Seat structure

Abstract

To provide a seat part structure which can suppress deterioration of seal performance of a gasket between seat parts of a cylinder cover and an exhaust valve seat.SOLUTION: In a seat part structure for joining, across an annular gasket, a cylinder cover of a cylinder having a combustion chamber of a marine diesel engine and an exhaust valve seat allowing an exhaust valve which opens and closes an exhaust port of the combustion chamber to be seated thereon, the cylinder cover comprises: a seat part which is formed into an annular shape so as to surround a longitudinal shaft of the cylinder, has an outside diameter larger than an outside diameter of the gasket, and is placed with the gasket; and a lock part arranged along an internal peripheral end part of the seat part, contacting with an internal peripheral face of the gasket which is placed on the seat part, and locking the gasket. The exhaust valve seat comprises a valve-seat seat part which is formed into an annular shape so as to oppose the seat part across the gasket, and has an outside diameter larger than an outside diameter of the gasket.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a seat structure for airtightly joining a cylinder cover and an exhaust valve seat of a marine diesel engine. [Background technology]

[0002] In marine diesel engines installed on ships, in order to prevent gas leakage from the combustion chamber, sealing members have conventionally been sandwiched between the joints of components such as the cylinder that face the combustion chamber, thereby sealing gaps at the joints. For example, the cylinder cover, which is one component of the cylinder, and the exhaust valve seat, on which the exhaust valve that opens and closes the exhaust port of the combustion chamber sits, are joined together with a gasket, which is an example of a sealing member.

[0003] Generally, an exhaust valve box that slidably supports the exhaust valve is attached to the top of the exhaust valve seat. The exhaust valve box is fixed to the top of the cylinder cover by tightening bolts, with the exhaust valve seat sandwiched between the exhaust valve box and the cylinder cover. A gasket is placed on the seat portion of the cylinder cover, and the exhaust valve seat is joined to the top of the cylinder cover so that the gasket is sandwiched between the seat portion of the cylinder cover and the seat portion of the exhaust valve seat. The cylinder cover and exhaust valve seat, with the gasket sandwiched between their seat portions, are fixed together with the exhaust valve box by the tightening force of the bolts. The seat portion here refers to the joint between the various parts that is sealed by sandwiching the gasket.

[0004] Patent Document 1 discloses a structure in which the lower surface of a cylinder cover and the upper surface of a cylinder liner are joined via a gasket. In the joining structure described in Patent Document 1, a circumferential groove is formed on the upper surface of the cylinder liner to eliminate local stress at the edge of the gasket. Patent Document 2 also discloses a structure in which a cylinder cover and an exhaust valve seat (valve seat ring) are joined via a metal buildup layer formed by laser metal buildup welding. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-126023 [Patent Document 2] Japanese Patent Publication No. 2020-51335 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional seat structure for joining the cylinder cover and the exhaust valve seat via the gasket, the gasket placed on the seat of the cylinder cover may become misaligned to one side of the seat (inside or outside of the cylinder) during the joining operation of the cylinder cover and the exhaust valve seat or when it is subjected to in-cylinder pressure from the combustion chamber. In this case, the gasket deforms to conform to the shape of the gap between the cylinder cover and the exhaust valve seat (for example, a curved shape), which reduces the sealing ability of the gasket between the seats and may result in gas leakage from the combustion chamber.

[0007] Furthermore, when a marine diesel engine is operating, the combustion chamber becomes extremely hot. The high heat transmitted from the combustion chamber causes the cylinder cover and exhaust valve seat to expand and deform, which can lead to the expansion and deformation of the gasket between these seats. While this expansion and deformation of the gasket is more strongly suppressed in areas closer to the bolts, it is less suppressed in areas farther from the bolts, leading to distortion (e.g., deformation from a circular to an oval shape). This also reduces the sealing ability of the gasket between the seats, potentially resulting in gas leakage from the combustion chamber.

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a seat portion structure that can suppress a decrease in the sealing performance of the gasket between the seat portion of the cylinder cover and the exhaust valve seat. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the object, the seat portion structure of the present invention is a seat portion structure for joining a cylinder cover of a cylinder having a combustion chamber of a marine diesel engine to an exhaust valve seat on which an exhaust valve that opens and closes an exhaust port of the combustion chamber is seated, by sandwiching an annular gasket that surrounds the longitudinal axis of the cylinder, wherein the cylinder cover is formed in an annular shape so as to surround the longitudinal axis of the cylinder, has an outer diameter larger than that of the gasket, and comprises a cylinder cover seat portion on which the gasket is placed, and a locking portion that is provided along an inner peripheral end of the cylinder cover seat portion and comes into contact with an inner peripheral surface of the gasket placed on the cylinder cover seat portion to lock the gasket, and the exhaust valve seat is formed in an annular shape so as to face the cylinder cover seat portion across the gasket, and comprises a valve seat portion that has an outer diameter larger than that of the gasket.

[0010] Furthermore, in the seat portion structure according to the present invention, in the above invention, the locking portion is formed in a convex shape that protrudes toward the valve seat portion side relative to the cylinder cover seat portion.

[0011] Furthermore, the seat portion structure according to the present invention is characterized in that, in the above invention, the locking portion is provided in a ring-shaped or arc-shaped form along the inner peripheral end portion of the cylinder cover seat portion.

[0012] Furthermore, in the seat structure according to the present invention, the cylinder cover further includes a groove portion along an outer peripheral edge of the locking portion. [Effects of the Invention]

[0013] According to the present invention, it is possible to suppress a decrease in the sealing performance of the gasket between the cylinder cover and the seat portion of the exhaust valve seat. [Brief explanation of the drawings]

[0014] [Figure 1]FIG. 1 is a schematic diagram showing an example of the configuration of the vicinity of a seat portion structure of a marine diesel engine according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a configuration example of a seat structure according to an embodiment of the present invention. [Figure 3] FIG. 3 is an enlarged schematic cross-sectional view showing a main part of the seat structure according to the embodiment of the present invention. [Figure 4] FIG. 4 is a schematic cross-sectional view of the seat structure shown in FIG. 2 taken along line AA. [Figure 5] FIG. 5 is a schematic diagram for explaining the function of the locking portion of the seat structure according to the embodiment of the present invention. [Figure 6] FIG. 6 is a schematic diagram for explaining the function of the cylinder cover seat portion and the valve seat seat portion of the seat portion structure according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] A preferred embodiment of the seat structure according to the present invention will be described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to this embodiment. It should be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may differ from those in reality. The drawings may also include parts whose dimensional relationships and ratios differ from one another. In addition, the same components are designated by the same reference numerals in each drawing.

[0016] (Configuration of marine diesel engines) First, a description will be given of the configuration of a marine diesel engine equipped with a cylinder cover and an exhaust valve seat to which a seat portion structure according to an embodiment of the present invention is applied. In the embodiment of the present invention, the seat portion structure is a joining structure for joining a cylinder cover of a cylinder having a combustion chamber of a marine diesel engine to an exhaust valve seat on which an exhaust valve that opens and closes an exhaust port of the combustion chamber is seated, via an annular gasket that surrounds the longitudinal axis of the cylinder.

[0017] FIG. 1 is a schematic diagram showing an example of the configuration of the vicinity of a seat portion structure of a marine diesel engine according to an embodiment of the present invention. The marine diesel engine 1 shown in FIG. 1 is a propulsion engine (main engine) that rotates a propulsion propeller (neither of which is shown) of a ship via a propeller shaft. For example, the marine diesel engine 1 is a two-stroke diesel engine such as a well-known uniflow scavenging and exhausting crosshead diesel engine. The marine diesel engine 1 may be a six-cylinder engine, but the number of cylinders is not particularly limited. The operational control system for the marine diesel engine 1 may be a cam system or an electronic control system, but is not particularly limited.

[0018] The configuration in the vicinity of the seat portion structure of the marine diesel engine 1 is the same for all cylinders. Therefore, the following will describe the configuration in the vicinity of the seat portion structure of the marine diesel engine 1 for one of the cylinders.

[0019] As shown in FIG. 1, the marine diesel engine 1 includes a cylinder liner 2, a cylinder cover 3, a piston 5, an exhaust valve 6, an exhaust valve seat 7, an exhaust valve case 9, and an upper valve gear 11.

[0020] The cylinder liner 2 is a cylindrical structure, and a cylinder cover 3 is attached to the top of the cylinder liner 2. The cylinder liner 2 and cylinder cover 3 constitute one cylinder 4 of the marine diesel engine 1, and form a cylindrical space (i.e., the space inside the cylinder 4) in which a piston 5 reciprocates. The piston 5 is provided so as to be able to reciprocate freely within this space. Although not specifically shown, a piston rod is connected to the bottom of the piston 5, and the bottom of this piston rod is connected to a crankshaft via a crosshead or the like. The crankshaft rotates in conjunction with the reciprocating motion of the piston 5, thereby rotating a propeller shaft or the like.

[0021] As shown in FIG. 1, the exhaust valve 6 includes a valve element 6a and a valve stem 6b. The exhaust valve seat 7 is annularly configured to have a seating surface on which the valve element 6a of the exhaust valve 6 can be seated over the entire circumference, and defines an exhaust port 7a therein that leads to an exhaust port of the combustion chamber 8. As shown in FIG. 1, the exhaust valve seat 7 is incorporated into the upper part of the cylinder cover 3. The cylinder liner 2, cylinder cover 3, piston 5, and valve element 6a form a combustion chamber 8 within the cylinder 4. A fuel (a fossil fuel such as heavy oil or diesel, or an alternative fuel such as hydrogen) or a liquid other than fuel, such as water, is injected into the combustion chamber 8 from a fuel injection valve (not shown) attached to the cylinder cover 3.

[0022] As shown in FIG. 1 , the exhaust valve box 9 is attached to the top of the cylinder 4 with the exhaust valve seat 7 sandwiched between it and the cylinder cover 3. In this embodiment, the exhaust valve box 9 is fixed to the top of the cylinder cover 3 by fastening a plurality of bolts 13a and 13b (two in FIG. 1 ) positioned at predetermined intervals around the longitudinal axis 4a of the cylinder 4. This connects the lower end of the exhaust valve box 9 to the upper end of the exhaust valve seat 7, which is assembled to the top of the cylinder cover 3. At the same time, the cylinder cover 3 and the exhaust valve seat 7 are joined and fixed by the fastening force of the bolts 13a and 13b with a gasket 15 sandwiched between their seat portions. The longitudinal axis 4a of the cylinder 4 is the central axis of the cylinder 4 in the longitudinal direction. The exhaust valve box 9 also has an exhaust port 9a communicating with the exhaust port 7a of the exhaust valve seat 7 and a valve stem guide 10 that slidably supports the valve stem 6b of the exhaust valve 6.

[0023] The upper valve train 11 is attached to the top of the exhaust valve box 9 and is configured to reciprocate the exhaust valve 6. The upper valve train 11 has an internal biasing member (not shown), such as a compression spring or an air spring, which biases the exhaust valve 6 in a direction to close the exhaust port 7a. The upper valve train 11 also uses the hydraulic pressure of hydraulic oil supplied from an oil supply pump (not shown) through piping to lower the exhaust valve 6 against the biasing member. In this way, the upper valve train 11 operates the exhaust valve 6 to open the exhaust port 7a. The exhaust valve 6 opens the exhaust port 7a only while hydraulic oil is supplied to the upper valve train 11, and closes the exhaust port 7a when the supply of hydraulic oil is stopped.

[0024] In such a marine diesel engine 1, combustion gas such as air is introduced into the combustion chamber 8 through a scavenging port (not shown), and then the piston 5 rises. The exhaust valve 6 closes the exhaust port 7a, compressing the combustion gas in the combustion chamber 8. In the combustion chamber 8, the compressed combustion gas mixes with an injection liquid such as fuel injected from a fuel injection valve and burns, and the piston 5 descends due to the combustion energy. When the exhaust valve 6 opens the exhaust port 7a of the exhaust valve seat 7, the exhaust gas in the combustion chamber 8 is discharged through the exhaust port 7a to an exhaust port 9a in an exhaust valve case 9. The exhaust gas is then discharged from the exhaust port 9a through a pipe to an exhaust manifold (not shown).

[0025] (Seat structure) Next, a seat portion structure according to an embodiment of the present invention will be described. The seat portion structure according to this embodiment is a joining structure for joining the above-mentioned cylinder cover 3 and the exhaust valve seat 7 with a gasket 15 sandwiched therebetween. Fig. 2 is a cross-sectional schematic diagram showing an example of the configuration of a seat portion structure according to an embodiment of the present invention. Fig. 3 is an enlarged cross-sectional schematic diagram showing a main part of the seat portion structure according to an embodiment of the present invention. Note that Fig. 3 shows an enlarged view of the part surrounded by the dashed line in Fig. 2. Fig. 4 is a cross-sectional schematic diagram taken along line AA of the seat portion structure shown in Fig. 2.

[0026] In the seat portion structure of this embodiment, as shown in Figures 2 to 4, the cylinder cover 3 has a cylinder cover seat portion 31 that is joined to the seat portion of the exhaust valve seat 7 with the gasket 15 sandwiched therebetween, and a locking portion 32 for locking the gasket 15.

[0027] As shown in Figures 3 and 4, the cylinder cover seat portion 31 is a joining surface that is joined to the valve seat portion 71 of the exhaust valve seat 7 with the gasket 15 sandwiched therebetween, and is formed in an annular shape so as to surround the longitudinal axis 4a of the cylinder 4 (see Figure 1). For example, as shown in Figure 4, the cylinder cover seat portion 31 preferably has an annular surface when viewed from above in the direction of the longitudinal axis 4a. Furthermore, as shown in Figure 3, the cylinder cover seat portion 31 has an outer diameter R2 that is larger than the outer diameter R1 of the annular gasket 15. The gasket 15 is placed on this cylinder cover seat portion 31, as shown in Figures 3 and 4.

[0028] The inner diameter of the cylinder cover seat portion 31 may be larger, smaller, or the same as the inner diameter of the gasket 15, as long as the gasket 15 can be placed on the cylinder cover seat portion 31 and the gasket 15 can seal between the seat portions of the cylinder cover 3 and the exhaust valve seat 7. The width of the cylinder cover seat portion 31 is the distance between its inner peripheral end portion 31a and outer peripheral end portion 31c, and is set, for example, so as to ensure a bonding area appropriate for the bonding strength and sealing performance between the gasket 15 and the cylinder cover seat portion 31.

[0029] The locking portion 32 is intended to position the gasket 15 to be placed on the cylinder cover seat portion 31 and to prevent the gasket 15 from shifting position after placement. Specifically, as shown in Figures 3 and 4, the locking portion 32 is provided in an annular or arc shape along the inner peripheral end portion 31a of the cylinder cover seat portion 31. For example, the locking portion 32 is located closer to the inner peripheral side of the cylinder cover 3 than the cylinder cover seat portion 31 and is provided in a continuous annular shape around the entire inner peripheral side of the cylinder cover seat portion 31.

[0030] 3 and 4, the locking portion 32 is formed in a convex shape that protrudes toward the valve seat portion 71 of the exhaust valve seat 7 relative to the cylinder cover seat portion 31, and has a side wall surface 32a that extends from the cylinder cover seat portion 31 toward the valve seat portion 71. The side wall surface 32a of the locking portion 32 faces the inner circumferential surface 15a of the gasket 15 on the cylinder cover seat portion 31 in the radial direction of the cylinder cover 3. For example, if the locking portion 32 is formed in an annular or arc-shaped shape along the inner circumferential end portion 31a of the cylinder cover seat portion 31, the side wall surface 32a of the locking portion 32 is an annular or arc-shaped outer circumferential surface. In particular, if the locking portion 32 is annular and extends around the entire inner circumferential side of the cylinder cover seat portion 31, the side wall surface 32a of the locking portion 32 is an outer circumferential surface that extends around the entire annular shape. The radial direction of the cylinder cover 3 is perpendicular to the longitudinal axis 4a of the cylinder 4. The locking portion 32 locks the gasket 15 by bringing the inner circumferential surface 15a of the gasket 15 placed on the cylinder cover seat portion 31 into contact with its own side wall surface 32a.

[0031] The locking portion 32 contacts the inner peripheral surface 15a of the gasket 15 placed on the cylinder cover seat portion 31 to lock the gasket 15, thereby positioning the gasket 15 on the cylinder cover seat portion 31. Furthermore, by locking the gasket 15, the locking portion 32 prevents the gasket 15 from shifting position when sandwiched between the cylinder cover seat portion 31 and the valve seat portion 71.

[0032] From the viewpoint of locking the gasket 15 by the locking portions 32, the locking portions 32 are preferably formed in the annular shape described above, but may be formed in an intermittent arc shape along the inner peripheral end portion 31a of the cylinder cover seat portion 31. In this case, from the viewpoint of being able to reliably lock the gasket 15 by the locking portions 32 at any position on the inner peripheral surface 15a, the arc-shaped locking portions 32 are preferably provided at equal intervals around the longitudinal axis 4a of the cylinder 4.

[0033] 3 and 4, the cylinder cover 3 has a groove 33 along the outer peripheral edge of the locking portion 32. The groove 33 is a groove that facilitates the formation of the locking portion 32 on the inner peripheral side of the cylinder cover seat portion 31. Specifically, in the seat portion structure between the cylinder cover 3 and the exhaust valve seat 7, the cylinder cover seat portion 31 is formed and the locking portion 32 that protrudes beyond the cylinder cover seat portion 31 is formed by, for example, machining the joining surface of the cylinder cover 3 that joins with the exhaust valve seat 7 via the gasket 15. In this case, the side wall surface 32a of the locking portion 32 is formed as a steeply inclined surface (preferably a vertical surface perpendicular to the radial direction of the cylinder cover seat portion 31) that slopes downward from the locking portion 32 side toward the cylinder cover seat portion 31 side. Such a side wall surface 32a can be easily formed by machining the outer peripheral surface of the locking portion 32 so that the groove 33 is formed along the outer peripheral edge of the locking portion 32. That is, the formation of the groove portion 33 makes it possible to easily form the side wall surface 32a of the locking portion 32 that faces the inner circumferential surface 15a of the gasket 15 described above.

[0034] On the other hand, as described above, the exhaust valve seat 7 seats the valve body 6a of the exhaust valve 6 that opens and closes the exhaust port of the combustion chamber 8. In the seat portion structure according to this embodiment, the exhaust valve seat 7 includes a valve seat portion 71 that is joined to the seat portion of the cylinder cover 3 with a gasket 15 sandwiched therebetween, as shown in Figures 2 and 3 .

[0035] As shown in Fig. 3, the valve seat portion 71 is a joining surface that is joined to the cylinder cover seat portion 31 with the gasket 15 sandwiched therebetween, and is formed in an annular shape so as to surround the longitudinal axis 4a of the cylinder 4. That is, the valve seat portion 71 is formed in an annular shape so as to face the cylinder cover seat portion 31 with the gasket 15 sandwiched therebetween. For example, the valve seat portion 71 preferably has an annular surface when viewed from below in the direction of the longitudinal axis 4a. Furthermore, as shown in Fig. 3, the valve seat portion 71 has an outer diameter R3 that is larger than the outer diameter R1 of the annular gasket 15.

[0036] The inner diameter of the valve seat portion 71 is not particularly limited as long as the cylinder cover seat portion 31 and the valve seat portion 71 can be joined via the gasket 15, but may be set to be smaller than the inner diameter of the cylinder cover seat portion 31. The width of the valve seat portion 71 is the distance between its inner peripheral end and outer peripheral end 71c, and is set to ensure a joining area suitable for the joining strength and sealing performance between the gasket 15 and the valve seat portion 71. For example, as shown in FIG. 3, the width of the valve seat portion 71 may be set to be equal to or larger than the width of the annular region extending from the outer peripheral end 31c of the cylinder cover seat portion 31 to the inner peripheral end of the locking portion 32.

[0037] As shown in FIG. 2, the gasket 15 is a sealing member sandwiched between the seat portions of the cylinder cover 3 and the exhaust valve seat 7, which are joined together. Specifically, the gasket 15 is a sealing member made of a material such as metal, and is formed in an annular (e.g., circular) shape that can surround the longitudinal axis 4a of the cylinder 4, as shown in FIGS. 3 and 4. The gasket 15 is placed on the cylinder cover seat portion 31 so as to be positioned on the outer periphery of the locking portion 32 of the cylinder cover 3. In this placed state, the inner circumferential surface 15a of the gasket 15 faces the outer circumferential side wall surface 32a of the locking portion 32. The inner circumferential surface 15a of the gasket 15 contacts the side wall surface 32a of the locking portion 32, thereby limiting radial displacement of the gasket 15 on the cylinder cover seat portion 31 and positioning the gasket 15. 3 and 4 show the state before the inner peripheral surface 15a of the gasket 15 and the side wall surface 32a of the engagement portion 32 come into contact, i.e., the state before the displacement of the gasket 15 on the cylinder cover seat portion 31 is restricted and the gasket 15 is positioned.

[0038] The gasket 15 placed on the cylinder cover seat portion 31 in this manner is sandwiched between the cylinder cover seat portion 31 and the valve seat portion 71 by the fastening force of the bolts 13a and 13b described above. As a result, the gasket 15 provides an airtight seal between the cylinder cover seat portion 31 and the valve seat portion 71.

[0039] (Effect of seat structure) Next, we will explain the function of the seat portion structure between the cylinder cover 3 and the exhaust valve seat 7 in this embodiment of the present invention. As an example of the function of the seat portion structure, we will first explain the function that the locking portion 32 of the cylinder cover 3 has on the gasket 15.

[0040] 5 is a schematic diagram illustrating the function of the locking portion of the seat portion structure according to an embodiment of the present invention. The cylinder cover 3 and the exhaust valve seat 7 are joined with a gasket 15 sandwiched between the cylinder cover seat portion 31 and the valve seat seat portion 71. In the seat portion structure between the cylinder cover 3 and the exhaust valve seat 7, the gasket 15 is interposed between the cylinder cover seat portion 31 and the valve seat seat portion 71, as shown in FIG. 5, with the gasket 15 surrounding the locking portion 32 on the inner circumferential side. The inner circumferential surface 15a of the gasket 15 faces the side wall surface 32a of the locking portion 32 (the outer circumferential surface of the locking portion 32 in this embodiment).

[0041] Between the cylinder cover 3 and the exhaust valve seat 7, which are joined together with the gasket 15 sandwiched therebetween, a gap is formed that connects the combustion chamber 8 and the inner circumferential surface 15a of the gasket 15 (see FIGS. 2 and 3). For example, as shown by the bold arrow in FIG. 5, the pressure of the combustion chamber 8 (intra-cylinder pressure) may be applied to the inner circumferential surface 15a of the gasket 15 through the gap 16 between the cylinder cover 3 and the exhaust valve seat 7. In this case, the inner circumferential surface 15a of the gasket 15 is pressed outward by the intra-cylinder pressure. As a result, the entire gasket 15, together with the portion of the inner circumferential surface 15a subjected to this intra-cylinder pressure, tends to displace excessively toward one side of the cylinder cover seat portion 31 (to the right side of the drawing in FIG. 5). Note that excessive displacement of the gasket 15 means that the outer circumferential edge of any portion of the annular gasket 15 is displaced outward beyond the outer circumferential edge 31c of the cylinder cover seat portion 31.

[0042] However, in the seat portion structure according to this embodiment, as shown in Fig. 5, the inner circumferential surface 15a of the gasket 15 faces the side wall surface 32a of the locking portion 32. Therefore, even if the gasket 15 tries to excessively displace to one side of the cylinder cover seat portion 31 as described above, the inner circumferential surface 15a of the gasket 15 on the opposite side, which faces the inner circumferential surface 15a subjected to the intra-cylinder pressure across the longitudinal axis 4a of the cylinder 4 (see Figs. 1 and 2), comes into contact with and is locked to the side wall surface 32a of the locking portion 32, as shown in Fig. 5. As a result, the entire gasket 15, together with the inner circumferential surface 15a on the opposite side, is locked by the locking portion 32. As a result, the displacement of the entire gasket 15 is limited by the locking portion 32, preventing the gasket 15 from being excessively displaced (misaligned) to one side of the cylinder cover seat portion 31.

[0043] Furthermore, in the seat portion structure of this embodiment, similar to the case of preventing the gasket from shifting due to the above-mentioned in-cylinder pressure, when the gasket 15 is placed on the cylinder cover seat portion 31, the action of the engaging portion 32 on the gasket limits the radial position of the gasket 15 on the cylinder cover seat portion 31, thereby enabling the positioning of the gasket 15.

[0044] Next, as an example of the function of the seat portion structure according to the embodiment of the present invention, the function of the cylinder cover seat portion 31 and the valve seat seat portion 71 on the gasket 15 will be described. Figure 6 is a schematic diagram for explaining the function of the cylinder cover seat portion and the valve seat seat portion of the seat portion structure according to the embodiment of the present invention.

[0045] In the seat portion structure for joining the cylinder cover 3 and the exhaust valve seat 7 via the gasket 15, as described above, the outer diameter R2 of the cylinder cover seat portion 31 and the outer diameter R3 of the valve seat seat portion 71 are both larger than the outer diameter R1 of the gasket 15 (see FIG. 3). That is, as shown in FIG. 3, the cylinder cover seat portion 31 has an outer peripheral portion 31b located radially outward from the outer peripheral end of the gasket 15. The valve seat seat portion 71 has an outer peripheral portion 71b located radially outward from the outer peripheral end of the gasket 15. Note that FIG. 3 illustrates a case in which the outer diameter R3 of the valve seat seat portion 71 is larger than the outer diameter R2 of the cylinder cover seat portion 31, but the present invention is not limited to this. That is, the outer diameter R2 of the cylinder cover seat portion 31 may be larger, smaller, or the same as the outer diameter R3 of the valve seat seat portion 71.

[0046] The outer peripheral portions 31b, 71b of the cylinder cover seat portion 31 and the valve seat seat portion 71 are bent and deformed in a direction toward each other due to the fastening force of the bolts 13a, 13b (see Figure 1) that secure the cylinder cover 3 and the exhaust valve box 9 together with the exhaust valve seat 7.

[0047] 6, the outer peripheral portion 31b of the cylinder cover seat portion 31 is located below the outer peripheral portion 71b of the valve seat portion 71, and is bent and deformed by the fastening force of the bolts 13a and 13b to form a gently rising inclined surface from the outer peripheral end of the gasket 15 toward the outer peripheral end 31c of the cylinder cover seat portion 31. The outer peripheral portion 71b of the valve seat portion 71 is located above the outer peripheral portion 31b of the cylinder cover seat portion 31, and is bent and deformed by the fastening force of the bolts 13a and 13b to form a gently descending inclined surface from the outer peripheral end of the gasket 15 toward the outer peripheral end 71c of the valve seat portion 71. As a result, the distance L between the outer peripheral ends 31c, 71c of the cylinder cover seat portion 31 and the valve seat portion 71 is narrower than in their pre-deformation states (see dashed lines in FIG. 6). As a result, the distance L between the outer peripheral end 31c of the cylinder cover seat portion 31 and the outer peripheral end 71c of the valve seat seat portion 71 becomes smaller than the thickness H of the gasket 15 (hereinafter referred to as the gasket 15 between the seat portions) sandwiched between the cylinder cover seat portion 31 and the valve seat seat portion 71.

[0048] The degree of bending deformation of the outer peripheral portions 31b, 71b of the cylinder cover seat portion 31 and the valve seat seat portion 71 described above varies depending on the distance from the bolts 13a, 13b. However, even if the degree of bending deformation differs, the distance L between the outer peripheral ends 31c, 71c of the cylinder cover seat portion 31 and the valve seat seat portion 71 is smaller than the thickness H of the gasket 15 between the seat portions over the entire circumference of the cylinder cover seat portion 31 and the valve seat seat portion 71.

[0049] Here, the cylinder cover 3 and the exhaust valve seat 7 expand and deform due to the high heat transmitted from the combustion chamber 8, which is in a high-temperature state when the marine diesel engine 1 is in operation. Accordingly, the gasket 15 between the seats may expand and deform due to the high heat. In this case, the expansion and deformation of the gasket 15 is more strongly suppressed by the fastening force at locations closer to the bolts 13a, 13b, but is more difficult to suppress at locations farther from the bolts 13a, 13b. Therefore, the gasket 15 between the seats tends to expand and deform, as exemplified by deformation from a circular shape to an elliptical shape.

[0050] In contrast, in the seat portion structure according to this embodiment, as shown in Fig. 6, the outer peripheral portions 31b, 71b of the cylinder cover seat portion 31 and the valve seat seat portion 71 are bent and deformed over their entire circumference so that the distance L between the outer peripheral ends 31c, 71c is smaller than the thickness H of the gasket 15 between the seat portions. The cylinder cover seat portion 31 and the valve seat seat portion 71, whose outer peripheral portions 31b, 71b are bent and deformed in this way, uniformly suppress the expansion and deformation of the gasket 15 between the seat portions toward the outer periphery over their entire circumference, thereby preventing the gasket 15 from expanding and deforming excessively.

[0051] As described above, in the seat portion structure according to an embodiment of the present invention, the cylinder cover 3 of the cylinder 4 having the combustion chamber 8 of the marine diesel engine 1 is provided with the cylinder cover seat 31, which is formed in an annular shape so as to surround the longitudinal axis 4a of the cylinder 4 and has an outer diameter R2 larger than the outer diameter R1 of the gasket 15, and the locking portion 32, which is arranged along the inner peripheral end 31a of the cylinder cover seat 31; the exhaust valve seat 7, on which the exhaust valve 6 that opens and closes the exhaust port of the combustion chamber 8 is seated, is provided with the valve seat 71, which is formed in an annular shape so as to face the cylinder cover seat 31 and has an outer diameter R3 larger than the outer diameter R1 of the gasket 15; the cylinder cover 3 and the exhaust valve seat 7 are joined together by sandwiching the annular gasket 15 surrounding the longitudinal axis 4a of the cylinder 4 between the cylinder cover seat 31 and the valve seat 71; and the gasket 15 is locked by the locking portion 32, which comes into contact with the inner peripheral surface 15a of the gasket 15 placed on the cylinder cover seat 31.

[0052] Therefore, the locking portion 32 can be used to position the gasket 15 when placing it on the cylinder cover seat portion 31, and the locking portion 32 can prevent the gasket 15 from being excessively misaligned to one side of the cylinder cover seat portion 31 even if in-cylinder pressure is applied to the inner circumferential surface 15a of the gasket 15 between the seats. Furthermore, the fastening force of the bolts 13a, 13b that secure the exhaust valve seat 7 and the exhaust valve case 9 to the cylinder cover 3 bends and deforms the outer circumferential portions 31b, 71b of the cylinder cover seat portion 31 and the valve seat seat portion 71, making it possible to reduce the distance L between these outer circumferential ends 31c, 71c to less than the thickness H of the gasket 15 between the seats. This makes it possible to suppress expansion and deformation of the gasket 15 due to high heat over the entire circumference of the cylinder cover seat portion 31 and the valve seat seat portion 71, thereby preventing excessive expansion and deformation of the gasket 15. As a result, the sealing performance of the gasket 15 between the cylinder cover seat portion 31 and the valve seat seat portion 71 is improved, which prevents a decrease in the sealing performance of the gasket 15 between the seat portions of the cylinder cover 3 and the exhaust valve seat 7. As a result, it is possible to prevent gas leakage from the combustion chamber 8 through the gap between the cylinder cover 3 and the exhaust valve seat 7.

[0053] In the above-described embodiment, the annular or arc-shaped locking portion 32 is provided on the inner circumferential side of the seat portion of the cylinder cover 3, but the present invention is not limited to this. For example, the locking portion 32 may be formed of a protruding member such as a plurality of pins or a frame attached to the cylinder cover 3 along the inner circumferential end portion 31a of the cylinder cover seat portion 31. In this case, the groove portion 33 described above does not need to be formed on the outer circumferential side of the locking portion 32.

[0054] In addition, in the above-described embodiment, the outer peripheral portions 31b, 71b of the cylinder cover seat portion 31 and the valve seat seat portion 71 are bent and deformed, but in the present invention, the bending and deformation of the outer peripheral portions 31b, 71b may be elastic deformation or plastic deformation.

[0055] In the above-described embodiment, the exhaust valve seat 7, the exhaust valve case 9, and the cylinder cover 3 are fixed together by two bolts 13a and 13b, but the number of bolts for fixing them together is not particularly limited in the present invention. For example, the number of bolts may be one, or two or more.

[0056] Furthermore, the present invention is not limited to the above-described embodiments, and any combination of the above-described components is also included in the present invention. In addition, other embodiments, examples, operational techniques, etc. made by those skilled in the art based on the above-described embodiments are all included in the scope of the present invention. [Explanation of symbols]

[0057] 1. Marine diesel engines 2 Cylinder Liners 3 Cylinder cover 4 cylinders 4a Longitudinal axis 5 pistons 6 Exhaust valve 6a Valve body 6b Valve stem 7 Exhaust valve seat 7a Exhaust port 8 Combustion chamber 9 Exhaust valve box 9a Exhaust port 10 Valve stem guide 11 Upper valve train 13a, 13b bolts 15 Gasket 15a Inner surface 16 Gap 31 Cylinder cover seat 31a Inner edge 31b Outer periphery 31c Outer edge 32 Locking part 32a Side wall 33 Groove 71 Valve seat 71b Outer periphery 71c Outer edge

Claims

1. A seat structure for joining a cylinder cover of a cylinder having a combustion chamber of a marine diesel engine to an exhaust valve seat on which an exhaust valve that opens and closes an exhaust port of the combustion chamber is seated, with an annular gasket surrounding the longitudinal axis of the cylinder, The cylinder cover is a cylinder cover seat portion formed in an annular shape so as to surround the longitudinal axis of the cylinder, having an outer diameter larger than an outer diameter of the gasket, and on which the gasket is placed; a locking portion provided along an inner peripheral end of the cylinder cover seat portion, the locking portion contacting an inner peripheral surface of the gasket placed on the cylinder cover seat portion to lock the gasket; Equipped with The exhaust valve seat is formed in an annular shape so as to face the cylinder cover seat portion across the gasket, and includes a valve seat portion having an outer diameter larger than an outer diameter of the gasket. A seat structure characterized by:

2. The locking portion is formed in a convex shape that protrudes toward the valve seat portion further than the cylinder cover seat portion. The seat structure according to claim 1 .

3. The locking portion is provided in a ring shape or an arc shape along the inner peripheral end portion of the cylinder cover seat portion.

3. The seat structure according to claim 1 or 2.

4. The cylinder cover further includes a groove along an outer peripheral edge of the locking portion.

4. The seat structure according to claim 1, wherein the seat structure is a seat portion structure having a width of 100 mm.

Images