passage 12 are both formed linearly by a drill and have a circular cross section.

  The first cylinder wall passage 11 includes a first crankshaft side segment 11 c that communicates with the water jacket space 4 and a first head side segment 11 h that communicates with the deck surface 7. The first crankshaft side segment 11c and the first head side segment 11h are connected by a connecting portion 13. The first cylinder wall passage 11 has a circular cross section, and its extending direction is inclined with respect to the orthogonal direction of the deck surface 7. And an oval first deck opening 11a. The first jacket opening 11j, which is a connecting portion of the first cylinder wall passage 11 with the water jacket space 4, is partly or entirely more than the upper end portion P of the piston when it is at bottom dead center. You may be located in the lower side (namely, the side far from the deck surface 7).

  The second cylinder wall passage 12 has a second head side segment 12 h that communicates with the deck surface 7 and communicates with the first cylinder wall passage 11. The second cylinder wall passage 12 has an elliptical second deck opening 12 a in the deck surface 7. The second cylinder wall passage 12 in the first embodiment does not have a crankshaft side segment and is configured only from the second head side segment 12h.

  The diameter of the first head side segment 11h is larger than that of the first crankshaft side segment 11c, whereby the cross-sectional area of the first head side segment 11h in the cross section is made larger than that of the first crankshaft side segment 11c. Yes. The first head side segment 11 h starts on the deck surface 7 and ends at the connection portion 13. The cross sectional areas of the first crankshaft side segment 11c of the first cylinder wall passage 11 and the second head side segment 12h of the second cylinder wall passage 12 are equal to each other.

  In the AA cross section of FIG. 1 shown in FIG. 2, that is, the cross section orthogonal to the arrangement direction of the plurality of bore regions 2, the first cylinder wall passage 11 and the second cylinder wall passage 12 have vertical axes (that is, They are inclined in the same direction with respect to the imaginary axis in the moving direction of the piston. The acute angle α formed by the first head-side segment 11 h with respect to the deck surface 7 is larger than the acute angle β formed by the second head-side segment 12 h with respect to the deck surface 7. The angle β is preferably set to 25 ° or less, for example. The first head-side segment 11h is completely closed (ie, closed in a substantially leak-free manner) by fitting a cylindrical stopper 14 corresponding to the inner shape thereof, thereby The cross-sectional area of the flow path extending through the first head side segment 11h is set to zero. As described above, since the diameter of the first head side segment 11h of the first cylinder wall passage 11 is larger than that of the first crankshaft side segment 11c, an engagement step portion is suitable for seating the plug 14 at a desired position. Formed. However, the cross-sectional area in the cross section of the first head side segment 11h may be equal to that of the first crankshaft side segment 11c.

  The first deck opening 11a of the first cylinder wall passage 11 is disposed on the first side, that is, the intake side with respect to the constriction position 15 where the interval between the two adjacent bore regions 2 is minimized. The second deck opening 12 a of the first cylinder wall passage 12 is disposed on the second side, that is, the exhaust side, which is opposite to the first side (that is, the intake side) with respect to the constriction position 15. The connection portion 13 is disposed on the first side, that is, the intake side with respect to the constriction position 15. The first jacket opening 11j, which is a connection portion of the first cylinder wall passage 11 with the water jacket space 4, is arranged on the first side, that is, the intake side with respect to the constriction position 15.

  In the cylinder block 1 configured as described above, cooling water such as so-called LLC (long-life coolant) is supplied from the cooling water inlet 4a (FIG. 1) into the water jacket space 4 by a water pump (not shown). The The cooling water flows around the bore wall 3 and then flows from the upper surface of the cylinder block 1 into a water jacket space (not shown). On the other hand, a part of the cooling water flows from the vicinity of the bottom of the water jacket space 4 into the first crankshaft side segment 11c of the first cylinder wall passage 11 through the first jacket opening 11j, and passes through the connecting portion 13. Similarly, the cylinder head flows through the second cylinder wall passage 12, that is, the second head side segment 12h, and from the second deck opening 12a via a cylinder head block communication passage (not shown) provided in the cylinder head. It flows in a common passage (not shown) provided in. A plurality of second head side segments 12h from a plurality of common cylinder walls 9 are connected to the common passage.

  In the present embodiment, the first and second head-side segments 11h and 12h extend through one head-side segment having a relatively large acute angle with respect to the deck surface 7, that is, the first head-side segment 11h. The minimum value of the cross-sectional area of the flow path is made zero by the plug 14. Therefore, the circulation of the cooling medium in the other head side segment, that is, the second head side segment 12h is promoted. In each common cylinder wall 9, the temperature tends to rise particularly on the exhaust side near the deck surface 7. The other head-side segment, that is, the second head-side segment 12h has a relatively small angle β with respect to the deck surface 7, and therefore is closer to the combustion chamber than the first head-side segment 11h. Will extend more. Therefore, by promoting the circulation of the cooling medium in the second head side segment 12h, it is possible to promote the cooling of the common cylinder wall 9 in the vicinity of the deck surface 7 having a large calorific value.

  The first head side segment, that is, the first deck opening 11a, which is an opening in the deck surface 7 of the first head side segment 11h, is located with respect to the constriction position 15 where the interval between the two bore regions 2 adjacent to each other is minimized. The first side, i.e., the intake side. The other head side segment, that is, the second deck opening 12a which is an opening in the deck surface 7 of the second head side segment 12h is a second side opposite to the first side with respect to the constriction position 15. On the exhaust side. The connecting portion 13 is disposed on the first side, that is, the intake side with respect to the constriction position 15. Therefore, the second head side segment 12h can be extended over a relatively long region in the common cylinder wall 9, and the vicinity of the combustion chamber can be suitably cooled.

  The first jacket opening 11j, which is a connection portion of the first cylinder wall passage 11 with the water jacket space 4, is arranged on the first side, that is, the intake side with respect to the constriction position 15. Therefore, a relatively low temperature cooling medium can be used, and cooling efficiency can be promoted. When the water pump is stopped or operating at a low speed, the temperature distribution in the water jacket space 4 is noticeably uneven, and the temperature rise of the cooling water tends to be slow at the bottom of the water jacket far from the combustion chamber. There is. In this embodiment, since a relatively low part of the cooling medium in the water jacket space 4 can be used, the flow of the cooling water via the first cylinder wall passage 11 and the second cylinder wall passage 12 is caused by natural convection. It can be promoted and the boiling of cooling water can be suppressed.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 4 is a sectional view showing the cylinder block 101 in the internal combustion engine according to the second embodiment of the present invention. In FIG. 4, a first cylinder wall passage 111 and a second cylinder wall passage 112 through which the cooling medium flows are provided inside the common cylinder wall 9. In the second embodiment, in the cross section shown in FIG. 4, that is, the cross section orthogonal to the arrangement direction of the plurality of bore regions 2, the first cylinder wall passage 111 and the second cylinder wall passage 112 are in relation to the vertical axis. They are inclined in opposite directions. The first jacket opening 111j, which is a connecting portion of the first cylinder wall passage 111 with the water jacket space 4, is disposed on the second side, that is, the exhaust side with respect to the constriction position 15. A part or all of the first jacket opening 111j may be located below the upper end portion P of the piston when it is at the bottom dead center (that is, the side far from the deck surface 7). Since the remaining configuration is the same as that of the first embodiment, the same reference numerals are given and detailed description thereof is omitted.

  In the second embodiment, the connection portion 113 is disposed on the first side, that is, the intake side with respect to the constriction position 15, whereas the first jacket opening 111j and the second deck opening 112a are the second side, That is, since it is arranged on the exhaust side, the total path length of the first cylinder wall passage 111 and the second cylinder wall passage 112 becomes relatively long, and the cooling efficiency can be promoted.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 5 is a cross-sectional view showing a cylinder block 201 in an internal combustion engine according to the third embodiment of the present invention. In FIG. 5, a first cylinder wall passage 211 and a second cylinder wall passage 212 through which the cooling medium flows are provided inside the common cylinder wall 9. In the third embodiment, in the cross section shown in FIG. 4, that is, the cross section orthogonal to the arrangement direction of the plurality of bore regions 2, the first cylinder wall passage 211 and the second cylinder wall passage 212 are in relation to the vertical axis. The second cylinder wall passage 212 has a second crankshaft side segment 212c in addition to the second head side segment 212h. The second crankshaft side segment 212c is open to the water jacket space 4 on the first side relative to the constriction position 15, that is, on the intake side. Since the remaining configuration is the same as that of the second embodiment, the same reference numerals are given and detailed description thereof is omitted.

  In the third embodiment, since the second crankshaft side segment 212c opened to the intake side is provided in addition to the configuration of the second embodiment, one of the first and second crankshaft side segments 211c and 212c The common cylinder wall 9 can be cooled even if it is blocked by foreign matter or deposits. Moreover, when the 2nd crankshaft side segment 212c is not obstruct | occluded, a comparatively low temperature cooling water can be utilized and cooling efficiency can be accelerated | stimulated.

  As mentioned above, although embodiment of this invention was described, each embodiment shown here can be variously deformed. First, in each of the above embodiments, the first head-side segments 11h, 111h, 211h are closed by fitting the plugs 14 having shapes corresponding to these, but in the present invention, this is completely closed. It is not essential and only a part of the cross-sectional area can be closed to control the minimum value. For this purpose, instead of the cylindrical plug 14, for example, a plug having a shape in which a part of a cylindrical outer peripheral surface is cut out in the axial direction can be used. For the same purpose, a plug having an axial through hole may be used. In addition, a plug can also be formed by performing welding or brazing within at least one head side segment.

  Of the first and second head side segments, the opening on the deck surface 7 of the head side segment having a relatively large acute angle with respect to the deck surface 7 is closed on the deck surface 7. It may be at least partially occluded by the element. As the closing element, for example, as shown in FIG. 6, a head gasket G disposed on the deck surface 7 when the cylinder block 1 and the cylinder head H are coupled can be used. The opening in the deck surface 7 of the head-side segment 311h can be completely closed (that is, closed in a substantially leak-free manner). This configuration has an advantage that the cross-sectional area of the flow path extending through the first head side segment 311h can be easily controlled on the deck surface. As the closing element, a weld bead or a brazed bead may be used.

  In the present invention, the lower surface of the cylinder head block can be used as a closing element. For example, as shown in FIG. 7, the head gasket G disposed on the deck surface 7 of the cylinder block 1 is provided with a head gasket through hole G1 having a diameter substantially equal to the head side segment 311h. Cylinder head block H is fixed. As a result, the opening in the deck surface 7 of the head-side segment 311h can be completely closed (that is, closed in a substantially leak-free manner) by the lower surface of the cylinder head block H.

  As another modification, in order to promote cooling of the common cylinder wall 9 in the vicinity of the deck surface 7 having a large calorific value, a coupling passage composed of a head side segment, a head gasket through hole, and a cylinder head block communication passage is provided. The minimum value of the cross-sectional area may be controlled.

  In the modification shown in FIG. 8, the first head side segment 411h has a relatively large acute angle with respect to the deck surface 7 as compared to the second head side segment 412h. The head gasket G is provided with a first head gasket through hole G41 so as to communicate with the first head side segment 411h. A first cylinder head block communication passage H11 is provided so as to communicate with the one head gasket passage hole G41 and the common passage H1 in the cylinder head block H. The first head side segment 411h, the first head gasket through hole G41, and the first cylinder head block communication passage H11 constitute a first coupling passage 451 that joins the water jacket 4 and the common passage H1.

  The head gasket G is provided with a second head gasket through hole G42 so as to communicate with the second head side segment 412h. A second cylinder head block communication passage H12 is provided so as to communicate with the second head gasket through hole G42 and the common passage H1. The second head side segment 412h, the second head gasket through hole G42, and the second cylinder head block communication passage H12 constitute a second coupling passage 452 that joins the water jacket 4 and the common passage H1.

  The opening area of the first head gasket through hole G41 is smaller than the opening area of the second head gasket through hole G42. In other words, the gasket G functions as a closing element configured to partially close the opening in the deck surface 7 of the first head side segment 411h. With the above configuration, the minimum value of the cross-sectional area of the first coupling passage 451 is made smaller than the minimum value of the cross-sectional area of the second coupling passage 452. As a result, in the modified example of FIG. 8, the circulation of the cooling medium in the second head side segment 412h is promoted, so that the region in the vicinity of the deck surface 7 having a large heat generation amount in the common cylinder wall 9 is cooled. Can be promoted. In addition, in order to control the cross-sectional areas of the first coupling passage 451 and the second coupling passage 452, another closing element for completely or partially closing the opening in the deck surface 7 of the first head side segment 411h. A plug for completely or partially closing the first head side segment 411h or a plug for completely or partially closing the first cylinder head block communication passage H11 may be used. Furthermore, as long as the minimum value of the cross-sectional area of the first coupling passage 451 is smaller than the minimum value of the cross-sectional area of the second coupling passage 452, the opening in the deck surface 7 of the second head side segment 412h is formed. A blocking element for partially blocking, a plug for partially blocking the second head side segment 412h, or a plug for partially blocking the second cylinder head block communication passage H12 may be used.

  The arrangement of the first cylinder wall passage and the second cylinder wall passage is not limited to that of each of the above-described embodiments. For example, the intake side and the exhaust side may be reversed from the above-described embodiments. In each said embodiment, although the 1st cylinder wall channel | path and the 2nd cylinder wall channel | path were provided in all the common cylinder walls, you may provide only in a part of common cylinder wall.

  At least one of the first cylinder wall passage and the second cylinder wall passage may be formed by a method other than a drill, such as laser light, electric discharge machining, or casting.

  The engine of the present invention is not limited to one mounted on a vehicle, but may be a generator engine. As the type of engine, the present invention may be applied not only to a gasoline engine but also to a diesel engine. In each of the above embodiments, an inline engine is shown, but the present invention is not limited to this, and the present invention can be applied to engines of V type, W type, horizontally opposed type, and the like. The engine may be a cross flow type or a turn flow type.

  In each of the above embodiments, the structure for cooling the common cylinder wall using cooling water is shown, but the present invention is not limited to this, and oil or other fluid can be poured into the water jacket space 4 as a cooling medium. It is.

  Embodiments of the present invention are not limited to the above-described embodiments, but include all modifications, applications, and equivalents included in the spirit of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Bore area | region 3 Bore wall part 4 Water jacket space 7 Deck surface 9 Common cylinder wall 11, 111, 211 1st cylinder wall path 11h, 111h, 211h, 311h, 411h 1st head side segment 11c, 111c, 211c , 411c First crankshaft side segment 11j, 111j, 211j First jacket opening 12, 112, 212 Second cylinder wall passage 12h, 112h, 212h Second head side segment 212c Second crankshaft side segment 212j Second jacket opening 13 , 113, 213, 413 Connection portion 15 Narrow position G Head gasket G1, G41, G42 Head gasket through hole H Cylinder head H1 Common passage H11 First cylinder head block communication passage H12 Second cylinder head block Communication passage

Claims (5)

An internal combustion engine configured to include a cylinder block, a head gasket, and a cylinder head block,
The cylinder block includes a water jacket, a common cylinder wall provided between two adjacent bore regions, and a deck surface on which the head gasket is to be placed,
A first cylinder wall passage and a second cylinder wall passage through which a cooling medium flows are provided inside the common cylinder wall;
The first cylinder wall passage has a crankshaft side segment communicating with the water jacket and a first head side segment communicating with the deck surface, and the crankshaft side segment and the first head side segment are connected to each other. Connected to each other in parts,
The second cylinder wall passage has a second head side segment communicating with the deck surface and communicating with the first cylinder wall passage at the connection portion,
An internal combustion engine configured according to any one of the following (i) to (iii):
(I) Of the first and second head side segments, one head side segment having a relatively large acute angle with respect to the deck surface is closed by a plug.
(Ii) Of the first and second head side segments, the end portion on the deck surface side of one head side segment having a relatively large acute angle with respect to the deck surface is blocked by a blocking element. Has been.
(Iii) Of the first and second head side segments, one head side segment having a relatively large acute angle with respect to the deck surface, and the head so as to communicate with the one head side segment One coupling passage is constituted by one head gasket passage hole provided in the gasket and one cylinder head block communication passage communicating with the one head gasket passage hole and the common passage in the cylinder head block,
Of the first and second head side segments, the other head side segment, the other head gasket through hole provided in the head gasket so as to communicate with the other head side segment, and the other head gasket passage. The other coupling passage is configured by the other cylinder head block communication passage communicating with the hole and the common passage,
The minimum value of the cross-sectional area of the one coupling passage is made smaller than the minimum value of the cross-sectional area of the other coupling passage. The internal combustion engine according to claim 1,
The internal combustion engine is configured according to the above (iii),
The one head side segment is partially blocked by a stopper, so that the minimum cross-sectional area of the one coupling passage is smaller than the minimum cross-sectional area of the other coupling passage. An internal combustion engine characterized by the above. The internal combustion engine according to claim 1,
The internal combustion engine is configured according to the above (iii),
The opening in the deck surface of the one head side segment is partially blocked by a blocking element, so that the minimum value of the cross-sectional area of the one coupling passage is the minimum of the cross-sectional area of the other coupling channel. An internal combustion engine characterized by being made smaller than the value. An internal combustion engine according to any one of claims 1 to 3,
When viewed in the axial direction of the two bore regions,
The opening on the deck surface of the one head side segment is disposed on the first side with respect to the narrowed position where the interval between the two adjacent bore regions is the minimum,
The opening on the deck surface of the other head side segment is disposed on a second side opposite to the first side with respect to the narrowed position,
The internal combustion engine, wherein the connecting portion is disposed on the first side. An internal combustion engine according to claim 4,
The internal combustion engine according to claim 1, wherein the first side is an intake side, and the second side is an exhaust side.