JP4760765B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine, and more particularly, to an internal combustion engine that preferably allows intake air to flow into a cylinder when generating a swirling airflow in the cylinder.

  Conventionally, in an internal combustion engine, a technique for generating a swirling airflow such as tumble (vertical vortex) or swirl (lateral vortex) in a cylinder is known. In the internal combustion engine that generates the swirling airflow, it is possible to expand the lean combustion region of the internal combustion engine and improve the output performance by generating the swirling airflow having higher strength. In this respect, in generating a strong swirling airflow, the inflow mode of intake air flowing into the cylinder is one of the important factors. On the other hand, for example, Patent Document 1 or 2 proposes a technique for improving the inflow mode of the intake air flowing into the cylinder.

JP-A-07-279751 Japanese Utility Model Publication No.59-135335

  By the way, the emission of unburned HC, CO, etc. contained in the exhaust gas of the internal combustion engine can be reduced by improving the combustibility of the air-fuel mixture, and in order to improve the combustibility, the mixing property of the air-fuel mixture is improved. Is effective. In this regard, in an internal combustion engine that generates a tumble flow in a cylinder, it is effective to add a swirl component to the tumble flow to improve the mixing property of the air-fuel mixture. However, since the technique proposed in Patent Document 1 is a technique for generating a pure tumble flow that does not substantially have a swirl component, compared to the case of generating a tumble flow having a swirl component, the mixing property of the air-fuel mixture is improved. There is a risk of lowering relatively. For this reason, with the technique proposed in Patent Document 1, there is a possibility that a sufficient or more preferable result cannot be obtained from the viewpoint of emission reduction.

  On the other hand, as a technique for generating a swirl flow, conventionally, for example, an internal combustion engine having an intake two-valve structure is used as an example. A technique for generating a swirl flow by giving directivity to inflowing intake air is known. For this reason, it is also conceivable to generate a tumble flow having a swirl component and improve the mixing property of the air-fuel mixture by using such a technique. However, when such a technique is used, the swirl component is applied at the expense of the intake air amount, so that the volumetric efficiency of the internal combustion engine decreases, and as a result, the high load performance of the internal combustion engine is increased. The problem is that this becomes difficult.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide an internal combustion engine in which intake air can suitably flow into a cylinder so as to generate a tumble flow having a swirl component.

In order to solve the above-mentioned problems, the present invention is an internal combustion engine having a plurality of intake valves per cylinder having an umbrella part and a stem connected to the umbrella part at one end, the cylinders being located at both ends of the cylinder. A first specific intake valve is provided as one intake valve of the intake valve, a second specific intake valve is provided as the other intake valve, and the first specific intake valve is the same as the first specific intake valve. Of the intake passage areas divided into two by a plane including the central axis of the stem, the outer passage area located outside the combustion chamber is enlarged, and the center of the stem of the first specific intake valve is increased. the so that the axis line does not contain the center point of the bottom surface of the umbrella portion of the first intake-valve first of the stem of the intake-valve are offset, the second intake-valve, the second The central axis of the stem of the specific intake valve of 2 The inner passage region located on the combustion chamber center side among the passage regions of the intake air divided into two by a flat surface increases, and the central axis of the stem of the second specific intake valve is the second The stem of the second specific intake valve is offset so as not to include the center point of the bottom surface of the umbrella portion of the specific intake valve . According to the present invention, by ensuring a large outside passage region, intake air can be suitably introduced into the cylinder so as to generate a tumble flow having a swirl component. In addition, according to the present invention in which the first specific intake valve with the stem offset as described above is provided to allow the intake air to flow appropriately into the cylinder, the air-fuel mixture is not particularly reduced without incurring a decrease in volumetric efficiency of the internal combustion engine. Thus, it is possible to improve the mixing performance, and to reduce emissions appropriately.

  In general intake valves, the stem is formed so that the central axis of the stem includes the center point of the bottom surface of the umbrella portion and extends perpendicularly to the bottom surface from the viewpoint of strength and ease of processing. However, in the first specific intake valve, the stem is offset so that the central axis of the stem does not include the center point of the bottom surface of the umbrella portion. In this respect, the first specific intake valve is a general intake valve. Is different.

  Further, the plane including the central axis of the stem described in the present invention is not necessarily limited to one plane as long as it is a plane that can divide the passage region of the intake air into the combustion chamber inside and outside of the stem. Is a plane that divides the intake passage region into an inner side and an outer side so that the main flow of the intake air flowing so as to be generated as a swirling airflow in the cylinder is included in the outer passage region. Is preferred. In this regard, considering the flow of intake air flowing into the cylinder from the viewpoint of adding a swirl component to the tumble flow, the stem is offset if the present invention is realized as a plane parallel to the cylinder axis. As a result, it is preferable in that the main flow of intake air can be included in the outer passage region more reliably and more reliably.

  Further, in order to increase the outer passage region described in the present invention, it means that the outer passage region becomes larger as compared with the case where the stem related to the first specific intake valve is not offset. In consideration of the passage region of the intake air flowing into the cylinder from the viewpoint of allowing the swirl component to be applied, the stem relating to the first specific intake valve is more specifically the outer passage region is the other inner passage region. It is preferable that the offset is made larger.

  According to the present invention, it is possible to secure a large inner passage region related to the second specific intake valve, and as a result of offsetting the first specific intake valve, the tumble component of the swirling airflow generated in the cylinder is more than necessary. It can suppress that it falls large. At the same time, according to the present invention, by reducing the other outer passage region related to the second specific intake valve, the amount of intake air flowing outside the combustion chamber rather than the stem of the first specific intake valve is reduced to the second. Since the amount of intake air that circulates outside the combustion chamber can be made relatively larger than the stem of the specific intake valve, it can contribute to the application of a larger swirl component. For this reason, according to the present invention, intake air can be flowed more suitably into the cylinder in order to generate a tumble flow having a swirl component.

  Depending on the degree of offset of each of the stems related to the first and second specific intake valves, the amount of intake air that flows toward the center of the combustion chamber increases compared to the case where each of these stems is not offset. It is also conceivable that a swirl component having a sufficient size cannot be imparted to the generated swirling airflow. In this regard, in order to be able to apply a sufficiently large swirl component, the amount of intake air flowing between the stems related to the first and second specific intake valves does not offset each of these stems. It is preferable to offset each of these stems so as to be equal to or smaller than the case.

  Specifically, for example, it is preferable that the stems related to the first and second specific intake valves are offset in the same direction to approximately the same degree in that a sufficiently large swirl component can be more reliably applied. . In addition, for example, the stem offset level of the second specific intake valve may be set to be equal to or lower than the stem offset level of the first specific intake valve to offset each of the stems related to the first and second specific intake valves. It is preferable in that a swirl component having a sufficient size can be more reliably applied. However, the present invention is not limited to this. For example, when the swirl component is effectively applied depending on the shape of the intake port, the tumble component of the swirling airflow generated in the cylinder is not excessively reduced. The offset degree of the stem related to the second specific intake valve may be made larger than the offset degree of the stem related to the first specific intake valve to offset each of the stems related to the first and second specific intake valves. Good.

In addition, the intake valves located at both ends of one cylinder described in the present invention correspond to two intake valves provided for each cylinder in an intake two-valve internal combustion engine, and the same applies to the invention described below. is there. In this case, one of the two intake valves provided per cylinder corresponds to the first specific intake valve, and the other corresponds to the second specific intake valve . Further, the plane including the central axis of the stem described in the present invention is not necessarily limited to one plane as long as it is a plane that can divide the passage region of the intake air into the combustion chamber inside and the outside of the stem. From the same viewpoint as the specific intake valve, the plane is preferably a plane that divides the intake passage region into an inner side and an outer side so that more main flow of intake air is included in the inner passage region.

  In this respect, more specifically, for example, if the present invention is realized by making this plane further parallel to the cylinder axis in the same manner as the first specific intake valve described above, the main flow of intake air is further increased as a result of offsetting the stem. It is preferable in that it can be included in the inner passage region more reliably and more reliably. Further, in order to increase the inner passage region described in the present invention, it means that the inner passage region becomes larger as compared with the case where the stem related to the second specific intake valve is not offset. From the same viewpoint as the case of the first specific intake valve described above, more specifically, the stem related to the specific intake valve is offset so that the inner passage region is larger than the other outer passage region. Is preferred.

In the present invention, the stem related to the first specific intake valve may be offset upstream of the center point related to the first specific intake valve in the flow direction of intake air. The stem related to the second specific intake valve may be offset upstream of the center point related to the second specific intake valve in the flow direction of intake air.

  When offsetting the stem of the specific intake valve, specifically, it is offset in a direction perpendicular to the flow direction of the intake air in the horizontal projection view, and in addition to this, the flow direction of the intake air further relates to the specific intake valve. It can be offset downstream of the center point, or can be offset upstream of the center point of the specific intake valve in the direction of intake air flow. That is, when the stem of the specific intake valve is offset, the first specific intake valve has the cylinder center axis, and the second specific intake valve has a side closer to a plane parallel to the flow of intake air. Can be offset respectively to the side away from a plane parallel to the intake air flow, including the cylinder center axis.

  In this regard, when the stem of the specific intake valve is offset downstream of the center point related to the specific intake valve in the flow direction of the intake air, the intake air is directly above the umbrella portion related to the specific intake valve and on the wake side. There is a risk that the flow of water will not be formed smoothly. Therefore, it is preferable that the stem related to the specific intake valve is specifically offset as in the present invention. According to the present invention, intake air can be suitably introduced into the cylinder so as to generate a tumble flow having a larger swirl component.

  Further, according to the present invention, the portion of the umbrella portion relating to the first specific intake valve that corresponds to the intake air that circulates outside the combustion chamber from the stem is closer to the combustion chamber center than the stem. The volume may be smaller than the portion corresponding to the intake air that circulates. According to the present invention, since it is possible to secure a larger passage region of the intake air that flows outside the combustion chamber than the stem related to the first specific intake valve, in order to generate a tumble flow having a larger swirl component, The intake air can be preferably introduced.

  Further, according to the present invention, the portion of the umbrella portion related to the second specific intake valve that corresponds to the intake air that flows through the combustion chamber center side of the stem portion is located outside the combustion chamber than the stem portion. The volume may be smaller than the portion corresponding to the intake air that circulates. According to the present invention, it is possible to secure a larger passage area of the intake air that circulates in the center of the combustion chamber than the stem related to the second specific intake valve, and at the same time, as compared with the stem of the second specific intake valve. The amount of intake air flowing outside the combustion chamber is relatively reduced. As a result, the amount of intake air flowing outside the combustion chamber is smaller than that of the first specific intake valve stem. Therefore, in order to generate a tumble flow having a sufficiently large tumble component and swirl component, the intake air is sucked into the cylinder. It can flow in suitably.

  ADVANTAGE OF THE INVENTION According to this invention, in order to produce | generate the tumble flow which has a swirl component, the internal combustion engine which can flow in intake air suitably in a cylinder can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram schematically showing a main part of an internal combustion engine 300 according to this embodiment for each cylinder in a vertical sectional view. The internal combustion engine 300 is an in-cylinder direct fuel injection gasoline engine, and the internal combustion engine 300 has an intake two-valve structure. However, the internal combustion engine 300 is not particularly limited as long as it can effectively implement the present invention, and may be, for example, a so-called lean burn engine, or may be an intake three-valve structure, for example. The internal combustion engine 300 may have an appropriate number of cylinders and a cylinder arrangement structure.

The internal combustion engine 300 includes a cylinder block 51, a cylinder head 52, a piston 53, and the like. A substantially cylindrical cylinder 51a is formed in the cylinder block 51, and a piston 53 is accommodated in the cylinder 51a. A cylinder head 52 is fixed to the cylinder block 51. The combustion chamber 54 is formed as a space surrounded by the cylinder block 51, the cylinder head 52, and the piston 53. The cylinder head 52 has intake ports 10a and 10b (hereinafter simply referred to as the intake port 10 when collectively referred to as intake ports 10) for introducing intake air into the combustion chamber 54 (hereinafter also referred to simply as cylinders). And an exhaust port 20 for exhausting the combusted gas from the combustion chamber 54, respectively, an intake valve 301 for opening and closing the intake port 10, and an exhaust for opening and closing the exhaust port 20 Valves 55 are respectively provided. In the present embodiment, the first specific intake valve is realized by the intake valve 301a, and the second specific intake valve is realized by the intake valve 301b.

  The spark plug 56 is disposed in the cylinder head 52 with an electrode protruding into the combustion chamber 54 from above. A fuel injection valve (not shown) is disposed in the cylinder head 52 with an injection hole protruding into the intake port 10 so that the fuel injection valve can directly inject fuel into the cylinder 51a during the intake stroke. It has become. The fuel injection valve is not limited to this. For example, the fuel injection valve is arranged in the cylinder head 52 at a position closer to the cylinder block 51 than the intake port 10 with the injection hole protruding into the combustion chamber 54 or above the combustion chamber 54. May be provided. The intake air flowing into the cylinder from the intake port 10 is generated as a swirling airflow in the cylinder. In this embodiment, the swirling airflow is specifically a tumble flow (hereinafter simply referred to as an oblique tumble flow) TS having a swirl component as shown in FIG.

  FIG. 2 is a diagram schematically showing a main part of the internal combustion engine 300 for each cylinder in a horizontal projection view. 3 is a view schematically showing the intake valve 301 in the CC section shown in FIG. As shown in FIG. 2, the intake port 10 extends so as to circulate intake air toward the combustion chamber 54 in a horizontal projection view. Thereby, macroscopically, the main flow of the intake air in which the intake air flows toward the combustion chamber 54 along the flow direction F of the intake air is formed macroscopically. In this embodiment, the flow direction F of the intake air is changed to the flow direction of the intake air. It is said.

In the present embodiment, the main flow of the intake air is further formed into a flow that circulates along the flow direction Ft of the intake air shown in FIG. 2 when flowing into the cylinder. In this respect, the flow direction of the intake air indicates the direction in which the main flow of the intake air flowing so as to be generated as a swirling air flow in the cylinder, for example, the main flow in the vicinity of the stem stm of the intake valve 301 and the umbrella portion ub. Focusing on the flow direction, the flow direction Ft of intake air can also be used. In this case, be carried out suitably present invention than when based on the flow direction of the intake air when viewed macroscopically, but the flow direction of the intake air when viewed macroscopically from the standpoint of ease of design for the present invention The case where it is based is also included. The intake air flow direction is not limited to the intake air flow direction F or Ft shown in FIG. For example, in the case where the intake port 10 is further curved to impart a swirl component more effectively, the same direction as the intake flow direction Ft even when the intake flow direction is viewed macroscopically. It may become.

  As shown in FIGS. 2 and 3, the stem stm of the intake valve 301 is offset so that the central axis P1 of the stem stm does not include the center point P2 of the bottom surface of the umbrella part ub. Specifically, in the present embodiment, the stem stm is offset in a direction substantially perpendicular to the intake air flow direction F in horizontal projection as shown in FIG. 2, in other words, in a direction substantially parallel to the axis P4. ing. The axis P4 is substantially parallel to a crank axis (not shown). Further, as shown in FIG. 2, the stem stm of the intake valve 301 is the combustion in the intake passage region inr, otr divided into two by the plane S1 including the central axis P1 of the stem stm in the intake valve 301a. The outer passage region otr located outside the chamber 54 is offset so as to increase. As a result, a large outside passage region otr related to the intake valve 301a can be secured, so that intake air can be suitably flown into the cylinder in order to generate the oblique tumble flow TS.

  Further, the stem stm of the intake valve 301 is offset so that the inner passage region inr located on the center side of the combustion chamber 54 becomes larger in the intake valve 301b. As a result, a large inner passage region inr related to the intake valve 301b can be secured, and therefore, the tumble component of the oblique tumble flow TS can be secured to a sufficient size. At the same time, since the other outer passage region otr related to the intake valve 301b can be reduced, the amount of intake air flowing outside the combustion chamber 54 rather than the stem stm of the intake valve 301a is made smaller than the stem stm of the intake valve 301b. It can also be made relatively larger than the amount of intake air that circulates outside, thereby contributing to the application of a larger swirl component.

  More specifically, the stem stm of the intake valve 301 is offset so that the outer passage region otr is larger than the other inner passage region inr in the intake valve 301a. Is offset so that the inner passage area inr is larger than the other outer passage area otr. Thereby, the swirl component of sufficient magnitude | size can be provided. Further, in this embodiment, as shown in FIG. 3, each stem stm of the intake valve 301 is offset by a substantially equal degree L2 in the same direction. As a result, the amount of intake air flowing between the stems stm of the intake valves 301a and 301b is equal to or smaller than the case where each of the stems stm is not offset. By increasing the tumble component of the tumble flow TS, it can be prevented that a sufficiently large swirl component cannot be applied. Therefore, a swirl component having a sufficient size can be more reliably applied. Further, by providing the intake valve 301 with the stem stm offset in this way, the flow mode of the intake air flowing into the cylinder has been improved, so that the mixing of the air-fuel mixture can be performed without particularly deteriorating the volumetric efficiency of the internal combustion engine 300. Thus, the emission can be improved and the emission can be suitably reduced.

  In FIG. 2, since the plane S1 is further assumed to be a plane substantially parallel to the cylinder center axis P3, the plane S1 is shown in a straight line in FIG. In addition, including a state where the stem stm of the intake valve 301 is interposed in the intake port 10 including a state where it is housed in a stem guide (not shown), a cross section of the intake port 10 (for example, a cross section perpendicular to the intake port 10 or a flow of intake air). When a cross section suitable for showing the shape of the intake port 10 at a certain position in the extending direction of the intake port 10 such as a cross section perpendicular to the direction F.) is taken, the cross section of the intake port 52 is divided into two parts by a plane S1. However, each of the parts divided in two corresponds to a part of the inner and outer passage areas inr and otr.

  In this regard, in the intake valve 301a, the portion corresponding to the outer passage region otr in all the cross sections of the intake port 10 is larger than the portion corresponding to the inner passage region inr. In the valve 301b, it is preferable that the portion corresponding to the inner passage region inr in all the cross sections of the intake port 10 is larger than the portion corresponding to the outer passage region otr. However, this is not necessarily limited to the shape of the intake port 10. Further, as described above, the inner and outer passage regions inr and otr are intake passage regions at positions where the stem stm of the intake valve 301 is interposed in the intake port 10, and therefore, the inner and outer passage regions inr and otr include In addition, the position where the stem stm of the intake valve 301 is not interposed in the intake port 10 does not include the intake passage region divided by the plane S1.

  FIG. 4 is a diagram showing the relationship between swirl strength and valve lift. FIG. 4 shows the result of comparison of swirl strength between the internal combustion engine 300X provided with an intake valve in which the stem stm is not offset instead of the intake valve 301, and the internal combustion engine 300. The internal combustion engine 300X is substantially the same as the internal combustion engine 300 except that the intake valve is different. FIG. 4 shows that the swirl strength is improved in the internal combustion engine 300 as compared with the internal combustion engine 300X. Moreover, it turns out that swirl intensity | strength is improving significantly, so that the valve lift amount becomes large.

  Next, the offset amount L2 of the stem stm of the intake valve 301 will be described in detail. FIG. 5 is a view schematically showing the intake valve 301b arranged on the right side in FIG. 2 in a line of sight from a direction perpendicular to the bottom surface of the umbrella portion ub and in the same direction as FIG. As shown in FIG. 5, the offset amount L2 is set to indicate the distance from the center point P2 to the stem stm (more specifically, the point P5 where the bottom surface of the umbrella ub and the center axis P1 of the stem stm intersect). ing. The valve outer diameter D2 indicates the outer diameter of the umbrella part ub of the intake valve 301b. As shown in FIG. 5, the sign of the offset amount L2 is positive when the stem stm is away from the cylinder center axis P4 in a direction substantially perpendicular to the intake air flow direction F.

If the offset amount L2 is set to be larger than 0 (zero), it is possible to improve the flow mode of the intake air flowing into the cylinder so as to give the swirl component. Therefore, the swirl strength can be improved if the offset amount L2 is within the range represented by the following equation (1).
(Equation 1)
0 <L2

On the other hand, when the offset amount L2 increases to about D2 / 4, there is a concern that the valve strength of the intake valve 301 may be significantly reduced. Further, when the offset amount L2 is larger than D2 / 4, the valve strength is greatly reduced, and the air flow rate may start to be greatly reduced. This is presumably because the amount of intake air that tries to pass through the inner passage region inr related to the intake valve 301a and the outer passage region otr related to the intake valve 301b is extremely reduced (see FIG. 6). For this reason, it is preferable that the offset amount L2 is within the allowable range with the range shown in the following equation 2 being the allowable range.
(Equation 2)
0 <L2 ≦ D2 / 4

Also, until the offset amount L2 becomes 0 (zero) to D2 / 12, it corresponds to a stage in which the swirl strength is greatly improved, so the offset amount L2 has a range shown in the following equation 3 as a recommended range. It is more preferable that it is within this recommended range.
(Equation 3)
D2 / 12 ≦ L2 ≦ D2 / 4

FIG. 7 is a diagram schematically showing the flow velocity distribution at the center of the combustion chamber 54. In FIG. 7, the magnitude of the swirl component is represented by a speed difference ΔV with respect to the reference flow velocity V ₀ . In addition, in FIG. 6, the flow velocity distribution similar to the flow velocity distribution shown in FIG. 7 is overlapped for reference. When the offset amount L2 is within the range shown in the following _equation 4, a flow velocity that is larger than the reference flow velocity V0 and less than the predetermined value V1 is obtained.
(Equation 4)
0 <L2 <D2 / 12

  On the other hand, when the offset amount L2 is within the recommended range shown in Equation 3, a flow velocity equal to or higher than the predetermined value V1 is obtained. This also indicates that the offset amount L2 is more preferably within the recommended range shown in Equation 3. Further, the ranges shown in Equations 3 and 4 are considered to be ranges in which a corresponding effect can be obtained even when the position of the stem stm of the intake valve 301 is changed in the intake flow direction F. For this reason, in FIG. 5, an area that is considered to have a more appropriate effect corresponding to the range shown in Expression 4 is shown as an area AR <b> 21, and is considered to have a more appropriate effect corresponding to the recommended range shown in Expression 3. This area is indicated as area AR22. As described above, it is possible to realize the internal combustion engine 300 capable of appropriately flowing the intake air into the cylinder so as to generate the oblique tumble flow TS.

The internal combustion engine 310 according to the present embodiment is basically the same as the internal combustion engine 300 according to the first embodiment except that the intake valve 301 is changed to an intake valve 311. The intake valve 311 differs from the intake valve 301 in that the stem stm is further offset upstream of the center point P2 in the intake flow direction F. In the present embodiment, a first specific intake valve is realized by the intake valve 311a, and a second specific intake valve is realized by the intake valve 311b.

  FIG. 8 is a view schematically showing the intake valve 311b arranged on the right side in the same manner as the intake valve 301b arranged on the right side in FIG. As shown in FIG. 8, an acute angle is set out of angles formed by a straight line P6 that is substantially orthogonal to the intake flow direction F and includes the center point P2 and a straight line P7 that includes the center point P2 and the point P5 related to the stem stm. The angle θ4 is set. Further, the sign of the installation angle θ4 is positive when the stem stm is offset upstream in the intake air flow direction F as shown in FIG. In FIG. 8, the offset amount L2 is set similarly to FIG.

As described above in the first embodiment, it can be said that the offset amount L2 is preferably within the recommended range shown in Equation 3. In this regard, when the installation angle θ4 is further set, if the installation angle θ4 is larger than about 70 degrees or smaller than about −70 degrees when the offset amount L is D / 4, the stem stm is in the area AR21. Will be included. For this reason, it is preferable that the installation angle θ4 is within the allowable range with the range shown in the following equation 5 being the allowable range.
(Equation 5)
-70 ° ≦ θ4 ≦ 70 °
However, since the area AR21 is an area where the swirl strength is considered to be improved to some extent, it can be considered that if the installation angle θ4 is −90 ° or more and 90 ° or less, a corresponding effect can be obtained.

On the other hand, when the installation angle θ4 is set to −90 ° and the stem stm is offset downstream, the swirl strength tends to decrease as the offset amount L2 increases. This is presumably because when the stem stm is offset downstream, it is difficult to smoothly form the intake air flow immediately upstream of the umbrella portion ub. For this reason, the installation angle θ4 is more preferably within the recommended range with the range shown in the following Equation 6 as a recommended range.
(Equation 6)
0 ° ≦ θ4 ≦ 70 °

  Even when the installation angle θ4 is set in this way, the valve strength decreases when the offset amount L2 becomes larger than D / 4. For this reason, when the installation angle θ4 is set, it is preferable to form the stem stm within a range satisfying both Equation 3 and Equation 6. The area corresponding to the case where the offset amount L2 is set within the range shown in Equation 3 and the installation angle θ4 is set within the range shown in Equation 6 is specifically shown as an area AR23 as shown in FIG. Therefore, in this embodiment, the stem stm of the intake valve 311b is offset so as to be included in the area AR23 as shown in FIG.

FIG. 9 is a diagram schematically showing the flow velocity distribution at the center of the combustion chamber 54. In FIG. 9, as in FIG. 7, the magnitude of the swirl component is defined by the speed difference ΔV from the reference flow velocity V ₀ . When the stem stm of the intake valve 311 is in the area AR23, a flow velocity larger than the predetermined value V2 is obtained. Since the predetermined value V2 is larger than the predetermined value V1, it can be seen that the internal combustion engine 310 can obtain a higher flow velocity than the internal combustion engine 300 described in the first embodiment. As described above, it is possible to realize the internal combustion engine 310 capable of appropriately flowing the intake air into the cylinder in order to generate the oblique tumble flow TS.

  The internal combustion engine 320 according to the present embodiment is substantially the same as the internal combustion engine 310 according to the second embodiment except that the intake valve 311 is changed to the intake valve 321. In the intake valve 321a, in the intake valve 321a, the portion of the umbrella portion ub corresponding to the outer passage region otr is formed to have a smaller volume than the portion corresponding to the inner passage region inr. In addition, in the intake valve 321b, the portion corresponding to the inner passage region inr of the umbrella portion ub is formed to have a smaller volume than the portion corresponding to the outer passage region otr. Thus, the intake valve 311 is different.

Here, when the volume is reduced, for example, when the portion corresponding to the inner passage region inr is formed to have a smaller volume than the portion corresponding to the outer passage region otr, When the portion corresponding to the outer passage region otr is rotated about the central axis P1 of the stem stm and superimposed on the portion corresponding to the inner passage region inr, these portions do not coincide with each other and the inner passage region inr The corresponding portion is at least partially included in the portion corresponding to the outer passage region otr. In this embodiment, the intake valve 321a realizes the first specific intake valve , and the intake valve 321b realizes the second specific intake valve .

  FIG. 10 is a view schematically showing the intake valve 321 in a cross section similar to the CC cross section shown in FIG. Specifically, the intake valve 321 includes a portion corresponding to the inner passage region inr and a portion corresponding to the outer passage region otr in the umbrella portion ub, both of which are formed in a circular arc shape in a cross section by a plane including the central axis P1. Has been. Further, the intake valve 321 is formed such that the radius of curvature of the portion corresponding to the outer passage region otr in the intake valve 321a is smaller than the portion corresponding to the inner passage region inr, and the intake valve 321b. In this case, the portion corresponding to the inner passage region inr is formed to have a smaller radius of curvature than the portion corresponding to the outer passage region otr.

  The outer passage area otr related to the intake valve 321a and the portion corresponding to the inner passage area otr related to the intake valve 321b have a radius of curvature R12, and the inner passage area inr related to the intake valve 321a and the outer passage area related to the intake valve 321b. The portions corresponding to otr are formed so as to be connected to the stem stm and smoothly at the curvature radius R11, respectively, and the curvature radius R12 is set smaller than the curvature radius R11. In the present embodiment, by forming the umbrella portion ub in this way, in the intake valve 321a, the portion corresponding to the outer passage region otr in the umbrella portion ub is more than the portion corresponding to the inner passage region inr. The volume is made small. As a result, the outside passage region otr related to the intake valve 321a can be further increased, so that the intake air can be suitably introduced into the cylinder so as to generate an oblique tumble flow TS having a larger swirl component.

  Further, in this embodiment, by forming the umbrella part ub in this way, in the intake valve 321b, the part corresponding to the inner passage area inr in the umbrella part ub is more than the part corresponding to the outer passage area otr. Also, the volume is made small. Thereby, since the inner passage region inr related to the intake valve 321b can be further ensured, it is possible to suppress the tumble component of the oblique tumble flow TS from being lowered more than necessary. At the same time, the amount of intake air flowing through the outer passage region otr related to the intake valve 321b is relatively reduced. As a result, the amount of intake air flowing through the outer passage region otr related to the intake valve 321a is reduced. In order to generate an oblique tumble flow TS having a sufficiently large tumble component and swirl component, it is relatively larger than the amount of intake air flowing through the outer passage region otr related to the valve 321b. The intake air can be suitably flowed into the interior. Note that the umbrella portion ub of the intake valve 321 is smoothly formed over the entire circumference so as not to hinder the flow of intake air, and the intake valves 301 and 311 described above are the same in this respect.

FIG. 11 is a view schematically showing the intake valve 321b arranged on the right side in the same manner as the intake valve 301b arranged on the right side in FIG. 2, similarly to FIG. 5 or FIG. In FIG. 11, the offset amount L2 is set as in FIG. 5, and the installation angle θ4 is set as in FIG. In the internal combustion engine 320 including the intake valve 321, it is possible to further increase the flow of intake air flowing through the outer passage region otr related to the intake valve 321 a and the inner passage region inr related to the intake valve 321 b. For this reason, in the internal combustion engine 320, even when the offset amount L2 is made smaller than that of the internal combustion engine 300 or 310, an effect equivalent to that of the internal combustion engine 300 or 310 can be obtained. Therefore, in the case of the internal combustion engine 320, the recommended range of the offset amount L2 can be expanded as shown in the following formula 7, compared with the recommended range shown in the formula 3.
(Equation 7)
D2 / 24 ≦ L2 ≦ D2 / 4
In FIG. 11, an area that is considered to have a corresponding effect corresponding to the recommended range shown in Equation 7 is indicated as area AR24.

On the other hand, when the installation angle θ4 is set, the stem stm is included in the area AR24 if the installation angle θ4 is larger than about 80 degrees or smaller than about −80 degrees when the offset amount L2 is D2 / 4. Will be. Therefore, in the case of the internal combustion engine 320, the allowable range of the installation angle θ4 can be expanded as shown in the following equation 8, compared with the allowable range expressed in equation 5.
(Equation 8)
−80 ° ≦ θ4 ≦ 80 °

Further, in the flow direction F of intake air, it is preferable that the stem stm is offset to the upstream side of the center point P2 as in the case of the internal combustion engine 310. Therefore, in the case of the internal combustion engine 320, the recommended range of the installation angle θ4 can be expanded as shown in the following formula 9, compared with the recommended range shown in the formula 6.
(Equation 9)
0 ° ≦ θ4 ≦ 80 °

  As a result, the strength of the intake valve 321 can be further maintained as much as the range of the offset amount L2 and the installation angle θ4 is expanded. In the case of the internal combustion engine 320, it is preferable that the stem stm is formed within a range satisfying both the equations 7 and 9. The area corresponding to the case where the offset amount L2 is set within the range shown in Expression 7 and the installation angle θ4 is set within the range shown in Expression 9 is specifically shown as area AR25 as shown in FIG. As described above, it is possible to realize the internal combustion engine 320 capable of appropriately flowing the intake air into the cylinder in order to generate the oblique tumble flow TS.

The internal combustion engine 350 according to the present embodiment is substantially the same as the internal combustion engine 300 except that it includes an intake valve 351 in which a stem stm is inclined as shown below, instead of the intake valve 301. It has become. In the present embodiment, a first specific intake valve is realized by the intake valve 351a, and a second specific intake valve is realized by the intake valve 351b. FIG. 12 is a diagram schematically showing the main part of the internal combustion engine 350 for each cylinder in a horizontal projection view. FIG. 13 is a diagram schematically showing the intake valve 351 in the DD section shown in FIG. In FIG. 12, the flow velocity distributions are also superimposed and shown at the same time for reference.

  As shown in FIGS. 12 and 13, the stem stm of the intake valve 351 is such that the tip P11 of the stem stm includes the cylinder center axis P3 and the crank axis when the intake valve 351a is closed. A plane S2 that is substantially orthogonal to the substantially parallel axis P4 (that is, substantially orthogonal to the crank axis) is inclined away from the center point P2 of the bottom surface of the umbrella portion ub in a direction substantially parallel to the crank axis. In the internal combustion engine 350, the inclined arrangement of the intake valve 351a can secure a larger amount of intake air flowing outside the combustion chamber 54 than the stem stm of the intake valve 351a. Therefore, in the internal combustion engine 350, intake air can be flowed into the cylinder so that a swirl component can be imparted to the oblique tumble flow TS generated in the cylinder.

  In addition, the stem stm of the intake valve 351 is the center of the bottom surface of the umbrella portion ub in the direction substantially parallel to the crank axis in the state in which the tip P11 of the stem stm is in the plane S2 when the intake valve 351b is closed. It inclines so that it may approach from point P2. In the internal combustion engine 350, the inclined arrangement of the intake valve 351b makes it possible to secure a larger amount of intake air that circulates in the combustion chamber 54 center side than the stem stm of the intake valve 351b, and thereby the oblique tumble flow generated in the cylinder It can suppress that the tumble component of TS falls large more than necessary.

  At the same time, with the inclined arrangement of the intake valve 351b in the internal combustion engine 350, the amount of intake air flowing outside the combustion chamber 54 can be less than the stem stm of the intake valve 351b. As a result, the combustion chamber is smaller than the stem stm of the intake valve 351a. Since the amount of intake air flowing outside 54 can be made relatively larger than the amount of intake air flowing outside the combustion chamber 54 than the stem stm of the intake valve 351b, it contributes to the addition of swirl components. it can. The tip P11 of the stem stm of the intake valve 351 and the center point P2 of the bottom surface of the umbrella part ub are both located on the central axis P1 of the stem stm.

  Further, in the present embodiment, as shown in FIG. 13, the intake valves 351 are arranged such that the stems stm of the intake valves 351 are inclined in the same direction at a substantially equal degree θ5. As a result, the amount of intake air flowing between the stems stm of the intake valves 351a and 351b is equal to or smaller than the case where each of the stems stm is not inclined and is generated in the cylinder. By increasing the tumble component of the inclined tumble flow TS, it is possible to prevent the swirl component having a sufficiently large size from being imparted. Therefore, a sufficiently large swirl component can be more reliably applied.

  Further, by providing the intake valve 351 with the stem stm inclined as described above, the flow mode of the intake air flowing into the cylinder is improved, so that the air-fuel mixture is not particularly reduced without causing a reduction in volume efficiency of the internal combustion engine 350. The mixing property can be improved, and the emission can be reduced. The inclination degree of the intake valve 351 can be changed by setting the inclination angle θ5 shown in FIG. 13. This inclination angle θ5 includes the central axis P1 of the stem stm and the central point P2, and is an axis substantially parallel to the cylinder central axis P3. Of the angles formed by P21, it is an acute angle.

Next, the inclination angle θ5 will be described in detail. In a general internal combustion engine, the inclination angle θ5 is set to 0 (zero) °. On the other hand, if the inclination angle θ5 is within the range represented by the following equation 10, swirl strength can be improved.
(Equation 10)
0 ° <θ5

On the other hand, as the inclination angle θ5 is set larger, it becomes physically difficult to appropriately arrange a cam (not shown) for opening and closing the intake valve 351. Therefore, in consideration of the cam arrangement, the inclination angle θ5 is preferably within the allowable range, with the range shown in the following equation 11 being an allowable range.
(Equation 11)
0 ° <θ5 ≦ 10 °

When the inclination angle θ5 is set to be large, the swirl component of the oblique tumble flow TS generated in the cylinder becomes too large depending on the shape of the combustion chamber 54 and the strength of the oblique tumble flow TS is greatly reduced. Such a situation may occur. On the other hand, when the inclination angle θ5 is set from 0 (zero) ° to less than 1 °, a great effect cannot be expected. For this reason, the inclination angle θ5 is more preferably within the recommended range, with the range shown in the following equation 12 being the recommended range.
(Equation 12)
1 ° ≦ θ5 ≦ 6 °

FIG. 14 is a diagram schematically showing the flow velocity distribution at the center of the combustion chamber 54. In FIG. 14, the magnitude of the swirl component is represented by the speed difference ΔV from the reference flow velocity V ₀ as in FIG. As shown in FIG. 14, when the inclination angle θ5 is within the range shown in Formula 11, a flow velocity larger than the predetermined value V11 is obtained. Also this predetermined value V11 has become larger than the reference velocity V _0. Further, when the inclination angle θ5 is within the range shown in Formula 12, a flow velocity of a predetermined value V12 or more is obtained. The predetermined value V12 has a larger flow rate than the predetermined value V11. As described above, in the internal combustion engine 350, it is possible to apply a larger swirl component by specifying the inclination angle θ5 in detail. As described above, it is possible to realize the internal combustion engine 350 capable of suitably flowing the intake air into the cylinder in order to generate the oblique tumble flow TS.

In the internal combustion engine 360 according to the present embodiment, in a state where the intake valve 351 is further closed, the stem stm related to the intake valve 351 is such that the tip P11 of the stem stm is closer to the exhaust port 55 than the center point P2 in the flow direction F of intake air. It is substantially the same as the internal combustion engine 350 except that it is inclined so as to be located on the side. Further, the intake valve 351 inclined in this way is hereinafter referred to as an intake valve 361. In this embodiment, the intake valve 361a realizes the first specific intake valve , and the intake valve 361b realizes the second specific intake valve . FIG. 15 is a diagram schematically showing the main part of the internal combustion engine 360 in a horizontal projection view for each cylinder, similarly to FIG. FIG. 16 is a diagram schematically showing the intake valve 361b arranged on the right side in FIG. 15 alone and in the same direction as in FIG.

  As shown in FIGS. 15 and 16, an acute angle among the angles formed by the straight line P6 that is substantially orthogonal to the intake air flow direction F and includes the center point P2 and the center axis P1 of the stem stm in the horizontal projection view is an installation angle θ6. And By setting this installation angle θ6, the stem stm can be inclined also in the flow direction F of the intake air. Note that the positive and negative signs of the installation angle θ6 are positive when the tip P11 of the stem stm is positioned on the exhaust port 55 side of the center point P2 in the flow direction F of the intake air as shown in FIG.

When the installation angle θ6 is 90 °, it is difficult to incline the intake valve 361 so that a swirl component can be applied. Even when the installation angle θ6 is decreased from 90 °, a large effect is obtained. I can not expect. On the other hand, when the installation angle θ6 is smaller than 0 (zero) °, it is considered that it may be difficult to smoothly form the intake air flow to the wake side immediately above the umbrella portion ub. Therefore, the installation angle θ6 is preferably within the allowable range with the range shown in the following equation 13 being an allowable range.
(Equation 13)
0 ° ≦ θ6 ≦ 70 °

On the other hand, depending on the size of the installation angle θ6, the flow mode of the intake air flowing into the cylinder along the umbrella portion ub within the range shown in Equation 13 can be made more preferable for the generation of the oblique tumble flow TS, As a result, the swirl component can be further increased. In this regard, when it is desired to further improve the swirl strength, the installation angle θ6 is more preferably within the recommended range, with the range shown in the following equation 14 being the recommended range.
(Equation 14)
10 ° ≦ θ6 ≦ 60 °

FIG. 17 is a diagram schematically showing the flow velocity distribution at the center of the combustion chamber 54. In FIG. 17, the magnitude of the swirl component is represented by the speed difference ΔV from the reference flow velocity V ₀ as in FIG. As shown in FIG. 17, installed in a case where the angle θ6 is within the range shown in Formula 13, a large flow rate can be obtained than a predetermined value V21, the predetermined value V21 is a larger than the reference velocity V ₀ Yes. Further, when the installation angle θ6 is within the range shown in Formula 14, a flow velocity larger than the predetermined value V22 is obtained, and the predetermined value V22 is larger than the predetermined value V21. In the internal combustion engine 360, the area of the installation angle θ6 corresponding to the case where the flow velocity is equal to or higher than the predetermined value V21 is specifically shown as an area AR26 as shown in FIG. Further, the area of the installation angle θ6 corresponding to the case where the flow velocity is equal to or higher than the predetermined value V22 is specifically shown as an area AR27 as shown in FIG. Therefore, in this embodiment, the installation angle θ6 of the intake valve 361 is set to be included in the AR 27. As described above, it is possible to realize the internal combustion engine 360 capable of appropriately flowing the intake air into the cylinder so as to generate the oblique tumble flow TS.

The internal combustion engine 370 according to the present embodiment is substantially the same as the internal combustion engine 360 according to the fifth embodiment except that the intake valve 361 is changed to the intake valve 371. In the intake valve 371, in the intake valve 371a, the portion of the umbrella portion ub corresponding to the intake air flowing outside the combustion chamber 54 rather than the stem stm corresponds to the intake air flowing through the center side of the combustion chamber 54. Further, in the intake valve 371b, the portion corresponding to the intake air flowing through the center of the combustion chamber 54 rather than the stem stm is further provided in the intake valve 371b. The intake valve 361 differs from the intake valve 361 in that the volume is smaller than the portion corresponding to the intake air flowing outside the combustion chamber 54. In this embodiment, the intake valve 371a realizes a first specific intake valve , and the intake valve 371b realizes a second specific intake valve .

  FIG. 18 is a diagram schematically showing the main part of the internal combustion engine 370 in a horizontal projection view for each cylinder as in FIG. FIG. 19 is a view schematically showing the intake valve 371 in the EE cross section and the FF cross section shown in FIG. Specifically, the intake valve 371 includes a portion of the umbrella portion ub corresponding to intake air that flows through the center side of the combustion chamber 54 relative to the stem stm (hereinafter simply referred to as an inner portion), and an intake air that flows outside the combustion chamber 54. And a portion corresponding to (hereinafter, simply referred to as an outer portion) are formed in an arc shape in cross section along the EE cross section including the central axis P1. Further, the intake valve 371 is formed so that the outer portion of the intake valve 371a has a smaller radius of curvature than the inner portion, and the inner portion of the intake valve 371b is less than the outer portion. Also, the radius of curvature is formed to be small.

  The outer portion related to the intake valve 371a and the inner portion related to the intake valve 371b have a radius of curvature R22, and the inner portion related to the intake valve 371a and the outer portion related to the intake valve 371b connect to the stem stm smoothly with a radius of curvature R21. Further, the radius of curvature R22 is set smaller than the radius of curvature R21. In this embodiment, the umbrella portion ub is formed in this way, so that in the intake valve 371a, the volume of the outer portion of the umbrella portion ub is smaller than that of the inner portion. As a result, a larger passage area of the intake air that flows outside the combustion chamber 54 than the stem stm of the intake valve 371a can be ensured, so that the intake air is suitable in the cylinder to generate an oblique tumble flow TS having a larger swirl component. Can be allowed to flow into.

  Further, in this embodiment, the umbrella part ub is formed in this way, so that in the intake valve 371b, the inner part of the umbrella part ub has a smaller volume than the outer part. As a result, it is possible to secure a larger passage area of the intake air that circulates in the center of the combustion chamber 54 than the stem stm of the intake valve 371b, so that it is possible to suppress the tumble component of the oblique tumble flow TS from greatly decreasing. At the same time, this reduces the amount of intake air flowing outside the combustion chamber 54 relative to the stem stm of the intake valve 371b. As a result, the intake air flowing outside the combustion chamber 54 rather than the stem stm of the intake valve 371a. Since the amount of air becomes relatively larger than the amount of intake air flowing through the center side of the combustion chamber 54 relative to the stem stm of the intake valve 371b, it has a sufficiently large tumble component and swirl component. In order to generate the oblique tumble flow TS, the intake air can be preferably introduced into the cylinder. In addition, it is preferable that the umbrella part ub of the intake valve 371 is formed smoothly over the entire circumference so as not to inhibit the flow of intake air.

FIG. 20 is a diagram schematically showing the intake valve 371b arranged on the right side in FIG. 18 alone and in the same direction as in FIG. In FIG. 20, the installation angle θ6 is set similarly to FIG. In the internal combustion engine 370 provided with the intake valve 371, it is possible to form a larger amount of intake air flowing outside the combustion chamber 54 than the stem stm of the intake valve 321a and on the center side of the combustion chamber 54 than the stem stm of the intake valve 321b. For this reason, in the internal combustion engine 370, even when the installation angle θ6 is made smaller than that of the internal combustion engine 360, an effect equivalent to that of the internal combustion engine 360 can be obtained. Therefore, in the case of the internal combustion engine 370, the allowable range of the installation angle θ6 can be expanded as shown in the following equation 15 compared with the allowable range expressed in equation 13.
(Equation 15)
0 ° ≦ θ6 ≦ 80 °
In FIG. 20, an area corresponding to the allowable range shown in Equation 15 is shown as area AR28.

On the other hand, depending on the size of the installation angle θ6, the flow mode of the intake air flowing into the cylinder along the umbrella portion ub within the range shown in Formula 15 can be made more preferable for the generation of the oblique tumble flow TS. The same applies to the internal combustion engine 370 as in the case of the internal combustion engine 360. In this regard, in the case of the internal combustion engine 370, when it is desired to further improve the swirl strength, the recommended range of the installation angle θ6 can be expanded as shown in the following formula 16, compared with the recommended range shown in the formula 14.
(Equation 16)
10 ° ≦ θ6 ≦ 70 °
In FIG. 20, an area corresponding to the recommended range shown in Equation 16 is shown as an area AR29. Thereby, in order to generate the oblique tumble flow TS having a sufficiently large tumble component and swirl component, the intake air can be suitably introduced into the cylinder. As described above, the internal combustion engine 370 can be realized in which intake air can be suitably flowed into the cylinder in order to generate the oblique tumble flow TS.

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the case where the internal combustion engine having the intake two-valve structure includes the second specific intake valve together with the first specific intake valve has been described in detail. However, the internal combustion engine is combined with the first specific intake valve. A general intake valve in which the stem is not offset or inclined may be provided. In addition, for example, in an internal combustion engine in which an intake port is formed so that not only a tumble component but also a swirl component can be given to a swirling airflow generated in a cylinder, the tumble component is sufficient. In order to ensure the size, an intake valve in which a stem is offset or inclined in a direction opposite to the second specific intake valve may be provided instead of the second specific intake valve.

FIG. 2 is a diagram schematically illustrating a main part of an internal combustion engine 300 in a vertical sectional view for one cylinder. FIG. 2 is a diagram schematically showing a main part of an internal combustion engine 300 in a horizontal projection view for one cylinder. It is a figure which shows typically the intake valve 301 in CC cross section shown in FIG. It is a figure which shows the relationship between swirl intensity | strength and valve lift amount. FIG. 3 is a diagram schematically showing the intake valve 301b arranged on the right side in FIG. 2 in a line of sight from a direction perpendicular to the bottom surface of the umbrella part ub and in the same direction as in FIG. It is a figure which shows typically a mode when offset amount L is made larger than D2 / 4, using the figure similar to the principal part figure of the internal combustion engine 300 shown in FIG. It is a figure which shows typically the flow-velocity distribution in the combustion chamber 54 center. FIG. 6 is a view schematically showing an intake valve 311b arranged on the right side in the same manner as the intake valve 301b arranged on the right side in FIG. It is a figure which shows typically the flow-velocity distribution in the combustion chamber 54 center. It is a figure which shows typically the flow-velocity distribution in the combustion chamber 54 center. It is a figure which shows typically the intake valve 321 in the cross section similar to CC cross section shown in FIG. FIG. 3 is a diagram schematically showing a main part of an internal combustion engine 350 in a horizontal projection view per cylinder. FIG. 13 is a diagram schematically showing an intake valve 351 in a DD section shown in FIG. 12. It is a figure which shows typically the flow-velocity distribution in the combustion chamber 54 center. FIG. 3 is a diagram schematically showing a main part of an internal combustion engine 360 in a horizontal projection view per cylinder. FIG. 16 is a diagram schematically showing a single intake valve 361b in the same direction as in FIG. It is a figure which shows typically the flow-velocity distribution in the combustion chamber 54 center. FIG. 3 is a diagram schematically showing a main part of an internal combustion engine 370 in a horizontal projection view for each cylinder, similarly to FIG. 2. It is a figure which shows typically the intake valve 371 in the EE cross section and FF cross section which are shown in FIG. FIG. 19 is a diagram schematically showing a single intake valve 371b in the same direction as in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Intake port 51 Cylinder block 52 Cylinder head 54 Combustion chamber 300,310,320,350,360,370 Internal combustion engine 301,311,321,351,361,371 Intake valve

Claims (5)

An internal combustion engine comprising a plurality of intake valves per cylinder having an umbrella part and a stem connected to the umbrella part at one end,
A first specific intake valve as one of the intake valves located at both ends of the cylinder, and a second specific intake valve as the other intake valve;
The first specific intake valve has a large outer passage region located outside the combustion chamber among the intake passage regions divided into two by a plane including the central axis of the stem of the first specific intake valve. The stem of the first specific intake valve is configured so that the central axis of the stem of the first specific intake valve does not include the center point of the bottom surface of the umbrella portion of the first specific intake valve. Is offset ,
The second specific intake valve has an inner passage region located on the combustion chamber center side among the intake passage regions divided into two by a plane including the central axis of the stem of the second specific intake valve. The central axis of the stem of the second specific intake valve does not include the center point of the bottom surface of the umbrella portion of the second specific intake valve so as to be larger. An internal combustion engine characterized in that the stem is offset . The stem according to the first specific intake valve is offset upstream of the center point related to the first specific intake valve in the flow direction of intake air . Internal combustion engine. The stem according to the second specific intake valve is offset upstream of the center point according to the second specific intake valve in the flow direction of intake air. The internal combustion engine described. The portion of the umbrella part related to the first specific intake valve that corresponds to the intake air that flows outside the combustion chamber rather than the stem of the umbrella portion flows in the combustion chamber center side rather than the stem. The internal combustion engine according to any one of claims 1 to 3, wherein the internal combustion engine is formed to have a volume smaller than a portion corresponding to . In the umbrella portion related to the second specific intake valve, the portion of the umbrella portion corresponding to the intake air that circulates in the center of the combustion chamber rather than the stem, the intake air that circulates outside the combustion chamber rather than the stem. 5. The internal combustion engine according to claim 1 , wherein the internal combustion engine is formed to have a volume smaller than a portion corresponding to .

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