JP6623235B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine.

Conventionally, fuel efficiency of the internal combustion engine, in order to promote the combustion toward improvement in output, Oite the low and medium load area of the engine, to generate a tumble (vertical vortex) in intake air flowing into the combustion chamber fuel A structure that promotes mixing of air and air has been proposed (see, for example, Patent Document 1).
In the above proposal, the pair of intake valves are provided in the cylinder head so as to be aligned in the axial direction of the crankshaft, and the tip ends of the shaft portions of the pair of intake valves are closer to the umbrella side of the shaft portions. It is possible to promote the occurrence of tumble.

JP 2008-274853 A

In Patent Document 1, since the shaft portions of the pair of intake valves are not parallel, the pair of fitting holes into which the valve guides for guiding the shaft portions are fitted are not parallel. In the case of forming by processing, it is not possible to perform drilling at the same time, and the processing time becomes longer and the productivity is lowered.
An object of the present invention is to provide an internal combustion engine capable of promoting tumble flow generation in intake air and improving productivity.

This specification includes all the contents of the Japanese patent application and Japanese Patent Application No. 2006-001251 filed on January 6, 2016.
In order to solve the above-described problems, the present invention provides a cylinder head (14) with a combustion chamber (30) and intake / exhaust ports (21a, 21b) communicating with the combustion chamber (30). , 21b) are opened and closed by intake / exhaust valves (63, 73) passing through the intake / exhaust ports (21a, 21b), respectively, to the combustion chamber (30). ) Is provided with a partition wall (21h) for generating a tumble flow in the combustion chamber (30), and the intake air flowing through the intake port (21a) is vertically divided by the partition wall (21h). in the upper intake passage (35) and the internal combustion engine is diverted to the lower intake passage (36), the lower the intake passage formed in the lower side of the partition wall (21h) (36) is a low load A passage for flow of air for generating the tumble flow forcibly the lower intake passage (36), the width (W3) is directed to the combustion chamber (30) from the upstream side of the intake port (21a) is formed to be gradually wider brought to the horizontal width of the lower air intake passage (36) (W3), the smaller than the width (W2) of the upper air intake passage (35), before Symbol lower intake passage (36), the intake The height (H) in the plane orthogonal to the flow direction of the engine is formed so as to gradually decrease from the upstream side of the intake port (21a) toward the combustion chamber (30), and the lower intake passage (36) Is formed such that a cross-sectional area perpendicular to the direction of intake air flow is smaller than a cross-sectional area of the upper intake passage (35), and the lower intake passage (36) has a cross-sectional area perpendicular to the direction of intake air flow. , Serial, characterized in that it is formed so that the same or progressively increases as from the upstream side toward the combustion chamber (30) of the intake port (21a).

In the above configuration, wherein the partition wall (21h) lower intake passage (36) side of the lower surface (25d) is not good even substantially flat in cross-section.

In the above configuration, the lower surface (21m) of the inner surface (21j) of the intake port (21a) is the upper portion (21k) of the inner surface (21j) of the intake port (21a) on the surface orthogonal to the direction of intake air flow. ) but it may also be formed along the upper (21k) of the inner surface (21j) of said intake port so as to be approximately constant distance (21a) from.
Also, in the above configuration, the partition wall (21h) is in the upper intake passage (35) side, the center has an upper surface (25c) recessed from both ends, thin middle width, both ends are formed thickly May be.

  One of the upper and lower intake passages of the present invention is formed so that its lateral width gradually increases from the upstream side of the intake port toward the combustion chamber, so that one intake flow of the intake passage is in the intake port. Since the intake valve and the valve guide that guides the intake valve are widened so as to spread, the intake air can flow smoothly into the combustion chamber, and tumble can be easily generated in the combustion chamber. Thereby, even at the time of low load, combustion can be promoted by sufficiently mixing the fuel and air in the combustion chamber. Further, since the shape of the inner surface of the intake port is simply formed by casting or the like, the cylinder head can be easily manufactured and the productivity can be improved.

In addition, one of the intake passages is formed so that a cross-sectional area perpendicular to the direction of the intake air flow is the same or gradually increased from the upstream side of the intake port toward the combustion chamber, and therefore flows through one of the intake passages. An increase in inhalation resistance of inhalation can be suppressed.
In addition, one of the intake passages is formed such that the height in a plane orthogonal to the direction of the intake air flow gradually decreases from the upstream side of the intake port toward the combustion chamber. When released into the chamber, the upper and lower diffusion of the intake air can be suppressed, and the intake air can be squeezed and flowed in a direction in which a tumble flow in the combustion chamber tends to occur.

In addition, in the plane orthogonal to the direction of the flow of intake air, the lower portion of the inner surface of the intake port is formed along the upper portion of the inner surface of the intake port so as to be a substantially constant distance from the upper portion of the inner surface of the intake port. The intake performance due to the shape of the intake port can be made equivalent to that of an intake port not provided with a partition wall.
In addition, since one of the upper and lower intake passages is formed with a cross-sectional area perpendicular to the direction of the intake air flow smaller than the other cross-sectional area of the intake air passage, one intake passage narrows the intake air flow to reduce the intake air flow. It is possible to flow in a predetermined direction in the combustion chamber while increasing the flow velocity of the fuel, and to promote the generation of a tumble flow.

FIG. 1 is a cross-sectional view showing an internal combustion engine according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the cylinder head body. 3 is a cross-sectional view taken along line III-III in FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a schematic diagram showing an intake port, FIG. 5 (A) is a view showing an intake port of an example (this embodiment), and FIG. 5 (B) is a view showing an intake port of a comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an internal combustion engine 10 according to an embodiment of the present invention.
The internal combustion engine 10 includes a cylinder block 12 into which a piston 11 is movably inserted, a cylinder head 14 attached to the cylinder block 12 via a head gasket 13, and a head cover 16 that closes an upper opening of the cylinder head 14. .

The cylinder block 12 is provided with a plurality of fins 12a on the outer surface and a cylinder hole 12b on the inner side. Heat release from the cylinder block 12 is promoted by the plurality of fins 12a. The piston 11 is fitted in the cylinder hole 12b.
The cylinder head 14 includes a cylinder head body 21 made of aluminum alloy die casting, and a valve mechanism 22 attached to the cylinder head body 21.
The cylinder head body 21 includes an intake port 21a and an exhaust port 21b through which intake and exhaust (intake and exhaust) respectively flow, and valve guide fitting holes 21c and 21d opened to open to the intake port 21a and the exhaust port 21b, respectively. A combustion chamber ceiling surface 21e constituting the ceiling of the combustion chamber 30 is formed.

  In the intake port 21a, an intake opening 21g that is an intake inlet is formed on one side surface 21f of the cylinder head body 21, and an intake valve seat 33 that is an intake outlet is embedded in a portion that opens to the combustion chamber 30, and the intake opening 21g To the intake valve seat 33 while extending in a convex shape. An opening 33j on the combustion chamber 30 side of the intake valve seat 33 is an outlet of the intake port 21a.

In addition, the intake port 21a is integrally formed so that a partition wall 21h that partitions the intake passage vertically is substantially along the upper portion 21k and the lower portion 21m of the inner surface 21j of the intake port 21a, and the upper intake passage 35 is located above the partition wall 21h. A lower intake passage 36 is formed on the lower side.
An intake pipe 41 is connected to one side surface 21f of the cylinder head body 21 via a spacer 38 so as to communicate with the intake port 21a. To the upstream side of the intake pipe 41, components constituting an intake device such as a slot body, a connecting tube, and an air cleaner are connected.

The spacer 38 and the intake pipe 41 are also formed with partition walls 38a and 41a that divide the interior of the spacer 38 and the intake pipe 41 in the vertical direction. The upper intake passages 43 and 44 are provided above the partition walls 38a and 41a, and the lower intake passages 46 and 47 are provided below. Are formed respectively.
The upper intake passages 35, 43 and 44 described above constitute an upper passage 51, and the lower intake passages 36, 46 and 47 constitute a lower passage 52.

The throttle body connected to the upstream side of the intake pipe 41 is provided with an intake distribution valve that distributes intake air into an upper passage 51 and a lower passage 52. The intake distribution valve closes the inlet of the upper passage 51 and opens the inlet of the lower passage 52 in a low load state of the internal combustion engine 10, so that the intake air reaches the combustion chamber 30 through the lower passage 52. At this time, tumble can be generated in the combustion chamber 30 by the intake air flowing into the combustion chamber 30 from the lower intake passage 36 of the intake port 21a. The imaginary line shown in the combustion chamber 30 in the figure indicates a tumble flow.
In the middle and high load state of the internal combustion engine 10, both the upper passage 51 and the lower passage 52 are opened, so that the intake air passes through the upper passage 51 and the lower passage 52 to the combustion chamber 30.

In the exhaust port 21b, an exhaust opening 21p that is an exhaust inlet is formed on the other side surface 21n of the cylinder head body 21, and an exhaust valve seat 54 that is an exhaust outlet is embedded in a portion that opens to the combustion chamber 30, and the exhaust opening 21p To the exhaust valve seat 54 while extending in a convex shape. The opening 54j on the combustion chamber 30 side of the exhaust valve seat 54 is an outlet of the exhaust port 21b.
The valve guide fitting holes 21c and 21d are portions into which the cylindrical intake valve guide 56 and the exhaust valve guide 57 are respectively fitted.
The combustion chamber ceiling surface 21e is formed in a substantially dome-shaped surface with a high center, a plug mounting hole is opened in the combustion chamber ceiling surface 21e, and an ignition plug is mounted in the plug mounting hole.

The valve mechanism 22 includes a camshaft 60, an intake rocker shaft 61, an intake rocker arm 62, an intake valve 63, an intake valve spring 64, an exhaust rocker shaft 71, an exhaust rocker arm 72, an exhaust valve 73, and an exhaust valve spring 74.
The camshaft 60 is rotatably supported by the cylinder head body 21, and an intake cam 60a and an exhaust cam 60b are integrally formed.

  The intake rocker shaft 61 is disposed offset from one side of the camshaft 60 and supported by the cylinder head body 21. The intake rocker arm 62 is swingably supported by the intake rocker shaft 61, a roller 81 that rotates while hitting the intake cam 60a of the camshaft 60 is provided at one end, and an adjustment bolt 82 is screwed to the other end. ing. The adjustment bolt 82 is prevented from rotating by a lock nut 83.

  The intake valve 63 includes a shaft portion 63a that is slidably supported by the intake valve guide 56, and an umbrella portion 63b that is integrally provided at a lower end portion of the shaft portion 63a. The upper end of the shaft portion 63a is pressed against the adjustment bolt 82. The umbrella portion 63b is formed with an annular male taper-shaped valve seal surface, and this valve seal surface is in close contact with the annular female taper-shaped valve seat seal surface formed on the intake valve seat 33. The opening 33j serving as the outlet of 21a is closed.

  The intake valve spring 64 is disposed so as to be sandwiched between a lower retainer 85 placed on the pedestal 21q of the cylinder head body 21 and an upper retainer 86 attached to the tip of the shaft 63a of the intake valve 63. ing. Due to the elastic force of the intake valve spring 64, the umbrella portion 63 b of the intake valve 63 is pressed against and closely contacts the intake valve seat 33. In the drawing, since the roller 81 of the intake rocker arm 62 rides on the peak portion of the intake cam 60a, the intake rocker arm 62 swings counterclockwise around the intake rocker shaft 61, and the intake rocker arm 62 is adjusted. The bolt 82 is in a state where the upper end of the shaft portion 63a of the intake valve 63 is pushed down. As a result, the umbrella portion 63b of the intake valve 63 is separated from the intake valve seat 33, and the intake port 21a is open.

  The exhaust rocker shaft 71 is offset from the upper side of the camshaft 60 to the other side and is supported by the cylinder head body 21. The exhaust rocker arm 72 is swingably supported by the exhaust rocker shaft 71, a roller 81 that rotates while hitting the exhaust cam 60b of the camshaft 60 is provided at one end, and an adjustment bolt 82 is screwed to the other end. ing. The adjustment bolt 82 is prevented from rotating by a lock nut 83.

  The exhaust valve 73 includes a shaft portion 73a that is slidably supported by the exhaust valve guide 57, and an umbrella portion 73b that is integrally provided at the lower end portion of the shaft portion 73a. The upper end of the shaft portion 73a is pressed against the adjustment bolt 82. The umbrella portion 73b is formed with an annular male taper-shaped valve seal surface, and this valve seal surface is in close contact with the annular female taper-shaped valve seat seal surface formed on the exhaust valve seat 54. The opening 54j serving as the outlet of 21b is closed.

  The exhaust valve spring 74 is disposed so as to be sandwiched between a lower retainer 85 placed on the pedestal 21r of the cylinder head body 21 and an upper retainer 86 attached to the tip of the shaft 73a of the exhaust valve 73. ing. Due to the elastic force of the exhaust valve spring 74, the umbrella portion 73 b of the exhaust valve 73 is pressed against and closely contacts the exhaust valve seat 54.

FIG. 2 is a cross-sectional view of the cylinder head main body 21 and shows a cross section of the cylinder head main body 21 shown in FIG.
In the intake port 21a, a bulging portion 21s bulging downward is integrally formed on an upper portion 21k of the inner surface 21j, and a valve guide fitting hole 21c is opened so as to penetrate the bulging portion 21s. Therefore, the intake valve guide 56 (see FIG. 1) and the intake valve 63 (see FIG. 1) protruding downward from the bulging portion 21s and the bulging portion 21s obstruct the flow of intake air in the intake port 21a.
Therefore, in this embodiment, the flow of the intake air is improved by improving the shape of the intake port 21a as follows.

Both the upper intake passage 35 and the lower intake passage 36 of the intake port 21a are passages through which intake air flows when the internal combustion engine 10 (see FIG. 1) is at a medium to high load, and the lower intake passage 36 is an intake air when the internal combustion engine 10 is under a low load. Is a flow passage.
As shown by the alternate long and short dash line, the partition wall 21 h has its tip 21 t directed to the combustion chamber 30, specifically, the upper part of the cylinder hole 12 b of the cylinder block 12. The height H of the lower intake passage 36 in a plane orthogonal to the direction of the intake air flow gradually decreases from the intake opening 21g of the intake port 21a toward the combustion chamber 30. When the height of the lower intake passage 36 at the intake opening 21g is H = H1, and the height of the lower intake passage 36 at the tip 21t of the partition wall 21h is H = H2, H1> H2. In this way, by gradually reducing the height H of the lower intake passage 36 from the intake opening 21g to the combustion chamber 30, the vertical width of the intake air flow in the lower intake passage 36 can be reduced. As a result, the direction of the flow of intake air from the lower intake passage 36 toward the combustion chamber 30 can be directed to a direction in which tumble is likely to occur in the combustion chamber 30.

The lower intake passage 36 is curved in an inverted S shape in this cross section. Specifically, the end of the inverted S-shaped intake opening 21g side is formed so as to be substantially orthogonal to the one side surface 21f, and the end of the inverted S-shaped combustion chamber 30 side is directed toward the combustion chamber ceiling surface 21e. are doing. The lower intake passage 36 is not limited to the inverted S-shape, but may be formed in a straight shape or a simple curved shape.
The leading end 21t of the partition wall 21h is provided at a position closer to the one side surface 21f than the lowermost end 21w of the bulging portion 21s. Further, the inner peripheral surface which is the portion closest to the side surface 21f among the inner peripheral surfaces 21y of the valve seat fitting hole 21x formed in the cylinder head body 21 for fitting the intake valve seat 33 (see FIG. 1). When the auxiliary line 88 is extended from the outermost surface 21z along the innermost outermost surface 21z, the distal end portion 21t of the partition wall 21h is located closer to the one side surface 21f than the auxiliary line 88.
Reference numeral 21u denotes a camshaft support portion formed on the cylinder head body 21 in order to rotatably support the camshaft 60.

3 is a cross-sectional view taken along line III-III in FIG.
When the lateral width of the bulging portion 21s of the inner surface 21j in the intake port 21a is W1, the lateral width of the upper intake passage 35 is W2, and the lateral width of the lower intake passage 36 is W3, the lateral width W2 of the upper intake passage 35 is the lateral width of the bulging portion 21s. It is larger than W1 (W2> W1). Further, the lateral width W3 of the lower intake passage 36 is smaller than the lateral width W2 of the upper intake passage 35 and larger than the lateral width W1 of the bulging portion 21s (W1 <W3 <W2). The horizontal widths W1, W2, and W3 described above are widths along the mating surface 25a of the cylinder head body 21 with the cylinder block 12 side.
Thus, by making the lateral width W2 of the upper intake passage 35 and the lateral width W3 of the lower intake passage 36 larger than the lateral width W1 of the bulging portion 21s, the combustion chamber 30 (see FIG. 2) avoiding the bulging portion 21s. It is possible to make it easier to flow in the intake air.

  2 and 3, the cross-sectional area of the upper intake passage 35, that is, the cross-sectional area orthogonal to the flow of intake air in the upper intake passage 35 is formed to be the same or gradually increased from the intake opening 21g toward the combustion chamber. Similarly, the cross-sectional area of the lower intake passage 36, that is, the cross-sectional area orthogonal to the flow of intake air in the lower intake passage 36 is formed to be the same or gradually increased from the intake opening 21g toward the combustion chamber. Further, the cross sectional area of the lower intake passage 36 is smaller than the cross sectional area of the upper intake passage 35.

  In FIG. 3, the partition wall 21h has an upper surface 25c in which the center of the lateral width W3 is recessed from both ends, and a substantially flat lower surface 25d, and the center of the lateral width W3 is thin and both ends are thick. The lower intake passage 36 includes a substantially flat lower surface 25d of the partition wall 21h, a lower portion 21m of an inner surface 21j formed in a substantially arc shape with the center recessed with respect to both ends, and both ends of the lower surface 25d and the lower portion 21m. Are formed by a pair of curved surfaces 25e, 25e.

As described above, by making the lower surface 25d of the lower intake passage 36 substantially flat, for example, compared with the case where the lower surface of the lower intake passage 36 is curved similarly to the upper surface 25c, The flow of the intake air flowing out into the combustion chamber 30 is difficult to diffuse upward, and can be made into a collective flow, which can promote the generation of strong tumble.
Reference numeral 21v denotes a cam chain insertion hole formed in the cylinder head body 21 for passing a cam chain (not shown) passed between a crankshaft (not shown) of the internal combustion engine 10 and the camshaft 60.

4 is a cross-sectional view taken along line IV-IV in FIG. 2, and is a view of the intake port 21a as viewed from below. In this figure, the intake valve 63 is drawn in an overlapping manner.
Reference numeral 90 in the figure denotes an intake port center line passing through the center of the width of each part of the intake port 21a, and 91 denotes a portion of the maximum width on the outlet side (the intake valve seat 33 (see FIG. 1) side) of the lower intake passage 36. This is an auxiliary line drawn parallel to the intake port center line 90.
The lower intake passage 36 gradually increases in lateral width WL from the intake opening 21g toward the combustion chamber 30 side (the umbrella portion 63b side of the intake valve 63). Further, the width WU of the upper intake passage 35 gradually increases from the intake opening 21g toward the combustion chamber 30 side.

Note that the lateral width WL of the lower intake passage 36 and the lateral width WU of the upper intake passage 35 are WL = W3 and WU = W2 in the cross section shown in FIG.
As described above, by increasing the lateral width WL of the lower intake passage 36 and the lateral width WU of the upper intake passage 35, the flow of the intake air in the intake port 21a is gradually widened so that it is less affected by the bulging portion 21s. The intake air can smoothly flow into the combustion chamber 30.

FIG. 5 is a schematic diagram showing the intake ports 21a and 101. As shown in FIG.
FIG. 5A is a view showing an intake port 21a of an example (this embodiment), and FIG. 5B is a view showing an intake port 101 of a comparative example.
As shown in FIG. 5A, by lowering the tip end 21t side of the partition wall 21h relative to the lower portion 21m of the inner surface 21j of the intake port 21a, the height of the lower intake passage 36 is reduced to the intake opening 21g (FIG. 5A). 2 reference) and gradually decreases from the side toward the combustion chamber 30 side. In the figure, θ is an angle of inclination of the lower surface 25d of the partition wall 21h from the horizontal.

As shown in FIG. 5B, the intake port 101 of the comparative example is formed with a partition wall 106 extending along the upper portion 103 and the lower portion 104 of the inner surface 102, and the upper intake passage 107 above the partition wall 106. A lower intake passage 108 is formed below the partition wall 106.
The lower intake passage 108 raises the combustion chamber 110 side of the lower portion 104 of the inner surface 102 of the intake port 101 with respect to the partition wall 106, so that the height of the lower intake passage 108 is increased from the upstream side of the intake port 101 to the combustion chamber. It is gradually lowered toward the 110 side. Α in the figure is an inclination angle from the horizontal of the lower portion 104 of the inner surface 102 in the intake port 101.

As described above, in the intake port 101, the shape of the lower portion 104 of the inner surface 102 is changed with respect to the upper portion 103, so that the basic flow of the intake air flowing into the combustion chamber 110 changes. Will be affected.
On the other hand, the shape of the lower intake passage 36 of the present embodiment shown in FIG. 5A promotes the generation of tumble while maintaining the performance of the internal combustion engine 10 (see FIG. 1).

  As shown in FIGS. 1, 3 and 4, the cylinder head 14 is formed with the combustion chamber 30 and intake / exhaust ports 21a, 21b communicating with the combustion chamber 30, and the combustion chamber 30 of the intake / exhaust ports 21a, 21b. Are opened and closed by intake and exhaust valves 63 and 73 penetrating the intake and exhaust ports 21a and 21b, respectively, and a partition wall 21h for generating a tumble flow in the combustion chamber 30 is provided at the intake port 21a. In the internal combustion engine 10 where the intake air flowing through the intake port 21a by the partition wall 21h is divided into the upper intake passage 35 and the lower intake passage 36 as upper and lower intake passages divided vertically, the upper intake passage 35 and the lower intake passage The lower intake passage 36, which is one of the passages 36, has a lateral width WL that increases from the upstream side of the intake port 21 a toward the combustion chamber 30. It is formed to be widely.

  According to this configuration, the intake air flow in the lower intake passage 36 spreads away from the intake valve 63 disposed in the intake port 21a and the intake valve guide 56 that guides the intake valve 63, so that the intake air enters the combustion chamber 30. It can be made to flow smoothly and tumble can be easily generated in the combustion chamber 30. Thereby, even when the internal combustion engine 10 is under a low load, fuel and air can be sufficiently mixed in the combustion chamber 30 to promote combustion. Further, since the inner surface shape of the intake port 21a is simply formed into the above shape by casting or the like, the cylinder head body 21 can be easily manufactured, and the productivity can be improved.

As shown in FIGS. 2 to 4, the lower intake passage 36 has the same or gradually increasing cross-sectional area perpendicular to the direction of the intake air flow as it goes from the upstream side of the intake port 21 a toward the combustion chamber 30. Therefore, an increase in the intake resistance of the intake air flowing through the lower intake passage 36 can be suppressed.
Further, as shown in FIG. 2, the lower intake passage 36 is formed such that the height H in a plane orthogonal to the direction of the intake air flow gradually decreases from the upstream side of the intake port 21a toward the combustion chamber 30. Therefore, when being discharged from the lower intake passage 36 to the combustion chamber 30, the upper and lower diffusion of the intake air can be suppressed, and the intake air can be squeezed and flowed in the direction in which the tumble flow in the combustion chamber 30 is likely to occur.

Further, as shown in FIGS. 5 (A) and 5 (B), the lower portion 21m of the inner surface 21j of the intake port 21a on the surface orthogonal to the direction of the intake air flow is substantially from the upper portion 21k of the inner surface 21j of the intake port 21a. Since it is formed along the upper portion 21k of the inner surface 21j of the intake port 21a so as to be a fixed distance, the intake performance due to the shape of the intake port 21a can be made equal to that of the intake port not provided with the partition wall 21h. it can.
As shown in FIGS. 2 to 4, the lower intake passage 36 is formed such that the cross sectional area perpendicular to the direction of the intake air flow is smaller than the cross sectional area of the upper intake passage 35. In this case, even when the internal combustion engine is under a low load, the flow of the intake air can be reduced to increase the flow velocity of the intake air while flowing in a predetermined direction in the combustion chamber, and the generation of a tumble flow can be promoted.

The above-described embodiment is merely an aspect of the present invention, and can be arbitrarily modified and applied without departing from the gist of the present invention.
For example, in the above embodiment, as shown in FIGS. 2 and 4, the lower intake passage 36 has a transverse area smaller than that of the upper intake passage 35 and increases from the upstream side of the intake port 21 a toward the combustion chamber 30. The WL is wide and the height H is low. However, the present invention is not limited to this, and the upper intake passage 35 is formed so as to have a cross-sectional area smaller than that of the lower intake passage 36 and to have the above shape. Tumble may be generated in the passage 35.

As shown in FIG. 2, the partition wall 21 h is formed integrally with the cylinder head main body 21. However, the present invention is not limited to this, and the partition wall 21 h may be formed separately from the cylinder head main body 21. In this case, for example, a partition wall is formed in the intake pipe 41, the throttle body, etc., and a part of this partition wall is inserted into the intake port 21a, and the upper intake passage 35 and the lower intake passage 36 are formed in the intake port 21a. It may be partitioned into
The internal combustion engine 10 of the present invention can be applied to, for example, a motorcycle, a saddle-type vehicle other than a motorcycle, an internal combustion engine mounted on an automobile, and an internal combustion engine mounted on an industrial machine other than the vehicle.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 14 Cylinder head 21a Intake port 21b Exhaust port 21h Partition wall 21j Inner surface of intake port 21k Upper part of inner surface of intake port 21m Lower part of inner surface of intake port 30 Combustion chamber 33j Opening of intake port to combustion chamber 35 Upper intake passage (Intake passage)
36 Lower intake passage (intake passage)
54j Opening of exhaust port to combustion chamber 63 Intake valve 73 Exhaust valve H Lower intake passage height (intake passage height)
WL Width of lower intake passage (width of intake passage)

Claims (4)

The cylinder head (14) is formed with a combustion chamber (30) and intake / exhaust ports (21a, 21b) communicating with the combustion chamber (30), and the intake / exhaust ports (21a, 21b) are connected to the combustion chamber (30). Openings (33j, 54j) are opened and closed by intake / exhaust valves (63, 73) penetrating the intake / exhaust ports (21a, 21b), respectively.
The intake port (21a) is provided with a partition wall (21h) for generating a tumble flow in the combustion chamber (30), and the intake air flowing through the intake port (21a) by the partition wall (21h) is provided. In an internal combustion engine that is divided into an upper intake passage (35) and a lower intake passage (36) that are divided vertically,
The lower intake passage (36) formed on the lower side of the partition wall (21h) is a passage for forcibly flowing intake air that generates the tumble flow at a low load,
The lower intake passage (36) is formed such that its lateral width (W3) gradually increases from the upstream side of the intake port (21a) toward the combustion chamber (30), and the lower intake passage (36). The lateral width (W3) of the upper intake passage (35) is smaller than the lateral width (W2),
The lower intake passage (36) has a height (H) in a plane perpendicular to the direction of intake air flow so that it gradually decreases from the upstream side of the intake port (21a) toward the combustion chamber (30). Formed ,
The lower intake passage (36) is formed such that a cross-sectional area perpendicular to the direction of intake air flow is smaller than a cross-sectional area of the upper intake passage (35),
The lower intake passage (36) is formed so that a cross-sectional area perpendicular to the direction of intake air flow is the same or gradually increased from the upstream side of the intake port (21a) toward the combustion chamber (30). An internal combustion engine characterized by comprising:   The internal combustion engine according to claim 1, wherein a lower surface (25d) of the partition wall (21h) on the lower intake passage (36) side is substantially flat in cross section. On the surface orthogonal to the direction of the intake air flow, the lower portion (21m) of the inner surface (21j) of the intake port (21a) is at a substantially constant distance from the upper portion (21k) of the inner surface (21j) of the intake port (21a). The internal combustion engine according to claim 1 or 2 , wherein the internal combustion engine is formed along an upper portion (21k) of an inner surface (21j) of the intake port (21a).   The partition wall (21h) has, on the upper intake passage (35) side, an upper surface (25c) whose center is recessed from both ends, the center of the lateral width is thin, and both ends are thick. The internal combustion engine according to claim 2.

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