JP6490440B2 - Monoblock engine cylinder structure - Google Patents

Description

  The present invention relates to a cylinder structure of a monoblock engine having a monoblock in which a cylinder head and a cylinder block are integrally formed.

  For example, as in Patent Document 1, there is a monoblock engine having a monoblock in which a cylinder head and a cylinder block are integrally formed. Since the monoblock engine does not require a head gasket or a head bolt, the number of components of the engine can be reduced.

  On the other hand, the monoblock requires tool escape and grinding fluid accumulation during honing on the side wall of the cylinder. Therefore, a recess is formed on the side wall of the cylinder at the end on the upper wall side of the cylinder over the entire circumference.

JP-A-6-229315

The recess functioning as a tool escape or a grinding fluid reservoir increases the dead volume, which is the gap between the cylinder and the top land of the piston, thereby reducing the thermal efficiency of the engine.
An object of this invention is to provide the cylinder structure of the monoblock engine which can suppress the fall of the thermal efficiency of an engine.

  A cylinder structure of a monoblock engine that solves the above-described problem is a cylinder structure of a monoblock engine having a monoblock in which a cylinder head and a cylinder block are integrally formed, and the monoblock includes a cylinder side wall. A concave portion is formed in the end on the upper wall side, and a ring-shaped spacer is attached to the concave portion. When the spacer is attached to the concave portion, the inner peripheral surface of the spacer is the top of the piston. It is located outside the cylinder from the land.

  According to the above configuration, the dead volume is reduced by mounting the spacer in the recess. Thereby, since the generation | occurrence | production of the unburned gas resulting from dead volume and the fall of a combustion pressure are suppressed, the fall of the thermal efficiency of an engine is suppressed.

  In the cylinder structure of the monoblock engine, the spacer has an abutment portion and can be reduced in diameter by elastic deformation, and in a state where the spacer is not attached to the recess, the spacer is larger than the maximum diameter of the cylinder in the recess. It is preferable to have a large outer diameter.

  According to the above configuration, the spacer is inserted into the cylinder in a reduced diameter when mounted in the recess, and presses the side wall of the cylinder with a restoring force after being mounted in the recess. As a result, it is difficult for the spacer to come off from the recess.

In the cylinder structure of the monoblock engine, it is preferable that the spacer is in surface contact with the concave surface of the recess when the spacer is mounted in the recess.
According to the said structure, the position of a spacer becomes difficult to shift | deviate.
In the cylinder structure of the monoblock engine, it is preferable that an inner peripheral surface of the spacer is located on an inner side of the cylinder with respect to an inner surface of the cylinder in a state where the spacer is mounted in the recess.

According to the said structure, a dead volume can be made still smaller because the inner peripheral surface of a spacer is located inward rather than the inner surface of a cylinder.
In the cylinder structure of the monoblock engine, it is preferable that the concave portion is formed of a curved surface.

In the cylinder structure of the monoblock engine, it is preferable that the thermal conductivity of the spacer is lower than the thermal conductivity of the monoblock.
According to the above configuration, it is possible to suppress the heat of combustion of the air-fuel mixture from being transferred to the monoblock via the spacer. Thereby, the fall of the temperature in a cylinder is suppressed and the production | generation of unburned gas and the fall of a combustion pressure are suppressed. As a result, a decrease in engine thermal efficiency is further suppressed.

  In the monoblock cylinder structure, the spacer preferably includes a spacer body and a ceramic layer coated on the spacer body and having a lower thermal conductivity than the spacer body.

  According to the said structure, compared with the case where a spacer is comprised only by a spacer main body by coating a ceramic layer on a spacer main body, the thermal conductivity of a spacer can be made still lower.

It is a figure which shows the cross-sectional structure of the cylinder structure of the monoblock engine of 1st Embodiment, Comprising: It is a figure which shows the state in which the piston is located in a top dead center. It is a perspective view which shows the perspective structure of the spacer in a free state. It is a figure for demonstrating the mounting method of a spacer. It is a figure which shows the cross-sectional structure of a cylinder periphery, Comprising: It is a figure which shows the state in which a piston is located in a top dead center, and the state in which a piston is located in a bottom dead center. It is sectional drawing which shows the cross-section of the spacer in 2nd Embodiment. It is sectional drawing which shows an example of the modification about a recessed part and a spacer. It is sectional drawing which shows an example of the modification about a recessed part and a spacer. It is sectional drawing which shows an example of the modification about a spacer. It is a top view which shows an example of the modification about the opening part of a spacer.

(First embodiment)
A first embodiment of a cylinder structure of a monoblock engine will be described with reference to FIGS.

  As shown in FIG. 1, an example of the monoblock engine 10 is a diesel engine including a monoblock 11 in which a cylinder head and a cylinder block are integrated. A piston 13 is accommodated in the cylinder 12 of the monoblock 11. The piston 13 is equipped with a top ring 14 and a second ring 15 that increase the airtightness of the combustion chamber, and an oil ring 16 that adjusts the amount of oil attached to the cylinder 12 as a piston ring. The piston 13 has a top land 13 </ b> T as an outer peripheral portion closer to the top surface of the piston 13 than the top ring 14. In the monoblock engine 10, intake air flows into the cylinder 12 through the intake port 17 that opens in the upper wall 21 of the cylinder 12. A fuel-air mixture is generated in the cylinder 12 by injecting fuel from the fuel injection valve 18 to the intake air in the cylinder 12. Then, the exhaust gas that burns the air-fuel mixture is discharged from the cylinder 12 through the exhaust port 19 that opens to the upper surface wall 21.

  A recess 22 is formed in the side wall 20 of the cylinder 12 at the end of the cylinder 12 on the side of the upper surface wall 21 over the entire circumference in the circumferential direction of the cylinder 12. The concave portion 22 is constituted by a concave surface 23 having an arcuate cross-sectional shape. The recess 22 functions as a tool escape or a grinding fluid pool during honing for the cylinder 12. The cylinder 12 has a maximum inner diameter φa in the recess 22 and an inner diameter φb on the inner side surface 24 that guides the reciprocation of the piston 13 by sliding of the piston ring. A ring-shaped spacer 25 is attached to the recess 22.

  The spacer 25 is made of a metal such as steel or cast iron. The spacer 25 has an outer peripheral surface 27 that is a surface facing the outer side of the cylinder 12 and an inner peripheral surface 28 that is a surface facing the inner side of the cylinder 12 in a state where the spacer 25 is mounted in the recess 22. The outer peripheral surface 27 of the spacer 25 has a semicircular cross-sectional shape projecting outward, has a cross-sectional portion that is the same cross-sectional shape as the concave surface 23, and is in surface contact with the concave surface 23 of the concave portion 22. The inner peripheral surface 28 of the spacer 25 is a flat surface extending along the central axis A of the cylinder 12 in a state where the spacer 25 is mounted in the recess 22. Further, the inner peripheral surface 28 is located on the outer side of the cylinder 12 than the top land 13T of the piston 13 and on the inner side of the cylinder 12 relative to the inner side surface 24 of the cylinder 12, and the piston 13 is at the top dead center. When it is located, it faces the top land 13T. That is, the spacer 25 has an outer diameter that is the same as the maximum inner diameter φa of the cylinder 12 when mounted in the recess 22, is larger than the outer diameter φc of the top land 13 </ b> T of the piston 13, and the cylinder 12. The inner surface 24 has an inner diameter φf that is smaller than the inner diameter φb.

  As shown in FIG. 2, the spacer 25 has an abutment portion 29 and is formed in a ring shape that can be reduced in diameter by elastic deformation. The spacer 25 has an outer diameter φd larger than the maximum inner diameter φa of the cylinder 12 in a state where the spacer 25 is not attached to the recess 22.

  As shown in FIG. 3, the spacer 25 is inserted into the cylinder 12 in a diameter-reduced state in which the end portions constituting the abutment portion 29 are close to each other. When the spacer 25 is inserted up to the upper wall 21 of the cylinder 12, the reduced diameter state is released, and the spacer 25 is attached to the recess 22 by expanding the diameter. In the spacer 25 attached to the concave portion 22, the outer peripheral surface 27 presses the concave surface 23 of the concave portion 22 by the restoring force.

  As shown in FIG. 4, in each cylinder 12 of the monoblock engine 10, the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke are repeated in order. In the intake stroke, the intake air is taken into the cylinder 12 through the intake port 17 as the piston 13 moves forward from the top dead center to the bottom dead center. In the compression stroke, the piston 13 moves backward from the bottom dead center to the top dead center, thereby compressing the intake air taken in the suction stroke. In the compression stroke, fuel is injected from the fuel injection valve 18 into the cylinder 12 to generate an air-fuel mixture. In the expansion stroke, the piston 13 moves forward from the top dead center to the bottom dead center due to the combustion pressure accompanying the combustion of the air-fuel mixture, thereby applying a rotational force to the crankshaft. In the exhaust stroke, the piston 13 returns from the bottom dead center to the top dead center, so that the exhaust gas in the cylinder 12 is discharged through the exhaust port 19. Since the inner peripheral surface 28 of the spacer 25 is located outward from the top land 13T of the piston 13, the piston 13 reciprocates in a state where interference with the spacer 25 is suppressed. Since the dead volume is reduced by mounting the spacer 25 on the recess 22, generation of unburned gas and a decrease in combustion pressure due to the dead volume are suppressed.

  In the monoblock 11 described above, a water jacket (not shown) through which engine coolant flows is formed around the cylinder 12. The monoblock 11 is cooled by engine cooling water, so that overheating due to combustion of the air-fuel mixture is suppressed, and mechanical strength is ensured. On the other hand, if the combustion heat of the air-fuel mixture is positively transferred to the monoblock 11 through the spacer 25, the temperature in the cylinder 12 is lowered, thereby causing the generation of unburned gas and the combustion pressure. The spacer 25 is not a member that retains the mechanical strength of the monoblock 11, and thermal deformation is allowed in a range where the inner peripheral surface 28 is located outside the top land 13 </ b> T. There is little need for. Therefore, it is desirable for the spacer 25 to suppress a temperature drop in the cylinder 12 due to heat transfer of combustion heat to the monoblock 11.

  The monoblock 11 described above is formed of, for example, an aluminum alloy or cast iron. Aluminum alloys have higher thermal conductivity than steels such as iron, steel, and stainless steel, and cast iron. For this reason, the aluminum alloy monoblock 11 uses a spacer 25 formed of one metal material selected from iron, steel, stainless steel, and cast iron, thereby transferring combustion heat to the monoblock 11. Heat can be suppressed. On the other hand, cast iron has lower thermal conductivity than iron and steel, and higher thermal conductivity than stainless steel. Therefore, the heat transfer of the combustion heat to the monoblock 11 can be suppressed by using the spacer 25 made of stainless steel for the monoblock 11 made of cast iron.

According to the cylinder structure of the monoblock engine, the following effects can be obtained.
(1) By mounting the spacer 25 in the recess 22, a decrease in engine thermal efficiency due to the formation of the recess 22 is suppressed.

  (2) The spacer 25 has an abutment portion 29 and can be reduced in diameter by elastic deformation, and has an outer diameter φd larger than the maximum inner diameter φa of the cylinder 12 when not mounted in the recess 22. According to such a configuration, since the spacer 25 is pressed against the side wall 20 of the cylinder 12 in a state where the spacer 25 is attached to the recess 22, the spacer 25 is difficult to come off from the recess 22.

  (3) Since the outer peripheral surface 27 of the spacer 25 is in surface contact with the concave surface 23 of the concave portion 22, the displacement of the spacer 25 is suppressed, the spacer 25 is not easily displaced, and abnormal noise caused by the vibration of the spacer 25 is also suppressed. It is done.

  (4) A force based on the combustion pressure acts on the portion of the monoblock 11 where the recess 22 is formed via the spacer 25. Therefore, if the contact area between the portion forming the recess 22 and the spacer 25 is small, a force based on the combustion pressure acts on the contact portion in a concentrated manner. Therefore, the portion forming the recess 22 and the spacer 25 are required to have sufficient mechanical strength against the above force.

  In this regard, in the above configuration, the outer peripheral surface 27 of the spacer 25 is in surface contact with the concave surface 23 of the concave portion 22, so that the contact area between the concave portion 22 and the spacer 25 can be increased. Thereby, the force based on the combustion pressure is easily dispersed at the contact portion between the recess 22 and the spacer 25. As a result, the mechanical strength required for the portion forming the recess 22 and the spacer 25, including the material and shape, is reduced.

  (5) Since the inner peripheral surface 28 of the spacer 25 is positioned inward from the inner side surface 24 of the cylinder 12, for example, compared with a case where at least a part of the inner peripheral surface 28 is positioned outward from the inner side surface 24. Thus, the dead volume can be reduced.

  (6) The outer peripheral surface 27 of the spacer 25 is in surface contact with the concave surface 23 of the concave portion 22, and the inner peripheral surface 28 of the spacer 25 is positioned inward of the inner side surface 24 of the cylinder 12. Most of the space is occupied by the spacer 25. As a result, the space in which the combustion gas can enter can be reliably reduced in the space in the recess 22.

  (7) Since the concave portion 22 is constituted by the concave surface 23 which is a curved surface, even if a force based on the combustion pressure is received via the spacer 25, for example, as shown in FIG. Compared to the above, stress concentration in the portion where the recess 22 is formed is suppressed.

  (8) The inner peripheral surface 28 of the spacer 25 is a flat surface extending along the central axis A of the cylinder 12. Therefore, it is possible to reduce the dead volume compared to the case where the inner peripheral surface includes a surface that makes the inner diameter of the spacer 25 larger than the inner diameter φf.

  (9) By forming the spacer 25 with a material having a lower thermal conductivity than the monoblock 11, it is possible to suppress the heat of combustion of the air-fuel mixture from being transferred to the monoblock 11 via the spacer 25. As a result, a decrease in the thermal efficiency of the monoblock engine 10 is further suppressed.

(Second Embodiment)
Next, a second embodiment of the cylinder structure of the monoblock engine will be described with reference to FIG. The second embodiment is different in the spacer structure from the cylinder structure of the monoblock engine of the first embodiment. Therefore, in 2nd Embodiment, the structure of a spacer is demonstrated in detail, and the detailed description is abbreviate | omitted by attaching | subjecting the same code | symbol about the part of 1st Embodiment and the same structure.

  As shown in FIG. 5, the spacer 50 according to the second embodiment includes a spacer body 51 and a ceramic layer 52 coated on the spacer body 51. The spacer body 51 is made of a steel material such as iron, steel, and stainless steel, cast iron, and one type of metal material selected from these. The ceramic layer 52 is made of a ceramic having a lower thermal conductivity than the metal material of the spacer body 51 and is formed by a surface treatment such as plasma spraying on the spacer body 51. For the ceramic layer 52, for example, mullite-based, cordierite-based, silicon nitride-based, alumina-based, and zirconia-based ceramics can be used, and among these ceramics, zirconia having a low thermal conductivity and a high melting point. It is preferred that a ceramic of the system is used.

  According to the spacer 50 having such a configuration, since the ceramic layer having a low thermal conductivity functions as a heat insulating layer, the thermal conductivity of the spacer 50 becomes lower than the fuel conductivity of the spacer body 51. As a result, the heat transfer of the combustion heat to the monoblock 11 is further suppressed.

  Since a diesel engine has a higher combustion pressure than a gasoline engine, cast iron having a mechanical strength higher than that of an aluminum alloy is often used for the monoblock 11. As described above, cast iron has a low thermal conductivity. Therefore, if a spacer is formed of a single metal material and heat transfer of combustion heat to the monoblock 11 is suppressed, there is a restriction on the metal material. Cheap. However, in the case of the spacer 50 described above, since the thermal conductivity is reduced by coating the ceramic body 52 on the spacer body 51, the degree of freedom with respect to the metal material constituting the spacer body 51 is improved.

In the cylinder structure of the monoblock engine of the second embodiment, the following effects can be obtained.
(10) Since the spacer 50 includes the spacer main body 51 and the ceramic layer 52, the heat transfer of the combustion heat to the monoblock 11 is further suppressed. Moreover, the freedom degree of the metal material which can be used for the spacer 50 improves.

In addition, the said embodiment can also be suitably changed and implemented as follows.
-The recessed part formed in the monoblock 11 should just be a shape which enlarges the internal diameter of the cylinder 12 in the edge part by the side of the upper surface wall 21 of the side wall 20, and cross-sectional shape is comprised by the concave surface 23 of circular arc shape. Not limited.

  For example, like the recess 30 shown in FIG. 6, the recess includes an inclined surface 31 that extends to the inner surface 24 and increases the inner diameter of the cylinder 12, and a flat surface 32 that extends to the inclined surface 31 and extends along the central axis A of the cylinder 12. It may be constituted by. It is preferable that a spacer 35 having an outer peripheral surface 37 that is in surface contact with these surfaces 31 and 32 and an inner peripheral surface 38 that is located inward of the inner side surface 24 is also attached to the recess 30. The spacer 35 may be composed of a single metal material, or may be composed of a spacer body and a ceramic layer coated on the spacer body.

  -The spacer should just occupy at least one part of the space in a recessed part, when an inner peripheral surface is located in the outer side of the top land 13T in the state with which the recessed part was mounted | worn. Therefore, the inner peripheral surface of the spacer may be a surface positioned outward from the inner side surface 24 of the cylinder 12 in a state where the spacer is mounted in the recess, or may be a surface along the inner side surface 24 of the cylinder 12.

  The inner peripheral surface of the spacer is a surface facing the inside of the cylinder 12 in a state where the spacer is mounted in the recess. Therefore, the inner peripheral surface is not limited to a flat surface extending along the central axis A of the cylinder 12, and may include an inclined surface or a curved surface that changes the inner diameter of the spacer.

  For example, the spacer may have an inner peripheral surface 43 that makes the inner diameter of the spacer 40 smaller as it is closer to the upper surface wall 21, like the spacer 40 shown in FIG. 7. In addition, the spacer may have an inner peripheral surface that increases the inner diameter of the spacer closer to the upper surface wall 21. These inner peripheral surfaces may be surfaces in which a part thereof is located outward from the inner surface 24 of the cylinder 12. The position and shape of the inner peripheral surface of the spacer are preferably designed in consideration of the swing motion of the piston 13. In addition, the spacer of such a structure may be comprised with a single metal material, and may be comprised with the ceramic body coated by the spacer main body and the spacer main body.

  The spacer only needs to occupy at least a part of the space in the recess by being attached to the recess, and the outer peripheral surface 27 does not have to be in surface contact with the recess 23 of the recess 22 like the spacer 25. For example, the spacer may be configured to close the opening of the recess in a state where a gap is formed between the concave surface of the recess and a part of the outer peripheral surface of the spacer.

  For example, as shown in FIG. 8, the outer peripheral surface 57 of the spacer 55 includes a contact surface 57 a that is in surface contact with the concave surface 23 of the concave portion 22 and a non-contact surface 57 b that forms a gap 60 between the concave surface 23 of the concave portion 22. You may have. The non-contact surface 57 b may be configured by a groove portion extending along the circumferential direction of the spacer 55 in the outer peripheral portion of the spacer 55, or may be configured by depressions scattered in the outer peripheral portion of the spacer 55. Even with such a configuration, the dead volume is reduced. Further, the contact area between the spacer 55 and the monoblock 11 is reduced, and the gap 60 functions as a heat insulating layer, whereby the amount of heat transferred from the spacer 55 to the monoblock 11 is reduced. As a result, it is possible to suppress the heat of combustion of the air-fuel mixture from being transferred to the monoblock 11 via the spacer 55. In addition, since a part of the expansion toward the concave surface 23 due to thermal deformation can be absorbed by the gap 60, the displacement of the inner peripheral surface 58 toward the piston 13 can be suppressed. The spacer 55 may be composed of a single metal material, or may be composed of a spacer body and a ceramic layer coated on the spacer body.

  The outer diameter φd of the spacer may be the same as the maximum inner diameter φa of the cylinder 12 when not installed in the recess. Further, the outer diameter φd of the spacer may be smaller than the maximum inner diameter φa of the cylinder 12 in the recess, for example, when a gap is formed between the concave surface of the recess and the outer peripheral surface of the spacer.

  The mating portion 29 of the spacer 25 is not limited to a right angle mating port, but may be a diagonal mating port or a stepped mating port 61 as shown in FIG. According to such a configuration, it is possible to increase the portion occupied by the spacer in the concave portion 22 and to suppress the ingress of combustion gas to the abutment portion.

  The monoblock engine 10 is not limited to a diesel engine, and may be a gasoline engine or a natural gas engine using natural gas as fuel.

  DESCRIPTION OF SYMBOLS 10 ... Monoblock engine, 11 ... Monoblock, 12 ... Cylinder, 13 ... Piston, 13T ... Top land, 14 ... Top ring, 15 ... Second ring, 16 ... Oil ring, 17 ... Intake port, 18 ... Fuel injection valve, DESCRIPTION OF SYMBOLS 19 ... Exhaust port, 20 ... Side wall, 21 ... Top wall, 22 ... Recess, 23 ... Concave surface, 24 ... Inner surface, 25 ... Spacer, 27 ... Outer surface, 28 ... Inner surface, 29 ... Mating part, 30 ... Recessed portion, 31 ... inclined surface, 32 ... flat surface, 35 ... spacer, 37 ... outer peripheral surface, 38 ... inner peripheral surface, 40 ... spacer, 43 ... inner peripheral surface, 50 ... spacer, 51 ... spacer body, 52 ... ceramic layer , 55 ... spacer, 57 ... outer peripheral surface, 57a ... contact surface, 57b ... non-contact surface, 58 ... inner peripheral surface, 60 ... gap, 61 ... stepped opening.

Claims (5)

A cylinder structure of a monoblock engine having a monoblock in which a cylinder head and a cylinder block are integrally formed,
In the monoblock, a recess is formed over the entire circumference at the end of the cylinder side wall on the upper surface wall side,
A ring-shaped spacer is attached to the recess,
In the state where the spacer is mounted in the recess, the inner peripheral surface of the spacer is located outside the cylinder from the top land of the piston ,
The spacer is
A spacer body having a lower thermal conductivity than the monoblock;
A cylinder structure of a monoblock engine comprising a ceramic layer coated on the spacer body and having a lower thermal conductivity than the spacer body . The spacer is
2. The monoblock according to claim 1, wherein the monoblock has an abutment portion and is configured to be able to be reduced in diameter by elastic deformation, and has an outer diameter larger than the maximum diameter of the cylinder in the recess when not mounted in the recess. Engine cylinder structure. The cylinder structure of the monoblock engine according to claim 2, wherein the spacer is in surface contact with the concave surface of the concave portion in a state where the spacer is attached to the concave portion. The monoblock engine according to any one of claims 1 to 3, wherein an inner peripheral surface of the spacer is positioned inward of the cylinder from an inner surface of the cylinder in a state where the spacer is mounted in the recess. Cylinder structure. The cylinder structure of the monoblock engine as described in any one of Claims 1-4 in which the said recessed part is comprised by the curved surface.

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