JP6861518B2 - Internal combustion engine - Google Patents

Description

The present invention relates to an internal combustion engine, and more particularly to the structure of a combustion chamber.

In an internal combustion engine, high temperature of intake air (air-fuel mixture) during combustion is known as one of the causes of knocking. Since the intake air is heated by convection heat transfer to the wall surface of the combustion chamber heated by the heat of combustion, if the flow velocity of the intake air increases due to the strengthening of the tumble flow, the convection heat transfer is promoted and the knocking resistance is lowered. Become.

In order to suppress convection heat transfer between the intake air and the wall surface of the combustion chamber, it is conceivable to make the wall surface of the combustion chamber a mirror surface. Although the purpose is different, a combustion chamber structure in which the wall surface of the combustion chamber is mirrored to suppress the transfer of radiant heat from the combustion gas to the wall surface of the combustion chamber and the cooling loss is reduced is known (for example, Patent Documents 1 and 2). ..

Jikkenhei 1-173417 Japanese Unexamined Patent Publication No. 2-123255

However, the intake air becomes hotter than the wall surface of the combustion chamber due to being compressed in the compression stroke. Therefore, if the wall surface of the combustion chamber is mirror-finished to suppress heat transfer between the gas in the combustion chamber and the wall surface of the combustion chamber, convection heat transfer from the intake air to the wall surface of the combustion chamber is suppressed, the temperature of the intake air becomes high, and knocking resistance is improved. There is a problem that it decreases.

In view of the above background, it is an object of the present invention to improve knocking resistance in an internal combustion engine.

In order to solve the above problems, one aspect of the present invention includes a cylinder inner peripheral surface that defines a cylinder, a cylinder head combustion chamber surface that closes the end of the cylinder, an intake port and an exhaust that are opened in the cylinder head combustion chamber surface. An internal combustion engine having a combustion chamber defined by a surface of a valve that closes a port and a crown surface of a piston received by the cylinder, the inner peripheral surface of the cylinder, the cylinder head combustion chamber surface, and the surface of the valve. And at least one of the crown surfaces of the piston has a portion formed on a mirror surface having an arithmetic average roughness of less than 0.3 μm and a portion formed on a rough surface having an arithmetic average roughness of 0.3 μm or more. It is characterized by that.

According to this aspect, in the intake stroke, convection heat transfer between the intake air and the cylinder wall surface member including the inner peripheral surface of the cylinder, the combustion chamber surface of the cylinder head, the surface of the valve, and the crown surface of the piston in the portion formed on the mirror surface. Is suppressed and the temperature rise of the intake air is suppressed. On the other hand, in the compression stroke, convection heat transfer between the intake air and the cylinder wall surface member is promoted in the portion formed on the rough surface, and the intake air is cooled. Due to these actions, the temperature rise of the intake air is suppressed and the knocking resistance is improved.

Further, in the above aspect, the valve has a shaft portion and an umbrella portion provided at one end of the shaft portion, and the umbrella portion comes into contact with an umbrella surface facing the combustion chamber side and a valve seat. It has an annular face surface and an umbrella peripheral surface forming a surface between the outer peripheral edge of the umbrella surface and the outer peripheral edge of the face surface, the umbrella surface is formed on the mirror surface, and the umbrella peripheral surface is the umbrella peripheral surface. It is preferable that it is formed on a rough surface.

According to this aspect, the convection heat transfer between the intake air and the surface of the umbrella is suppressed in the intake stroke to suppress the temperature rise of the intake air, and the convection heat transfer between the intake air and the peripheral surface of the umbrella is promoted in the compression stroke to cool the intake air. Will be done.

Further, in the above aspect, the crown surface of the piston includes a crown surface central portion formed on the mirror surface and a crown surface outer peripheral portion arranged on the outer periphery of the crown surface central portion and formed on the rough surface. It is good to have.

According to this aspect, the convection heat transfer between the intake air and the central portion of the crown surface is suppressed in the intake stroke to suppress the temperature rise of the intake air, and the convection heat transfer between the intake air and the outer peripheral portion of the crown surface is promoted in the compression stroke. Heat dissipation is promoted. Since the flow velocity of the intake air is faster in the central portion of the crown surface than in the outer peripheral portion of the crown surface in the intake stroke, convection heat transfer between the crown surface and the intake air is efficiently suppressed by making the central portion of the crown surface a mirror surface. On the other hand, since the flow velocity of the intake air is faster in the outer peripheral portion of the crown surface than in the central portion of the crown surface in the compression stroke, convection heat transfer between the crown surface and the intake air is promoted by making the outer peripheral portion of the crown surface rough. The intake air is cooled efficiently.

Further, in the above aspect, the outer peripheral portion of the crown surface may include a portion corresponding to the squish of the combustion chamber.

According to this aspect, in the compression stroke, the flow velocity of the intake air in the outer peripheral portion of the crown surface is further increased by the squish, so that the convection heat transfer between the outer peripheral portion of the crown surface formed on the rough surface and the intake air is promoted, and the intake air is further increased. It is cooled.

Further, in the above aspect, it is preferable to further have an oil jet that injects oil into a portion of the back surface of the piston corresponding to the outer peripheral portion of the crown surface.

According to this aspect, the outer peripheral portion of the crown surface is cooled by the oil jet, so that the intake air that transfers convection heat to the outer peripheral portion of the crown surface is further cooled.

Further, in the above aspect, the cylinder head combustion chamber surface is arranged on the outer periphery of the combustion chamber surface central portion formed on the mirror surface and the combustion chamber surface central portion, and is formed on the rough surface. It is preferable to have an outer peripheral portion.

According to this aspect, the convection heat transfer between the intake air and the central portion of the combustion chamber surface is suppressed in the intake stroke, the temperature rise of the intake air is suppressed, and the convection heat transfer between the intake air and the outer peripheral portion of the combustion chamber surface is promoted in the compression stroke. The heat dissipation of the intake air is promoted. In the intake stroke, the flow velocity of the central part of the combustion chamber surface is faster than that of the outer peripheral part of the crown surface. Therefore, by making the central part of the crown surface a mirror surface, convection heat transfer between the cylinder head combustion chamber surface and the intake air is efficient. It is suppressed. On the other hand, in the compression stroke, the flow velocity of the outer peripheral portion of the combustion chamber surface is faster than that of the central portion of the combustion chamber surface. Therefore, by making the outer peripheral portion of the combustion chamber surface rough, convection between the cylinder head combustion chamber surface and the intake air. Heat transfer is promoted and the intake air is cooled efficiently.

Further, in the above aspect, the outer peripheral portion of the combustion chamber surface may include a squish surface.

According to this aspect, in the compression stroke, the flow velocity of the intake air at the outer periphery of the combustion chamber surface is further increased by the squish, so that the convection heat transfer between the outer periphery of the crown surface formed on the rough surface and the intake air is promoted, and the intake air is generated. It is further cooled.

According to this aspect, it is preferable to further have a water jacket provided around the outer peripheral portion of the combustion chamber surface.

Further, in the above embodiment, the water jacket cools the outer peripheral portion of the combustion chamber surface, so that the intake air that transfers convection heat to the outer peripheral portion of the combustion chamber surface is further cooled.

According to this aspect, by cooling the outer peripheral portion of the combustion chamber surface by the water jacket, the intake air that transfers convection heat to the outer peripheral portion of the combustion chamber surface is further cooled.

Further, in the above aspect, the outer peripheral portion of the combustion chamber surface may include a portion of the valve seat that is in contact with the radial portion with reference to the center of the cylinder head combustion chamber surface.

According to this aspect, a portion where the flow velocity of the intake air becomes high in the compression stroke is included in the outer peripheral portion of the combustion chamber surface and is formed on the rough surface, so that convection heat transfer between the intake air and the outer peripheral portion of the combustion chamber surface is promoted. ..

Further, in the above aspect, the inner peripheral surface of the cylinder is arranged on the exhaust side where the exhaust port is located in the circumferential direction, and the exhaust side portion formed on the mirror surface and the intake air where the intake port is located in the circumferential direction. It is preferable to have an intake side portion arranged on the side and formed on the rough surface.

According to this aspect, the convection heat transfer between the intake air and the exhaust side portion of the cylinder is suppressed in the intake stroke to suppress the temperature rise of the intake air, and the convection heat transfer between the intake air and the intake side portion of the cylinder is promoted in the compression stroke. The heat dissipation of the intake air is promoted. In the intake stroke, the flow velocity of the exhaust side portion of the cylinder is faster than that of the intake side portion. Therefore, by making the exhaust side portion a mirror surface, convection heat transfer between the cylinder and the intake air is efficiently suppressed. On the other hand, in the intake stroke, the flow velocity of the intake side portion of the cylinder is faster than that of the exhaust side portion in the compression stroke. Therefore, by making the intake side portion a rough surface, convection heat transfer with the intake side portion is promoted, and the intake air is intake. Is cooled efficiently.

Further, in the above aspect, the two intake ports are provided side by side in the crank axis direction, and the exhaust side portion is equal to or larger than the distance between the outer ends of the two intake ports in the crank axis direction and the inner diameter of the cylinder. It should have the following width.

According to this aspect, convection heat transfer between the intake air flowing into the cylinder from the two intake ports and the exhaust side portion of the cylinder is suppressed in the intake stroke, and the temperature rise of the intake air is suppressed.

According to the above configuration, the knocking resistance of the internal combustion engine is improved.

Sectional drawing in the intake stroke of the internal combustion engine which concerns on embodiment Sectional drawing in the compression stroke of the internal combustion engine which concerns on embodiment (A) Side view of the valve, (B) Bottom view of the valve Bottom view showing the cylinder head combustion chamber surface (A) Side view of the piston, (B) Plan view of the piston VI-VI sectional view of FIG.

Hereinafter, embodiments in which the present invention is applied to an internal combustion engine of an automobile will be described with reference to the drawings.

(overall structure)
As shown in FIGS. 1 and 2, the internal combustion engine 1 of an automobile has a cylinder block 2 and a cylinder head 3 coupled to an upper portion of the cylinder block 2. A cylinder bore 8 is formed on the upper part of the cylinder block 2. The upper end of the cylinder bore 8 opens to the upper end surface 2A of the cylinder block 2, and the lower end thereof communicates with the crank chamber 9 formed in the lower portion of the cylinder block 2. A cylindrical cylinder sleeve 10 having both ends open is press-fitted and coupled to the inside of the cylinder bore 8. The inner peripheral surface 11 (cylinder inner peripheral surface) of the cylinder sleeve 10 defines a cylindrical cylinder 12 (cylinder). Let the axis of the cylinder 12 be the cylinder axis A. A block-side water jacket 7 is formed around the cylinder bore 8 in the cylinder block 2. The upper end of the block-side water jacket 7 is open to the upper end surface 2A of the cylinder block 2.

A crankshaft (not shown) is arranged in the crank chamber 9. The crankshaft is rotatably supported by a bearing formed by a bearing cap coupled to the bottom of the cylinder block 2. The crankshaft is coupled via a connecting rod 18 to a piston 20 that is reciprocally received by the cylinder 12. The lower part of the cylinder block 2 is closed by an oil pan (not shown).

The piston 20 includes a disc-shaped crown portion 21 provided above (cylinder head 3 side), a pair of skirt portions 22 extending downward (crankshaft side) from the crown portion 21, and a pair of bearing wall portions 23. Has. The pair of skirt portions 22 and the pair of bearing wall portions 23 are alternately arranged in the circumferential direction and are connected to each other. The upper surface of the crown portion 21 is referred to as a piston crown surface 24.

An oil jet 28 that injects oil toward the back surface of the crown portion 21 is provided on the wall portion that defines the crank chamber 9 of the cylinder block 2. The oil stored in the oil pan is supplied to the oil jet 28 via an oil pump (not shown).

The lower end surface 3A of the cylinder head 3 has a cylinder head combustion chamber surface 30 that is coupled to the upper end surface 2A of the cylinder block 2 and closes the upper end portion of the cylinder 12 at a position corresponding to the cylinder 12. The cylinder head combustion chamber surface 30 has a squish surface 31 at a portion corresponding to the outer peripheral portion of the cylinder 12, and a combustion chamber concave surface 32 corresponding to the central portion of the cylinder 12 and recessed upward. The squish surface 31 is formed on the same plane as the lower end surface 3A of the cylinder head 3 and is arranged at a position facing the cylinder 12. The concave surface 32 of the combustion chamber is open to the ends of the two intake ports 35 and the ends of the two exhaust ports 36. The two intake ports 35 extend from the concave surface 32 of the combustion chamber to one side surface of the cylinder head 3, and the two exhaust ports 36 extend from the concave surface 32 of the combustion chamber to the other side surface of the cylinder head 3. The side of the cylinder head 3 where the intake port 35 is arranged is the intake side, and the side where the exhaust port 36 is arranged is the exhaust side.

The cylinder head 3 is formed with a head-side water jacket 37 around the cylinder head combustion chamber surface 30. A part of the head-side water jacket 37 opens to the lower end surface 3A of the cylinder head 3 and is connected to the block-side water jacket 7. A part of the head-side water jacket 37 is arranged around the outer peripheral portion 52 of the combustion chamber surface.

An annular valve seat 38 is provided at the boundary between each intake port 35 and each exhaust port 36 with the concave surface 32 of the combustion chamber. Each intake port 35 is provided with an intake valve 40 that opens and closes the intake port 35 by seating and leaving the valve seat 38. Each exhaust port 36 is provided with an exhaust valve 41 that opens and closes the exhaust port 36 by sitting on and off the valve seat 38. The intake valve 40 and the exhaust valve 41 are driven by a valve operating mechanism (not shown) and open and close at a predetermined timing according to the rotation position of the crankshaft.

The combustion chamber 44 is defined by the inner peripheral surface 11 of the cylinder sleeve 10, the cylinder head combustion chamber surface 30, the crown surface of the piston 20, and the surfaces of the valves 40 and 41. The direction and shape of the intake port 35 are set so that the intake air that has passed through the intake port 35 and flows into the combustion chamber 44 forms a tumble flow in the combustion chamber 44.

An injector (not shown) for injecting fuel may be provided on either the intake port 35 or the concave surface 32 of the combustion chamber.

(Intake valve and exhaust valve)
As shown in FIGS. 3A and 3B, the intake valve 40 and the exhaust valve 41 (hereinafter, simply referred to as valves 40 and 41) are provided substantially coaxially with the shaft portion 46 at one end of the shaft portion 46. It is a poppet valve having an umbrella portion 47. The valves 40 and 41 are slidably supported in the axial direction by a cylindrical valve guide 48 provided on the cylinder head 3 at the shaft portion 46. The umbrella portion 47 is formed in a disk shape having a predetermined thickness, and its outer diameter is formed to be larger than the outer diameter of the shaft portion 46. The surface of the umbrella portion 47 facing the combustion chamber 44 side is the umbrella surface 47A, and the surface of the umbrella portion 47 facing the combustion chamber 44 side is the umbrella back surface 47B. The back surface 47B of the umbrella is formed on a substantially conical surface, and has a face surface 47C on the outer peripheral portion thereof that can come into contact with the valve seat 38. The face surface 47C is formed in an annular shape with the shaft portion 46 as the center. The surface of the outer peripheral edge of the umbrella portion 47 is an umbrella peripheral edge surface 47D that smoothly connects the umbrella surface 47A and the umbrella back surface 47B with a curved surface. The umbrella peripheral surface 47D forms a surface between the outer peripheral edge of the umbrella surface 47A and the outer peripheral edge of the face surface 47C. The umbrella peripheral surface 47D is arranged with the valve seat 38 and the concave surface 32 of the combustion chamber via a gap.

The umbrella surface 47A is a mirror surface portion M formed on a mirror surface. Here, the mirror surface is defined as a surface having an arithmetic mean roughness (Ra) of less than 0.3 μm. The mirror surface may be a surface having an arithmetic mean roughness (Ra) of less than 0.1 μm. On the other hand, the umbrella peripheral surface 47D is a rough surface portion R formed on the rough surface. Here, the rough surface is defined as a surface having an arithmetic mean roughness (Ra) of 0.3 μm or more. That is, the rough surface is a surface having a larger surface roughness (arithmetic mean roughness) than the mirror surface. The surface can be mirrored and roughened by a known processing technique, for example, by shot blasting.

(Cylinder head combustion chamber surface)
As shown in FIG. 4, the cylinder head combustion chamber surface 30 is a combustion chamber surface central portion 51 including the central portion of the combustion chamber concave surface 32, and a combustion chamber concave surface 32 arranged on the outer peripheral side of the combustion chamber surface central portion 51. It has a combustion chamber surface outer peripheral portion 52 including a peripheral edge portion and a squish surface 31. The squish surface 31 projects radially inward from the other portions on the intake side portion and the exhaust side portion of the cylinder head combustion chamber surface 30 which is circular in a plan view. In the present embodiment, the squish surface 31 on the intake side is set to have a larger amount of protrusion inward in the radial direction than the squish surface 31 on the exhaust side. The combustion chamber concave surface 32 included in the combustion chamber surface outer peripheral portion 52 includes a portion of the valve seat 38 that contacts the radial portion with reference to the center of the cylinder head combustion chamber surface 30. The central portion 51 of the combustion chamber surface forms a mirror surface portion M formed on a mirror surface, and the outer peripheral portion 52 of the combustion chamber surface forms a rough surface portion R formed on a rough surface.

(piston)
As shown in FIG. 5B, the piston crown surface 24 has a crown surface central portion 55 located at the center and an annular crown surface outer peripheral portion 56 arranged on the outer periphery of the crown surface central portion 55. The crown surface outer peripheral portion 56 includes a portion facing the squish surface 31. The outer peripheral portion 56 of the crown surface has a portion facing the squish surface 31 on the intake side and a portion facing the squish surface 31 on the exhaust side. The central portion 55 of the crown surface forms a mirror surface portion M formed on a mirror surface, and the outer peripheral portion 56 of the crown surface forms a rough surface portion R formed on a rough surface.

(Cylinder sleeve)
As shown in FIG. 6, the inner peripheral surface 11 of the cylinder sleeve 10 forms a mirror surface portion M whose exhaust side portion is formed on a mirror surface, and a rough surface portion R whose intake side portion is formed on a rough surface. The mirror surface portion M of the cylinder sleeve 10 has a width equal to or greater than the distance between the outer ends of the two intake ports 35 and equal to or less than the inner diameter of the cylinder 12 in the crank axis direction. In the present embodiment, the width of the mirror surface portion M of the cylinder sleeve 10 in the crank axis direction is set to be equal to the distance between the outer ends of the two intake ports 35. The rough surface portion R of the cylinder sleeve 10 may include all portions except the mirror surface portion M of the cylinder sleeve 10. The rough surface portion R may extend to the exhaust side when the inner peripheral surface 11 of the cylinder sleeve 10 is bisected on the intake side and the exhaust side.

The operation and effect of the internal combustion engine 1 configured as described above will be described. In the internal combustion engine 1, the intake valve 40 is opened and the piston 20 is lowered in the intake stroke, and the intake air flows into the combustion chamber 44 from the intake port 35. The intake air here may be only air or an air-fuel mixture containing fuel. The intake air flows from the gap between the valve seat 38 of the intake port 35 and the intake valve 40 in the radial direction centered on the intake valve 40, and flows into the combustion chamber 44. At this time, the main flow of intake air flows into the combustion chamber 44 from the exhaust side of the umbrella portion 47 of the intake valve 40, and the concave surface 32 of the combustion chamber, the umbrella surface 47A of the exhaust valve 41, and the inner peripheral surface 11 of the cylinder sleeve 10. It flows downward and on the exhaust side so as to pass through the exhaust side portions in order, and then the central portion 55 of the crown surface of the piston 20, the intake side portion of the inner peripheral surface 11 of the cylinder sleeve 10, the concave surface 32 of the combustion chamber, and the umbrella of the intake valve 40. It flows on the intake side and upward so as to pass through the surface 47A in order to form a tumble flow. At this time, since the flow velocity of the intake air is the fastest when it flows into the combustion chamber 44 from the intake port 35, the concave surface 32 of the combustion chamber, the umbrella surface 47A of the exhaust valve 41, and the exhaust side portion of the inner peripheral surface 11 of the cylinder sleeve 10. The flow velocity at the central portion 55 of the crown surface of the piston 20 becomes faster than the flow velocity at the other portions.

In the compression stroke, as the piston 20 rises, the intake air compressed between the outer peripheral portion 56 of the crown surface of the piston 20 and the outer peripheral portion 52 of the combustion chamber surface including the squish surface 31 flows to the center of the combustion chamber 44. Therefore, in the compression stroke, the flow velocity of the intake air becomes faster in the outer peripheral portion 56 of the crown surface of the piston 20 and the outer peripheral portion 52 of the combustion chamber surface including the squish surface 31 than in other portions. Further, in the compression stroke, the compressed intake air flows into the gap formed between the umbrella peripheral surface 47D of the valves 40 and 41 and the valve seat 38 and the concave surface 32 of the combustion chamber. Is faster than the other parts.

In the internal combustion engine 1, the concave surface 32 of the combustion chamber where the flow rate of intake air becomes faster than the other parts in the intake stroke, the umbrella surface 47A of the valves 40 and 41, the exhaust side portion of the cylinder sleeve 10, and the central portion 55 of the crown surface of the piston 20. Is a mirror surface portion M, so that convection heat transfer between the intake and the concave surface 32 of the combustion chamber, the umbrella surface 47A of the valves 40 and 41, the exhaust side portion of the cylinder sleeve 10, and the central portion 55 of the crown surface of the piston 20 is suppressed. The temperature rise of the intake air is suppressed. In the intake stroke, since the temperature of the structure defining the combustion chamber 44 is higher than that of the intake air, it is preferable that the convection heat transfer is suppressed in order to suppress the temperature rise of the intake air. As for convection heat transfer, the faster the flow velocity, the more disturbed and thin the temperature boundary layer is, so that the heat transfer coefficient increases. Therefore, in the portion where the flow velocity of the intake air is high, the intake air receives a large amount of heat from the structure defining the combustion chamber 44. In the present embodiment, the concave surface 32 of the combustion chamber, the umbrella surface 47A of the valves 40 and 41, the exhaust side portion of the cylinder sleeve 10, and the central portion 55 of the crown surface of the piston 20 in which the flow velocity of the intake air becomes faster than the other portions in the intake stroke. Since the mirror surface portion M is formed, the disturbance of the temperature boundary layer is suppressed, and the heat transfer coefficient in this portion is lowered. As a result, the amount of heat received from the structure defining the combustion chamber 44 of the intake air is reduced, and the temperature rise is suppressed.

On the other hand, in the compression stroke, the compressed intake air has a higher temperature than the structure defining the combustion chamber 44, so that heat exchange between the intake air and the structure defining the combustion chamber 44 can be promoted. Preferred for cooling the intake air. In the present embodiment, the flow velocity of the intake air becomes faster than the other parts in the compression stroke, the outer peripheral portion 56 of the crown surface of the piston 20, the outer peripheral portion 52 of the combustion chamber surface including the squish surface 31, and the outer peripheral surface of the umbrella of the valves 40 and 41. Since 47D forms the rough surface portion R, the turbulence of the temperature boundary layer is promoted, and the heat transfer coefficient in these portions is increased. Further, the outer peripheral portion 56 of the crown surface of the piston 20, the outer peripheral portion 52 of the combustion chamber surface including the squish surface 31, and the outer peripheral surface 47D of the umbrella peripheral surface of the valves 40 and 41 form a rough surface portion R, so that the surface area becomes large, and these portions. Increases the amount of heat transfer in. As a result, the amount of heat radiated from the intake air to the structure defining the combustion chamber 44 increases, and the temperature rise is suppressed. Further, since the inner peripheral surface 11 of the cylinder sleeve 10 has a rough surface portion R in a region other than the exhaust side portion including the intake side portion, heat dissipation from the intake air to the cylinder sleeve 10 is promoted.

When the outer peripheral portion 52 of the combustion chamber surface including the squish surface 31 is formed as a mirror surface and the central portion 51 of the combustion chamber surface is formed as a rough surface on the cylinder head combustion chamber surface 30, the outer peripheral portion 52 of the combustion chamber surface and the center of the combustion chamber surface are formed. It was confirmed that the ignition timing can be advanced to the MBT side within a range where knocking does not occur, as compared with the case where all the portions 51 are formed on a rough surface. When the exhaust side portion is formed as a mirror surface and the other portion including the intake side portion is formed as a rough surface on the inner peripheral surface 11 of the cylinder sleeve 10, the entire region including the intake side portion and the exhaust side portion is roughened. It was confirmed that the ignition timing can be advanced to the MBT side within a range in which knocking does not occur, as compared with the case of forming the above. In the crown surface of the piston 20, when the crown surface central portion 55 is formed as a mirror surface and the crown surface outer peripheral portion 56 is formed as a rough surface, or when the crown surface central portion 55 and the crown surface outer peripheral portion 56 are formed as a rough surface. In comparison, it was confirmed that the ignition timing can be advanced to the MBT side within a range where knocking does not occur. In the valves 40 and 41, when the umbrella surface 47A is formed as a mirror surface and the umbrella peripheral surface 47D is formed as a rough surface, knocking does not occur as compared with the case where the umbrella surface 47A and the umbrella peripheral surface 47D are formed as a rough surface. It was confirmed that the ignition timing can be advanced to 1.0 deg toward the MBT side in the range. The above experimental results were all obtained under the conditions of an engine speed of 2500 rpm and a full load.

Although the description of the specific embodiment is completed above, the present invention can be widely modified without being limited to the above embodiment. In the above embodiment, the inner peripheral surface 11 of the cylinder sleeve 10 defines the inner peripheral surface of the cylinder 12, but the inner peripheral surface of the cylinder bore 8 is the inner peripheral surface of the cylinder 12 by omitting the cylinder sleeve 10. May be configured to define.

The rough surface portion R of the inner peripheral surface 11 of the cylinder sleeve 10 does not have to be provided in the entire area of the inner peripheral surface 11 in the direction along the cylinder axis A, and may be provided only on the cylinder head 3 side. For example, the rough surface portion R is provided only in a range of 1/2 or less or 1/4 or less of the stroke of the piston 20 from the cylinder head 3 side of the inner peripheral surface 11, and all other portions are mirror surface portions M. May be good.

1: Internal combustion engine 2: Cylinder block 3: Cylinder head 10: Cylinder sleeve 11: Inner peripheral surface 12: Cylinder 20: Piston 24: Piston crown surface 30: Cylinder head combustion chamber surface 31: Squish surface 32: Combustion chamber concave surface 35: Intake port 36: Exhaust port 37: Head side water jacket 38: Valve seat 40: Intake valve 41: Exhaust valve 44: Combustion chamber 47A: Umbrella surface 47B: Umbrella back surface 47C: Face surface 47D: Umbrella peripheral surface 51: Combustion chamber surface Central portion 52: Combustion chamber surface outer peripheral portion 55: Crown surface central portion 56: Crown surface outer peripheral portion M: Mirror surface portion R: Rough surface portion

Claims (3)

The inner peripheral surface of the cylinder that defines the cylinder, the surface of the combustion chamber of the cylinder head that closes the end of the cylinder, the surface of the valve that closes the intake port and the exhaust port opened in the surface of the combustion chamber of the cylinder head, and the surface of the piston received by the cylinder. An internal combustion engine with a combustion chamber defined by a crown.
The valve has a shaft portion and an umbrella portion provided at one end of the shaft portion.
The umbrella portion includes an umbrella surface facing the combustion chamber side, an annular face surface in contact with the valve seat, and an annular face surface.
It has an umbrella peripheral surface forming a surface between the outer peripheral edge of the umbrella surface and the outer peripheral edge of the face surface.
An internal combustion engine characterized in that the surface of the umbrella is formed on a mirror surface having an arithmetic average roughness of less than 0.3 μm, and the peripheral surface of the umbrella is formed on a rough surface having an arithmetic average roughness of 0.3 μm or more. The inner peripheral surface of the cylinder that defines the cylinder, the surface of the combustion chamber of the cylinder head that closes the end of the cylinder, the surface of the valve that closes the intake port and the exhaust port opened in the surface of the combustion chamber of the cylinder head, and the surface of the piston received by the cylinder. An internal combustion engine with a combustion chamber defined by a crown.
The inner peripheral surface of the cylinder is arranged on the exhaust side where the exhaust port is located in the circumferential direction.
It is arranged on the exhaust side portion formed on a mirror surface having an arithmetic mean roughness of less than 0.3 μm and on the intake side where the intake port is located in the circumferential direction, and is formed on a rough surface having an arithmetic mean roughness of 0.3 μm or more. inner combustion engine it characterized as having an intake-side moiety. Two intake ports are provided side by side in the crank axis direction.
The internal combustion engine according to claim 2 , wherein the exhaust side portion has a width equal to or greater than the distance between the outer ends of the two intake ports and equal to or less than the inner diameter of the cylinder in the direction of the crank axis.

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