Gas seal structure of an internal combustion engine

Abstract

To improve gas seal performance in a gas seal structure of an internal combustion engine.SOLUTION: An internal combustion engine comprises: a cylinder block comprising a space part having a columnar shape; a cylinder liner having a cylindrical shape, and arranged in the space part; a piston supported by the cylinder liner so as to be movable in an axial direction; a cylinder head fastened to an upper part of the cylinder block; and a gasket arranged between the cylinder block and the cylinder liner, and the cylinder head. A contact area between the cylinder liner and the gasket is equal to a contact area between the cylinder head and the gasket.SELECTED DRAWING: Figure 3

Description

【Technical Field】 【0001】 The present disclosure relates to a gas seal structure for an internal combustion engine. 【Background Art】 【0002】 An internal combustion engine includes a cylinder block, a cylinder head, and a piston. The cylinder block has a plurality of cylindrical spaces provided at intervals in the horizontal direction along the vertical direction. A cylinder liner having a cylindrical shape is fitted into each of the plurality of spaces. The piston is supported movably in the axial direction with respect to the cylinder liner. The cylinder head is fastened to the cylinder block via a gasket at the upper part, so that a combustion chamber is defined facing the piston. The combustion chamber communicates with an intake port and an exhaust port respectively. The intake port is openable and closable by an intake valve, and the exhaust port is openable and closable by an exhaust valve. And, a fuel injection valve for injecting fuel into the combustion chamber is provided in the cylinder head. 【0003】 External leakage of combustion gas in the combustion chamber is prevented by a gasket disposed between the cylinder liner and the cylinder head. That is, the cylinder head is fastened to the cylinder block by a plurality of bolts with a gasket disposed between the cylinder head and the cylinder block. At this time, the upper surface of the gasket is in close contact with the lower surface of the cylinder head, and the lower surface is in close contact with the upper surface of the cylinder liner. Therefore, a predetermined load acts on the contact surface between the gasket and the cylinder head and the contact surface between the gasket and the cylinder liner, so that they are in close contact with each other and sealed. As such a gas seal structure of an internal combustion engine, for example, there is one described in the following patent document. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Utility Model Publication No. 63-020850 【Patent Document 2】 Japanese Patent Application Laid-Open No. 2014-126023 [Overview of the project] [Problems that the invention aims to solve] 【0005】 When a gasket is subjected to a predetermined load between the cylinder head and the cylinder liner, its upper and lower surfaces come into close contact with the cylinder head and cylinder liner. At this time, the contact area of ​​the gasket with the cylinder head and the contact area of ​​the cylinder liner are different. That is, the surface pressure between the gasket, which has a larger contact area, and the cylinder head is lower than the surface pressure between the gasket, which has a smaller contact area, and the cylinder liner. On the other hand, when an internal combustion engine is in operation, the cylinder liner deforms in accordance with the rigidity of the cylinder block, which deforms under the explosion load, but the cylinder head deforms in a different manner from the cylinder liner due to its own rigidity under the explosion load. Therefore, relative slip occurs at the contact surface between the gasket and the cylinder head on the side with lower surface pressure. This results in surface roughness on the surfaces where relative slip occurs, i.e., the upper surface of the gasket and the lower surface of the cylinder head, which leads to a problem in that the gas sealing performance of the gasket is reduced. 【0006】 This disclosure aims to solve the aforementioned problems and to provide a gas seal structure for an internal combustion engine that improves gas seal performance. [Means for solving the problem] 【0007】 To achieve the above objective, the gas seal structure for an internal combustion engine of the present disclosure comprises a cylinder block having a cylindrical space, a cylindrical cylinder liner disposed in the space, a piston supported by the cylinder liner so as to be movable in the axial direction, a cylinder head fastened to the upper part of the cylinder block, and a gasket having a firing ring disposed between the cylinder block and the cylinder liner and the cylinder head, wherein the contact area between the cylinder liner and the firing ring is the same as the contact area between the cylinder head and the firing ring. [Effects of the Invention] 【0008】 According to the gas seal structure for an internal combustion engine of this disclosure, it is possible to improve the gas seal performance. [Brief explanation of the drawing] 【0009】 [Figure 1] Figure 1 is a cross-sectional view of the main components of the diesel engine of this embodiment. [Figure 2] Figure 2 is a cross-sectional view of the main part of the gas seal structure of an internal combustion engine before fastening. [Figure 3] Figure 3 is a cross-sectional view of the main part of the gas seal structure of an internal combustion engine after fastening. [Figure 4] Figure 4 is a graph showing the radial pressure distribution at the contact surface between the gasket and the cylinder head. [Modes for carrying out the invention] 【0010】 Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. However, these embodiments do not limit the present disclosure, and where there are multiple embodiments, they may be combinations of these embodiments. Furthermore, the components in the embodiments include those readily conceivable by those skilled in the art, those that are substantially identical, and those that are equivalent. 【0011】 <Engine> Figure 1 is a cross-sectional view of the main components of the diesel engine of this embodiment. 【0012】 As shown in Figure 1, the diesel engine (internal combustion engine) 10 comprises a cylinder block 11, a cylinder liner 12, a cylinder head 13, a piston 14, and a gasket 15. In this embodiment, the internal combustion engine is a diesel engine 10, but other types of engines such as a gasoline engine may also be used. 【0013】 The cylinder block 11 has a block shape and is provided with a cylindrical space 21 along the vertical direction. Although not shown, multiple spaces 21 are provided at intervals in the horizontal direction of the cylinder block 11. The cylinder liner 12 has a cylindrical shape and is fitted and fixed into the space 21. The cylinder head 13 is positioned on top of the cylinder block 11 and the cylinder liner 12 and is fastened and fixed to the cylinder block 11 by multiple bolts (not shown). 【0014】 The piston 14 is cylindrical in shape, and multiple (three in this embodiment) piston rings 22 are mounted on its outer circumference at axial intervals. The piston 14 is positioned inside the cylinder liner 12 and is supported so as to be movable along the axial direction. At this time, the outer circumference of the piston rings 22 slides against the inner circumference of the cylinder liner 12. The cylinder block 11, although not shown, has a crankshaft rotatably supported at its lower part, and the piston 14 and the crankshaft are connected via a connecting rod 23. 【0015】 The gasket 15 is positioned between the cylinder block 11 and the cylinder liner 12 and the cylinder head 13. The cylinder head 13 is fastened to the cylinder block 11 with the gasket 15 positioned between it and the cylinder block 11. The upper surface of the gasket 15 is in close contact with the lower surface of the cylinder head 13, and the lower surface is in close contact with the upper surface of the cylinder liner 12, thus providing a gas seal function. 【0016】 The combustion chamber 24 is a space partitioned by the lower surface of the cylinder head 13, the inner circumferential surface of the cylinder liner 12, and the upper surface of the piston 14. The ends of the intake port 25 and exhaust port 26 provided in the cylinder head 13 are in communication with each other in the combustion chamber 24. The lower end of the intake valve 27 is located in the intake port 25, and the lower end of the exhaust valve 28 is located in the exhaust port 26. The intake valve 27 and exhaust valve 28 are supported by the cylinder head 13 so as to be movable along the axial direction, and are biased by a biasing member (not shown) in a direction that closes the intake port 25 and exhaust port 26 (upward in Figure 1). 【0017】 The intake valve 27 and the exhaust valve 28 open and close the intake port 25 and the exhaust port 26 by the action of intake cams and exhaust cams (not shown). Further, a fuel injection valve 29 is disposed above, that is, at the lower part of the cylinder head 13, with respect to the combustion chamber 24. The fuel injection valve 29 can inject high-pressure fuel into the combustion chamber 24 at a predetermined timing. 【0018】 The diesel engine 10 executes four strokes, namely, an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke, while the crankshaft rotates twice. At this time, the intake camshaft and the exhaust camshaft rotate once, and the intake valve 27 and the exhaust valve 28 open and close the intake port 25 and the exhaust port 26. When air is supplied from the intake port 25 to the combustion chamber 24, the intake air is compressed by the upward movement of the piston 14. Further, when high-pressure fuel is injected from the fuel injection valve 29 into the combustion chamber 24, the high-pressure fuel self-ignites and burns. Due to the explosion load at this time, the piston 14 is pushed down to rotate the crankshaft. The combustion gas generated in the combustion chamber 24 is discharged as exhaust gas from the exhaust port 26. 【0019】 <Gas sealing structure> FIG. 2 is a cross-sectional view of a main part showing the gas sealing structure of the internal combustion engine before fastening, and FIG. 3 is a cross-sectional view of a main part showing the gas sealing structure of the internal combustion engine after fastening. 【0020】 The gasket 15 adheres to the upper surface of the cylinder liner 12 and the lower surface of the cylinder head 13 by the fastening force of the cylinder head 13 with respect to the cylinder block 11. The combustion chamber 24 is prevented from external leakage of gas (combustion gas or exhaust gas) generated by the gasket 15 disposed between the cylinder liner 12 and the cylinder head 13. 【0021】 As shown in FIG. 2, the gasket 15 has a flat plate shape with a rectangular cross-section having a predetermined thickness, and circular holes 15a corresponding to the number of cylinders of the combustion chamber 24 are formed. The gasket 15 has a gasket body 31 and a firing 32. The gasket body 31 is provided with a circular hole 31a. The firing 32 has a ring shape and is disposed on the inner peripheral portion of the circular hole 31a of the gasket body 31. 【0022】 The gasket 15 is arranged such that the gasket body 31 is disposed between the cylinder block 11 and the cylinder head 13, and the firing 32 is disposed between the cylinder liner 12 and the cylinder head 13. The gasket 15 causes the lower surface 32a to closely contact the upper surface 12a of the cylinder liner 12 and the upper surface 32b to closely contact the lower surface 13a of the cylinder head 13 when the firing 32 receives a fastening load from the cylinder liner 12 and the cylinder head 13. 【0023】 At this time, the firing 32 has different radial lengths L1 of the cylinder liner 12 on the contact surface between the lower surface 32a and the upper surface 12a of the cylinder liner 12 and radial length L2 of the cylinder liner 12 on the contact surface between the upper surface 32b and the lower surface 13a of the cylinder head 13. That is, the radial length L2 is longer than the radial length L1. Therefore, the firing 32 has different contact areas with the cylinder liner 12 and the cylinder head 13, and as a result of receiving the same load from above and below, the surface pressures of both are also different, and the relative slip due to the different behaviors of the cylinder head 13 and the cylinder liner 12 is borne by the lower surface 32a with a lower surface pressure. 【0024】 Therefore, in this embodiment, the gas seal structure makes the contact area between the gasket 15 (firing 32) and the cylinder liner 12 the same as the contact area between the gasket 15 (firing 32) and the cylinder head 13. To this end, the cylinder liner 12 has a first groove 41 that runs circumferentially on the contact surface (region with radial length L1) that contacts the lower surface 32a of the firing 32 in the gasket 15 on its upper surface 12a. The cylinder head 13 has second grooves 42 and 43 that run circumferentially on the contact surface (region with radial length L2) that contacts the upper surface 32b of the firing 32 in the gasket 15 on its lower surface 13a. In this case, the number of second grooves 42 and 43 is greater than the number of first grooves 41. In other words, the cylinder head 13 has two second grooves 42 and 43, and the cylinder liner 12 has one first groove 41 on its upper surface 12a. Furthermore, the cross-sectional shape and dimensions of the first groove 41 and the second grooves 42, 43 are the same. 【0025】 Specifically, the cylinder liner 12 has a first groove 41 along the circumferential direction on its upper surface 12a. The first groove 41 is located in the contact area (region with radial length L1) of the cylinder liner 12 where the lower surface 32a of the firing ring 32 makes contact. On the other hand, the cylinder head 13 has two second grooves 42 and 43 along the circumferential direction on its lower surface 13a. The second grooves 42 and 43 are located in the contact area (region with radial length L2) of the cylinder head 13 where the upper surface 32b of the firing ring 32 makes contact. Therefore, the contact area between the cylinder liner 12 and the firing ring 32 is reduced by the amount of the first groove 41, and the contact area between the cylinder head 13 and the firing ring 32 is reduced by the amount of the second grooves 42 and 43. As a result, the contact area between the firing ring 32 and the cylinder liner 12 in the gasket 15 becomes the same as the contact area between the firing ring 32 and the cylinder head 13 in the gasket 15. Here, having the same contact area means, for example, that the area ratio is in the range of 0% to 5%. 【0026】 The first groove 41 and the second grooves 42 and 43 are positioned offset from each other in the radial direction of the cylinder liner 12. The first groove 41 is located at the midpoint of the radial length L1. That is, the radial length L1a between the first groove 41 and one end of the radial length L1 is the same as the radial length L1b between the first groove 41 and the other end of the radial length L1. The second groove 42 functions as an inner second groove located radially inward from the first groove 41, and the second groove 43 functions as an outer second groove located radially outward from the first groove 41. The radial length L2a between the first groove 41 and the second groove (inner second groove) 42 is the same as the radial length L2b between the first groove 41 and the second groove (outer second groove) 43. 【0027】 As shown in Figure 3, when the diesel engine 10 is assembled, the gasket 15 is positioned between the cylinder block 11 and the cylinder head 13. At this time, the firing ring 32 is positioned between the cylinder liner 12 and the cylinder head 13. In this state, when the cylinder head 13 is fastened to the cylinder block 11 with a predetermined bolting force, the firing ring 32 is subjected to a compressive load, as shown in Figure 2, with its lower surface 32a in close contact with the upper surface 12a of the cylinder liner 12 and its upper surface 32b in close contact with the lower surface 13a of the cylinder head 13. 【0028】 The cylinder liner 12 and cylinder head 13 are made of cast iron. On the other hand, the firing ring 32 of the gasket 15 is made of SPCC (Steel Plate Cold Commercial), which is a cold-rolled steel sheet. In other words, the firing ring 32 is made of a softer material than the cylinder liner 12 and cylinder head 13. 【0029】 Therefore, when the firing ring 32 is subjected to a compressive force in the thickness direction due to the fastening of the cylinder head 13 to the cylinder block 11, it undergoes plastic deformation due to the application of surface pressure exceeding the yield point of the material. As a result, a portion of the lower surface 32a of the firing ring 32, which is not subjected to compressive force by the first groove 41, protrudes downward, forming a first protrusion 51 that fits into the first groove 41. Also, a portion of the upper surface 32b of the firing ring 32, which is not subjected to compressive force by the second grooves 42 and 43, protrudes upward, forming second protrusions 52 and 53 that fit into the second grooves 42 and 43. 【0030】 In this embodiment, one first groove 41 is provided on the upper surface 12a of the cylinder liner 12, and two second grooves 42 and 43 are provided on the lower surface 13a of the cylinder head 13, but the configuration is not limited to this. As long as the contact area between the gasket 15 and the cylinder liner 12 is the same as the contact area between the gasket 15 and the cylinder head 13, the number of first grooves 41 and second grooves 42 and 43 is not limited. For example, a second groove may be provided on the lower surface 13a of the cylinder head 13, and the first groove 41 may not be provided on the upper surface 12a of the cylinder liner 12. Also, the formation position and shape of the first groove 41 and second grooves 42 and 43 can be set as appropriate. 【0031】 <Function of gas seal structure> As shown in Figure 2, the cylinder liner 12 has a first groove 41 on its upper surface 12a facing the lower surface 32a of the firing ring 32, and the cylinder head 13 has second grooves 42 and 43 on its lower surface 13a facing the upper surface 32b of the firing ring 32. Therefore, the contact area between the firing ring 32 and the cylinder liner 12 is the same as the contact area between the firing ring 32 and the cylinder head 13. Consequently, the surface pressure at the contact surface between the firing ring 32 and the cylinder liner 12 is the same as the surface pressure at the contact surface between the firing ring 32 and the cylinder head 13. 【0032】 When the diesel engine 10 is in operation, the cylinder liner 12 deforms in accordance with the rigidity of the cylinder block 11, which deforms under the explosion load, and the cylinder head 13 deforms under the explosion load due to its own rigidity. Here, since the contact pressure of the firing ring 32 with the cylinder liner 12 and the contact pressure of the cylinder head 13 are the same, the amount of sliding is small because the relative sliding at the contact surfaces of the cylinder liner 12, the firing ring 32 and the cylinder head 13 is not borne by one side. As a result, surface roughness at the contact surfaces between the firing ring 32 and the cylinder liner 12 and between the firing ring 32 and the cylinder head 13 is suppressed, and the deterioration of the gas seal performance by the gasket 15 is suppressed. 【0033】 Furthermore, when the firing ring 32 receives compressive force from the cylinder liner 12 and cylinder head 13, its lower surface 32a and upper surface 32b deform, causing the first protrusion 51 to engage with the first groove 41 of the cylinder liner 12, and the second protrusions 52 and 53 to engage with the second grooves 42 and 43 of the cylinder head 13. As a result, the first protrusion 51 and the second protrusions 52 and 53 act as anchors to the cylinder liner 12 and cylinder head 13, further suppressing relative slippage in addition to the effect of equalizing the surface pressure on the upper and lower surfaces. In this case, by making the firing ring 32 from a softer material than the cylinder liner 12 and cylinder head 13, the slippage is absorbed by the elastic deformation of the protrusions within the range of the Young's modulus of the anchor portion, and the low hardness of the anchor portion prevents cracking of the groove. 【0034】 Figure 4 is a graph showing the radial pressure distribution at the contact surface between the gasket and the cylinder head. 【0035】 Figure 4 shows the radial surface pressure distribution of the firing ring 32 at the contact surface between the upper surface 32b of the firing ring 32 of the gasket 15 and the lower surface 13a of the cylinder head 13. As shown in Figure 4, when the second grooves 42 and 43 are not provided, the surface pressure (dotted line in Figure 4) has a distribution in which the middle part in the radial direction is relatively high. On the other hand, when the second grooves 42 and 43 are provided, the surface pressure (solid line in Figure 4) increases towards the second grooves 42 and 43 and becomes zero at the location of the second grooves 42 and 43. In other words, at both ends of the second grooves 42 and 43, a peak surface pressure higher than the average surface pressure acts, improving the gas seal performance compared to the surface pressure distribution when the surface is smooth. 【0036】 [Effects of this embodiment] The gas seal structure for an internal combustion engine according to the first embodiment is a diesel engine (internal combustion engine) 10 comprising a cylinder block 11 having a cylindrical space 21, a cylindrical cylinder liner 12 disposed in the space 21, a piston 14 supported by the cylinder liner 12 so as to be movable in the axial direction, a cylinder head 13 fastened to the upper part of the cylinder block 11, and a gasket 15 disposed between the cylinder block 11 and the cylinder liner 12 and the cylinder head 13 and having a firing ring 32, wherein the contact area between the cylinder liner 12 and the firing ring 3215 is the same as the contact area between the cylinder head 13 and the firing ring 32. 【0037】 According to the gas seal structure for an internal combustion engine of the first embodiment, the contact area between the firing ring 32 and the cylinder liner 12 is the same as the contact area between the firing ring 32 and the cylinder head 13, resulting in the same surface pressure at each contact surface. Consequently, when the cylinder liner 12 and cylinder head 13 deform under the explosion load from the combustion chamber 24, relative slippage of the firing ring 32 at the contact surface with the cylinder liner 12 and the contact surface with the cylinder head 13 is less likely to occur, and surface roughness due to relative slippage is suppressed. As a result, the gas seal performance of the gasket 15 can be improved. 【0038】 The gas seal structure for an internal combustion engine according to the second embodiment is provided with a first groove 41 along the circumferential direction on the contact surface of the cylinder liner 12 that contacts the firing ring 32, and second grooves 42 and 43 along the circumferential direction on the contact surface of the cylinder head 13 that contacts the firing ring 32. This makes it possible to make the contact area between the firing ring 32 and the cylinder liner 12 the same as the contact area between the firing ring 32 and the cylinder head 13 with a simple configuration, thereby suppressing structural complexity. 【0039】 In the third embodiment of the gas seal structure for an internal combustion engine, the first groove 41 and the second grooves 42, 43 are arranged to be offset radially from the cylinder liner 12. This allows the position where the surface pressure on the firing ring 32 is released to be shifted radially, thereby suppressing the occurrence of relative slippage at the contact surfaces between the firing ring 32 and the cylinder liner 12 and cylinder head 13. 【0040】 The gas seal structure for the internal combustion engine according to the fourth embodiment has a number of second grooves 42 and 43 greater than the number of first grooves 41. This makes it possible to appropriately make the contact area between the firing ring 32 and the cylinder liner 12 the same as the contact area between the firing ring 32 and the cylinder head 13. 【0041】 The gas seal structure for an internal combustion engine according to the fifth embodiment includes a second groove (inner second groove) 42 provided radially inward from the first groove 41 and a second groove (outer second groove) 43 provided radially outward from the first groove 41, with the radial length L2a between the first groove 41 and the second groove 42 being the same as the radial length L2b between the first groove 41 and the second groove 43. As a result, the cylinder liner 12 and the cylinder head 13 apply a uniform radial load to the firing ring 32 of the gasket 15, thereby suppressing a decrease in gas seal performance. 【0042】 The gas seal structure for an internal combustion engine according to the sixth embodiment is made of a soft material that allows the gasket 15 to form a first protrusion 51 and a second protrusion 52, 53 that penetrate the first groove 41 and the second grooves 42, 43 by plastic deformation under surface pressure. As a result, the first protrusion 51 and the second protrusions 52, 53 act as anchors to the cylinder liner 12 and the cylinder head 13, effectively suppressing the occurrence of relative slip. [Explanation of Symbols] 【0043】 10. Diesel engine (internal combustion engine) 11 Cylinder block 12 Cylinder Liners 13 Cylinder head 14 pistons 15 Gasket 21 Space section 22 Piston Rings 23 Connecting Rods 24 Combustion chamber 25 intake ports 26 exhaust ports 27 Intake valve 28 Exhaust valve 29 Fuel Injector 31 Gasket body 32 firings 41. First groove 42 Second groove (inner second groove) 43 Second groove (outside second groove) 51 First protrusion 52, 53 Second convex part

Claims

[Claim 1] A cylinder block having a cylindrical space, A cylinder liner having a cylindrical shape and positioned in the space, A piston is supported in the cylinder liner so as to be movable in the axial direction, A cylinder head fastened to the upper part of the cylinder block, A gasket having a firing ring is disposed between the cylinder block and the cylinder liner and the cylinder head, In an internal combustion engine equipped with, A first groove is provided on the contact surface of the cylinder liner that contacts the firing ring, along the circumferential direction of the firing ring, and a second groove is provided on the contact surface of the cylinder head that contacts the firing ring, along the circumferential direction of the firing ring. The firing ring has a rectangular cross-sectional shape, and the radial length of the second groove and the contact surface area on the contact surface side between the firing ring and the cylinder head is longer than the radial length of the first groove and the contact surface area on the contact surface side between the firing ring and the cylinder liner. The contact area of ​​the contact surface between the cylinder liner and the firing ring is the same as the contact area of ​​the contact surface between the cylinder head and the firing ring. Gas seal structure for internal combustion engines. [Claim 2] The first groove and the second groove are arranged to be offset from each other in the radial direction of the cylinder liner. The gas seal structure for an internal combustion engine according to claim 1. [Claim 3] The number of the second grooves is greater than the number of the first grooves. A gas seal structure for an internal combustion engine according to claim 1 or claim 2. [Claim 4] The second groove portion has an inner second groove portion provided radially inward from the first groove portion and an outer second groove portion provided radially outward from the first groove portion, and the radial length between the first groove portion and the inner second groove portion is the same as the radial length between the first groove portion and the outer second groove portion. The gas seal structure for an internal combustion engine according to claim 3. [Claim 5] The firing ring is made of a soft material that can form a first protrusion and a second protrusion that penetrate the first groove and the second groove by plastically deforming under surface pressure. A gas seal structure for an internal combustion engine according to any one of claims 1 to 4.

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