Internal combustion engine

Abstract

To improve sealability by increasing surface pressure applied to a gasket and accurately position the gasket and a cylinder liner.SOLUTION: A gasket 10 includes: a body part 11; and a projection 12 projecting on an inner diameter side from the body part 11. The body part 11 is pinched by a cylinder head 1 and a cylinder liner 2 from both sides in a thickness direction. The projection 12 has a dimension in the thickness direction that is smaller than the body part 11 and has an inner diameter end that is fitted to an outer peripheral surface 2d of the cylinder liner 2.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an internal combustion engine, and more particularly to a seal structure between a cylinder head and a cylinder liner. [Background technology]

[0002] For example, the following Patent Document 1 shows a seal structure for a diesel engine. Specifically, as shown in Fig. 4, a gasket 102 is sandwiched between a cylinder head 101 and a cylinder liner 103 from both sides in the thickness direction (the vertical direction in the figure), thereby preventing combustion gas from leaking out from the gap between the cylinder head 101 and the cylinder liner 103. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-159517 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above diesel engine, the outer circumferential portion 103a of the upper surface of the cylinder liner 103 is lower than the inner circumferential portion 103b by one step, and the gasket 102 is disposed on the outer circumferential portion 103a. The gasket 102 is positioned relative to the cylinder liner 103 by fitting the inner circumferential surface of the flat ring-shaped gasket 102 into the step (outer circumferential surface 103c) between the outer circumferential portion 103a and the inner circumferential portion 103b of the upper surface of the cylinder liner 103.

[0005] In the above-mentioned diesel engine, in order to improve the sealing performance of the combustion gas, it is effective to increase the surface pressure between the gasket 102 and the cylinder head 101 and the cylinder liner 103. For example, when the inner diameter of the gasket 102 is enlarged from that of FIG. 4 as shown in FIG. 5, the contact area between the gasket 102 and the cylinder head 101 and the cylinder liner 103 decreases, so that the surface pressure applied to the gasket 102 increases and the sealing performance is improved. However, in this case, the radial gap δ1 between the inner peripheral surface 102a of the gasket 102 and the outer peripheral surface 103c of the cylinder liner 103 increases, so that the positioning accuracy of the gasket 102 decreases, which may deteriorate the sealing performance.

[0006] 6, when the outer diameter of the gasket 102 is reduced from that of FIG. 4, the surface pressure applied to the gasket 102 increases and the sealing performance is improved, but the following problems occur. The cylinder head 101 does not abut against the cylinder liner 103 or the engine frame 104 provided on the outer periphery of the cylinder head 101 in the vertical direction, and the gasket 102 arranged between the cylinder head 101 and the cylinder liner 103 is sandwiched by fastening the cylinder head 101 and the engine frame 104 with bolts (in FIG. 6, the bolts are not shown, and only the axial force F generated by fastening the bolts is shown). In this case, when the outer diameter of the gasket 102 is reduced, the radial distance δ2 between the region of the cylinder head 101 that contacts the gasket 102 (the outer periphery 102b of the gasket 102) and the region to which the axial force F is applied by the bolts increases, so that the cylinder head 101 is likely to bend as shown by the dotted line.

[0007] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to increase the surface pressure applied to the gasket to improve the sealing performance, and to position the gasket and the cylinder liner with high accuracy. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides an internal combustion engine having a cylinder head, a cylinder liner, and a flat ring-shaped gasket disposed therebetween, The present invention provides an internal combustion engine in which the gasket has a main body portion that is sandwiched from both sides in the thickness direction between the cylinder head and the cylinder liner, and a protrusion portion that protrudes from the main body portion toward the inner diameter side, has a thickness direction dimension smaller than that of the main body portion, and has an inner diameter end that fits into the outer peripheral surface of the cylinder liner.

[0009] In the above gasket, the main body is sandwiched between the cylinder head and the gasket, but the protruding portion is not sandwiched between the cylinder head and the gasket because the thickness dimension of the protruding portion is smaller than that of the main body. In this case, the contact area between the gasket and the cylinder head and the cylinder liner is reduced by the amount of the protruding portion compared to when the entire radial area of ​​the gasket is sandwiched between the cylinder head and the cylinder liner, so the surface pressure applied to the gasket increases. In addition, the inner diameter end of the protruding portion of the gasket can be fitted into the outer circumferential surface of the cylinder liner, allowing the gasket to be positioned with high precision relative to the cylinder liner.

[0010] It is preferable that the inner diameter end of the protruding portion of the gasket is provided below the upper end of the outer circumferential surface of the cylinder liner, so that the inner diameter end of the protruding portion can be reliably fitted into the outer circumferential surface of the cylinder liner, and the gasket can be reliably positioned relative to the cylinder liner.

[0011] If fuel supplied to the combustion chamber is retained in the gap between the upper surface of the protruding portion of the gasket and the lower surface of the cylinder head, this may cause early deterioration of the gasket. Therefore, it is preferable to provide the protruding portion of the gasket in an area spaced downward from the upper end of the main body. In this case, a relatively wide gap is formed between the upper surface of the protruding portion and the lower surface of the cylinder head, making it difficult for fuel supplied to the combustion chamber to be retained in this gap, and early deterioration of the gasket can be prevented.

[0012] In the above internal combustion engine, it is preferable to provide an annular groove in the cylinder head or the cylinder liner. In this case, the gasket material undergoes plastic flow due to the compressive force applied when the gasket is sandwiched between the cylinder head and the cylinder liner, forming a protrusion in the annular groove in the gasket. This improves the sealing performance at the contact portion between the cylinder head or the cylinder liner and the gasket. Effect of the Invention

[0013] As described above, according to the present invention, it is possible to increase the surface pressure applied to the gasket to improve the sealing performance, and to position the gasket and the cylinder liner with high accuracy. [Brief description of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of an internal combustion engine (diesel engine) according to one embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged view of the gasket and its surroundings in FIG. [Diagram 3] FIG. 11 is an enlarged cross-sectional view of the vicinity of a gasket of an internal combustion engine according to another embodiment. [Figure 4] FIG. 1 is a cross-sectional view of a conventional internal combustion engine. [Diagram 5] 5 is a cross-sectional view showing the internal combustion engine of FIG. 4 with an enlarged inner diameter of the gasket. [Figure 6] 5 is a cross-sectional view showing a case where the outer diameter of the gasket of the internal combustion engine of FIG. 4 is reduced. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] FIG. 1 shows a diesel engine (e.g., a marine diesel engine) as an internal combustion engine according to an embodiment of the present invention. This diesel engine has a cylinder head 1, a cylinder liner 2, an engine frame 3, and a fuel supply unit (not shown). This diesel engine is operated by repeating an intake stroke in which air is supplied to a combustion chamber 5 formed by the cylinder head 1, the cylinder liner 2, and a piston 4, a compression stroke in which the air in the combustion chamber 5 is compressed by the rise of the piston 4, an explosion stroke in which liquid fuel (e.g., heavy oil) is injected from the fuel supply unit into the compressed air and ignited, and an exhaust stroke in which exhaust gas after combustion is discharged from the combustion chamber 5. For convenience of explanation, in this specification, the cylinder head 1 side is referred to as the upper side and the opposite side is referred to as the lower side in the moving direction of the piston 4 (the vertical direction in FIG. 1). The diesel engine of this embodiment is installed so that the moving direction of the piston 4 is vertical.

[0017] The cylinder liner 2 is attached to the inner periphery of the engine frame 3. A step 2a on the outer periphery of the cylinder liner 2 and a step 3a on the inner periphery of the engine frame 3 are brought into contact with each other, so that the two are positioned in the vertical direction.

[0018] A circular flat ring-shaped gasket 10 is disposed between the cylinder head 1 and the cylinder liner 2. The gasket 10 is made of, for example, metal, specifically, carbon steel such as SPCC material. In this embodiment, the outer annular region 2b provided on the outer periphery of the upper surface of the cylinder liner 2 is disposed one step lower than the inner annular region 2c provided on the inner periphery, and the gasket 10 is disposed in this outer annular region 2b. Both the outer annular region 2b and the inner annular region 2c are flat surfaces perpendicular to the up-down direction.

[0019] As shown in FIG. 2, the gasket 10 integrally has a main body 11 and a protruding portion 12 protruding from the main body 11 toward the inner diameter side. The main body 11 is in the shape of a flat ring with a rectangular cross section. An upper surface 11a (region excluding a convex portion 11e described below) and a lower surface 11b of the main body 11 are flat surfaces. An inner peripheral surface 11c (region excluding the protruding portion 12) and an outer peripheral surface 11d of the main body 11 are cylindrical surfaces. A thickness t (distance between the upper surface 11a and the lower surface 11b) of the main body 11 is greater than a vertical distance d between the outer annular region 2b and the inner annular region 2c on the upper surface of the cylinder liner 2.

[0020] The protrusion 12 forms a continuous ring shape around the entire circumference of the inner circumferential surface of the main body 11. The protrusion 12 in the illustrated example has a rectangular cross section. The thickness dimension (vertical dimension) t2 of the protrusion 12 is smaller than the thickness t1 of the main body 11. The protrusion 12 is provided in a region spaced downward from the upper end of the main body 11. In the illustrated example, the protrusion 12 is provided in a middle part in the thickness direction excluding the upper and lower ends of the main body 11, and is particularly provided in the center in the thickness direction of the main body 11. The cylindrical inner circumferential surface 12a provided at the inner diameter end of the protrusion 12 is provided below the upper end of the outer circumferential surface 2d of the cylinder liner 2, that is, below the inner annular region 2c of the upper surface of the cylinder liner 2. In the illustrated example, the upper surface 12b of the protrusion 12 is provided at the same height as the upper end of the outer circumferential surface 2d of the cylinder liner 2 and is provided on the same plane as the inner annular region 2c.

[0021] An annular groove 1b is formed in a region of the lower surface 1a of the cylinder head 1 that faces the main body 11 of the gasket 10 in the up-down direction. For example, a plurality of annular grooves 1b are provided, and in the illustrated example, the annular grooves 1b are provided at two locations spaced apart in the radial direction. The annular groove 1b in the illustrated example has a V-shaped cross section. Alternatively, the cross section of the annular groove 1b may be rectangular or semicircular.

[0022] The assembly of the cylinder head 1 and the cylinder liner 2 is carried out in the following manner.

[0023] First, the cylinder liner 2 is inserted from above into the inner circumference of the engine frame 3, and the step 2a of the cylinder liner 2 is abutted against the step 3a of the engine frame 3 from above. Then, the gasket 10 is placed in the outer annular region 2b on the upper surface of the cylinder liner 2. In the gasket 10 of this embodiment, the protrusion 12 is provided at the center of the thickness direction of the main body 11. Furthermore, before the gasket 10 is sandwiched between the cylinder head 1 and the cylinder liner 2, the upper surface 11a of the main body 11 of the gasket 10 is a flat surface without the protrusion 11e. Therefore, since the gasket 10 has a symmetrical shape with respect to the center in the thickness direction, it can be placed in the outer annular region 2b on the upper surface of the cylinder liner 2 without worrying about the up and down direction.

[0024] At this time, the gasket 10 can be positioned (centered) with high accuracy in the radial direction with respect to the cylinder liner 2 by fitting the inner diameter end of the gasket 10, i.e., the cylindrical inner peripheral surface 12a of the protruding portion 12, with the outer peripheral surface 2d of the cylinder liner 2. In the illustrated example, the cylindrical inner peripheral surface 12a of the protruding portion 12 of the gasket 10 is provided below the upper end of the outer peripheral surface 2d of the cylinder liner 2, i.e., below the inner annular region 2c of the upper surface of the cylinder liner 2, so that the cylindrical inner peripheral surface 12a of the protruding portion 12 and the outer peripheral surface 2d of the cylinder liner 2 can be fitted together reliably to position the gasket 10. At this time, the cylindrical inner peripheral surface 12a of the gasket 10 and the outer peripheral surface 2d of the cylinder liner 2 are fitted together with a slight radial gap therebetween.

[0025] Next, the cylinder head 1 is attached to the cylinder liner 2 and the upper part of the engine frame 3. Specifically, the inner peripheral surface 1c of the cylinder head 1 is fitted to the outer peripheral surface 2e of the cylinder liner 2, which faces the inner peripheral surface 1c in the radial direction, to position the two in the radial direction. In this state, the cylinder head 1 is placed on the gasket 10 arranged in the outer annular region 2b on the upper surface of the cylinder liner 2. Then, by fastening the cylinder head 1 and the engine frame 3 with bolts 20 (see FIG. 1), the body portion 11 of the gasket 10 is sandwiched and compressed from both sides in the thickness direction (vertical direction) between the outer annular region 2b on the upper surface of the cylinder liner 2 and the lower surface 1a of the cylinder head 1 via the abutting portion between the step portion 2a of the cylinder liner 2 and the step portion 3a of the engine frame 3.

[0026] At this time, since the protruding portion 12 of the gasket 10 has a smaller thickness dimension than the main body portion 11, it is not sandwiched between the cylinder head 1 and the cylinder liner 2 and is not in contact with them. In this case, compared to when the entire gasket 10 is sandwiched between the cylinder head 1 and the cylinder liner 2, the contact area between the gasket 10 and the cylinder head 1 and the cylinder liner 2 is smaller, so the surface pressure applied to the gasket 10 is larger and the sealing performance is improved.

[0027] As described above, when the gasket 10 is compressed from both sides in the thickness direction by the cylinder head 1 and the engine frame 3, the gasket 10 undergoes plastic deformation, causing the thickness dimension to become slightly smaller and the radial dimension to become slightly larger. In this embodiment, when the cylinder head 1 is fixed to the cylinder liner 2 and the engine frame 3 with the bolts 20, vertical gaps remain between the cylinder head 1 and the cylinder liner 2 and the engine frame 3, as well as radial gaps remain between the inner diameter end of the gasket 10 (the cylindrical inner peripheral surface 12a of the protruding portion 12) and the outer peripheral surface 2d of the cylinder liner 2.

[0028] In addition, the material of the gasket 10 undergoes plastic flow due to the compressive force applied when the gasket 10 is sandwiched between the cylinder head 1 and the cylinder liner 2 from both sides in the thickness direction, forming a protrusion 11e that fits into the annular groove 1b on the upper surface 11a of the main body 11. This improves the sealing performance between the upper surface 11a of the main body 11 of the gasket 10 and the lower surface 1a of the cylinder head 1.

[0029] The present invention is not limited to the above-described embodiment. Other embodiments of the present invention will be described below, but redundant description of the same points as those in the above-described embodiment will be omitted.

[0030] In the embodiment shown in Fig. 3, the protruding portion 12 of the gasket 10 has a tapered shape in which the thickness dimension decreases toward the inner diameter side. Specifically, the upper surface 12b of the protruding portion 12 is a tapered surface connecting the upper surface 11a of the main body portion 11 and the inner peripheral surface 12a of the protruding portion 12, and the lower surface 12c of the protruding portion 12 is a tapered surface connecting the lower surface 11b of the main body portion 11 and the inner peripheral surface 12a of the protruding portion 12. Even in this case, since the protruding portion 12 is not sandwiched between the cylinder head 1 and the cylinder liner 2, it is possible to increase the surface pressure between the gasket 10 and the cylinder head 1 and the cylinder liner 2, and to position the gasket 10 by fitting the inner peripheral surface 12a of the protruding portion 12 to the outer peripheral surface 2d of the cylinder liner 2, as in the embodiment shown in Fig. 2.

[0031] 3, however, a gap S2 having a wedge-like cross section that narrows toward the outer diameter side is provided between the upper surface 12b of the protruding portion 12 and the lower surface 1a of the cylinder head 1. In this case, the fuel G supplied to the combustion chamber 5 is likely to accumulate at the outer diameter end (narrow width portion) of the wedge-shaped gap S2, and there is a concern that the accumulated fuel G will deteriorate the gasket 10, thereby deteriorating the sealing performance.

[0032] In contrast, in the embodiment shown in FIG. 2, the protruding portion 12 of the gasket 10 is provided in a region spaced downward from the upper end of the main body portion 11. In this case, the gap S1 formed between the upper surface 12b of the protruding portion 12 and the lower surface 1a of the cylinder head 1 is wider than the gap S1 having a wedge-shaped cross section as shown in FIG. 3. In particular, in the illustrated example, the cylindrical inner peripheral surface 11c of the main body portion 11 is provided between the upper surface 11a of the main body portion 11 of the gasket 10 and the upper surface 12b of the protruding portion 12, so that the width of the outer diameter end of the gap S1 is wider, and specifically, the gap S1 has a rectangular cross section. This makes it difficult for fuel to accumulate in the above-mentioned gap S1, and deterioration of the gasket 10 can be prevented.

[0033] In the above embodiment, the case has been described in which the lower surface 1a of the cylinder head 1 is provided with an annular groove 1b and the gasket 10 is provided with a convex portion that fits into the annular groove 1b, but instead of or in addition to this, an annular groove may be provided on the upper surface of the cylinder liner 2 and a convex portion that fits into this annular groove may be provided on the gasket 10. Furthermore, if such an annular groove is not necessary, the areas of the lower surface 1a of the cylinder head 1 and the upper surface of the cylinder liner 2 that face the main body portion 11 of the gasket 10 may be flat surfaces without an annular groove.

[0034] In the above embodiment, the protruding portion 12 of the gasket 10 forms a continuous ring shape around the entire circumference, but this is not limited thereto, and the protruding portion 12 may be provided at a plurality of locations spaced apart in the circumferential direction. Also, in the above embodiment, the cross section of the protruding portion 12 is rectangular or trapezoidal, but the cross-sectional shape of the protruding portion is not limited thereto, and may be, for example, semicircular or triangular.

[0035] The present invention is not limited to diesel engines using liquid fuel (heavy oil), but can also be applied to gas engines using gas fuel (LNG), dual fuel engines that can selectively use liquid fuel and gas fuel, etc. Furthermore, the present invention is not limited to internal combustion engines for ships, but can also be applied to internal combustion engines for power generation used on land, for example. [Explanation of symbols]

[0036] 1. Cylinder head 1b Annular groove 2 Cylinder Liner 3 Engine frame 4 Piston 5. Combustion chamber 10 Gasket 11 Main body 11e Convex part 12 Protrusion 20 Volts

Claims

1. An internal combustion engine having a cylinder head, a cylinder liner, and a flat ring-shaped gasket disposed therebetween, The gasket is a main body portion sandwiched between the cylinder head and the cylinder liner from both sides in a thickness direction; a protruding portion protruding from the main body portion toward an inner diameter side, having a thickness direction dimension smaller than that of the main body portion, and an inner diameter end facing an outer circumferential surface of the cylinder liner; having an internal combustion engine, wherein a radial gap is provided between an inner diameter end of the protruding portion of the gasket and an outer peripheral surface of the cylinder liner when the cylinder head and the cylinder liner are fixed together.

2. 2. The internal combustion engine according to claim 1, wherein an inner diameter end of the protrusion is provided below an upper end of the outer circumferential surface of the cylinder liner.

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