Cylinder head

Abstract

To making the suppression of obstructing a flow of intake air by a valve seat and the suppression of deteriorating the holding force of the valve seat by a cylinder head, compatible.SOLUTION: A cylinder head is equipped with an intake port connected to a combustion chamber, an annular valve seat in which an intake valve opening / closing the intake port can be seated, and an installing portion that is provided around an opening portion on the combustion chamber side of the intake port and to which the valve seat is installed. The valve seat has an annular projection that is disposed on an outer peripheral side of the valve seat and projects out in an axial direction of the valve seat. The installing portion has an annular groove capable of storing the annular projection of the valve seat, and an outer peripheral surface of the annular projection contacts with a first inner surface on an outer peripheral side of the annular groove while the valve seat is installed to the installing portion.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a cylinder head. [Background technology]

[0002] An engine cylinder head is formed with an intake port and other components. An intake valve opens and closes the opening of the intake port on the combustion chamber side. An annular valve seat is provided around this opening. For example, Patent Document 1 discloses an example of a valve seat for an engine. When the intake valve closes the opening, the intake valve seats on the valve seat. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 62-23512 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, the length of an intake port is inclined relative to the normal to the intake port opening. Therefore, a portion of the inner circumferential surface of the valve seat located at the opening protrudes inward relative to the inner surface of the intake port. This can cause intake air introduced into the combustion chamber from the intake port to hit the protruding portion of the valve seat, potentially impeding the flow of intake air into the combustion chamber. If the flow of intake air is obstructed, it becomes difficult to create an appropriate tumble flow, potentially resulting in reduced combustion efficiency.

[0005] One solution is to reduce the height of the valve seat, which is the axial width of the valve seat. By reducing the height of the valve seat, the amount by which the valve seat protrudes from the inner surface of the intake port is reduced, making it less likely that the intake air introduced into the combustion chamber from the intake port will hit the protruding part of the valve seat. This makes it possible to prevent obstruction of the flow of intake air.

[0006] However, if the height of the valve seat is reduced, the contact area between the cylinder head and the valve seat decreases when the valve seat is press-fitted into the cylinder head around the opening of the intake port, which reduces the force with which the cylinder head holds the valve seat, potentially causing the valve seat to fall off the cylinder head.

[0007] Therefore, an object of the present invention is to provide a cylinder head that can simultaneously prevent the intake air flow from being obstructed by the valve seat and prevent a decrease in the holding force of the valve seat by the cylinder head. [Means for solving the problem]

[0008] In order to solve the above problem, a cylinder head according to one embodiment of the present invention comprises: an intake port connected to the combustion chamber; an annular valve seat on which an intake valve that opens and closes the intake port can be seated; a mounting portion provided around an opening of the intake port on the combustion chamber side, to which the valve seat is attached; and Equipped with The valve seat is A circular plate-shaped main body, Located on the outer circumferential side of the valve seat, Orthogonal to the body, An annular protrusion protruding in the axial direction of the valve seat and, and the outer circumferential surface of the annular protrusion and the inner circumferential surface of the annular protrusion are arranged parallel to each other, The outer circumferential surface of the annular protrusion is continuous with the outer circumferential surface of the main body, an outer diameter of the annular protrusion and an outer diameter of the body are equal along the axial direction of the valve seat; the mounting portion has an annular groove capable of accommodating the annular protrusion of the valve seat, When the valve seat is attached to the attachment portion, the outer circumferential surface of the annular protrusion and the outer circumferential surface of the body is in contact with a first inner surface on the outer circumferential side of the annular groove. At the same time, the inner peripheral surface of the annular protrusion is in contact with a second inner surface on the inner peripheral side of the annular groove. . [Effects of the Invention]

[0009] According to the present invention, it is possible to simultaneously suppress the valve seat from obstructing the flow of intake air and suppress a decrease in the holding force of the valve seat by the cylinder head. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an engine according to this embodiment. [Figure 2] FIG. 2 is a schematic enlarged view of an intake port in the cylinder head of the first comparative example. [Figure 3] FIG. 3 is a schematic enlarged view of an intake port in a cylinder head of a second comparative example. [Figure 4] FIG. 4 is a schematic enlarged view of an intake port in a cylinder head of a third comparative example. [Figure 5] FIG. 5 is a schematic enlarged view of an intake port in the cylinder head of this embodiment. [Figure 6] FIG. 6 is a perspective view of the valve seat according to this embodiment. [Figure 7] FIG. 7 is a detailed enlarged cross-sectional view of the opening of the intake port in the cylinder head of this embodiment. [Figure 8] FIG. 8 is an internal plan view of the cylinder head as seen from the combustion chamber side. [Figure 9] FIG. 9 is a detailed enlarged cross-sectional view of the opening of the intake port with the valve seat attached. [Figure 10] FIG. 10 is a diagram showing the relationship between the amount of intake air introduced into the combustion chamber and the strength of the tumble flow of the intake air introduced into the combustion chamber. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Specific dimensions, materials, numerical values, etc. shown in the embodiments are merely examples for facilitating understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0012] 1 is a schematic diagram showing the configuration of an engine 10 according to this embodiment. The engine 10 is mounted on, for example, a vehicle. The engine 10 includes a cylinder block 20, a piston 22, a cylinder head 24, an intake valve 26, and an exhaust valve 28.

[0013] A plurality of cylinders 30 are formed in the cylinder block 20. Pistons 22 are slidably housed in the cylinders 30 and are capable of reciprocating in the axial direction of the cylinders 30. The pistons 22 are connected to a crankshaft (not shown) via connecting rods 32. The crankshaft rotates in accordance with the reciprocating motion of the pistons 22.

[0014] The cylinder head 24 is disposed on the opposite side of the cylinder block 20 from the crankshaft. The cylinder head 24 is disposed on the cylinder 30 so as to cover the upper opening of the cylinder 30, and is connected to the cylinder block 20. A combustion chamber 34 is a space surrounded by the inner surface of the cylinder 30, the inner surface of the cylinder head 24, and the crown surface of the piston 22.

[0015] The cylinder head 24 has an intake port 40 and an exhaust port 42. The intake port 40 and the exhaust port 42 are in communication with the combustion chamber 34. Specifically, the intake port 40 is connected to the combustion chamber 34 through an opening 44a of the intake port 40 on the combustion chamber 34 side. The exhaust port 42 is connected to the combustion chamber 34 through an opening 44b of the exhaust port 42 on the combustion chamber 34 side.

[0016] The intake valve 26 is provided in the intake port 40 and opens and closes an opening 44a of the intake port 40. When the intake valve 26 opens the opening 44a of the intake port 40, air is sent into the combustion chamber 34 through the intake port 40. The exhaust valve 28 is provided in the exhaust port 42 and opens and closes an opening 44b of the exhaust port 42. When the exhaust valve 28 opens the opening 44b of the exhaust port 42, gas within the combustion chamber 34 is discharged through the exhaust port 42.

[0017] The cylinder head 24 includes an attachment portion 50a on the intake port 40 side and a valve seat 52a on the intake port 40 side. The attachment portion 50a is provided around the opening 44a of the intake port 40 on the combustion chamber 34 side. The attachment portion 50a is formed in an annular shape surrounding the opening 44a. The attachment portion 50a is recessed, for example, on the side opposite the combustion chamber 34. The valve seat 52a is formed in an annular shape. The valve seat 52a is attached to the attachment portion 50a. The intake valve 26 can be seated on the valve seat 52a. The intake valve 26 closes the opening 44a of the intake port 40 by contacting the valve seat 52a. The valve seat 52a on the intake port 40 side will be described in detail later.

[0018] The cylinder head 24 includes an attachment portion 50b on the exhaust port 42 side and a valve seat 52b on the exhaust port 42 side. The attachment portion 50b is provided around an opening 44b of the exhaust port 42 on the combustion chamber 34 side. The attachment portion 50b is formed in an annular shape that surrounds the opening 44b. The attachment portion 50b is recessed, for example, on the side opposite the combustion chamber 34. The valve seat 52b is formed in an annular shape. The valve seat 52b is attached to the attachment portion 50b. The valve seat 52b is configured so that the exhaust valve 28 can be seated on it. The exhaust valve 28 closes the opening 44b of the exhaust port 42 by coming into contact with the valve seat 52b.

[0019] An injector 60 and a spark plug 62 are provided in the cylinder head 24. The injector 60 is positioned with its nozzle facing the combustion chamber 34. The injector 60 injects fuel such as gasoline into the combustion chamber 34 at a predetermined timing. The spark plug 62 is positioned with its electrode facing the combustion chamber 34. The spark plug 62 ignites a mixture of air and fuel in the combustion chamber 34 at a predetermined timing, causing combustion. This combustion causes the piston 22 to reciprocate within the cylinder 30.

[0020] Next, cylinder heads according to first to third comparative examples will be described with reference to Figures 2 to 4. Then, the cylinder head 24 according to this embodiment will be described in detail with reference to Figure 5, in comparison with these first to third comparative examples.

[0021] FIG. 2 is a schematic enlarged view of the intake port 40 in the cylinder head A10 of the first comparative example. The cylinder head A10 of the first comparative example is equipped with the valve seat B10 of the first comparative example. The valve seat B10 has a height H1. In this specification, the height of the valve seat refers to the axial width of the valve seat. The height H1 of the valve seat B10 is, for example, 6 mm.

[0022] Generally, the length of the intake port 40 is inclined relative to the normal direction of the opening 44a of the intake port 40. As a result, a portion of the inner circumferential surface of the valve seat B10 provided at the opening 44a protrudes relative to the inner surface of the intake port 40. In FIG. 2, the inner circumferential surface of the upper right portion of the valve seat B10 protrudes inward relative to the inner surface of the intake port 40. As a result, as indicated by the dashed arrow in FIG. 2, intake air introduced from the intake port 40 into the combustion chamber 34 hits the protruding portion of the valve seat B10, changing the flow of the intake air and weakening its momentum, which may obstruct the flow of intake air introduced into the combustion chamber 34. If the flow of intake air is obstructed, it becomes difficult to form an appropriate tumble flow, which may result in reduced combustion efficiency.

[0023] FIG. 3 is a schematic enlarged view of the intake port 40 in the cylinder head A12 of the second comparative example. The cylinder head A12 of the second comparative example is equipped with the valve seat B12 of the second comparative example. The valve seat B12 is a laser-clad valve seat formed by thermally spraying a predetermined alloy onto the opening 44a using laser clad technology. The inner circumferential surface of this valve seat B12 barely protrudes from the inner surface of the intake port 40. Therefore, as indicated by the dashed arrow in FIG. 3, the intake air introduced from the intake port 40 into the combustion chamber 34 does not hit the valve seat B12, and the intake air is smoothly introduced into the combustion chamber 34.

[0024] However, laser clad valve seats require advanced manufacturing techniques and are expensive to produce, so there is a need for technology that can prevent intake air flow obstruction caused by valve seats without using laser clad valve seats.

[0025] 4 is a schematic enlarged view of the intake port 40 in the cylinder head A14 of the third comparative example. The cylinder head A14 of the third comparative example is equipped with the valve seat B14 of the third comparative example. The valve seat B14 has a height H2. The height H2 is shorter than the height H1 in FIG. 2. The height H2 is, for example, 3 mm or less.

[0026] The height of the valve seat B14 is reduced, so the amount of protrusion of the valve seat B14 from the inner surface of the intake port 40 is reduced. In FIG. 4, the amount of protrusion of the inner circumferential surface of the upper right portion of the valve seat B14 is reduced compared to FIG. 2. This makes it less likely that the intake air introduced into the combustion chamber 34 from the intake port 40 will hit the protruding portion of the valve seat B14. This makes it possible to prevent the flow of intake air from being obstructed, as indicated by the dashed arrow in FIG. 4.

[0027] However, if the height of the valve seat B14 is reduced, the contact area between the cylinder head A14 and the valve seat B14 decreases when the valve seat B14 is press-fitted into the cylinder head A14. This reduces the holding force of the cylinder head A14 to hold the valve seat B14. This could result in the valve seat B14 falling off the cylinder head A14. Therefore, in order to increase the holding force of the valve seat by the cylinder head, it is preferable to increase the height of the valve seat.

[0028] In contrast to these, Figure 5 is a schematic enlarged view of the intake port 40 in the cylinder head 24 of this embodiment. The cylinder head 24 of this embodiment is provided with a valve seat 52a. Figure 6 is a perspective view of the valve seat 52a according to this embodiment.

[0029] The valve seat 52a has a main body 70 and an annular protrusion 74. The main body 70 of the valve seat 52a is formed in the shape of an annular plate. The main body 70 of the valve seat 52a has a height H3. The height H3 is approximately the same as the height H2 in FIG. 4. The height H3 is, for example, 3 mm, but is not limited to this example and may be any value that minimizes the amount of protrusion of the inner circumferential surface of the valve seat 52a.

[0030] The main body 70 of the valve seat 52a has a seating surface 72 on which the intake valve 26 can be seated. The seating surface 72 is formed by cutting the inner circumferential surface of the main body 70 on the combustion chamber 34 side at an angle. The seating surface 72 is formed to fit the shape of the head of the intake valve 26.

[0031] The annular protrusion 74 of the valve seat 52a is formed in a circular ring shape and is disposed on the outer periphery of the valve seat 52a. The annular protrusion 74 protrudes in the axial direction of the valve seat 52a, i.e., in the height direction of the valve seat 52a. The annular protrusion 74 protrudes from the main body 70 toward the opposite side from the combustion chamber 34.

[0032] An outer peripheral surface 76 of the annular protrusion 74 is continuous with the outer peripheral surface of the main body 70. The outer diameter of the outer peripheral surface 76 of the annular protrusion 74 is equal to the outer diameter of the outer peripheral surface of the main body 70. The inner diameter of the inner peripheral surface 78 of the annular protrusion 74 is larger than the inner diameter of the inner peripheral surface of the main body 70.

[0033] The valve seat 52a has a height H4 on the outer peripheral surface side. In other words, the height H4 is the height from the surface of the main body 70 facing the combustion chamber 34 to the tip of the annular protrusion 74. The height H4 is at least higher than the height H3. For example, the height H4 is approximately the same as the height H1 in FIG. 2. The height H4 is, for example, 6 mm, but is not limited to this example and may be any value higher than the height H3. The protrusion amount of the annular protrusion 74 corresponds to the value obtained by subtracting the height H3 from the height H4.

[0034] Figure 7 is a detailed enlarged cross-sectional view of the opening 44a of the intake port 40 in the cylinder head 24 of this embodiment. Figure 8 is an internal plan view of the cylinder head 24 as seen from the combustion chamber 34 side. Figures 7 and 8 omit the valve seat 52a and show the state before the valve seat 52a is attached to the attachment portion 50a.

[0035] The mounting portion 50a provided around the opening 44a has an annular groove 80. The annular groove 80 is formed in a circular ring shape and is located on the outer periphery of the mounting portion 50a. The annular groove 80 is recessed on the side opposite to the combustion chamber 34.

[0036] The annular groove 80 is configured to accommodate the annular protrusion 74 of the valve seat 52a. Specifically, the annular groove 80 has a first inner surface 82 (outer inner wall surface) on the outer periphery side and a second inner surface 84 (inner inner wall surface) on the inner periphery side. The first inner surface 82 on the outer periphery side of the annular groove 80 is continuous with the inner surface on the outer periphery side of the mounting portion 50a. The diameter of the first inner surface 82 of the annular groove 80 is approximately equal to the diameter of the inner surface of the mounting portion 50a. The diameter of the first inner surface 82 of the annular groove 80 is approximately equal to the diameter of the outer periphery surface 76 of the annular protrusion 74. The diameter of the second inner surface 84 on the inner periphery side of the annular groove 80 is approximately equal to the diameter of the inner periphery surface 78 of the annular protrusion 74. The depth of the annular groove 80 is approximately equal to the protrusion amount of the annular protrusion 74.

[0037] The diameter of the second inner surface 84 of the annular groove 80 may be smaller than the diameter of the inner circumferential surface 78 of the annular protrusion 74. The depth of the annular groove 80 may be larger than the protrusion amount of the annular protrusion 74.

[0038] The annular groove 80 is formed so that the central axis of the opening 44a of the intake port 40 overlaps with the central axis of the annular groove 80. For example, in the manufacturing process of forming the opening 44a, the annular groove 80 may be formed by a tool that is coaxial with the central axis of the tool that forms the opening 44a.

[0039] 9 is a detailed enlarged cross-sectional view of the opening 44a of the intake port 40 with the valve seat 52a attached. The intake valve 26 shown by the solid line in FIG. 9 is in the open state, and the intake valve 26 shown by the dashed line in FIG. 9 is in the closed state.

[0040] The valve seat 52a is attached to the mounting portion 50a by press-fitting the valve seat 52a into the mounting portion 50a of the cylinder head 24. When the valve seat 52a is attached to the mounting portion 50a, the annular protrusion 74 of the valve seat 52a is housed in the annular groove 80 of the mounting portion 50a, and the annular protrusion 74 and the annular groove 80 fit together.

[0041] When the valve seat 52a is attached to the attachment portion 50a, the outer peripheral surface 76 of the annular protrusion 74 of the valve seat 52a contacts the first inner surface 82 on the outer periphery side of the annular groove 80. In addition, the outer peripheral surface of the body 70 of the valve seat 52a also contacts the inner surface of the attachment portion 50a.

[0042] In the cylinder head 24 of this embodiment, the outer peripheral surface 76 of the annular protrusion 74 contacts the first inner surface 82 of the annular groove 80, thereby increasing the contact area between the cylinder head 24 and the valve seat 52a compared to the third comparative example in FIG. 4 . As a result, the frictional force between the cylinder head 24 and the valve seat 52a is greater in the cylinder head 24 of this embodiment compared to the third comparative example in FIG. 4 . Therefore, in the cylinder head 24 of this embodiment, even if the height of the main body 70 of the valve seat 52a is reduced, the annular protrusion 74 can prevent a decrease in the holding force of the cylinder head 24 to hold the valve seat 52a. As a result, in the cylinder head 24 of this embodiment, the valve seat 52a can be stably fixed to the mounting portion 50a of the cylinder head 24, preventing the valve seat 52a from falling off the cylinder head 24.

[0043] Although not shown, as long as the outer peripheral surface 76 of the annular protrusion 74 is in contact with the first inner surface 82 of the annular groove 80 when the valve seat 52a is attached to the attachment portion 50a, the inner peripheral surface 78 of the annular protrusion 74 does not have to be in contact with the second inner surface 84 on the inner periphery of the annular groove 80. Even in this embodiment, the valve seat 52a can be stably fixed to the attachment portion 50a of the cylinder head 24 by the frictional force between the outer peripheral surface 76 of the annular protrusion 74 and the first inner surface 82 of the annular groove 80.

[0044] 9 , when the valve seat 52a is attached to the attachment portion 50a, it is preferable that the outer peripheral surface 76 of the annular protrusion 74 contacts the first inner surface 82 of the annular groove 80, and that the inner peripheral surface 78 of the annular protrusion 74 also contacts the second inner surface 84 of the annular groove 80. In this manner, by having the inner peripheral surface 78 of the annular protrusion 74 contact the second inner surface 84 of the annular groove 80 in addition to the contact between the outer peripheral surface 76 of the annular protrusion 74 and the first inner surface 82 of the annular groove 80, it is possible to further increase the frictional force between the annular groove 80 and the annular protrusion 74. Therefore, in this embodiment, it is possible to further increase the holding force of the valve seat 52a by the cylinder head 24, and the valve seat 52a can be more stably fixed to the attachment portion 50a of the cylinder head 24.

[0045] Furthermore, in an embodiment in which both the outer peripheral surface 76 and the inner peripheral surface 78 of the annular protrusion 74 contact the annular groove 80, the amount of protrusion of the annular protrusion 74 can be made smaller than in an embodiment in which the inner peripheral surface 78 of the annular protrusion 74 does not contact the annular groove 80. For example, the amount of protrusion of the annular protrusion 74 can be set to a value such that the sum of the surface area of ​​the outer peripheral surface of the valve seat 52a and the surface area of ​​the inner peripheral surface 78 of the annular protrusion 74 is equal to or greater than the surface area of ​​the outer peripheral surface of the valve seat B10 in the first comparative example shown in FIG.

[0046] In the cylinder head 24 of this embodiment, the height H3 of the main body 70 of the valve seat 52a can be reduced to approximately the same as the height H2 of the third comparative example in Figure 4. As a result, the cylinder head 24 of this embodiment can reduce the amount of protrusion of the inner circumferential surface of the main body 70 of the valve seat 52a from the inner surface of the intake port 40, as shown in Figure 5. Therefore, the cylinder head 24 of this embodiment can reduce the obstruction of the flow of intake air by the valve seat 52a, as shown by the dashed arrow in Figure 5.

[0047] Fig. 10 is a diagram showing the relationship between the amount of intake air introduced into the combustion chamber 34 and the strength of the tumble flow of the intake air introduced into the combustion chamber 34. The black circle C10 in Fig. 10 represents the case of the cylinder head A10 of the first comparative example in Fig. 2. The white circle C12 in Fig. 10 represents the case of the cylinder head 24 of this embodiment.

[0048] As shown in Figure 10, the cylinder head 24 of this embodiment has a larger intake air volume and a stronger tumble flow than the cylinder head A10 of the first comparative example. Because the cylinder head 24 of this embodiment has a larger intake air volume, the intake air is smoothly introduced into the combustion chamber 34. Furthermore, because the cylinder head 24 of this embodiment has a stronger tumble flow, a more appropriate tumble flow is formed within the combustion chamber 34. In other words, the cylinder head 24 of this embodiment can effectively prevent the flow of intake air from being obstructed by the valve seat 52a.

[0049] Therefore, according to the cylinder head 24 of this embodiment, it is possible to simultaneously suppress the obstruction of the intake air flow by the valve seat 52a and suppress a decrease in the holding force of the valve seat 52a by the cylinder head 24.

[0050] In the above embodiment, the annular protrusion 74 is provided on the valve seat 52a of the intake port 40. However, the valve seat 52b of the exhaust port 42 may also be provided with the annular protrusion 74. In this case, an annular groove 80 capable of accommodating the annular protrusion 74 of the valve seat 52b is provided in the mounting portion 50b of the exhaust port 42. Then, with the valve seat 52b of the exhaust port 42 mounted on the mounting portion 50b, the outer peripheral surface 76 of the annular protrusion 74 comes into contact with a first inner surface 82 on the outer peripheral side of the annular groove 80.

[0051] While the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such embodiments. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that such modifications and alterations also fall within the technical scope of the present invention. [Explanation of symbols]

[0052] 24 Cylinder head 34 Combustion chamber 40 intake port 26 Intake valve 52a valve seat 44a opening 50a attachment part 74 Annular protrusion 80 Annular groove 76 Outer surface 82 First inner surface 78 Inner surface 84 Second inner surface

Claims

1. an intake port connected to the combustion chamber; an annular valve seat on which an intake valve that opens and closes the intake port can be seated; a mounting portion provided around an opening of the intake port on the combustion chamber side, to which the valve seat is attached; and Equipped with The valve seat is A circular plate-shaped main body, an annular protrusion disposed on the outer circumferential side of the valve seat and protruding in the axial direction of the valve seat so as to be perpendicular to the main body; the outer circumferential surface of the annular protrusion and the inner circumferential surface of the annular protrusion are arranged parallel to each other, The outer circumferential surface of the annular protrusion is continuous with the outer circumferential surface of the main body, an outer diameter of the annular protrusion and an outer diameter of the body are equal along the axial direction of the valve seat; the mounting portion has an annular groove capable of accommodating the annular protrusion of the valve seat, a cylinder head, wherein, when the valve seat is attached to the attachment portion, the outer peripheral surface of the annular protrusion and the outer peripheral surface of the main body are in contact with a first inner surface on the outer peripheral side of the annular groove, and the inner peripheral surface of the annular protrusion is in contact with a second inner surface on the inner peripheral side of the annular groove.

2. 2. The cylinder head according to claim 1, wherein the annular groove is formed so that a central axis of the opening of the intake port and a central axis of the annular groove overlap.

3. A cylinder head as described in claim 1 or 2, wherein the amount of protrusion of the annular protrusion is such that the sum of the surface area of ​​the outer surface of the valve seat and the surface area of ​​the inner surface of the annular protrusion is greater than or equal to a predetermined surface area.

Images