JP6683278B2 - engine - Google Patents

Description

  The present invention relates to an engine having a valve seatless intake port, and more particularly to the shape of the downstream end of the valve seatless intake port.

  There is an engine provided with an intake port that guides intake air so as to be biased toward the exhaust side cylinder with respect to the center line of the cylinder so that a tumble flow is formed in the cylinder (see Patent Document 1).

JP, 2004-316609, A

  By the way, in the current engine, the occurrence of knocking is suppressed by increasing the amount of fuel, especially in the medium rotation speed and high load region, as a measure against knocking. Due to this increase in fuel, fuel efficiency becomes worse. In this case, the tumble flow is generated by the intake air flowing into the combustion chamber from the downstream end of the intake port. It has been found that knocking can be avoided by strengthening the tumble flow.

  However, the technique of Patent Document 1 is based on a general engine. In a typical engine, the valve seat parts are pressed into the throat of the intake port. Before press fitting the valve seat part, the prepared hole for housing the valve seat part is cut with a throat cutter. As a result, a cylindrical wall parallel to the axis of the intake valve is formed in the intake port immediately above the valve seat component prepared hole forming portion. The intake air moves downward in the combustion chamber using the cylindrical wall as a guide. This has a limit in strengthening the tumble flow.

  In this case, there is a hard surface treatment method (for example, a cold spray method) as a method for forming the valve seat without press-fitting the valve seat component. If the valve seat of the intake valve is formed by using this hard surface treatment method (that is, the intake port is a valve seatless), the above cylindrical wall does not occur and the downstream end portion of the intake port is not formed. The degree of freedom of shape increases. Therefore, the present invention strengthens the tumble flow by improving the shape of the downstream end portion of the valve seatless intake port, compared to the current engine, and in particular, knocking without increasing fuel in the medium rotation speed and high load range. An object is to provide an engine capable of suppressing the occurrence.

In the present invention, the piston connected to the crankshaft strokes the cylinder in the vertical direction. The pent roof has a combustion chamber in which an intake port is opened on the intake side roof and an exhaust port is opened on the exhaust side roof. The intake valve has a first valve seat on which an intake valve is seated at the opening end of the intake port to the combustion chamber, and a second valve seat on which an exhaust valve is seated at the opening end of the exhaust port to the combustion chamber. A tumble flow is generated in the combustion chamber by the intake air flowing into the combustion chamber from the downstream end of the intake port. In the above engine, the first valve seat is formed as a hard film made of a material that is harder than the base material of the cylinder head. In the cross section orthogonal to the crankshaft direction, the angle of the intake port wall immediately above the first valve seat on the cylinder center side rising from the horizontal line is equal to or smaller than the first angle or equal to or larger than the second angle. In the cross section orthogonal to the crankshaft direction, the above-mentioned first angle is the most downstream point of the intake port wall immediately above the first valve seat on the cylinder center side and the piston crown at the exhaust side cylinder wall and bottom dead center. It is an acute angle formed by the straight line connecting the points of intersection with the plane and the crown surface of the piston. In the cross section orthogonal to the crankshaft direction, the second angle is an acute angle formed by a line passing through the center of a tumble after the intake air flowing into the combustion chamber is reflected in the combustion chamber and the piston crown surface . The straight line formed by the intake port wall of the first valve seat on the cylinder center side and the straight line formed by the first seat surface of the first valve seat on the cylinder center side are aligned with each other so that the straight line forms a straight line. The first sheet surface is configured.

In the present invention, a valve seatless intake port is used, which increases the degree of freedom in the shape of the downstream end of the intake port. Therefore, a cylindrical wall parallel to the axis of the intake valve is not formed at the downstream end of the intake port, and the downstream end of the intake port can be brought closer to the combustion chamber than the comparative engine. Further, the angle of the intake port wall immediately above the first valve seat on the cylinder center side and rising from the horizontal plane can be arbitrarily set, for example, below the first angle or above the second angle. The intake air flowing along the intake port wall just above the first valve seat on the cylinder center side passes through the exhaust side of the upper part of the combustion chamber, and the tumble flow is strengthened as compared with the comparative engine. Thereby, the occurrence of knocking can be suppressed especially in the high load region. Further, the intake port wall and the first seat surface are aligned so that the straight line formed by the intake port wall of the first valve seat on the cylinder center side and the straight line formed by the first seat surface of the first valve seat on the cylinder center side are aligned. Therefore, when intake air flowing from the upstream side along the intake port wall flows through the first seat surface of the valve seat, loss such as separation or stagnation does not occur. This allows the intake air to smoothly flow into the combustion chamber, so that the tumble flow can be strengthened.

It is a schematic structure figure for explaining the shape of the combustion chamber of the engine of a 1st embodiment of the present invention. It is a schematic block diagram of the engine of 1st Embodiment. It is the YY sectional view taken on the line of FIG. FIG. 3 is a schematic configuration diagram of an engine for explaining a desired tumble flow seen in a cross section orthogonal to a crankshaft direction. It is a schematic block diagram of the comparison engine seen in the cross section orthogonal to the crankshaft direction. It is a schematic block diagram of the comparison engine seen in the cross section orthogonal to the crankshaft direction. FIG. 3 is a schematic configuration diagram of the engine seen in a cross section orthogonal to the crankshaft direction, for explaining the flow of intake air flowing from the most downstream point. FIG. 3 is a schematic configuration diagram of the engine seen in a cross section orthogonal to the crankshaft direction, for explaining the flow of intake air flowing from the most downstream point. FIG. 3 is a schematic configuration diagram of the engine seen in a cross section orthogonal to the crankshaft direction, for explaining the flow of intake air flowing from the most downstream point. FIG. 3 is a schematic configuration diagram of the engine seen in a cross section orthogonal to the crankshaft direction, for explaining the flow of intake air flowing from the most downstream point. It is a schematic block diagram of the engine of 2nd Embodiment. It is a schematic block diagram of the engine of 3rd Embodiment. It is a schematic block diagram of the engine of 4th Embodiment. It is a schematic block diagram of the engine of 5th Embodiment. It is a schematic block diagram of the engine of 6th Embodiment. It is a schematic block diagram of the engine of 7th Embodiment. FIG. 16 is a sectional view taken along line YY of FIG. 15. It is a schematic block diagram of the engine of 8th Embodiment. It is a schematic block diagram of the engine of 9th Embodiment. It is a schematic block diagram of the engine of 10th Embodiment. It is a schematic block diagram of the engine of 11th Embodiment. It is a schematic block diagram of the engine of 12th Embodiment. It is a schematic block diagram of the engine of 13th Embodiment. It is sectional drawing in the crankshaft direction of the downstream end part of the intake port of 14th Embodiment. It is sectional drawing in the crankshaft direction of the downstream end part of the intake port of 15th Embodiment. It is sectional drawing in the crankshaft direction of the downstream end part of the intake port of 16th Embodiment. It is sectional drawing in the crankshaft direction of the downstream end part of the intake port of 17th Embodiment. It is sectional drawing in the crankshaft direction of the downstream end part of the intake port of 18th Embodiment. FIG. 3 is a schematic configuration diagram of the engine seen in a cross section orthogonal to the crankshaft direction, for explaining the flow of intake air flowing from the most downstream point. FIG. 3 is a schematic configuration diagram of the engine seen in a cross section orthogonal to the crankshaft direction, for explaining the flow of intake air flowing from the most downstream point.

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

(First and second embodiments)
FIG. 1 is a schematic configuration diagram for explaining the shape of a combustion chamber 30 of the engine 1 of the first embodiment when seen through from above, and FIG. 2 is the engine 1 of the first embodiment as seen in a cross section orthogonal to the crankshaft direction. Is a schematic configuration diagram of FIG. 3, and FIG. 3 is a sectional view taken along the line YY of FIG. FIG. 2 is also a sectional view taken along line XX of FIG. FIG. 9 shows a second embodiment, which replaces FIG. 2 of the first embodiment. 9, the same parts as those in FIG. 2 are designated by the same reference numerals. The vertical direction of the engine will be considered mainly with reference to FIG. 2, which is a schematic view of the engine viewed in a cross section orthogonal to the crankshaft direction.

  The engine 1 is, for example, a direct injection in-line three-cylinder gasoline engine mounted on a vehicle. The three cylinders are arranged in a line as shown in FIG. The engine 1 is not limited to the 3-cylinder engine, but may be a 4-cylinder engine, a 6-cylinder engine, or the like.

  The engine 1 includes a cylinder block 20 and a cylinder head 10. The cylinder block 10 has as many vertical cylinders 11 as the number of cylinders. A piston 12 is slidably arranged in each cylinder 11 as shown in FIG.

  A cylinder head 20 is attached to the top of the cylinder block 10. On the lower surface 21 of the cylinder head 20, recesses 24 are formed at positions facing the three cylinders 11, the recesses having the number of cylinders recessed upward in a pent roof shape. The recess 24 is composed of a flat rectangular ridge 25 and left and right roofs 26 and 27. That is, the most recessed portion toward the upper side becomes the ridge 25, and the ridge 25 is directed in the crankshaft direction. From this ridge 25, roofs 26 and 27 that are inclined to the left and right as shown in FIG. 1 are formed. Hereinafter, one roof 26 is referred to as an "intake side roof" and the other roof 27 is referred to as an "exhaust side roof". Here, an acute angle (hereinafter, this angle is referred to as “roof angle”) α at which the straight line of the exhaust side roof 27 rises from the horizontal line in a cross section orthogonal to the crankshaft direction is predetermined (FIG. 4, FIG. 4). 7). It is also assumed that the straight line of the intake side roof 26 rising from the horizontal line in the cross section orthogonal to the crankshaft direction is an acute angle that is also the same roof angle α (see FIGS. 4 and 7).

  The pentroof-shaped recess 24 formed on the lower surface 21 of the cylinder head 20, the side wall of the cylinder 11, and the crown surface 15a of the piston 15 form a combustion chamber 30 for one cylinder.

  The engine 1 is provided with two intake ports 40 and two exhaust ports 60 per cylinder. Each intake port 40 is formed from a diagonally upper right to a diagonally lower left in FIG. One of the intake ports 40 opens to the side wall 22 (the right side wall in FIG. 1) of the cylinder head 20, and the other opens to the intake side roof 26. Each exhaust port 60 is formed from a diagonally upper left to a diagonally lower right in FIG. One of the exhaust ports 60 is opened to the side wall 23 (the left side wall in FIG. 1) of the cylinder head 20, and the other is opened to the exhaust side roof 27. Although FIG. 1 shows the case where the intake port 40 is composed of two independent ports, the intake port 40 may be a sized port. Here, a case where four valves are provided per cylinder will be described. It does not matter even if it is provided with two valves or three valves per cylinder.

  A valve seat 41 (first valve seat) is formed at an opening end of the intake port 40 to the intake side roof 26, and a tulip-shaped intake valve 50 opens and closes the valve seat 41. Here, the intake valve 50 is arranged so as to be inclined from the upper right to the lower left. Therefore, the intake valve 50 tilts to the right and lifts. The direction in which the vehicle is tilted to the right and lifted is predetermined. The intake valve 50 includes a valve head 51 as a valve body, a rod-shaped valve stem 52, and the like. The intake valve 50 can slide a valve guide 53 provided on the cylinder head 20 in the axial direction of the valve stem 52.

  The center of the valve seat 41 is in the direction in which the intake valve 50 is arranged. That is, in the cross section orthogonal to the crankshaft direction shown in FIG. 2, the isosceles trapezoidal valve seat is inclined to the right. The valve seat 41 includes a seat surface 41a on which the intake valve 50 is seated, a ring-shaped upper surface 41b, and a ring-shaped lower surface 41c. The seat angle, which is the angle formed by the center of the valve seat 41 and the seat surface 41a, is, for example, 45 °. The seat angle is not limited to 45 °. The intake valve 50 is not limited to the tulip type.

  A valve mechanism 54 is provided above the intake valve 50. The valve mechanism 54 includes an intake cam 55, a valve spring 56 and the like. The intake valve 50 is biased upward by the valve spring 56 while the intake cam 55 is in the base circle. A seat surface 51a is formed on the upper surface of the valve head 51, and the seat surface 51a abuts the seat surface 41a of the valve seat 41 to close (seat) the valve seat 41. When the intake valve 55 is lifted downward by the intake cam 55 against the valve spring 56 in the intake stroke, a gap is created between the valve head 51 and the valve seat 41. Intake air flows into the combustion chamber 30 from the intake port 40 through this gap.

  A valve seat 61 (second valve seat) is formed at the opening end of the exhaust port 60 to the exhaust side roof 27, and a tulip-shaped exhaust valve 70 opens and closes the valve seat 61. Here, the exhaust valve 70 is arranged so as to be inclined from the upper left to the lower right. Therefore, the exhaust valve 70 tilts to the left and lifts. The direction of tilting to the left and lifting is predetermined. The exhaust valve 70 includes a valve head 71 as a valve body, a rod-shaped valve stem 72, and the like. The exhaust valve 70 can slide a valve guide 73 provided on the cylinder head 20 in the axial direction of the valve stem 72.

  The center of the valve seat 61 is in the direction in which the exhaust valve 70 is arranged. That is, in the cross section orthogonal to the crankshaft direction shown in FIG. 2, the isosceles trapezoidal valve seat 61 is inclined to the left. The valve seat 61 includes a seat surface 61a on which the exhaust valve 70 is seated, a ring-shaped upper surface 61b, and a ring-shaped lower surface 61c. The seat angle, which is the angle formed by the center of the valve seat 61 and the seat surface 61a, is 45 °, for example. The seat angle is not limited to 45 °. The exhaust valve 60 is not limited to the tulip type.

  A valve mechanism 74 is provided above the exhaust valve 70. The valve operating mechanism 74 includes an exhaust cam 75, a valve spring 76, and the like. The exhaust valve 70 is biased upward by the valve spring 76 while the exhaust cam 75 is in the base circle. A seat surface 71a is formed on the upper surface of the valve head 71, and the seat surface 71a abuts the seat surface 61a of the valve seat 61 to close (seat) the valve seat 61. When the exhaust valve 70 is lifted downward by the exhaust cam 70 against the valve spring 76 in the exhaust stroke, a gap is created between the valve head 71 and the valve seat 61. Combustion gas flows out from the combustion chamber 30 to the exhaust port 60 through this gap. An acute angle formed by the axis of the exhaust valve 70 and the axis of the intake valve 50 is called a "valve holding angle", and the roof angle α is exactly 1/2 of the valve holding angle.

  At the center of each ridge 25 of the three cylinders, as shown in FIG. 1, an ignition plug 80 is provided which faces the combustion chamber 30 and stands upright. A fuel injector 81, which faces the combustion chamber 30 from immediately above the lower surface 21 of the cylinder head 20, is provided on the intake side sidewall 22 side of the cylinder head 20. Although the fuel injector 81 is not shown in FIG. 2, the portion 28 in which the fuel injector 81 is housed is shown in FIGS. 5 and 6. The fuel injector 81 injects fuel into the combustion chamber 30 at a predetermined timing in the intake stroke and the compression stroke. This injected fuel mixes with the air in the combustion chamber 30 to generate an air-fuel mixture. The spark plug 80 ignites the mixture in the combustion chamber 30 at a predetermined timing before and after the compression top dead center. Due to this ignition, the air-fuel mixture in the combustion chamber 30 burns, and the combustion pressure of the air-fuel mixture is received by the piston 15. The piston 15 which has received the combustion pressure makes a stroke (reciprocating motion) in the vertical direction along the cylinder 11.

  One end of a connecting rod (not shown) is connected to each piston pin 16 of the three pistons 12, and the lower ends of these connecting rods are all connected to one crankshaft. The reciprocating motion of each piston 12 is converted into a rotary motion via the connecting rod and the crankshaft. The crankshaft is arranged in the longitudinal direction of the cylinder head 20 in FIG. That is, the longitudinal direction of the cylinder head 20 is the crankshaft direction. Although a direct injection engine is described here, a port injection engine may be used.

  Now, basically, in terms of exhaust gas measures, it is preferable to efficiently burn the fuel supplied to the engine 1 in the entire operating range of the engine 1 in the atmosphere of the theoretical air-fuel ratio. However, in the current engine, the occurrence of knocking is suppressed by increasing the amount of fuel in the engine 1 especially in the medium rotation speed and high load region as a measure against knocking. Due to this increase in fuel, fuel efficiency becomes worse. Knocking is a phenomenon that spontaneously ignites before the combustion flame arrives, so it has been proved that knocking can be avoided by making the tumble flow stronger than the current engine. This is because the increased tumble flow increases the turbulence of the intake air generated just before the compression top dead center, and the increased turbulence promotes flame propagation. This is because if the flame propagation is promoted, the combustion period will be shortened and the knock resistance will be improved. Then, if the tumble flow can be made stronger than the current engine, it is not necessary to increase the fuel amount, and it is possible to increase the set compression ratio and advance the ignition timing by the amount of improvement in antiknock performance. Fuel efficiency is improved. Therefore, there is a demand to strengthen the tumble flow more than the current engine. Here, the above tumble flow is generated by the intake air flowing into the combustion chamber 30 from the downstream end portion (hereinafter referred to as “intake port downstream end portion”) 42 of the intake port 40.

  FIG. 4 is a schematic configuration diagram of the engine 1 for explaining the tumble flow seen in a cross section orthogonal to the crankshaft direction. FIG. 4 shows the desired state of the intake port 40 on a demand basis. The tumble flow is a swirling flow around the crankshaft (counterclockwise in FIG. 4) on a plane orthogonal to the crankshaft direction. Here, the present inventor has considered whether or not the place where the shape of the intake port downstream end portion 42 is restricted in order to make the tumble flow stronger than the current engine can break through. This consideration will be explained below. In consideration, the intake port downstream end 42 is distinguished between the cylinder center BC side (left side in FIG. 4) and the side opposite to the cylinder center BC (right side in FIG. 4). Hereinafter, the intake port downstream end portion 43 on the cylinder center BC side is referred to as a “first port downstream end portion”, and the intake port downstream end portion 45 on the side opposite to the cylinder center BC is referred to as a “second port downstream end portion”. Further, the combustion chamber 30a on the exhaust side of the cylinder center BC is distinguished as the "exhaust side combustion chamber", and the combustion chamber 30b on the intake side of the cylinder center BC is distinguished as the "intake side combustion chamber".

  In order to strengthen the tumble flow, it is necessary to increase the kinetic energy (flow velocity energy) of the intake air flowing into the combustion chamber 30 from the first port downstream end portion 43. In order to obtain a tumble flow with a large kinetic energy, the exhaust side combustion chamber 30a is located above the horizontal line passing through the stroke center SC of the piston 15 in a cross section orthogonal to the crankshaft direction, and at a position where the distance from the tumble center TC is large. Is to pass. Here, the above "tumble center" is the swirl center of the tumble flow. There are two main points in this case. One is to inject intake air linearly along the wall surface of the exhaust side roof 27 from the first port downstream end portion 43 in a cross section orthogonal to the crankshaft direction. For that purpose, it is necessary to bring the intake port downstream end portion 42 closer to the combustion chamber 30 side (that is, lower side) than the current engine. The other is to generate a tumble flow, which is a counterclockwise swirl flow in FIG. 4, from the gap on the cylinder center BC side (left side in FIG. 4) of the gap between the valve seat 41 and the valve head 51. To flow into the exhaust side combustion chamber 30a.

  5 and 6 are schematic configuration diagrams of an engine for comparison with the engine 1 of the present embodiment (hereinafter referred to as "comparison engine"). Of these, FIG. 5 is a schematic configuration diagram of the comparative engine as seen in a cross section orthogonal to the crankshaft direction. FIG. 6 is a schematic configuration diagram of a comparative engine seen in a cross section orthogonal to the crankshaft direction, for explaining a prepared hole forming method for housing the valve seat component 90 using the throat cutter 100. The comparative engine is a two-valve engine having one intake valve and one exhaust valve per cylinder. Therefore, the portion 28 in which the fuel injector 81 is housed is described in the cross section orthogonal to the crankshaft direction. However, the comparison engine is not limited to a two-valve engine and may be a four-valve engine as in FIG. The above FIG. 4 is also basically described in the case of a two-valve engine.

  In the comparative engine, it is difficult to strengthen the tumble flow due to the shape restriction of the intake port downstream end portion 42 due to having the valve seat component 90. There are two reasons.

  The first reason is that the valve seat component 90, which is an iron sintered member, is press-fitted into the throat portion of the intake port 40 as shown in FIG. Before press-fitting the valve seat component 90, the prepared hole for accommodating the valve seat component 90 is cut by the throat cutter 100 as shown in FIG. The throat cutter 100 moves along the axial direction of the intake valve 50 (see the arrow in FIG. 6). Therefore, after the pilot hole is cut by the throat cutter 100, as shown in FIG. 5, the cylindrical wall 101 parallel to the axial center CC of the intake valve 50 is provided in the intake port immediately above the pilot seat forming portion of the valve seat component. You can Here again, the cylindrical wall 101 is divided into a cylinder center BC side (left side in FIG. 5) and a side opposite to the cylinder center BC (right side in FIG. 5). The cylinder wall 102 on the cylinder center BC side is referred to as a "first cylinder wall", and the cylinder wall 103 on the side opposite to the cylinder center BC is referred to as a "second cylinder wall". The first cylindrical wall 102 is formed at the first port downstream end portion 43, and the second cylindrical wall 103 is formed at the second port downstream end portion 45.

  When the first cylindrical wall 102 is formed by the throat cutter 100, the first cylindrical wall 102 becomes the intake air flowing down along the upper wall of the intake port 40 (hereinafter referred to as the “intake port upper wall”) 40a. On the other hand, it becomes a standing wall (step). The direction is changed by being guided by the first cylindrical wall 102 as the standing wall, and the intake air flows downward in the direction along the first cylindrical wall 102 (see the thick broken arrow in FIG. 5). That is, in the cross section orthogonal to the crankshaft direction, the gas flows toward the exhaust side combustion chamber 30a below the horizontal line passing through the stroke center SC. This tendency is magnified in an engine having a relatively small valve holding angle such as a comparative engine. In the comparative engine, the intake air flowing from the upstream side along the intake port upper side wall 40a is linearly moved to a position in the exhaust side combustion chamber 30a above the horizontal line passing through the stroke center SC, where the distance from the tumble center TC is large. You can't enter it.

  The second reason is that in the comparative engine, since the valve seat component 90 needs to be press-fitted, the second cylindrical wall 103 needs to have a wall thickness that can withstand the press-fitting in the vertical direction. In order to secure the vertical wall thickness of the second cylindrical wall 103, the position of the first port downstream end portion 43 cannot be brought close to the combustion chamber 30 side (downward). For the above two reasons, the shape of the first cylindrical wall 102 formed at the first port downstream end portion 43 of the comparison engine shown in FIG. 5 is far from the ideal shape of the intake port shown in FIG.

By the way, a thermal spraying technique called a cold spray method is known as a general-purpose technique. The cold spray method, which is included in the hard surface treatment methods, is a technique for forming a film on the surface of a base material by causing a powder material to collide with the base material in a solid state below the melting temperature. The present inventor forms the valve seat 41 of the intake valve 50 by using the technique, thereby making the valve seatless intake port. The engine with a valve seatless intake port was newly conceived. That is, the material of the cylinder head 20 is a casting aluminum alloy. The cylinder head 20 having a temporary seat surface slightly larger than the seat surface of the valve seat 41 is integrally cast. After casting, a film, which is harder than the aluminum alloy for casting of the temporary seat surface base material formed as the valve seat portion, is formed as the valve seat layer by the cold spray method. That is, by using He or N ₂ as a working gas by the cold spray method, metal particles harder than the aluminum alloy for casting of the base material are driven into the base material of the temporary sheet surface, whereby aluminum for casting of the base material is cast. A film harder than the alloy is formed as the valve seat layer. In this way, after the valve seat layer (hard surface) is roughly formed by the cold spray method, the valve seat layer roughly formed by the cold spray method is cut using a throat cutter. Finally, the valve seat layer after the cutting process is polished to complete the seat surface of the valve seat 41 according to specifications (according to dimensions). Since the valve seat 61 for the exhaust valve 70 is not related to the present invention, it may be a valve seatless or a valve seat component may be press-fitted.

  In the present invention, the cold spray method is applied to the valve seat 41 of the intake valve 50, and the valve seat component of the intake valve is not press-fitted, whereby the shape of the first port downstream end portion 43 can be greatly changed. In FIG. 2 of the first embodiment, the cold spray method is applied to the valve seat 41 of the intake valve 50, and the valve seat parts of the intake valve 50 are not press-fitted. The valve seatless intake port 40 increases the degree of freedom in the shape of the first port downstream end portion 43. That is, since the valve seat layer formed by the cold spray method is precisely cut by the throat cutter to complete the seat surface 41a of the valve seat 41, the cylindrical wall 101 which is inevitably generated when the valve seat component is press-fitted. Can be eliminated by the present invention. As a result, the intake air flowing from the upstream side along the intake port upper side wall 40a from the first port downstream end portion 43 to the exhaust side combustion chamber 30a above the horizontal line passing through the stroke center SC and from the tumble center TC. It is possible to linearly flow into a position with a large distance. Next, in the present invention, the vertical wall thickness required for press-fitting and holding the valve seat component is not necessary for the second port downstream end portion 45. Therefore, the position of the second port downstream end portion 45, and thus the position of the first port downstream end portion 43, can be brought closer to the combustion chamber 30 side (lower side) than the comparison engine. With these two, in the present invention, it is possible to realize the desired appearance of the intake port shown in FIG.

  Since the degree of freedom of the shape of the first port downstream end portion 43 increases, theoretically consider what the specific first port downstream end portion 43 should be to obtain a tumble flow stronger than the comparison engine. To do. The first port downstream end portion 43 is immediately above the valve seat 41 and is adjacent to the valve seat 41. In the following, among the intake port walls immediately above the valve seat 41, the cylinder center BC side (left side in FIG. 4) and the side opposite to the cylinder center BC (right side in FIG. 4) are distinguished. The intake port wall 44 immediately above the valve seat 41 on the cylinder center BC side is referred to as a “first port wall immediately above the valve seat”. On the other hand, the intake port wall 46 immediately above the valve seat 41 on the side opposite to the center BC of the cylinder is referred to as a “second port wall immediately above the valve seat”. In the following, first, the shape of the first port wall 44 immediately above the valve seat will be considered, and the shape of the second port wall 46 immediately above the valve seat will be considered in the seventh and subsequent embodiments described later.

  Further, the side wall of the cylinder 11 is also distinguished between the exhaust side and the intake side. The side wall 12 on the exhaust side of the cylinder 11 is called an “exhaust side cylinder wall”, and the side wall 13 on the intake side of the cylinder 11 is called an “intake side cylinder wall”.

  As shown in FIG. 7, the shape of the first port wall 44 just above the valve seat has a particularly strong influence on the generation of the tumble flow. The reason for this is as follows. That is, here, the intake air flowing into the combustion chamber 30 from the intake port 40 will be considered by being divided into three parts as indicated by a, b, and c below.

a: intake air flowing from the upstream side along the intake port upper side wall 40a,
b: From the upstream side, the lower wall of the intake port 40 (hereinafter referred to as the “intake port lower wall”) 40b
Intake air flowing along
c: the remaining intake air excluding the above a and b, that is, most of the intake air flowing from the upstream to the center side of the intake port 40,
The intake air of the above a is guided by the first port wall 44 immediately above the valve seat and flows into the exhaust side combustion chamber 30a. The intake air of the above c flows in following the intake air of the above a. This is because the inhaled air moves as a lump without splitting unless the obstacle is placed in front of the incoming inhaled air (that is, if nothing is done). In other words, the intake air of a acts as a leading role of the intake air of c, and the intake air of a and the intake air of c move as a mass. In this way, the behavior of almost the entire intake air, which is the sum of the above a and c, is determined by the shape of the first port wall 44 immediately above the valve seat. Hereinafter, when the "intake air of a" is referred to, the intake air of "a" includes the intake air of c. Note that the intake air of the above b is not considered in the first embodiment to the sixth embodiment described later. The intake air of b above is dealt with in the seventh and subsequent embodiments described later. Here, FIG. 7 is a schematic configuration diagram of the engine for explaining the flow of intake air flowing into the combustion chamber 30, as seen in a cross section orthogonal to the crankshaft direction.

  In FIG. 7, in addition to the horizontal line passing through the stroke center SC of the piston 15, the respective positions of the top dead center TDC and the bottom dead center BDC of the piston 15 are shown. When the intake valve 50 is lifted downward in the intake stroke, the piston 15 descends to the bottom dead center BDC, so that the pressure in the combustion chamber 30 becomes lower than the pressure in the intake port 40, and this pressure difference causes The intake air in the intake port 40 is drawn into the exhaust side combustion chamber 30a. The intake air that has been drawn and has collided with the exhaust side cylinder wall 12 is reflected and changes the flow direction to below the intake side cylinder wall 13. After that, the piston 15 rises to the top dead center TDC via the intake bottom dead center BDC. In response to the upward movement of the piston 15, the flow of the intake air, which has been reflected and directed toward the lower side of the intake side cylinder wall 13, changes to the upper side of the intake side cylinder wall 13. Due to such related lift of the intake valve 50 and vertical stroke (reciprocating motion) of the piston 15, a counterclockwise tumble flow is generated in the combustion chamber 30 (see the thick arrow in FIG. 7). ). Therefore, the tumble center TC is considered to come to the point where the horizontal line passing through the stroke center SC of the piston 15 and the cylinder center BC intersect.

  The first port wall 44 immediately above the valve seat constitutes a part of the cylindrical wall when viewed in a cross section in the crankshaft direction as shown in FIG. Here, in particular, a cross section orthogonal to the crankshaft direction will be considered. As shown in FIG. 7, it is assumed that the first port wall 44 immediately above the valve seat is a straight line in a cross section orthogonal to the crankshaft direction. The reason why the first port wall 44 immediately above the valve seat is made straight is that the intake air along the first port wall 44 immediately above the valve seat flows without causing separation or turbulence, which is a loss of kinetic energy in this case. is there. The angle θ1 which is an acute angle (hereinafter, referred to as “first port wall angle immediately above the valve seat”) θ1 at which this straight line rises from the horizontal line in the cross section orthogonal to the crankshaft direction will be considered. Let S be the most downstream point of the first port wall 44 immediately above the valve seat (hereinafter also simply referred to as the “most downstream point”). Here, the "downstream point" is the point where the straight line of the first port wall 44 immediately above the valve seat and the straight line of the upper surface 41b of the valve seat 41 intersect in the cross section orthogonal to the crankshaft direction. The flow of the intake air flowing into the combustion chamber 30 from the most downstream point S is collectively approximated by one line, and the intake air colliding with the exhaust side cylinder wall 12 is reflected at an angle substantially equal to the incident angle. For simplification, the intake port upper side wall 40a adjacent to the first port wall 44 immediately above the valve seat is also a straight line in a cross section orthogonal to the crankshaft direction, and two adjacent straight lines form one straight line. It is assumed that

  FIG. 7 illustrates the behavior of the intake air flowing from the upstream side along the intake port upper side wall 40a in the combustion chamber 30 by superimposing the following four cases. In FIG. 7, the intake air flowing from the upstream side along the intake port upper side wall 40a basically collides once with the wall surface (exhaust side cylinder wall 12 or piston crown surface 15a) in the combustion chamber 30 from the most downstream point S. Then, consider the case where the collision of intake air is reflected.

A: When the intake air heads toward the exhaust side cylinder wall 12 from the most downstream point S, collides, is reflected, and then goes below the intake side cylinder wall 13,
B: After the intake air collides from the most downstream point S to a point A where the straight line (vertical line) of the exhaust side cylinder wall 12 and the horizontal line passing through the stroke center SC where the tumble center TC is present, collides and is reflected, When facing the piston crown surface 15a,
C: After the intake air directly collides with the piston crown surface 15a from the most downstream point S and is reflected,
When going above the exhaust side cylinder wall 12,
D: When the intake air collides from the most downstream point S to a point C where the straight line (vertical line) of the exhaust side cylinder wall 12 and the horizontal line of the piston crown surface 15a at the bottom dead center intersect and is reflected,
Note that the piston crown surface 15a is not provided with a cavity, and the entire piston crown surface 15a is a flat surface. The piston crown surface 15a, which is a flat surface, and the surface (horizontal surface) orthogonal to the cylinder center BC are in a parallel positional relationship.

  In the cases of A and B, after the intake air collides with the exhaust side cylinder wall 12, it is reflected and flows toward the lower side of the intake side cylinder wall 13, so that a left-turning tumble flow is generated. In the above case (c), after the intake air collides with the piston crown surface 15a, it is reflected and flows toward the upper side of the exhaust side cylinder wall 12, so that the flow is a right-handed swirl and a left-turned tumble flow is not generated. Therefore, the above case d is the boundary of whether or not the tumble flow is generated. If an angle β, which is an acute angle formed by the oblique straight line of d and the horizontal line of the piston crown surface 15a in the cross section orthogonal to the crankshaft direction, is defined as “first angle”, the first port wall angle θ1 immediately above the valve seat is The condition that the tumble flow is generated is that the angle is equal to or smaller than the first angle β.

  Actually, the flow of intake air from the most downstream point S toward the exhaust side cylinder wall 12 spreads in a conical shape as shown in FIG. In the case of the above d, the oblique straight line of d passes through the center of the flow of the intake air having the conical spread. If the lower boundary of the divergent intake air flow is "o" and the upper boundary thereof is "c", the slanting straight line of "d" will be above the case of FIG. In FIG. 8, assuming that the point where the oblique straight line of d and the straight line (vertical line) of the exhaust side cylinder wall 12 intersect is C ′, the point C ′ is the straight line of the exhaust side cylinder wall 12 and the piston crown surface 15a at the bottom dead center. It comes above the point C where the horizontal line of intersects. In addition, the degree of conical spread varies depending on the engine operating conditions. Therefore, in practice, the first angle β needs to be determined under specific operating conditions depending on the adaptation.

  In FIG. 7, the case where the intake air flowing along the intake port upper side wall 40a from the upstream side once collides with the wall surface in the combustion chamber 30 from the most downstream point S is considered. That is, FIG. 7 simply shows the behavior of the intake air flowing from the upstream along the upper wall 40a of the intake port in the combustion chamber 30, but the actual behavior of the intake air is limited to this case. Absent.

  Therefore, next, as shown in FIG. 9, the intake air flowing along the intake port upper side wall 40a from the upstream side reaches the wall surface in the combustion chamber 30 from the most downstream point S (the exhaust side roof 27 and the exhaust side cylinder wall). Consider the case of two collisions with 12). 9, the same parts as those in FIG. 7 are designated by the same reference numerals. Also in this case, the flow of the intake air flowing into the combustion chamber 30 from the most downstream point S is collectively approximated by one line, and the intake air colliding with the wall surface in the combustion chamber 30 is reflected at an angle substantially the same as the incident angle. I shall.

  It is theoretically possible that the intake air collides with the wall surface in the combustion chamber 30 from the most downstream point S three or more times, but it is considered that the ratio of contribution to the tumble flow is extremely small when the intake air collides three or more times. , Ignore in this case. In addition, although it is possible that the intake air collides with the umbrella back portion of the intake valve 50 from the most downstream point S and then collides with the wall surface in the combustion chamber 30, this case is also ignored.

  FIG. 9 illustrates the behavior of the intake air flowing from the upstream side along the intake port upper side wall 40a in the combustion chamber 30 in the following three cases. In FIG. 9, consider a case where the intake air flowing along the intake port upper side wall 40a from the upstream side collides with the wall surface in the combustion chamber 30 twice from the most downstream point S, and the colliding intake air is reflected respectively.

S: Intake air is reflected twice from the most downstream point S on the wall surface in the combustion chamber 30 and the piston crown surface 15a
When heading to
S: Intake air is reflected twice from the most downstream point S on the wall surface inside the combustion chamber 30 and the intake side cylinder wall 1
When heading to 3,
S: When the intake air is reflected twice from the most downstream point S on the wall surface in the combustion chamber 30 and passes through the tumble center TC toward the intake side cylinder wall 13,
Also in FIG. 9, it is assumed that the piston crown surface 15a is not provided with a cavity and the entire piston crown surface 15a is a flat surface. The piston crown surface 15a, which is a flat surface, and the surface (horizontal surface) orthogonal to the cylinder center BC are in a parallel positional relationship.

  In the case of the above-mentioned S, the intake air collides with the piston crown surface 15a, then is reflected and heads above the intake side cylinder wall 13. As a result, a left-turning tumble flow is generated. In the above case, after the intake air collides with the intake side cylinder wall 13, the intake air is reflected and travels below the exhaust side cylinder wall 12. At this time, since the flow is a right turn, a tumble flow for a left turn is not generated. Therefore, the above case is the boundary of whether or not the tumble flow is generated. In the cross section orthogonal to the crankshaft direction, the point where the oblique line of the spur and the straight line (vertical line) of the intake side cylinder wall 13 intersect is defined as F, and the acute angle δ formed by the oblique straight line of the spur and the horizontal line is defined. "Second angle". Then, the condition for generating the tumble flow is that the first port wall angle θ1 just above the valve seat is equal to or larger than the second angle δ. In FIG. 7, the first angle β is an angle that is an acute angle at which a slanting straight line d rises from the horizontal line of the piston crown surface 15a in the cross section orthogonal to the crankshaft direction. Also in FIG. 9, an angle that is an acute angle at which a diagonal straight line of a vertical line rises from a horizontal line parallel to the horizontal line of the piston crown surface 15a in a cross section orthogonal to the crankshaft direction is referred to as a second angle δ.

  Actually, the flow of the intake air reflected from the wall surface in the combustion chamber 30 twice from the most downstream point S to the tumble center TC spreads in a conical shape as shown in FIG. In the case of the above-mentioned gas, the oblique straight line of the gas passes through the center of the flow of the intake air having the conical spread. If the upper boundary of the divergent intake air flow is S and the lower boundary is S0, the slanted straight line of the above-mentioned line becomes lower than in the case of FIG. In FIG. 10, when the point where the oblique straight line of the line and the straight line of the intake side cylinder wall 13 intersect is F ', the point F'is below the point F in FIG. In addition, the degree of conical spread varies depending on the engine operating conditions. Therefore, the second angle δ actually needs to be set under specific operating conditions due to adaptation.

  So far, the limit condition for generating the tumble flow has been considered for the engine having the valve seatless intake port. Next, let us consider when the strongest tumble flow is obtained for an engine having a valve seatless intake port. As shown in FIG. 29, a circle centering on the tumble center TC (see the alternate long and short dash line in FIG. 29) is drawn in the cross section orthogonal to the crankshaft direction, and the straight line of the exhaust side cylinder wall 12 becomes the tangent to this circle. To do so. It is supposed that the tumble flow is generated counterclockwise along the locus of the circle indicated by the one-dot chain line. In reality, since the upper and lower shapes of the combustion chamber 30 are restricted, the actual tumble flow is a flow along the locus of an ellipse (see the alternate long and two short dashes line in FIG. 29) which is vertically slanted. In this case, the intersection of the horizontal line passing through the stroke center SC and the straight line (vertical line) of the exhaust side cylinder wall 12, that is, the point A is the contact point to the ellipse shown by the chain double-dashed line. In other words, the point A of the exhaust side cylinder wall 12 is a contact point to one end (left side in FIG. 29) of the long axis of the ellipse shown by the alternate long and two short dashes line, but the other end of the long axis (in FIG. 29). Let J be the contact point for the right side). Further, a contact point to one end (lower side in FIG. 29) of the minor axis of the ellipse shown by a two-dot chain line is I, and a contact point to the other end (upper side in FIG. 29) of the short axis is K. Here, similarly to FIGS. 7 to 10, FIG. 29 is also a schematic configuration diagram of the engine for explaining the flow of intake air flowing into the combustion chamber 30, as seen in a cross section orthogonal to the crankshaft direction.

  Now, since the points A, I, J, and K are the points of contact with the ellipse shown by the chain double-dashed line, theoretically, the points A, I, J, and K are tangential to (below) the ellipse. The strongest tumble flow is obtained when the intake air flows toward each of them. From this viewpoint, the case where the strongest tumble flow is obtained for the engine having the valve seatless intake port 40 is the following two cases.

  The first case where the strongest tumble flow is obtained is the case of the next key shown in FIG.

G: When the intake air flowing from the upstream side along the intake port upper side wall 40a flows from the most downstream point S along the wall surface of the exhaust side roof 27,
The reason why the strongest tumble flow is obtained in the case of K is that the behavior of the intake air in the case of K is almost the same as the optimum flow of the intake air for generating the tumble flow. However, here, unlike FIG. 7 to FIG. 10, it is assumed that the intake air only changes the flow direction by collision and is hardly reflected.

  That is, in the above case (i), the intake air flows along the wall surface of the exhaust side roof 27 and then heads toward the exhaust side cylinder wall 12. The intake air that collides with the exhaust side cylinder wall 12 changes its flow direction to a downward direction along the exhaust side cylinder wall 12. Then, the intake air flows down along the exhaust side cylinder wall 12, passes through the contact point A in the tangential direction of the ellipse, and collides with the piston crown surface 15a. The colliding intake air changes its flow direction, flows toward the intake side cylinder wall 13 along the cylinder crown surface 15a, passes through the contact point I in the tangential direction of the ellipse, and collides with the intake side cylinder wall 13. The colliding intake air changes its flow direction, and then flows upward in the direction along the intake side cylinder wall 13, passes through the contact point J in the tangential direction of the ellipse, and collides with the wall surface of the intake side roof 26. The colliding intake air changes its flow direction, flows along the wall surface of the intake side roof 26, and collides with the exhaust side roof 27. The collisional intake air changes its flow direction and flows toward the intake side cylinder wall 13 along the cylinder crown surface 15a. In this way, while the intake air changes its direction on the wall surface in the combustion chamber 30, it flows through the contact points A, I, and J in each tangential direction of the ellipse (see the thick arrow in FIG. 29), and the intake air flows near the contact point K. By flowing, a tumble flow, which is an elliptical locus, is generated. Since the contact point K is a point in space, the intake air does not flow in the tangential direction of the ellipse indicated by the chain double-dashed line, so the intake air does not accurately follow the locus of the ellipse on the figure. However, it will follow an elliptical locus to the extent that there is no practical problem. In this way, in the case of the above-described case, the intake air flowing down along the exhaust side cylinder wall 12 first flows downward in the tangential direction of the ellipse indicated by the two-dot chain line at the point A, so that the strongest tumble flow occurs. Will be obtained. This point is confirmed by actually performing a simulation.

  Specifically, the case of the above-mentioned case is shown in the second embodiment shown in FIG. In the second embodiment shown in FIG. 11, the first port wall angle θ1 immediately above the valve seat is substantially the same as the exhaust side roof angle α in a cross section orthogonal to the crankshaft direction. It can be said that the roof angle α is exactly ½ of the valve holding angle, and therefore the first port wall angle θ1 immediately above the valve seat is almost the same as just ½ of the valve holding angle. . In this way, by adopting the case of the above-mentioned case in the second embodiment, in the engine having the valve seatless intake port 40, one of the strongest tumble flows can be efficiently stored while efficiently storing the kinetic energy of the intake air. You can get one.

  Next, the second case in which the strongest tumble flow is obtained is the above-mentioned case a in FIG. That is, it is a case where the intake air collides from the most downstream point S to a point A where a straight line of the exhaust side cylinder wall 12 and a horizontal line passing through the stroke center SC intersect, is reflected, and then heads to the piston crown surface 15a. The reason that the strongest tumble flow is obtained in the case of b) is that the behavior of the intake air in the case of b) draws an elliptical locus. However, here, it is assumed that the intake air is reflected by collision, as in FIGS. 7 to 10.

  To explain this, as shown in FIG. 30, the ellipse shown by the chain double-dashed line is inscribed with the diamond shown by the thin solid line. At this time, the inner contact point of the diamond and the contact point of the ellipse match. That is, the point A is a point of contact with one end (left side in FIG. 30) of the major axis of the ellipse, and at the same time, coincides with one end (left side in FIG. 30) of the longer diagonal line of the diamond. Point I is a point of contact with one end of the ellipse's minor axis (downward in FIG. 30) and at the same time with one end of the shorter diagonal of the diamond (downward in FIG. 30). Point J is a point of contact with the other end of the ellipse's major axis (right side in FIG. 30) and at the same time with the other end of the longer diagonal of the diamond (right side in FIG. 30). Point K is a point of contact with the other end of the ellipse's minor axis (upper in FIG. 30) and at the same time with the other end of the shorter diagonal of the diamond (upper in FIG. 30). Here, similarly to FIG. 29, FIG. 30 is also a schematic configuration diagram of the engine for explaining the flow of intake air flowing into the combustion chamber 30, as seen in a cross section orthogonal to the crankshaft direction.

  Now, the intake air that collides with the point A bounces, the bounced intake air goes to the point I, the intake air that collides with the point I bounces, the bounced intake air goes to the point J, and the intake air that collides with the point J It is considered that the rebounded and rebounded intake air is directed to the point K. That is, the intake air that linearly follows the locus of the rhombus passes through the three adjacent contacts A, I, and J of the ellipse shown by the chain double-dashed line, and at the contact K, if not reflected, Intake air flows in the vicinity as if reflected. In other words, the intake air is reflected at the same reflection angle as the incident angle, loses almost no kinetic energy before and after the collision, and if a flow of the intake air that follows the locus of a rhombus is given, it is a tumble flow trajectory. It is assumed that the elliptical intake air flow can be approximated.

  On the other hand, if the intake air is directed to a point other than the point A on the exhaust side cylinder wall 12, a rhombic flow inscribed in the ellipse shown by the chain double-dashed line cannot be created. That is, in the intake air that collides with the exhaust side cylinder wall 12 from the most downstream point S and is reflected, the tumble flow passing through the three contact points A, I, and J of the ellipse is the most efficient in the above case a. It is thought to occur.

  It should be noted that the intake air actually flows from the most downstream point S, not from the point K. That is, there is some deviation between the acute angle η1 rising from the horizontal line connecting the points S and A and the acute angle η2 rising from the horizontal line connecting the points K and A. . Therefore, the intake air directed from the point S to the point A is not always reflected and accurately directed to the point I (a slight deviation may occur). However, a simulation was actually performed in the case where the intake air is fed from the most downstream point S to the point A. Then, when the intake air is flown from the most downstream point S to the point A, the knocking is the most knocked as compared with the case where the intake air is flown from the most downstream point S to a point other than the point A on the exhaust side cylinder wall 12. Has been confirmed to be less likely to occur, that is, the most satisfactory tumble flow can be obtained.

  Specifically, the above case (a) is shown in the first embodiment shown in FIG. As described above, by adopting the above case a in the first embodiment, one of the strongest tumble flows can be obtained while efficiently storing the kinetic energy of the intake air in the engine having the valve seatless intake port 40. Can be obtained.

  Whether the intake air collides with the wall surface in the combustion chamber 30 and is reflected, or whether only the flow direction is changed without being reflected depends on the velocity of the intake air passing through the most downstream point S and the amount of the intake air. Dependent. When the velocity of the intake air passing through the most downstream point S is relatively small, for example, the intake air only collides with the wall surface in the combustion chamber 30 and changes its flow direction without being reflected. On the other hand, when the velocity of the flow of the intake air passing through the most downstream point S is relatively high, it is considered that the intake air collides with the wall surface in the combustion chamber 30 and reflects. Here, the speed of the flow of intake air passing through the most downstream point S and the amount of intake air differ depending on the engine specifications and engine operating conditions. Therefore, in an engine in which the velocity of the intake air passing through the most downstream point S in the operating range where knocking occurs is relatively small, for example, the intake air simply changes its flow direction without being reflected. Should be adopted. On the other hand, in an engine in which the velocity of the intake air passing through the most downstream point S in the operating range where knocking occurs is relatively large, for example, the intake air collides with the wall surface in the combustion chamber 30 and is reflected. One embodiment may be adopted. Alternatively, when the velocity of the intake air passing through the most downstream point S in the operating range where knocking occurs is relatively small, for example, the intake air only changes its flowing direction without being reflected, so the second embodiment Should be adopted. On the other hand, when the velocity of the flow of the intake air passing through the most downstream point S in the operating range where knocking occurs is relatively high, for example, the intake air collides with the wall surface in the combustion chamber 30 and is reflected. One embodiment may be adopted.

  Here, the effects of the first and second embodiments will be described.

  In the first and second embodiments, the piston 15 connected to the crankshaft strokes the cylinder 11 in the vertical direction. The intake side roof 26 (intake side roof of the pent roof) is provided with an intake port 40, and the exhaust side roof 27 (exhaust side roof) is provided with a combustion chamber 30 in which an exhaust port 60 is opened. A valve seat 41 (first valve seat on which the intake valve 50 is seated) is located at the open end of the intake port 40 to the combustion chamber 30, and a valve seat 61 (exhaust valve is seated at the open end of the exhaust port 60 to the combustion chamber 30). Each has a second valve seat). A tumble flow is generated in the combustion chamber 30 by the intake air flowing into the combustion chamber 30 from the downstream end of the intake port 40. In the above engine, the valve seat 41 (first valve seat) is formed by using a hard surface treatment method. In a cross section orthogonal to the crankshaft direction, the angle θ1 of the first port wall 44 immediately above the valve seat (the intake port wall immediately above the first valve seat on the cylinder center side) rising from the horizontal plane is less than or equal to the first angle β. Or is greater than or equal to the second angle δ. In the cross section orthogonal to the crankshaft direction, the above-mentioned first angle β is determined by the intersection point between the most downstream point S of the first port wall 44 immediately above the valve seat and the exhaust side cylinder wall 12 and the piston crown surface 15a at the bottom dead center. It is an acute angle formed by a straight line connecting C and the piston crown surface 15a. In the cross section orthogonal to the crankshaft direction, the second angle δ is such that the intake air flowing into the combustion chamber 30 is reflected inside the combustion chamber 30 and the line passing through the center of the tumble (line of the line) and the piston crown surface 15a. It is an angle that is an acute angle. In the first embodiment, a valve seatless intake port in which the degree of freedom of the shape of the intake port downstream end portion 42 is increased is adopted. Therefore, the cylindrical wall 101 parallel to the axial center CC of the intake valve 50 is not formed at the intake port downstream end portion 42, and the intake port downstream end portion 42 can be brought closer to the combustion chamber 30 than the comparative engine. . Further, the first port wall angle θ1 immediately above the valve seat (the angle at which the intake port wall immediately above the first valve seat on the cylinder center side rises from the horizontal plane) is arbitrarily set to, for example, the first angle β or less or the second angle. It is possible to set δ or more. The intake air flowing along the first port wall 44 immediately above the valve seat (the intake port wall immediately above the first valve seat on the cylinder center side) passes through the exhaust side above the combustion chamber 30, and the tumble flow occurs. Is stronger than the comparison engine. As a result, the occurrence of knocking can be suppressed without increasing the amount of fuel, particularly in the medium rotation speed and high load range.

  In the first embodiment, in the cross section orthogonal to the crankshaft direction, the first port wall 44 immediately above the valve seat (the intake port wall immediately above the first valve seat on the cylinder center side) is guided along the intake port upper side wall 40a. As a result, intake air flows into the combustion chamber 30. The intake air (intake air of the above “a”) flowing directly to the valve seat is directed toward a point A where a horizontal line passing through the stroke center SC of the piston 15 and a straight line of the exhaust side cylinder wall 12 (exhaust side cylinder wall) intersect. The upper first port wall 44 is formed (see the dashed arrow in FIG. 2). As described above with reference to FIG. 29, this is because if a rhombus is inscribed in the ellipse that is the locus of the tumble flow and the flow of the intake air that follows the locus of the rhombus is given, the suction of the ellipse that is the locus of the tumble flow is given. It is assumed that the air flow can be approximated. Thus, when the intake air collides with the wall surface in the combustion chamber 30 and is reflected once in the engine having the valve seatless intake port 40, the kinetic energy of the intake air is efficiently preserved and the strongest. You can get one of the tumble streams.

  In the second embodiment, in the cross section orthogonal to the crankshaft direction, the first port wall 44 immediately above the valve seat (the intake port wall immediately above the first valve seat on the cylinder center side) 44 is transmitted along the intake port upper side wall 40a. Intake air flows into the combustion chamber 30 as a guide. The first port wall 44 immediately above the valve seat is formed so that the intake air flowing into the combustion chamber 30 (that is, the intake air of the above a) flows along the wall surface of the exhaust side roof 27 (exhaust side roof). (Refer to the dashed arrow in FIG. 11). Therefore, after the intake air flows along the wall surface of the exhaust side roof 27, the flowing direction is changed to the downward direction along the exhaust side cylinder wall 12. Then, the intake air flows down along the exhaust side cylinder wall 12. The intake air that collides with the piston crown surface 15a changes its flow direction and flows toward the intake side cylinder wall 13 along the piston crown surface 15a. The intake air that has collided with the intake-side cylinder wall 13 changes its flow direction, and this time flows along the intake-side cylinder wall 13 toward the wall surface of the intake-side roof 26. As described above with reference to FIG. 30, when the intake air only collides with the wall surface in the combustion chamber 30 and changes its flow direction without being reflected, first, the intake air is moved downward along the exhaust side cylinder wall 12. Flow intake air to. As a result, three elliptical points A, I, and J, which are the loci of the tumble flow, flow tangentially, and the point K does not flow tangentially, but the intake air flows near the point K. It is assumed that intake air following the locus of is obtained. Thus, in an engine having a valve seatless intake port 40, the kinetic energy of the intake air is efficiently preserved when the intake air only changes its flow direction even when the intake air collides with the wall surface in the combustion chamber 30. , You can get one of the strongest tumble flows.

(Third Embodiment)
FIG. 12 shows a third embodiment of the present invention, which replaces FIG. 2 of the first embodiment. The same parts as those in FIG. 2 of the first embodiment are designated by the same reference numerals. The third embodiment will be described on the premise of the first embodiment, but may be on the premise of the second embodiment.

  In the third embodiment, the angle θ2, which is an acute angle formed by the straight line of the first port wall 44 immediately above the valve seat and the straight line of the upper surface 41b of the valve seat 41 in the cross section orthogonal to the crankshaft direction, is taken as the valve seat of the intake valve 50. It is related to the seat angle ε of 41. Explaining this, first, a seat surface 41a on the cylinder center BC side (left side in FIG. 12) of the valve seat 41 and a seat surface 41a opposite to the cylinder center BC of the valve seat 41 (right side in FIG. 12) are distinguished. . Hereinafter, the seat surface 41a on the cylinder center BC side of the valve seat 41 is referred to as a "first seat surface", and the reference numeral is "41aa". On the other hand, the seat surface 41a on the side opposite to the cylinder center BC of the valve seat 41 is referred to as a "second seat surface", and the reference numeral is "41ab".

  As shown enlarged in the upper right of FIG. 12, the straight line of the first port wall 44 immediately above the valve seat 41 and the straight line of the first seat surface 41aa of the valve seat 41 are straight in a cross section orthogonal to the crankshaft direction. To configure. Then, consider an acute angle θ2 formed by the straight line of the first port wall 44 immediately above the valve seat and the straight line of the upper surface 41b of the valve seat 41. In the enlarged view on the upper right of FIG. 12, an auxiliary line m is drawn in association with the isosceles trapezoidal valve seat 41 inclined to the right. That is, the auxiliary line m is drawn so as to pass through the second seat surface 41ab. Let G be the intersection of the auxiliary line m and the straight line of the first port wall 44 immediately above the valve seat, and H be the intersection of the auxiliary line m and the straight line of the upper surface 41b of the valve seat 41. The intersection of the straight line of the first port wall 44 immediately above the valve seat and the straight line of the upper surface 41b of the valve seat 41 is S. When the points of the auxiliary lines m, G and H are thus determined, the triangle GSH is an isosceles triangle. Since the vertex angle ∠SGH of the isosceles triangle is equal to twice the seat angle ε of the valve seat 41, the following equation holds.

θ2 × 2 + ε × 2 = 180 (1)
By solving the equation (1) for the angle θ2, the following equation is obtained.

θ2 = 90−ε (2)
That is, by associating the angle θ2 with the seat angle ε of the valve seat 41 by the expression (2), the first port wall 44 immediately above the valve seat and the first seat surface 41aa of the valve seat 41 become the same surface. In other words, the straight line of the first port wall 44 just above the valve seat and the straight line of the first seat surface 41aa of the valve seat 41 are connected in a straight line in a cross section orthogonal to the crankshaft direction.

  As described above, in the third embodiment, the straight line of the first port wall 44 immediately above the valve seat and the straight line of the first seat surface 41aa of the valve seat 41 are connected in a straight line in a cross section orthogonal to the crankshaft direction. Therefore, when the intake air flowing from the upstream side along the intake port upper side wall 40a flows through the first seat surface 41aa of the valve seat 41, loss such as peeling or stagnation does not occur. As a result, the intake air can smoothly flow into the combustion chamber 30 from the most downstream point S without causing loss such as separation or stagnation. Since the first seat surface 41aa of the valve seat 41 does not cause loss such as separation or stagnation, the tumble flow can be strengthened.

(4th-6th embodiment)
13 to 15 are fourth to sixth embodiments, which replace FIG. 2 of the first embodiment. The same parts as those in FIG. 2 of the first embodiment are designated by the same reference numerals. The fourth to sixth embodiments will be described in the case of assuming the first embodiment, but may be in the case of assuming the second embodiment.

  In the first embodiment, the first port wall 44 immediately above the valve seat is a straight line in the cross section orthogonal to the crankshaft direction. On the other hand, in the fourth to sixth embodiments, the first port wall 44 immediately above the valve seat is not straight in the cross section orthogonal to the crankshaft direction. That is, in the fourth embodiment shown in FIG. 13, the shape of the first port wall 44 immediately above the valve seat is a convex curve protruding toward the center of the intake port 40 in the cross section orthogonal to the crankshaft direction. In the cross section orthogonal to the crankshaft direction, the first port wall 44 immediately above the valve seat of this convex curve and the intake port upper side wall 40a adjacent thereto are smoothly connected. In the fifth embodiment shown in FIG. 14, the shape of the first port wall 44 immediately above the valve seat in the cross section orthogonal to the crankshaft direction is a concave curve that is recessed away from the center of the intake port 40. In the cross section orthogonal to the crankshaft direction, the first port wall 44 immediately above the concave valve seat and the intake port upper side wall 40a adjacent thereto are smoothly connected. In the sixth embodiment shown in FIG. 15, the first port wall 44 immediately above the valve seat has a stepped shape in a cross section orthogonal to the crankshaft direction. That is, in the sixth embodiment, the first seat surface 41aa of the valve seat 41 projects outward in the radial direction of the cylindrical intake port 40 from the first port wall 44 immediately above the valve seat in the cross section orthogonal to the crankshaft direction. In addition, a step is formed between the valve seat 41 and the first seat surface 41aa.

  In the first embodiment, for the engine having the valve seatless intake port 40, the shape of the first port wall 44 immediately above the valve seat is a straight line in the cross section orthogonal to the crankshaft direction from the viewpoint of enhancing the tumble flow more than the comparative engine. And Then, the first port wall angle θ1 immediately above the valve seat was examined. However, the first port wall 44 immediately above the valve seat has a requirement from another viewpoint, and it is also necessary to satisfy the requirement from this other viewpoint. Here, another point of view is, for example, the guarantee of component functions such as cooling performance and strength. The fourth to sixth embodiments are variations for meeting engine demands from other viewpoints. However, variations are allowed within a range in which the operational effects of the first embodiment are not impaired.

  Also in the fourth to sixth embodiments, the same operational effects as in the first embodiment can be obtained. The fourth to sixth embodiments have been described on the premise of the first embodiment, but may be premised on the second and third embodiments.

(Seventh embodiment)
16 and 17 show a seventh embodiment of the present invention, which replaces FIGS. 2 and 3 of the first embodiment. The same parts as those in FIGS. 2 and 3 of the first embodiment are designated by the same reference numerals. In the seventh embodiment as well, the case where the first embodiment is assumed will be described, but the case where the second embodiment is assumed may be used.

  Up to the sixth embodiment, regarding an engine having a valve seatless intake port 40, how to enhance the tumble flow by the intake air of the above a (intake air flowing along the intake port upper side wall 40a from the upstream side) is considered. Came. Next, on the premise of the first embodiment shown in FIG. 2, the tumble flow generated is not weakened by the above-described intake air b (intake air flowing from the upstream side along the intake port lower side wall 40b). Think about

  Now, in the comparative engine in which the valve seat component 90 is press-fitted, as shown in FIG. 5, the throat cutter 100 forms the first cylindrical wall 102 at the first port downstream end 43, and the second engine The second cylindrical wall 103 is formed at the port downstream end portion 45. The intake air flowing from the upstream side along the intake port lower side wall 40b changes its direction and flows along the second cylindrical wall 103 unless separated. Then, the intake air is guided by the second cylindrical wall 103 and flows toward the intake side combustion chamber 30b. This tendency is magnified in an engine having a relatively small valve holding angle such as a comparative engine. When considering the intake air flowing into the combustion chamber 30 from the intake port 40 by dividing it into three, a, b, and c as described above, the intake air guided into the intake side combustion chamber 30b by the second cylindrical wall 103 is It becomes the intake air of the above b, and it is a small amount from the intake air of the above c. However, the flow of the intake air that is guided by the second cylindrical wall 103 and flows into the intake-side combustion chamber 30b (see the thin broken line arrow in FIG. 5) is just the reverse of the tumble flow, so the direction of weakening the tumble flow is reduced. Will work.

  On the other hand, it is considered that the amount of intake air flowing into the combustion chamber 30 from the downstream end 45 of the second port relatively increases as the flow velocity of the intake air flowing through the intake port 40 decreases, even if the valve angle is the same. To be This is because the kinetic energy of the intake air decreases as the flow velocity of the intake air decreases, and the inertial force that tends to move in the same direction decreases. Further, it is conceivable that the amount of intake air flowing into the combustion chamber 30 from the second port downstream end portion 45 becomes relatively large as the valve holding angle becomes relatively small. This is because when the valve holding angle is relatively small, the intake air is less likely to move toward the first port downstream end portion 43 side than when the valve holding angle is relatively large.

  For example, the intake air flowing into the combustion chamber 30 from the intake port 40 will be considered by dividing it into two parts as in the following e and f.

e: Intake air flowing from the upstream side to above the center of the intake port 40,
f: Intake air flowing from the upstream side below the center of the intake port 40,
About half of the intake air of e is guided by the first cylindrical wall 102, and about half of the intake air of f is guided by the second cylindrical wall 103 and flows in respectively. In this case, the amount of intake air, which is just the opposite flow to the tumble flow, relatively increases, so the increased amount increases the degree of weakening the tumble flow.

  In this case, in the case of the valve seatless intake port 40, not only the downstream end portion 43 of the first port but also the downstream end portion 45 of the second port has a greater degree of freedom in shape. Therefore, a theoretical consideration will be given to what the specific shape of the downstream end portion 45 of the second port should be to prevent the flow of the intake air that acts in the direction of weakening the tumble flow. However, also here, the intake air flowing into the combustion chamber 30 from the intake port 40 will be considered by being divided into the three a, b, and c as described above.

  As shown in FIG. 4, the shape of the second port wall 46 immediately above the valve seat has a particularly strong influence on suppressing the generated tumble flow. This is because the intake air flowing from the upstream side along the intake port lower side wall 40b (that is, the intake air of b above) is guided by the second port wall 46 immediately above the valve seat and flows into the intake side combustion chamber 30b. This is because the intake air flows in the direction opposite to the tumble flow.

  Therefore, in order to prevent the intake air that has flowed in from flowing in the direction opposite to the tumble flow, make sure that the intake air that flows into the combustion chamber 30 from the second port downstream end portion 45 flows in the same direction as the tumble flow. do it. Specifically, in a cross section orthogonal to the crankshaft direction, the intake air flowing from the second port downstream end portion 45 passes above the valve center E of the intake valve 50 at the time of full lift and heads toward the exhaust side combustion chamber 30a. To do. Here, when the valve head 51 of the intake valve 50 is a short line in the horizontal direction and the valve stem 52 is a long line in the vertical direction, the intersection of the short line and the long line (see the chain double-dashed line in FIG. 16) is the intake air. It is the “valve center” of the valve 50. Alternatively, the centroid of the valve head 51 is the “valve center” of the intake valve 50.

  In reality, the valve head 51 has a vertical thickness. Therefore, in the cross section orthogonal to the crankshaft direction, the intake air that flows in using the second port downstream end portion 45 as a guide passes above the exhaust side umbrella back portion 51b of the umbrella back portion of the intake valve 50 at the time of full lift. Then, it is directed to the exhaust side combustion chamber 30a. This is because if the intake air is directed toward the top of the umbrella back portion 51c on the intake side, the flow becomes the opposite of the tumble flow and the tumble flow is weakened. In order to direct it upward from the exhaust side umbrella back portion 51b, the valve seat upper second port wall 46 is formed so as to project toward the center of the intake port 40. Then, the intake port lower side wall 40b is extended and connected to the end portion 48 of the second port wall 46 immediately above the valve seat formed by projecting toward the center of the intake port 40.

  In this case, as shown enlarged in the upper right of FIG. 16, the second sealing surface 41ab of the valve seat 41 is formed from the diagonally lower right to the diagonally upper left in a cross section orthogonal to the crankshaft direction. Therefore, a second port wall 46 immediately above the valve seat is formed on the extension of the second sealing surface 41ab of the valve seat 41 to the upper left, and is projected toward the center of the intake port. Then, it is extended from the intake port lower side wall 40b and connected to the end portion 48 of the second port wall 46 immediately above the valve seat formed so as to project toward the center of the intake port 40. Hereinafter, the portion extending from the intake port lower side wall 40b and connected to the end portion 48 of the valve seat immediately above second port wall 46 is referred to as a "valve seat immediately above second port wall connecting portion", and the symbol is "47". And

  The second port wall connecting portion 47 immediately above the valve seat is made to be a straight line in a cross section orthogonal to the crankshaft direction. The reason why the second port wall connecting portion 47 directly above the valve seat is made straight is that the intake air along the second port wall connecting portion 47 immediately above the valve seat causes separation or turbulence, which is a loss of kinetic energy in this case. Because it flows without. Further, the straight line of the second port wall connecting portion 47 immediately above the valve seat and the straight line of the intake port lower side wall 40b on the upstream side thereof are made to be the same straight line. Here, an angle ζ that is an acute angle at which a straight line of the second port wall 46 immediately above the valve seat intersects a straight line of the second port wall connecting portion 47 immediately above the valve seat in a cross section orthogonal to the crankshaft direction is defined as “third Angle ". In this case, the intake air is directed (flowing into the combustion chamber 30) mainly in the position of the second port wall connection portion 47 immediately above the valve seat and the second port wall connection portion 47 immediately above the valve seat rises from the horizontal plane. It is determined by the angle κ that is an acute angle (this angle is referred to as the “fourth angle”). Therefore, it is necessary to adjust the position of the second port wall connecting portion 47 immediately above the valve seat and the fourth angle κ so that the intake air is directed to above the exhaust side umbrella back portion 51b of the intake valve 50 at the time of full lift. .

  In the first embodiment, the second port wall 46 immediately above the valve seat forms a part of the cylindrical wall as shown in FIG. On the other hand, in the seventh embodiment, the protrusion 48, which is the connecting end of the valve seat just above the second port wall 46 and the valve seat just above the second port wall connecting portion 47, is located at the center of the intake port 40 as shown in FIG. Protruding towards. Then, as shown in FIG. 17, the protrusion 48 is formed in a straight line along the crankshaft direction.

As described above, in the seventh embodiment, the second port wall immediately above the valve seat 46, the second port wall connecting portion 47 immediately above the valve seat, and the projection 48 form a cylindrical intake air at the downstream end 45 of the second port. A pointed jump platform was formed that protrudes toward the center of the port 40. Specifically, the jump table is created in advance at the stage of casting the cylinder head 20. After the cylinder head 20 is cast, a film that is harder than the aluminum alloy for casting of the base material of the temporary seat surface formed as the valve seating portion is formed as the valve seat layer by the cold spray method as described above. That is, by using He or N ₂ as a working gas by the cold spray method, metal particles harder than the casting aluminum alloy of the base material are driven into the temporary sheet surface of the base material, thereby casting the aluminum alloy for the casting material of the base material. A harder film is formed as the valve seat layer. In this way, after the valve seat layer (hard surface) is roughly formed by the cold spray method, the valve seat layer roughly formed by the cold spray method is cut using a throat cutter. Finally, the valve seat layer after the cutting process is polished to complete the seat surface of the valve seat 41 according to specifications (according to dimensions).

  When the intake valve 50 is lifted downward by the above jump base, the intake air of the above b (the intake air flowing along the intake port lower side wall 40b from the upstream side) is guided by the second port wall connecting portion 47 immediately above the valve seat. Air) flows in. Most of the intake air b flowing into the exhaust valve of the intake valve 50 at the time of full lift when the flow speed of the intake air passing through the second port wall connecting portion 47 immediately above the valve seat is equal to or higher than a predetermined value. Peel off toward the top of the portion 51b. Of the intake air of the above b, the amount of intake air that flows from the second port wall connecting portion 47 immediately above the valve seat to the second port wall 46 immediately above the valve seat and flows along the second port wall 46 immediately above the valve seat is Very small and negligible. The intake air separated from the second port wall connection portion 47 immediately above the valve seat passes above the exhaust side umbrella back portion 51b of the intake valve 50 at the time of full lift and flows into the exhaust side combustion chamber 30a. The flow of the intake air (the intake air of the above b) guided by the second port wall connecting portion 47 immediately above the valve seat is the direction of the tumble flow generated by the intake air of the above a (including the intake air of the above c). Is the same as. The inflow of intake air in the same direction as the tumble flow does not weaken the tumble flow. In the seventh embodiment, the intake air hardly flows into the intake side combustion chamber 30b using the second port wall 46 immediately above the valve seat corresponding to the second cylindrical wall 103 of the comparative engine as a guide.

  In this case, the extent to which the intake air is separated from the second port wall connecting portion 47 directly above the valve seat is the same as the speed of the flow of intake air passing through the second port wall connecting portion 47 immediately above the valve seat and the amount of intake air. If so, it is determined by the third angle ζ. For example, the smaller (the sharper) the third angle ζ is, the easier the intake air is separated from the second port wall connecting portion 47 immediately above the valve seat. On the other hand, the third angle ζ cannot be made so small in terms of manufacturing and strength. Therefore, the third angle ζ may be adapted so that the two are balanced.

  On the other hand, if the third angle ζ is the same, as the flow velocity of the intake air passing through the valve port immediately above the second port wall connection portion 47 increases, the air is separated from the valve seat immediately above the second port wall connection portion 47. Intake air goes further. Here, the speed of the flow of the intake air passing through the intake port lower side wall 40b depends on the engine specifications and the operating conditions of the engine. Therefore, for example, it is assumed that the driving conditions in which the same engine is desired to avoid knocking are determined. After that is determined, under operating conditions where knocking is desired to be avoided, intake air from the second port wall connection portion 47 immediately above the valve seat passes above the exhaust valve side umbrella back portion 51b of the intake valve at full lift and exhaust side combustion is performed. The third angle ζ is adapted to face the chamber 30a.

  Here, the effects of the seventh embodiment will be described.

  In the seventh embodiment, the second port wall connecting portion 47 immediately above the valve seat (the intake port wall in the portion directly above the first valve seat opposite to the cylinder center BC) is transmitted along the intake port lower side wall 40b (intake port lower side wall). ) As a guide, the intake air flows into the combustion chamber 30. The intake air (intake air of the above b) flowing in passes through above the exhaust side umbrella back portion 51b (valve center E) of the intake valve 50 at the time of full lift and goes to the exhaust side combustion chamber 30a so that the intake air is directed directly to the valve seat. The upper second port wall connecting portion 47 is formed. The flow of the intake air passing above the exhaust side umbrella back portion 51b of the intake valve 50 toward the exhaust side combustion chamber 30a at the time of full lift is generated by the intake air from the first port wall 44 immediately above the valve seat. It is the same as the direction of flow. The inflow of intake air in the same direction as the tumble flow does not weaken the tumble flow. For the engine having the valve seatless intake port 40, the tumble flow is stronger than that of the comparative engine or the first embodiment. As a result, the occurrence of knocking can be suppressed without increasing the amount of fuel, particularly in the medium rotation speed and high load range.

  Here, the intake air flowing into the combustion chamber 30 from the intake port 40 is considered as being divided into the three a, b, and c as described above, and the intake air of the above b is connected to the second port wall immediately above the valve seat. The seventh embodiment is applied when the portion 47 is used as a guide. On the other hand, the intake air flowing from the intake port 40 into the combustion chamber 30 is considered as divided into two, e and f as described above, and the intake air of the above-mentioned f causes the second port wall connecting portion 47 right above the valve seat. The seventh embodiment can be applied to the case of flowing in as a guide. When the intake air flowing into the combustion chamber 30 from the intake port 40 is divided into three, a, b, and c as described above, or the intake air flowing from the intake port 40 into the combustion chamber 30 is e, f as described above. Whether it is divided into two depends on the engine specifications including the valve holding angle and the engine operating conditions. Therefore, it is particularly useful to apply the seventh embodiment to an engine in which the intake air flowing from the intake port 40 into the combustion chamber 30 is divided into two, e and f, as described above. By applying the seventh embodiment to the engine, the exhaust passage-side combustion chamber is guided by the second port wall connecting portion 47 immediately above the valve seat and passes above the exhaust-side umbrella back portion 51b of the intake valve 50 at the time of full lift. The amount of intake air toward 30a relatively increases, and the tumble flow is strengthened. In the operating range where the tumble flow is strengthened, the occurrence of knocking can be further suppressed.

  In the seventh embodiment, the second port wall 46 immediately above the valve seat (the intake port wall immediately above the first valve seat on the side opposite to the cylinder center) is formed so as to project toward the center of the intake port 40. . Then, the second port wall 46 immediately above the valve seat is connected to the end portion 48 of the second port wall 46 so as to extend from the intake port lower side wall 40b (intake port lower side wall). As a result, a jump base is formed which protrudes from the intake port lower side wall 40b toward the center of the cylindrical intake port 40. In this case, the second port wall connecting portion 47 immediately above the valve seat serves as the sliding surface of the jump base. Therefore, the intake air (that is, the intake air of b) flowing into the combustion chamber 30 by using the second port wall connection portion 47 immediately above the valve seat as a guide passes above the exhaust side umbrella back portion 51b of the intake valve 50 at the time of full lift. It is possible to pass through and go to the exhaust side combustion chamber 30a.

  In addition, in the technique of the above-mentioned Patent Document 1, a step portion protruding inside the intake port is provided at the boundary between the intake port lower side wall 40b and the throat portion of the valve seat that is continuous with the intake port. Although the stepped portion corresponds to the jump base of the present invention, the technique of the above-mentioned Patent Document 1 is premised on the engine in which the valve seat component is press-fitted. Therefore, the stepped portion is provided directly above the second cylindrical wall 103 described in FIG. There is no choice but to form. On the other hand, in the seventh embodiment, since the degree of freedom in the shape of the second port downstream end portion 45 is increased, the position where the jump base is formed in the seventh embodiment is lower than in the case of the technique of Patent Document 1 described above. Is set to.

(Eighth to Eleventh Embodiments)
18 to 21 are eighth to twelfth embodiments, which replace FIG. 16 of the seventh embodiment. The same parts as those in FIG. 16 of the seventh embodiment are designated by the same reference numerals.

  In the seventh embodiment, the shapes of the second port wall 46 immediately above the valve seat and the second port wall connecting portion 47 immediately above the valve seat are straight in a cross section orthogonal to the crankshaft direction. On the other hand, the eighth to twelfth embodiments are mainly variations of the shape of the second port wall 46 immediately above the valve seat. That is, in the present invention, the second port wall immediately above the valve seat 46 is mainly related to the degree of separation of intake air from the second port wall connection portion immediately above the valve seat 47. The direction of the intake air flowing from the wall connecting portion 47 is not so affected. For example, as the end portion 48 is more rounded, the proportion of the intake air that wraps around from the valve seat just above the second port wall connection portion 47 to the valve seat just above the second port wall 46 increases in the intake air b. Further, even if the shape of the second port wall immediately above the valve seat 46 is not a straight line, the intake air of b can be separated from the second port wall connecting portion 47 immediately above the valve seat. In other words, the intake air that flows in using the second port wall connection portion 47 just above the valve seat as a guide can be separated toward the top of the valve seat just above the exhaust side umbrella back portion 51b of the intake valve 50 at the time of full lift. The second port wall 46 can take various shapes.

  First, in the eighth embodiment shown in FIG. 18, in the cross section orthogonal to the crankshaft direction, the shape of the second port wall immediately above the valve seat is a convex curve protruding toward the center of the intake port 40. The convex curve of the second port wall 46 right above the valve seat and the straight line of the second port wall connection 47 right above the valve seat are connected smoothly. In the ninth embodiment shown in FIG. 19, the shape of the second port wall 46 immediately above the valve seat in the cross section orthogonal to the crankshaft direction is a concave curve that is recessed away from the center of the intake port 40. In order to smoothly connect this concave curve of the valve seat just above the second port wall 46 and the straight line of the valve seat just above the second port wall connecting portion 47, the downstream end of the valve seat just above the second port wall connecting portion 47 is It is not a straight line but an upwardly convex curve. In the tenth embodiment shown in FIG. 20, the second port wall 46 immediately above the valve seat has a stepped shape in a cross section orthogonal to the crankshaft direction. That is, in the tenth embodiment, since the second seat surface 41ab of the valve seat 41 projects outward in the radial direction of the cylindrical intake port 40 from the second port wall 46 immediately above the valve seat, the second seat surface 41ab of the valve seat 41 is A step is formed between the seat surface 41ab and the seat surface 41ab. In the eleventh embodiment shown in FIG. 21, the shape of the second port wall 46 immediately above the valve seat in the cross section orthogonal to the crankshaft direction is set as a part of a polygon projecting toward the center of the intake port 40. There is. A part of this polygon of the second port wall 46 right above the valve seat and the straight line of the second port wall connection 47 right above the valve seat are connected at a predetermined angle.

  Also in the eighth to eleventh embodiments, the same operational effects as in the seventh embodiment can be obtained.

(Twelfth Embodiment)
22 shows a twelfth embodiment, which replaces FIG. 16 of the seventh embodiment. The same parts as those in FIG. 16 of the seventh embodiment are designated by the same reference numerals.

  In the seventh embodiment, the respective shapes of the valve seat just above the second port wall 46 and the valve seat just above the second port wall connecting portion 47 are straight in a cross section orthogonal to the crankshaft direction. On the other hand, in the twelfth embodiment, the shape of the second port wall connecting portion 47 immediately above the valve seat is a downwardly convex smooth curve in a cross section orthogonal to the crankshaft direction. In other words, the shape of the second port wall connecting portion 47 immediately above the valve seat is a downwardly convex, smooth curved surface in the vicinity of a predetermined range in the crankshaft direction around the cross section orthogonal to the crankshaft direction. . The reason for this is that the shape of the jump table described above in the seventh embodiment is improved so that the intake air b is directed toward the upper portion of the exhaust side combustion chamber 30a. That is, it is assumed that the velocity of the intake air flowing through the intake port lower side wall 40b is the same. At this time, when the flow is performed using the second seat wall connection part 47 directly above the valve seat, which is a smooth curved surface that is convex downward, as a guide, the second seat port wall connection part 47 immediately above the valve seat, which has a linear cross-sectional shape, is used. The intake air goes diagonally upward to the left rather than when it flows as a guide. In the case where the intake air of b above is guided by the second port wall connecting portion 47 immediately above the valve seat, which is a smooth curved surface convex downward, the intake air of b above is given an inertial force directed diagonally upward to the left. is there. Due to this inertial force, the intake air of b flowing from the second port wall connecting portion 47 immediately above the valve seat is directed toward the upper portion of the exhaust side combustion chamber 30a.

  In the twelfth embodiment, in the cross section orthogonal to the crankshaft direction, the shape of the second port wall connection portion 47 immediately above the valve seat (the portion that extends and connects the lower side wall of the intake port) has a smooth downward convex shape. Curved. As a result, the intake air flowing from the upstream side along the intake port lower side wall 40b (that is, the intake air of b above) is guided by the second port wall connection portion 47 immediately above the valve seat, which is a smooth curved surface convex downward. Flowing. Then, while the intake air of the above b flows through the second port wall connecting portion 47 immediately above the valve seat, which is a smooth curved surface convex downward, the intake air is given an inertial force directed obliquely upward to the left. Due to this inertial force, the intake air b described above flowing from the second port wall connecting portion 47 immediately above the valve seat, which is a smooth curved surface that is convex downward, can be directed toward the upper portion of the exhaust side combustion chamber 30a.

  By the way, in the seventh to tenth embodiments shown in FIGS. 16 to 20, the shapes of the second port wall immediately above the valve seat 46 and the first port wall 44 immediately above the valve seat are orthogonal to the crankshaft direction. The cross section of the intake valve 50 is line-symmetrical about the axis CC of the intake valve 50. The reason for this is as follows. That is, if the first port wall 44 just above the valve seat and the second port wall 46 just above the valve seat have different shapes, the production cost will increase. In this respect, the shapes of the first port wall 44 immediately above the valve seat and the second port wall 46 immediately above the valve seat are line-symmetrical with respect to the axial center CC of the intake valve 50 in a cross section orthogonal to the crankshaft direction. Then, it becomes possible to use an axially symmetric rotating body tool. By using an axially symmetric rotating tool, the valve port just above the first port wall 44 and the valve seat just above the second port wall 46 can be manufactured at once. This can reduce the production cost.

  In the seventh to tenth embodiments, the axial center CC of the intake valve 50 in the cross section in which the shapes of the second port wall immediately above the valve seat 46 and the first port wall 44 immediately above the valve seat are orthogonal to the crankshaft direction. The line is symmetrical about the center. This can further reduce the production cost.

(13th Embodiment)
FIG. 23 shows a thirteenth embodiment of the present invention, which replaces FIG. 16 of the seventh embodiment. The same parts as those in FIG. 16 of the seventh embodiment are designated by the same reference numerals.

  In the seventh embodiment, the projection 48 protruding toward the center of the cylindrical intake port 40 is formed by the valve port just above the second port wall connecting portion 47 and the valve seat just above the second port wall 46. On the other hand, the intake port downstream end 42 is throttled (see FIGS. 16 and 17). In other words, the cross-sectional area of the intake port downstream end portion 42 (43, 45) is narrower than that in the case where the protrusion 48 protruding toward the center of the cylindrical intake port 40 is not formed.

  Therefore, in the thirteenth embodiment, while achieving the effect originally aimed at by the seventh embodiment, even if the second port downstream end portion 45 has almost no protrusion, the port flow rate is maximized. It is a thing. That is, in the cross section orthogonal to the crankshaft direction, the intake port lower side wall 40b is connected to the upper surface 41b of the valve seat 41 on the side away from the cylinder center BC (right side in FIG. 23).

  In the thirteenth embodiment, the second port wall 46 immediately above the valve seat and the second port wall connecting portion 47 immediately above the valve seat are not provided. Instead, the intake port lower side wall 40b at the portion connected to the upper surface 41b on the side away from the cylinder center BC of the valve seat 41 plays the role of the second port wall connection portion 47 immediately above the valve seat. Here, the intake port lower side wall 40b at the part connected to the upper surface 41b on the side away from the cylinder center BC of the valve seat 41 is defined as "intake port lower side wall connection part", and the reference sign is "40c". That is, the intake port lower side wall connection portion 40c is formed so that the intake air of the above b passes above the exhaust side valve umbrella back portion 51b of the intake valve 50 at the time of full lift and heads toward the exhaust side combustion chamber 30a.

  In this case, the entire intake port lower side wall connecting portion 40c and the upstream side intake port lower side wall 40b connected thereto have a downwardly convex curve in a cross section orthogonal to the crankshaft direction. This is for the following reason. That is, in the thirteenth embodiment, since the valve seat just above the second port wall 46 and the valve seat just above the second port wall connecting portion 47 are not provided, the position of the intake port lower side wall connecting portion 40c is the case of the seventh embodiment. Move downward. If the amount of movement to the lower side is not taken into consideration, the intake air of b may not go above the exhaust side umbrella back 51b of the intake valve 50 at the time of full lift. Therefore, even if the position of the intake port lower side wall connection portion 40c is moved lower than in the case of the seventh embodiment, the intake air b is directed toward the exhaust side umbrella back part 51b of the intake valve 50 at the time of full lift. This is because As described above, by injecting the intake air of b along the intake port lower side wall connection portion 40c which is a downwardly convex curve, an inertial force in a diagonally upward left direction is applied to the intake air of b. As a result, the intake air of b separated from the intake port lower side wall connection portion 40c passes above the exhaust side valve umbrella back portion 51b of the intake valve 50 at the time of full lift and heads toward the exhaust side combustion chamber 30a. Become.

  For comparison, the case of the seventh embodiment in which the protrusion 48 protruding toward the center of the intake port 40 is formed by the second port wall connecting portion 47 immediately above the valve seat and the second port wall 46 immediately above the valve seat will be described. 23 are overlapped with a broken line. A detailed diagram is shown in the upper right of FIG. As shown in FIG. 23, in the thirteenth embodiment, since the valve seat just above the second port wall 46 and the valve seat just above the second port wall connecting portion 47 are not provided, the intake port lower side wall connecting portion 40c is a broken line. Is closer to the combustion chamber side 13 than in the case of the seventh embodiment shown by. In the seventh embodiment shown by the broken line in FIG. 23, the port diameter has a predetermined value R1, whereas in the thirteenth embodiment, the port diameter has a predetermined value R2 larger than R1. Since the port cross-sectional area is proportional to 1/2 the port diameter squared, the port cross-sectional area increases as the port diameter increases from R1 to R2. As described above, in the thirteenth embodiment, the port cross-sectional area is enlarged by reducing the vertical thickness of the protrusion 48 protruding toward the center of the intake port 40 to the limit.

  In the thirteenth embodiment, in the cross section orthogonal to the crankshaft direction, the intake port lower side wall connection portion 40c (the lower side wall of the intake port) is provided on the second seat surface 41ab (the upper surface 41b on the side away from the cylinder center BC of the first valve seat). ) Is connected. As a result, the intake air b flowing into the intake port lower side wall connecting portion 40c as a guide passes above the exhaust side valve canopy back portion 51b of the intake valve 50 at the time of full lift and is directed toward the exhaust side combustion chamber 30a. The port cross-sectional area can be increased while

  In the thirteenth embodiment, in the cross section orthogonal to the crankshaft direction, the shape of the intake port lower side wall connecting portion 40c (the lower side wall of the intake port of the portion connecting to the upper surface of the first valve seat on the side away from the cylinder center) is made lower. It has a convex curve. As a result, even if the position of the intake port lower side wall connecting portion 40c is moved downward as compared with the case of the seventh embodiment, the intake air b is directed to the upper side of the exhaust side umbrella back 51b of the intake valve 50 at the time of full lift. You can

(14th-18th Embodiment)
24 to 28 are the fourteenth to eighteenth embodiments, which replace FIG. 17 of the seventh embodiment. The same parts as those in FIG. 17 of the seventh embodiment are designated by the same reference numerals.

  In the seventh embodiment, as shown in FIG. 17, the protruding end portion 48 is linear in the cross section in the crankshaft direction. On the other hand, the fourteenth to eighteenth embodiments are variations of the shape of the protrusion end portion 48. That is, in the fourteenth embodiment shown in FIG. 24, the shape of the protrusion end portion 48 in the cross section in the crankshaft direction is a convex curve whose center projects toward the center of the intake port 40 rather than the periphery. In the fifteenth embodiment shown in FIG. 25, the shape of the protrusion end portion 48 in the cross section in the crankshaft direction is a concave curve whose center is recessed toward the intake port lower side wall (40b) rather than the periphery. In the sixteenth embodiment shown in FIG. 26, in the cross section in the crankshaft direction, the projection end portion 48 has a shape in which short straight lines extending outward in the radial direction are connected to both ends of the semicircle. In the seventeenth embodiment shown in FIG. 27, the protrusion end portion 48 has a sawtooth shape in a cross section in the crankshaft direction.

  In the fourteenth to eighteenth embodiments, in the cross section in the crankshaft direction, the shapes of the projection ends 48 are all line-symmetric with respect to the line orthogonal to the crankshaft direction. On the other hand, in the eighteenth embodiment shown in FIG. 28, as in the seventh embodiment, the shape of the protrusion end portion 48 is a straight line in the cross section in the crankshaft direction. However, unlike the seventh embodiment, the shape of the protrusion end portion 48 is asymmetric with respect to the line orthogonal to the crankshaft direction.

  Also in the fourteenth to eighteenth embodiments, the same operational effects as in the seventh embodiment can be obtained. Further, in the seventeenth embodiment shown in FIG. 27, since the flow velocity varies, a turbulent flow can be generated in addition to the tumble flow. In the eighteenth embodiment shown in FIG. 28, a swirl flow can be generated in addition to the tumble flow.

  In the embodiment, the intake air flowing into the combustion chamber 30 from the intake port 40 is divided into three parts, and the intake air flowing into the combustion chamber 30 from the intake port 40 is divided into two parts. The present invention is not limited to these cases.

  The respective embodiments from the first embodiment to the eighteenth embodiment can be combined within a range that does not contradict.

  In the embodiment, the case of a gasoline engine has been described, but a diesel engine may be used.

  The vertical dimension of the embodiment does not represent the actual dimension. That is, although the engine of the embodiment looks like a short stroke engine, the actual engine is a long stroke engine. Of course, the present invention is not limited to a long stroke engine, and the present invention is also applicable to a short stroke or square stroke engine.

1 engine 11 cylinder 12 exhaust side cylinder wall (exhaust side cylinder wall)
15 Piston 15a Piston crown 26 Intake side roof (intake side roof of pent roof)
27 Exhaust side roof (Exhaust side roof)
30 Combustion chamber 30a Exhaust side combustion chamber (combustion chamber on exhaust side from cylinder center)
40 intake port 40a intake port upper side wall (intake port upper side wall)
40b Intake port lower side wall (intake port lower side wall)
40c Intake port lower side wall connection part 41 Valve seat (first valve seat)
41a valve seat seat surface 41aa valve seat first seat surface 41ab valve seat second seat surface (upper side of first valve seat away from cylinder center)
41b Upper surface of valve seat 42 Inlet port downstream end 43 First port downstream end 44 First valve wall immediately above valve seat (intake port wall immediately above the first valve seat on the cylinder center side)
45 Downstream end of 2nd port 46 2nd port wall just above valve seat (intake port wall directly above the 1st valve seat on the side opposite to the cylinder center)
47 2nd port wall immediately above the valve seat 50 Intake valve 51 Valve head 51a Sealing surface 51b Exhaust side valve umbrella back 60 Exhaust port 61 Valve seat (second valve seat)

Claims (1)

A piston connected to the crankshaft strokes the cylinder in the vertical direction,
The roof of the pent roof has a combustion chamber with an intake port on the intake side roof and an exhaust port on the exhaust side roof,
A first valve seat on which an intake valve is seated at an opening end of the intake port to the combustion chamber; and a second valve seat on which an exhaust valve seats at an opening end of the exhaust port to the combustion chamber.
In an engine in which a tumble flow is generated in the combustion chamber by intake air flowing into the combustion chamber from a downstream end of the intake port,
A cylinder head is provided at the top of the combustion chamber,
The first valve seat is formed as a hard film made of a material that is harder than the base material of the cylinder head,
In a cross section orthogonal to the crankshaft direction, the angle of the intake port wall on the cylinder center side immediately above the first valve seat, which rises from the horizontal line, is the intake port wall on the cylinder center side immediately above the first valve seat. Of the piston and the straight line connecting the intersection of the cylinder wall on the exhaust side and the piston crown surface at the bottom dead center with the piston crown surface is less than or equal to the first acute angle or flows into the combustion chamber. A second angle or more, which is an acute angle formed by a line passing through the center of the tumble by reflecting the intake air in the combustion chamber and the piston crown surface,
The straight line formed by the intake port wall of the first valve seat on the cylinder center side and the straight line formed by the first seat surface of the first valve seat on the cylinder center side are aligned with each other so that the straight line forms a straight line. An engine having a first seat surface .

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