JP2017053267A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of: achieving high thermal efficiency through heat insulation; appropriately keeping a temperature in a combustion chamber; and preventing combustion failure.SOLUTION: An internal combustion engine comprises: a cylinder block which has a cylinder; a cylinder head which is installed on an upper edge of the cylinder block; and a piston which is arranged in a manner that can reciprocate inside the cylinder. The internal combustion engine also has an insulation member, which prevents heat inside the cylinder from transmitting to the cylinder block, within a range from the upper edge of the cylinder block to a position where a first piston ring reaches when the piston is at a top dead center.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an internal combustion engine that provides heat insulation to a combustion chamber to improve efficiency.

  Many internal combustion engines use cooling liquid or air to cool and maintain the temperature of the combustion chamber appropriately. On the other hand, it is preferable that the heat dissipation from the combustion chamber is small from the viewpoint of improving the efficiency of the internal combustion engine.

  For example, Patent Document 1 shows an example in which an adjustment ring having high heat insulation is provided on the inner peripheral portion of a cylinder liner. Patent Document 2 shows an example in which a heat insulating layer is provided on the wall surface of a cylinder.

JP-A-8-42389 JP 2013-53607 A

  However, if the internal combustion engine is not sufficiently cooled by heat insulation, the temperature of the combustion chamber rises, and there is a risk of causing combustion failure such as knocking.

  An object of the present invention is to provide an internal combustion engine that can obtain high thermal efficiency by heat insulation, can appropriately maintain the temperature of a combustion chamber, and can prevent poor combustion.

  In order to solve the above-described problems, the present invention has an internal combustion engine configured as follows. The internal combustion engine includes a cylinder block having a cylinder, a cylinder head attached to an upper end of the cylinder block, and a piston provided in a reciprocating manner in the cylinder. Further, the internal combustion engine has heat insulation that suppresses heat transfer from the inside of the cylinder to the cylinder block in a range from the upper end of the cylinder block to a position equivalent to the position of the first piston ring when the piston is at the top dead center. A member is provided.

  According to the present invention, it is possible to provide an internal combustion engine that can obtain high thermal efficiency by heat insulation, appropriately maintain the temperature of the combustion chamber, and prevent defective combustion.

1 is a cross-sectional view showing an internal combustion engine of a first embodiment according to the present invention. The fragmentary sectional view which shows a piston. Sectional drawing which shows the internal combustion engine of 2nd Embodiment. Sectional drawing which shows the internal combustion engine of 3rd Embodiment. Sectional drawing which shows the internal combustion engine of 4th Embodiment. Sectional drawing which shows the internal combustion engine of 5th Embodiment. The graph which shows the relationship between a heat flux and a crank angle.

(First embodiment)
A first embodiment according to the present invention will be described. FIG. 1 shows an engine 10 that is the internal combustion engine of the first embodiment. As shown in FIG. 1, the engine 10 includes a cylinder head 12, a piston 14, a cylinder block 16 having a cylinder 15, and a crankcase 18. Hereinafter, the engine 10 will be described with the cylinder head 12 side as the upper side of the engine 10 as viewed from the cylinder block 16 and the opposite side as the lower side in a state where the central axis P of the cylinder 15 is vertically arranged.

  The engine 10 is, for example, an in-line four-cylinder liquid-cooled gasoline engine. The engine 10 includes a combustion chamber 19 surrounded by a cylinder head 12, a piston 14, and a cylinder 15. In the present invention, the number of cylinders of the engine 10 and the arrangement of the cylinders 15 are not particularly limited. Also, a diesel engine may be used instead of a gasoline engine. FIG. 1 shows a state in which the engine 10 is broken along a plane passing through the central axis P of one cylinder 15 provided in the cylinder block 16.

  The cylinder head 12 is made of, for example, an aluminum alloy. The cylinder head 12 is provided with an intake passage 20 and an exhaust passage 22 that communicate with the combustion chamber 19. The intake passage 20 is provided with an intake valve 24 and a fuel injection valve. The intake valve 24 is driven by a cam to open and close the intake passage 20. The fuel injection valve injects fuel into the intake passage 20 according to the control of the control device. An exhaust valve 26 is provided in the exhaust passage 22. The exhaust valve 26 is driven by a cam to open and close the exhaust passage 22.

  A spark plug 23 is attached to the ceiling wall 21 of the cylinder head 12. The spark plug 23 generates a spark at the ignition timing in the combustion chamber 19 according to the control of the control device. The ceiling wall 21 of the cylinder head 12 and the bottom surfaces 25 and 27 of each valve of the intake valve 24 and the exhaust valve 26 are subjected to heat insulation treatment with a heat insulating material.

  Note that the engine 10 may supply the fuel with a carburetor instead of the fuel injection valve. A fuel injection valve may be provided so as to inject fuel directly into the combustion chamber 19. Moreover, the heat insulation process to the ceiling wall 21 and the bottom surfaces 25 and 27 of each valve may not be required. A cylinder block 16 is provided below the cylinder head 12.

  The cylinder block 16 is made of, for example, an aluminum alloy, and four cylinders 15 are arranged perpendicular to the paper surface. A cylinder liner 40 is provided in the cylinder block 16. The cylinder liner 40 is a cylindrical member made of cast iron, for example, and is cast into the cylinder block 16. The cylinder 15 as a cylinder is formed by each cylinder liner 40 provided in the cylinder block 16.

  The cylinder block 16 is provided with a coolant passage 42 outside the cylinder liner 40. The coolant passage 42 communicates with the radiator and allows the coolant cooled by the radiator to pass therethrough. A piston 14 is assembled in each cylinder 15.

  The piston 14 is substantially cylindrical, and includes a piston head 17 on the upper surface and a side wall 28 on the side surface. The piston head 17 is formed with a recess 62 that avoids the valve and an inclined surface 64. The inclined surface 64 is provided on the outer peripheral portion of the piston 14 and forms a squish area in the combustion chamber 19 with the ceiling wall 21.

  A first piston ring groove 29, a second piston ring groove 31, and an oil ring groove 33 (see FIG. 2) are provided on the outer periphery of the side wall 28 from above. A first piston ring 30 is attached to the first piston ring groove 29, a second piston ring 32 is attached to the second piston ring groove 31, and an oil ring 34 is attached to the oil ring groove 33. Each of the first piston ring 30, the second piston ring 32, and the oil ring 34 is in contact with the inner surface of the cylinder liner 40 with an appropriate spring force.

  One end of a connecting rod 36 is coupled to the piston 14 via a piston pin. The other end of the connecting rod 36 is connected to the crankshaft 37. The piston 14 is provided in the cylinder 15 so as to freely reciprocate. When the piston 14 reciprocates, the crankshaft 37 is rotated in the direction of the arrow A via the connecting rod 36.

  FIG. 1 shows a state where the piston 14 is located at the top dead center of the reciprocating motion. The cylinder liner 40 is provided beyond the lower end of the reciprocating range of the piston 14 from the upper end of the cylinder block 16. A heat insulating sleeve 44 as a heat insulating member is provided outside the cylinder liner 40.

  The heat insulating sleeve 44 has a cylindrical shape and is formed of a heat insulating material such as ceramic. The heat insulating sleeve 44 has an inner diameter substantially equal to the outer diameter of the cylinder liner 40 and is attached to the entire outer periphery of the cylinder liner 40. As shown in FIG. 1, the heat insulating sleeve 44 is provided from the upper end of the cylinder block 16 to the position of the lower end of the first piston ring 30 when the piston 14 is at the top dead center.

  In addition, the position of the lower end of the heat insulating sleeve 44 is not only when the position of the lower end of the first piston ring 30 is completely coincident with the position of the lower end of the first piston ring 30 when the piston 14 is at the top dead center. It may be located slightly below the position. The heat insulating member may be formed of a space provided in the cylinder block 16, that is, an air layer, instead of the heat insulating sleeve 44 made of ceramic or the like.

  Next, the operation and effect of the engine 10 will be described. It is assumed that the engine 10 has been warmed up and is operating in a normal operating state. When the engine 10 enters the intake stroke, the intake valve 24 opens, the piston 14 moves down in the cylinder 15, and the air-fuel mixture is sucked into the combustion chamber 19 through the intake passage 20.

  Subsequently, when the process proceeds to the compression stroke, the intake valve 24 is operated and the intake passage 20 is closed. The piston 14 that has passed through the bottom dead center moves up in the cylinder 15 and compresses the air-fuel mixture in the combustion chamber 19. The air-fuel mixture rises in temperature as it is compressed, but the ceiling wall 21 of the cylinder head 12 of the engine 10 and the bottom surfaces of the valves of the intake valve 24 and the exhaust valve 26 are subjected to heat insulation. Through these, heat is hardly absorbed from the combustion chamber 19 into the cylinder head 12 or the like.

  On the other hand, the piston 14 is in contact with the inner surface of the cylinder liner 40 via the first piston ring 30, the second piston ring 32, and the oil ring 34. Accordingly, the heat of the piston 14 is transmitted to the cylinder block 16 through the first piston ring 30 and the like in the compression stroke, and is absorbed by the coolant from the cylinder block 16.

  When the engine 10 reaches the ignition timing, the spark plug 23 is activated and combustion of the air-fuel mixture is started in the combustion chamber 19. Since the ignition is performed at a stage that is normally before top dead center, the piston 14 reaches top dead center while the air-fuel mixture is being burned in the combustion chamber 19.

  As shown in FIG. 1, when the piston 14 reaches top dead center, the first piston ring 30 reaches substantially the same position as the lower end of the heat insulating sleeve 44. Since the heat insulation sleeve 44 suppresses the heat transfer from the cylinder liner 40 to the cylinder block 16, the heat from the piston 14 to the cylinder block 16 through the first piston ring 30 when the piston 14 is at the top dead center. Movement is suppressed. Further, the heat insulating sleeve 44 insulates the cylinder liner 40 from the upper end of the cylinder block 16 to the first piston ring 30.

  Thus, in the engine 10, the portion of the cylinder liner 40 from the upper end of the cylinder block 16 to the first piston ring 30 is thermally insulated by the heat insulating sleeve 44. Further, since the piston head 17 faces the combustion chamber 19, the temperature tends to rise due to combustion in the combustion chamber 19. However, when the piston 14 is at the position of the compression top dead center, the heat radiation through the first piston ring 30 located closest to the piston head 17 is suppressed, so that the cylinder block that has passed the piston 14 from the combustion chamber 19 Heat dissipation to 16 is effectively prevented. Therefore, the engine 10 suppresses the temperature drop of the combustion chamber 19 at the top dead center, and high thermal efficiency is obtained.

  On the other hand, when the expansion stroke is started and the piston 14 is lowered from the top dead center, the first piston ring 30 is detached from the position of the heat insulating sleeve 44. Thereby, the heat of the piston 14 is absorbed by the cylinder block 16 and the like through the first piston ring 30 from the expansion stroke to the exhaust stroke. Thereby, the heat of the piston 14 is absorbed by the coolant, and the engine 10 enters the next combustion cycle following the combustion cycle without excessively increasing the temperature of the piston 14.

  Therefore, according to the engine 10, high efficiency is obtained, the piston 14 is appropriately cooled, and occurrence of defective combustion such as knocking due to overheating of the combustion chamber 19 is suppressed.

(Second Embodiment)
A second embodiment according to the present invention will be described. In FIG. 3, the partial cross section of the engine 11 of 2nd Embodiment is shown. The engine 11 includes a heat insulating sleeve 50 as a heat insulating member on an upper portion of the cylinder liner 40.

  The heat insulating sleeve 50 is formed of a heat insulating material having a predetermined heat insulating action such as ceramic. The heat insulating sleeve 50 is cylindrical and has an inner diameter equal to the inner diameter of the cylinder liner 40. The heat insulation sleeve 50 is provided from the upper end of the cylinder block 16 to the same position as the position of the lower end of the first piston ring 30 when the piston 14 is at the top dead center. The heat insulating sleeve 50 is continuously provided on the upper end of the cylinder liner 40 coaxially with the cylinder liner 40. That is, the cylinder 15 is formed by a combination of the cylinder liner 40 and the heat insulating sleeve 50 provided on the upper portion of the cylinder liner 40. Other configurations of the engine 11 are the same as those of the engine 10 of the first embodiment.

  When the engine 11 is operated and the piston 14 reaches the compression top dead center, the first piston ring 30 reaches the heat insulation sleeve 50 from the cylinder liner 40. Then, like the engine 10 of the first embodiment, the movement of heat from the piston 14 to the cylinder block 16 through the first piston ring 30 is suppressed, and the efficiency of the engine 11 at the top dead center is increased.

  When the piston 14 is lowered, the first piston ring 30 is out of contact with the heat insulating sleeve 50. Thereafter, the heat of the piston 14 is absorbed by the cylinder block 16 through the first piston ring 30, and the piston 14 is appropriately cooled.

  The first piston ring 30 crosses the boundary portion between the heat insulating sleeve 50 and the cylinder liner 40 immediately before the piston 14 reaches top dead center and immediately after passing through the top dead center. At this time, since the moving speed of the piston 14 is almost close to 0, the first piston ring 30 passes through the boundary between the heat insulating sleeve 50 and the cylinder liner 40 at a very low speed.

  As a result, even if the friction coefficient of the heat insulating sleeve 50 and the friction coefficient of the cylinder liner 40 are different, or a slight level difference or the like occurs between them, the first piston ring 30 does not interfere with the heat insulating sleeve 50. The boundary with the cylinder liner 40 can be exceeded. Therefore, even if the cylinder block 16 is provided with the heat insulating sleeve 50, the piston 14 can be operated smoothly.

  When the position of the lower end portion of the heat insulating sleeve 50 completely coincides with the position of the first piston ring 30 of the piston 14 when the top dead center is reached, and the piston 14 moves even slightly, the heat insulating sleeve 50 and the first piston The contact with the ring 30 is preferably removed from the point that the piston 14 can be smoothly operated in the cylinder 15.

  Therefore, the engine 11 has high efficiency as in the case of the engine 10, and the piston 14 is appropriately cooled, so that occurrence of combustion failure such as knocking due to overheating of the combustion chamber 19 is suppressed.

(Third embodiment)
A third embodiment according to the present invention will be described. In FIG. 4, the partial cross section of the engine 13 of 3rd Embodiment is shown. The engine 13 is provided with a heat insulating layer 54 as a heat insulating member on the inner surface of the cylinder liner 40. The heat insulating layer 54 is formed by attaching a heat insulating material to the inner surface of the cylinder liner 40.

  The heat insulating layer 54 is provided from the upper end of the cylinder block 16 to the position of the lower end of the first piston ring 30 of the piston 14 at the top dead center. The heat insulating layer 54 has a sufficient heat insulating performance, is in close contact with the cylinder liner 40, and is not easily worn by the reciprocating motion of the piston 14. Other configurations of the engine 13 are the same as those of the engine 10 of the first embodiment.

  In the engine 13, when the piston 14 reaches top dead center, the first piston ring 30 contacts the heat insulating layer 54. Then, like the engine 10, the movement of heat from the piston 14 through the first piston ring 30 is suppressed, and the thermal efficiency of the engine 13 is increased.

  Then, when the piston 14 is lowered, the first piston ring 30 is immediately out of contact with the heat insulating layer 54. Thereafter, the heat of the piston 14 is absorbed by the cylinder block 16 through the first piston ring 30, and the piston 14 is appropriately cooled.

  Therefore, in the engine 13, the thermal efficiency of the engine 13 is improved by the heat insulating layer 54, the piston 14 is appropriately cooled, and occurrence of combustion failure such as knocking due to overheating of the combustion chamber 19 is suppressed.

(Fourth embodiment)
A fourth embodiment according to the present invention will be described. In FIG. 5, the partial cross section of the engine 60 of 4th Embodiment is shown. In the engine 60, the cylinder 15 is provided in the cylinder block 16. Piston 14 is assembled | attached inside the cylinder 15 directly provided in the cylinder block 16 made from aluminum alloy.

  The engine 60 includes a heat insulating sleeve 44 at a position slightly outside the inner surface of the cylinder 15. The heat insulating sleeve 44 is cylindrical and is provided coaxially with the cylinder 15. As shown in FIG. 5, the heat insulating sleeve 44 is provided from the upper end of the cylinder block 16 to substantially the same position as the position of the lower end of the first piston ring 30 when the piston 14 is at the top dead center. The heat insulating sleeve 44 is provided in the cylinder block 16 at the same time when the cylinder block 16 is cast or by being incorporated into a groove formed in the cylinder block 16, for example. Other configurations of the engine 60 are the same as those of the engine 10 of the first embodiment.

  In the engine 60, as shown in FIG. 5, when the piston 14 reaches top dead center, the first piston ring 30 is disposed on the side of the heat insulating sleeve 44. Then, like the engine 10 of the first embodiment, the movement of heat from the piston 14 to the cylinder block 16 through the first piston ring 30 is suppressed, and the thermal efficiency of the engine 60 increases.

  In the engine 60, when the piston 14 is lowered, the first piston ring 30 moves away from the position of the heat insulating sleeve 44. Thereafter, the heat of the piston 14 is absorbed by the cylinder block 16 through the first piston ring 30, and the piston 14 is appropriately cooled.

  Therefore, the engine 60 has high efficiency as with the engine 10, and the piston 14 is appropriately cooled, and the occurrence of combustion failure such as knocking due to overheating of the combustion chamber 19 is suppressed.

(Fifth embodiment)
A fifth embodiment according to the present invention will be described. In FIG. 6, the partial cross section of the engine 70 of 5th Embodiment is shown. The engine 70 includes a heat insulating sleeve 72 as a heat insulating member outside the cylinder liner 40. The heat insulating sleeve 72 is different in length from the heat insulating sleeve 44 of the engine 10 of the first embodiment.

  The heat insulating sleeve 72 is formed of a heat insulating material such as ceramic and is provided between the cylinder liner 40 and the coolant passage 42. The heat insulating sleeve 72 has a cylindrical shape and is provided concentrically on the outer peripheral surface of the cylinder liner 40.

  As shown in FIG. 5, the heat insulating sleeve 72 is located at the lower end of the first piston ring 30 of the piston 14 when the crankshaft 37 is rotated in the positive direction by 40 degrees from the position of the top dead center from the upper end of the cylinder block 16. It is provided to the same position. Other configurations of the engine 70 are the same as those of the engine 10 of the first embodiment.

  FIG. 7 shows an actual measurement example of heat flux from the inside of the cylinder 15 to the cylinder block 16 during combustion for a general engine. FIG. 7 shows the value of the crank angle θ (degrees) on the horizontal axis and the value of heat flux (MW / square m) on the vertical axis. As shown in FIG. 7, the heat flux has a very large value in the range from the position of the top dead center (TDC) of the piston to the position where the crank angle is rotated by 40 degrees, and the crank angle is 40 from the position of the top dead center. It can be seen that when the degree is exceeded, it decreases rapidly. In this example, the predetermined value of the heat flux referred to in the claims is a value when the crank angle is rotated by 40 degrees.

  In the engine 70, the heat insulating sleeve 72 is provided from the position of the upper end of the cylinder block 16 to the position of the lower end of the first piston ring 30 of the piston 14 when the crankshaft 37 is rotated 40 degrees from the position of the top dead center. Yes. Thereby, in the engine 70, the movement of heat from the piston 14 through the first piston ring 30 to the cylinder block 16 in a region where the heat flux is large is suppressed, and the thermal efficiency of the engine 70 increases.

  On the other hand, in the engine 70, when the crankshaft 37 (see FIG. 1) rotates 40 degrees or more from the top dead center, the first piston ring 30 is separated from the heat insulating sleeve 72. Therefore, when the crankshaft 37 is outside the range of 40 degrees before and after the top dead center, the heat of the piston 14 is absorbed by the cylinder block 16 through the first piston ring 30 and the piston 14 is appropriately cooled.

  Therefore, the engine 70 is insulated in a wide range by the heat insulating sleeve 72, and high efficiency can be obtained like the engine 10. Further, in the engine 70, the piston 14 is appropriately cooled in a region outside the heat insulating sleeve 72, and occurrence of combustion failure such as knocking due to overheating of the combustion chamber 19 is suppressed.

  In the fifth embodiment, instead of the heat insulating sleeve 72, a structure equivalent to that of the second to fourth embodiments may be used as a heat insulating member. If the relationship between the crank angle and the heat flux differs from the graph of FIG. 7 depending on the characteristics of the engine, the length of the heat insulating sleeve 72 may be changed accordingly.

  Further, the present invention is not limited to the above embodiment, and can be changed as appropriate.

  The present invention can be used for an automobile engine.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 12 ... Cylinder head, 14 ... Piston, 15 ... Cylinder, 16 ... Cylinder block, 17 ... Cylinder head, 18 ... Crankcase, 20 ... Intake passage, 22 ... Exhaust passage, 30 ... First piston ring, 32 2nd piston ring, 34 ... oil ring, 37 ... crankshaft, 40 ... cylinder liner, 42 ... coolant passage, 44 ... heat insulation sleeve.

Claims (7)

A cylinder block having a cylinder;
A cylinder head attached to the upper end of the cylinder block;
A piston reciprocally provided in the cylinder;
Provided in the cylinder block, within the range from the position of the upper end of the cylinder block to the same position as the first piston ring of the piston when the piston is at the top dead center of the reciprocating motion, from within the cylinder An internal combustion engine comprising: a heat insulating member that suppresses heat transfer to the cylinder block. A cylinder block having a cylinder;
A cylinder head attached to the upper end of the cylinder block;
A piston connected to the crankshaft and provided in the cylinder so as to be able to reciprocate the crank;
A heat insulating member that suppresses heat transfer from inside the cylinder to the cylinder block, and
Furthermore, the heat insulating member is provided from the upper end of the cylinder block to the position of a boundary point where the value of the heat flux that moves from the cylinder to the cylinder block during combustion in the cylinder falls below a predetermined value. .   The internal combustion engine according to claim 2, wherein the position of the boundary point at which the value of the heat flux falls below a predetermined value is the position of the first piston ring of the piston when the crankshaft rotates 40 degrees after top dead center. The cylinder is formed inside a cylinder liner provided in the cylinder block,
The internal combustion engine according to any one of claims 1 to 3, wherein the heat insulating member is provided outside the cylinder liner. The cylinder is formed inside a cylinder liner provided in the cylinder block,
The internal combustion engine according to claim 1, wherein the heat insulating member is provided on an inner surface of the cylinder liner. The cylinder is formed inside a cylinder liner provided in the cylinder block,
The internal combustion engine according to any one of claims 1 to 3, wherein the heat insulating member is continuously provided coaxially with the cylinder liner above the cylinder liner.   The internal combustion engine according to claim 1, wherein the heat insulating member is formed by a space provided in the cylinder block.

Images