Head gasket

Abstract

To enhance seal performance among a cylinder block, a cylinder head, and a cover member.SOLUTION: A head gasket comprises: a first baseboard in which a cylinder axial direction is set as a thickness direction; a second baseboard arranged at one side of the first baseboard in the cylinder axial direction; and a third baseboard arranged at one side of the second baseboard in the cylinder axial direction; and a protrusion protruding to one side or the other side of the cylinder axial direction. A ridge line extending toward a mating face of a cover member in the cylinder axial direction is provided at least at either of the first and third baseboards. Penetration holes which are formed at a position being the vicinity of the protrusion in a view of the cylinder axial direction, penetrate front surfaces and rear surfaces of the baseboards, and are overlapped on each other in the view of the cylinder axial direction are formed at the second baseboard and the third baseboard, and a hole diameter of the penetration hole of the second baseboard is set smaller than a hole diameter of the penetration hole of the third baseboard.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a head gasket. [Background technology]

[0002] In an internal combustion engine having a cylinder block and a cylinder head, a head gasket having a protrusion, known as a bead, that protrudes to one side in the cylinder axial direction is disposed between the cylinder block and the cylinder head to seal the gap between them.

[0003] Furthermore, as disclosed in Patent Document 1, in an internal combustion engine having a cover member (a chain case in Patent Document 1) having mating surfaces that abut the end faces of the cylinder block and the cylinder head in the direction perpendicular to the cylinder axial direction, it is known that the so-called three-surface mating portion where these three components face each other is sealed with a liquid sealant (a liquid gasket in Patent Document 1).

[0004] Specifically, Patent Document 1 discloses a method of assembling an engine in which liquid sealant is applied to both sides of the head gasket in the cylinder axial direction, and then the cylinder head and cylinder block are fastened together to place the liquid sealant in the above-mentioned three-surface mating portion. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5978918 Summary of the Invention [Problem to be solved by the invention]

[0006] In the configuration of Patent Document 1, when the head gasket is a multi-layered gasket in which multiple substrates are laminated, there is a risk that the sealing performance of the three-surface mating portion may not be sufficiently ensured. Specifically, in a multi-layered head gasket, if liquid sealant is simply placed on both sides in the cylinder axial direction, when the cylinder head and the cylinder block are fastened together, the air in the passage partitioned between the protrusion of a certain substrate, its surrounding portion, and the substrate facing it is pushed toward the cover member, causing the liquid sealant in the three-surface mating portion to be blown away, and there is a risk that a sufficient amount of liquid sealant may not be ensured in the three-surface mating portion.

[0007] The present invention has been made in consideration of the above circumstances, and has an object to provide a head gasket that can improve the sealing performance between the cylinder block, the cylinder head, and the cover member. [Means for solving the problem]

[0008] In order to solve the above problem, the present invention provides a head gasket for an engine including a cylinder block and a cylinder head overlapping in a cylinder axial direction, and a cover member having mating surfaces abutting end faces of the cylinder block and the cylinder head in a direction perpendicular to the cylinder axial direction, and in which lubricating oil is used inside the cover member, the head gasket being interposed between the cylinder block and the cylinder head, the head gasket comprising a first substrate having a thickness direction in the cylinder axial direction, a second substrate arranged on one side of the first substrate in the cylinder axial direction, and a third substrate arranged on one side of the second substrate in the cylinder axial direction, at least one of the first to third substrates including a protrusion protruding to one or the other side in the cylinder axial direction and having a ridge line extending toward the mating surface of the cover member as viewed in the cylinder axial direction, the second substrate and the third substrate each having a through hole formed at a position near the protrusion as viewed in the cylinder axial direction, penetrating through a front and rear of each substrate and overlapping with each other as viewed in the cylinder axial direction, the hole diameter of the through hole of the second substrate being smaller than the hole diameter of the through hole of the third substrate.

[0009] In the present invention, in the multi-layer type head gasket, the second substrate and the third substrate are each formed with a through hole. Therefore, the liquid sealant can be introduced through each through hole to the vicinity of the protrusion between the third substrate and the second substrate and the vicinity of the protrusion between the second substrate and the first substrate, and a part of the passage formed around the protrusion can be sealed with the liquid sealant. Moreover, the through hole of the second substrate and the through hole of the third substrate are configured to overlap with each other, and the hole diameter of the through hole of the second substrate is smaller than the hole diameter of the through hole of the third substrate. Therefore, the liquid sealant that flows into the through hole of the third substrate can be reliably introduced into the through hole of the second substrate and further into the space between the second substrate and the first substrate, and a part of the liquid sealant that passes through the through hole of the third substrate can be blocked by the second substrate and introduced into the space between the second substrate and the third substrate, and the part of the passage can be reliably sealed with the liquid sealant.

[0010] As described above, according to the present invention, when the cylinder block and the cylinder head are fastened to each other, it is possible to prevent air from being forcefully pushed out from the end of the head gasket through the passage toward the cover member, thereby preventing the liquid sealant arranged around the end from being blown away, thereby improving the sealing performance between the cylinder block, the cylinder head, and the cover member.

[0011] In the above configuration, the through hole of the second substrate is preferably disposed inside the through hole of the third substrate when viewed in the cylinder axial direction (claim 2).

[0012] According to this configuration, the overlapping area between the through hole of the second substrate and the through hole of the third substrate can be increased, so that the liquid sealant can be more reliably introduced between the second substrate and the first substrate.

[0013] In the above configuration, the through hole of the second substrate is preferably arranged so that its center coincides with the center of the through hole of the third substrate (claim 3).

[0014] In this configuration, the second substrate protrudes inward from the periphery of the through hole of the third substrate all around the circumference, so that the liquid sealant can be introduced between the second substrate and the third substrate all around the circumference of the through hole of the third substrate, and the gap between the second substrate and the third substrate can be more reliably sealed with the liquid sealant.

[0015] In the above configuration, the second substrate preferably has a guide portion on a periphery of the through hole, the guide portion being bent toward one side in the cylinder axial direction and toward the inside in the radial direction (claim 4).

[0016] According to this configuration, the guide portion can guide the liquid sealant to between the second substrate and the third substrate, and the gap between them can be more reliably sealed with the liquid sealant.

[0017] In the above configuration, the first substrate preferably has a shape that blocks the through hole of the second substrate from the other side in the cylinder axial direction (claim 5).

[0018] According to this configuration, the liquid sealant is held back by the first substrate, so that a larger amount of the liquid sealant can be introduced between the substrates.

[0019] In the above configuration, preferably, the device further includes a fourth substrate arranged between the first substrate and the second substrate, and the fourth substrate has a through hole that penetrates the front and back of the fourth substrate and overlaps with the through hole of the second substrate when viewed in the cylinder axial direction (Claim 6).

[0020] According to this configuration, by providing four substrates between the cylinder head and the cylinder block and introducing liquid sealant between each substrate, the sealing performance between the cylinder head and the cylinder block can be improved even more reliably. Effect of the Invention

[0021] As described above, according to the head gasket of the present invention, it is possible to improve the sealing performance between the cylinder block, the cylinder head, and the cover member. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic side view showing the configuration of the engine. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a part of the cross section taken along line II-II in FIG. [Diagram 3] FIG. 3 is an enlarged view of a portion of FIG. [Figure 4] FIG. 4 is a schematic plan view of the head gasket. [Diagram 5] FIG. 5 is a schematic perspective view showing an enlarged portion of the front end portion of the head gasket. [Figure 6] FIG. 6 is a schematic cross-sectional view taken along line VI-VI in FIG. [Figure 7] 7(a) to (d) are diagrams each showing a schematic cross-sectional view taken along line VII-VII in FIG. 5, showing a state during engine assembly. [Figure 8] 8(a) to 8(c) are diagrams each showing a schematic diagram of a state during engine assembly and correspond to FIG. [Figure 9] FIG. 2 is a side view showing a schematic view of the head gasket after being assembled to the engine body. [Figure 10] FIG. 8 is a diagram showing a schematic view of an engine assembly using a head gasket according to a comparative example, the diagram corresponding to FIG. 7(c). [Figure 11] FIG. 8 is a diagram showing a schematic view of a state in which the head gasket according to the embodiment of the present invention is used during assembly of an engine, and corresponds to FIG. 7(c). [Figure 12] FIG. 7 is a schematic cross-sectional view of a head gasket according to a modified example, and corresponds to FIG. 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings, in which: Fig. 1 is a schematic side view showing a configuration of an engine 1 to which a head gasket 50 according to an embodiment of the present invention is applied.

[0024] The engine 1 has an engine body 2 including a cylinder block 20 in which cylinders 23 are formed, a cylinder head 10, and a head gasket 50, and a chain cover 30 assembled to the engine body 2. The engine body 2 is, for example, an in-line six-cylinder engine, and the cylinder block 20 has, for example, six cylinders 23 arranged in a row. The chain cover 30 is disposed on one side of the engine body 2 in the direction in which the cylinders 23 are arranged.

[0025] In the following, the arrangement direction of the cylinders 23 is referred to as the front-rear direction, and the side of the chain cover 30 with respect to the engine body 2 is referred to as the front, and the opposite side is referred to as the rear. In the embodiment, the cylinder head 10 is fastened to the upper surface of the cylinder block 20, and the axial direction of the cylinders 23, i.e., the cylinder axis direction, coincides with the up-down direction. For this reason, in the following, the arrangement direction of the cylinder head 10 and the cylinder block 20 and the axial direction of the cylinders 23 are referred to as the up-down direction, and the cylinder head 10 side with respect to the cylinder block 20 is referred to as the up-down direction, and the opposite side is referred to as the down-down direction. In the following, the left-right direction in a direction perpendicular to the front-rear direction and the up-down direction and facing forward is referred to as the left-right direction. In the up-down direction, the lower side corresponds to "one side in the cylinder axis direction" of the present invention, and the upper side corresponds to "the other side in the cylinder axis direction". In the following, the cylinder axis direction view, that is, the view along the up-down direction, is referred to as a plan view as appropriate.

[0026] A timing chain 40, which is rotated by a crankshaft (not shown) connected to pistons (not shown) fitted in each cylinder 23, is arranged in front of the engine body 2 so as to run along the front end surface 2A of the engine body 2.

[0027] The chain cover 30 is a member that covers auxiliary machinery such as a timing chain 40. The chain cover 30 has a rear end surface 32 that abuts against the front end surface 2A of the engine body 2, i.e., the front end surface 12 of the cylinder head 10 and the front end surface 22 of the cylinder block 20. The chain cover 30 is fastened to the engine body 2 with the front end surface 2A and the rear end surface 32 of the engine body 2 abutting against each other, and defines a chain housing section 39 that houses the timing chain 40 between the engine body 2 and the chain cover 30. Specifically, the central parts of the front end surface 2A of the engine body 2, i.e., the front end surface 12 of the cylinder head 10 and the front end surface 22 of the cylinder block 20, in the left-right direction are recessed backward. The central part of the rear end surface 32 of the chain cover 30 in the left-right direction is recessed forward. The engine body 2 and the chain cover 30 are fastened to each other with both left and right ends of the front end face 2A of the engine body and both left and right ends of the rear end face 32 of the chain cover 30 in contact with each other, and a chain accommodating section 39 is defined between the left and right central portion of the front end face 2A of the engine body 2 and the left and right central portion of the rear end face 32 of the chain cover 30. Inside the chain cover 30, specifically inside the chain accommodating section 39, lubricating oil is used to lubricate the timing chain 40 and the like. The chain cover 30 corresponds to the "cover member" in this invention, and the rear end face 32 of the chain cover 30 corresponds to the "mating surface" in this invention.

[0028] The head gasket 50 is intended to prevent combustion gas and lubricating oil from leaking to the outside from between the cylinder head 10 and the cylinder block 20, and is interposed between the cylinder head 10 and the cylinder block 20. That is, the head gasket 50 is disposed between the lower surface 11 of the cylinder head 10 and the upper surface 21 of the cylinder block 20 so as to close the gap X1 between them, and the cylinder head 10 and the cylinder block 20 are fastened to each other with the head gasket 50 sandwiched therebetween.

[0029] (Head gasket configuration) Next, the configuration of the head gasket 50 according to the embodiment will be described using the direction of the head gasket 50 placed on the upper surface 21 of the cylinder block 20. FIG. 2 is a schematic cross-sectional view of a part of the cross section taken along line II-II in FIG. 1, showing the front part of the engine 1 in the cross section taken along line II-II. FIG. 3 is a schematic cross-sectional view of a part of FIG. 2, showing an enlarged front and right part of the engine 1 in the cross section taken along line II-II. FIG. 4 is a schematic plan view of the head gasket 50. FIG. 5 is a perspective view of the right part of the front end part of the head gasket 50 as viewed from below. FIG. 6 is a schematic cross-sectional view taken along line VI-VI in FIG. 5.

[0030] The head gasket 50 has a generally plate-like shape extending in the front-rear and left-right directions. The head gasket 50 has cylinder holes 53 penetrating from the front to the back at positions corresponding to the cylinders 23. As described above, the cylinder block 20 has six cylinders 23 aligned in the front-rear direction, and the head gasket 50 has six cylinder holes 53 aligned in the front-rear direction.

[0031] The head gasket 50 is a multi-layer type gasket, and has a plurality of plate-shaped gasket substrates whose thickness direction is in the vertical direction. The head gasket 50 of this embodiment is a four-layer type gasket having four gasket substrates 150, 250, 350, 450. Specifically, the head gasket 50 has a first gasket substrate 150 constituting the top layer, a second gasket substrate 250 arranged below the first gasket substrate 150 and constituting the third layer from the top, a third gasket substrate 350 arranged below the second gasket substrate 250 and constituting the fourth layer from the top, i.e., the bottom layer, and a fourth gasket substrate 450 arranged between the first gasket substrate 150 and the second gasket substrate 250 and constituting the second layer from the top. Each of the gasket substrates 150, 250, 350, 450 is made of metal, for example, SUS material.

[0032] The first gasket substrate 150, the third gasket substrate 350, and the fourth gasket substrate 450 have substantially the same thickness, that is, the same vertical dimension. On the other hand, the second gasket substrate 250 has a smaller thickness than the other gasket substrates 150, 450, and 350.

[0033] The gasket substrates 150, 250, 350, 450 have substantially the same outer shape in plan view. The outer shape of each of the gasket substrates 150, 250, 350, 450 in plan view is substantially the same as the upper surface 21 of the cylinder block 20, and a recess 59 that is recessed rearward in correspondence with the chain accommodating portion 39 is formed in the center portion in the left-right direction of the front edge of each of the gasket substrates 150, 250, 350, 450.

[0034] On the other hand, the front-to-rear dimension of each of the gasket substrates 150, 250, 350, 450, i.e., the front-to-rear length of the head gasket 50, is set to a dimension slightly smaller than the front-to-rear length of the upper surface 21 of the cylinder block 20. As a result, when the cylinder block 20 and the cylinder head 10 are fastened together and the chain cover 30 is fastened to the cylinder block 20 and the cylinder head 10, as shown in Figure 1 etc., a gap X2 is defined between the front end 51 of the head gasket 50 and the rear end surface 32 of the chain cover 30.

[0035] If the gap X2 is open, lubricating oil or the like will leak through the gap X2 from inside the chain accommodating portion 39 or from between the cylinder block 20 and the cylinder head 10 to the outside of the engine 1. For this reason, the gap X2 is sealed with a liquid sealant S when the engine 1 is assembled. The liquid sealant S is a sealant having fluidity, and for example, one containing silicon is used.

[0036] First gasket substrate 150, second gasket substrate 250 and fourth gasket substrate 450 each have a bead formed thereon that protrudes upward or downward.

[0037] A first bead 151 is formed on the front end of the first gasket substrate 150. The first bead 151 extends along a bead line L1. The bead line L1 is a line that extends approximately parallel to the inner peripheral edge of the recess 59 (chain accommodating portion 39) at a position spaced from the inner peripheral edge of the recess 59 to the radially outer side of the recess 59 in a plan view.

[0038] Specifically, the bead line L1 is composed of a right line L11 extending rearward from the front end of the right portion of the first gasket substrate 150, a left line L12 extending rearward from the front end of the left portion of the first gasket substrate 52, and a center line L13 extending in the left-right direction between the rear ends of the right line L11 and the left line L12. The first bead 151 is composed of a right bead 151B extending rearward from the front end of the right portion of the first gasket substrate 150 along the right line L11, a left bead 152B extending rearward from the front end of the left portion of the first gasket substrate 150 along the left line L12, and a center bead 153B extending in the left-right direction between the rear ends of the right bead 151B and the left bead 152B along the center line L13.

[0039] In this embodiment, the first bead 151 is inclined so that the outer position in the radial direction of the recess 59 (chain accommodating portion 39) is located lower. That is, in this embodiment, the front end portion of the first gasket substrate 150 is bent so that the outer portion in the radial direction (radial direction of the recess 59 and the chain accommodating portion 39) is located lower than the inner portion and is inclined downward toward the outer side in the radial direction, thereby forming the first bead 151. As a result, the front end portion of the first bead 151 is formed with two ridgelines 152, 153 that run along the bead line L1 and extend forward, that is, toward the rear end surface 32 of the chain cover 30.

[0040] A third bead 351 is formed at the front end of the third gasket substrate 350. The third bead 351 extends along the first bead 151 and the bead line L1 in a plan view, and faces the first bead 151 in the up-down direction. That is, like the first bead 151, the third bead 351 also has a portion extending rearward from the front end of the right part of the third gasket substrate 350, a portion extending rearward from the front end of the left part of the third gasket substrate 350, and a portion extending left-right along the center line L13. In addition, two ridgelines 352, 353 are formed at the front end of the third bead 351 along the bead line L1 in a plan view, which extend forward, that is, toward the rear end surface 32 of the chain cover 30. The width dimension of the third bead 351, i.e., the distance between the two ridges 352, 353, is approximately the same as the width dimension of the first bead 151, i.e., the distance between the two ridges 152, 153. The third bead 351 has a structure similar to that of the first bead 151, and is inclined so that the outer positions in the radial direction (the radial direction of the recess 59 and the chain accommodating portion 39) are positioned lower.

[0041] A fourth bead 451 is formed at the front end of the fourth gasket substrate 450. The fourth bead 451 extends along the first bead 151, the third bead 351, and the bead line L1 in a plan view, and faces the first bead 151 and the third bead 351 in the up-down direction. That is, like the first bead 151 and the third bead 351, the fourth bead 451 also has a portion extending rearward from the front end of the right part of the fourth gasket substrate 450, a portion extending rearward from the front end of the left part of the fourth gasket substrate 450, and a portion extending left-right along the center line L13. In addition, two ridgelines 452, 453 are formed at the front end of the fourth bead 451 along the bead line L1 in a plan view, which extend forward, that is, toward the rear end surface 32 of the chain cover 30. The width dimension of the fourth bead 451, i.e., the distance between the two ridgelines 452, 453, is approximately the same as the width dimension of the first bead 151 and the third bead 351, i.e., the distance between the two ridgelines 152, 153 and the distance between the two ridgelines 352, 353. On the other hand, the fourth bead 451 has a structure symmetrical in the up-down direction to the first bead 151, and is inclined so that the outer positions in the radial direction (the radial direction of the recess 59 and the chain accommodating portion 39) are positioned higher.

[0042] Here, the first gasket substrate 150 corresponds to the "first substrate" of the present invention, the second gasket substrate 250 corresponds to the "second substrate", the third gasket substrate 350 corresponds to the "third substrate", and the fourth gasket substrate 450 corresponds to the "fourth substrate". Also, the first bead 151 and the third bead 351 each correspond to the "protrusion" of the present invention.

[0043] In addition to the first bead 151, the third bead 351 and the fourth bead 451, beads 58 protruding upward or downward are provided on the first gasket substrate 150, the third gasket substrate 350 and the fourth gasket substrate 450. For example, each of the gasket substrates 150, 350 and 450 has a bead along the periphery of each cylinder hole 53, or a bead extending along the outer periphery of each of the gasket substrates 150, 350 and 450.

[0044] Next, a detailed configuration will be described for both the left and right ends 50R, 50L of the front end of the head gasket 50. The right end 50R and the left end 50L of the front end of the head gasket 50 are generally symmetrical, and the following description will be limited to the configuration of the right end 50R of the front end of the head gasket 50.

[0045] At the right end 50R of the front end of the second gasket substrate 250, the third gasket substrate 350 and the fourth gasket substrate 450, overlapping through holes 254, 354, 454 are formed in the vicinity of the first bead 151, the third bead 351 and the fourth bead 451 in a plan view, respectively, which penetrate the front and back of each substrate in the thickness direction. In this embodiment, each through hole is a circular hole.

[0046] Specifically, a second through hole 254 penetrating the front and back of the second gasket substrate 250 is formed at a position near the first bead 151, the third bead 351, and the fourth bead 451 in a plan view at the right end of the front end of the second gasket substrate 250. A third through hole 354 penetrating the front and back of the third gasket substrate 350 is formed near the third bead 351 at the right end of the front end of the third gasket substrate 350. A fourth through hole 454 penetrating the front and back of the fourth gasket substrate 450 is formed near the fourth bead 451 at the right end of the front end of the fourth gasket substrate 450. The hole diameter of the fourth through hole 454 is set to a dimension smaller than the hole diameter of the second through hole 254, and the hole diameter of the second through hole 254 is set to a dimension smaller than the hole diameter of the third through hole 354.

[0047] In this embodiment, the second through hole 254, the third through hole 354 and the fourth through hole 454 are provided on the left side of the first bead 151, the third bead 351 and the fourth bead 451, respectively, that is, on the side closer to the recess 59 and the chain accommodating portion 39 and radially inward of these.

[0048] Here, the vicinity of the bead in this specification means a range in which the shortest distance from the bead is less than half the diameter of the third through hole 354, which has the largest diameter, that is, less than the radius, and each through hole 254, 354, 454 is formed at a position where the distance between each right end and the first bead 151, the third bead 351, and the fourth bead 451 is less than the radius of the third through hole 354 in a plan view. In this embodiment, the third through hole 354 is formed at a position where the distance between its right end and the third bead 351 is about 1 / 5 of the radius of the third through hole 354. For example, the distance between the right end of the third through hole 354 and the third bead 351 is set to about 1 mm. In addition, this distance is about half the width dimension (dimension in the left-right direction) of the third bead 351. Further, the second through hole 254 is formed at a position where the distance between its right end and the first bead 151, the third bead 351, and the fourth bead 451 is about 2 / 5 of the radius of the third through hole 354 in a plan view. The fourth through hole 454 is formed at a position where the distance between its right end and the fourth bead 451 is about 4 / 5 of the radius of the third through hole 354.

[0049] In this embodiment, each of the through holes 254, 354, 454 is provided at a position where the distance between its front end and the front edge of each of the gasket substrates 250, 350, 450 is equal to or less than the hole diameter (diameter) of the third through hole 354. For example, the distance between the front end of the third through hole 354 and the front edge of each of the gasket substrates 250, 350, 450 is set to about 3 mm.

[0050] In this embodiment, the second through hole 254, the third through hole 354, and the fourth through hole 454 are formed such that, in a plan view, the second through hole 254 is located inside the third through hole 354, and the fourth through hole 454 is located inside the second through hole 254. Furthermore, the centers of the second through hole 254, the third through hole 354, and the fourth through hole 454 coincide with each other in a plan view, and these centers are located on the same line L20 extending in the up-down direction.

[0051] With the above configuration, in this embodiment, when viewed from below, the underside 255 of the second gasket substrate 250 protrudes radially inward from the periphery of the third through hole 354 around the entire circumference, and the underside 255 of the fourth gasket substrate 450 protrudes radially inward from the periphery of the second through hole 254 around the entire circumference.

[0052] The second gasket substrate 250 is provided with a guide portion 256 that is bent downward and toward the inside in the radial direction of the second through hole 254 on the periphery of the second through hole 254. The guide portion 256 is provided around the entire circumference of the second through hole 254. In this embodiment, the guide portion 256 is formed so that its tip enters the upper part of the third through hole 354, as shown in FIG.

[0053] As described above, the second gasket substrate 250, the third gasket substrate 350, and the fourth gasket substrate 450 among the four gasket substrates 150, 250, 350, and 450 have through holes 254, 354, and 454 formed near the first bead 151, the third bead 351, and the fourth bead 451. On the other hand, no holes are formed in the first gasket substrate 150 at positions facing these through holes 254, 354, and 454, and the fourth through hole 454 is blocked by the first gasket substrate 150 when viewed from above. In other words, the first gasket substrate 150 has a shape that blocks each of the through holes 254, 354, and 454 from above when viewed from above.

[0054] As described above, the left and right ends 50R, 50L of the front end of the head gasket 50 are generally symmetrical, and the second gasket substrate 250, the third gasket substrate 350 and the fourth gasket substrate 450 have through holes 259, 359, 459 penetrating the front and back of the first bead 151, the third bead 351 and the fourth bead 451 on the right side of the first bead 151, the third bead 351 and the fourth bead 451 and near the beads 151, 351, 451, respectively, similar to the right through hole 254, 354, 454 described above. Also, a guide portion (not shown) is provided on the periphery of the left through hole 259 of the second gasket substrate 250, bending downward and toward the inside in the radial direction of the through hole 259.

[0055] (Engine assembly procedure) The procedure for assembling the engine 1 configured as above will be described. Figures 7 and 8 are diagrams that show the state when the engine is assembled. Figures 7(a) to (d) are schematic cross-sectional views taken along line VII-VII in Figure 5, with time passing in the order of Figures 7(a), (b), (c), and (d). Figures 8(a) to (c) are diagrams that correspond to Figure 6, with time passing in the order of Figures 8(a), (b), and (c).

[0056] 7(a) and 8(a), in a state in which liquid sealant S is applied to the front end portion of the upper surface 21 of the cylinder block 20, the head gasket 50 is placed on the upper surface 21 of the cylinder block 20. In addition, liquid sealant S is applied to the upper surface of the head gasket 50 after placement.

[0057] Next, as shown in FIG. 7(b) and FIG. 8(b), the cylinder head 10 is placed on the head gasket 50 from above.

[0058] Next, as shown by the arrow Y10 in FIG. 7(c) and FIG. 8(c), the cylinder head 10 is pressed downward, that is, toward the cylinder block 20, and these are fastened together with bolts or the like. At this time, as shown in FIG. 7(c), a part of the liquid sealant S is pushed up or down toward the front of the head gasket 50, covering the head gasket 50 from the front. A part of the liquid sealant S also spreads along the upper surface 21 of the cylinder block 20 and the lower surface 11 of the cylinder head 10. A part of the liquid sealant S also flows into the inside of the third through hole 354, the second through hole 254, and the fourth through hole 454. A part of the liquid sealant S that has flowed into these through holes 254, 354, and 454 enters the gaps between the gasket substrates 150, 250, 350, and 450 and spreads into the gaps.

[0059] Next, as shown in Figure 7(d), the rear end surface 32 of the chain cover 30 is abutted against the front end surface 2A of the engine body 2 (the front end surface 12 of the cylinder head 10 and the front end surface 22 of the cylinder block 20), and the chain cover 30 is fastened to the engine body 2 with bolts or the like.

[0060] In this manner, the cylinder head 10, the cylinder block 20, and the chain cover 30 are connected to one another. Then, the liquid sealant S disposed in front of the head gasket 50 closes the gap X2 between the front end 51 of the head gasket 50 and the rear end face 32 of the chain cover 30, thereby sealing the gap X2.

[0061] (effect, etc.) According to the head gasket 50 according to the embodiment configured as described above, the gap X2 between the front end 51 of the head gasket 50 and the rear end surface 32 of the chain cover 30 can be reliably sealed. FIG. 9 is a side view showing the head gasket 50 after the engine body 2 is assembled, that is, in a state where the cylinder block 20 and the cylinder head 10 are fastened, and shows the cylinder head 10, the cylinder block 20 and the right end 50R of the front end of the head gasket 50 from the front. In FIG. 9, the liquid sealant S is omitted. FIG. 10 is a comparative example, and corresponds to FIG. 7(c) when a head gasket in which the second through hole 254, the third through hole 354 and the fourth through hole 454 are omitted from the head gasket 50 of the embodiment is used, and shows the state when the engine 1 is assembled. FIG. 11 is a schematic view showing the state when the engine 1 is assembled when the head gasket 50 of the embodiment is used, and corresponds to FIG. 7(c). Note that Figures 10 and 11 show the state when the cylinder head 10 is fastened to the cylinder block 20 but before the chain cover 30 is fastened to the engine body 2, and in Figures 10 and 11 the chain cover 30 is shown by virtual lines (dash lines).

[0062] As described above, when the cylinder block 20 and the cylinder head 10 are fastened, the head gasket 50 is pressed against the upper surface 21 of the cylinder block 20 by the lower surface 11 of the cylinder head 10. This pressing force causes the beads, including the first bead 151, the third bead 351, and the fourth bead 451, to elastically deform and generate a resilient force. As a result, the beaded portions of each gasket substrate 150, 250, 350, 450 are in close contact with the adjacent other gasket substrates, the lower surface 11 of the cylinder head 10, or the upper surface 21 of the cylinder block 20, and the gap X1 between the cylinder block 20 and the cylinder head 10 is closed. However, as shown in FIG. 9, the peripheral portions of the beads of each gasket substrate 150, 250, 350, 450 are not completely closed. Therefore, around the first bead 151, the third bead 351 and the fourth bead 451, a passage X3 is defined by each of the gasket substrates 150, 250, 350, 450, extending along the bead line L1 and opening at the front end face of the head gasket 50.

[0063] In the head gasket according to the comparative example, the second through hole 254, the third through hole, and the fourth through hole 454 are not formed, and therefore, as shown in FIG. 10, the liquid sealant S is not introduced inside the head gasket, that is, between the gasket substrates 150, 250, 350, and 450. Therefore, the inner space of the passage X3 extending along the bead line L1 is hollow over almost its entire length. As a result, when the cylinder head 10 is pressed toward the cylinder block 20 and a downward pressing force is applied to the head gasket, most of the air in the passage X3 and the air in the gaps between the gasket substrates 150, 250, 350, and 450 communicating with the passage X3 is pushed forward, that is, toward the chain cover 30, through the passage X3 from the opening at the front end of the passage X3, as shown by the arrow Y11 in FIG. 10. As a result, in the comparative example, a portion of the liquid sealant S arranged in front of the head gasket, i.e., a portion of the liquid sealant S arranged in the gap X2, is blown away, and a gap X10 is formed inside the liquid sealant S. Therefore, in the head gasket according to the comparative example, there is a risk that lubricating oil will leak from the chain accommodating portion 39 side to the outside of the engine 1 through the gap X10. In other words, there is a risk that the gap X2 will not be properly sealed.

[0064] In contrast, in the head gasket 50 according to the above embodiment, the liquid sealant S is introduced into the gaps between the gasket substrates 150, 250, 350, 450 via the second through hole 254, the third through hole 354 and the fourth through hole 454, as described above.

[0065] Specifically, the second through hole 254, the third through hole 354, and the fourth through hole 454 are formed at positions overlapping each other. That is, these through holes 254, 354, and 454 communicate with each other. Therefore, as the head gasket 50 is pressed toward the cylinder block 20, a part of the liquid sealant arranged between the head gasket 50 and the cylinder block 20 moves through the third through hole 354 to the upper side of the third gasket substrate 350, moves through the second through hole 254 to the upper side of the second gasket substrate 250, and moves through the fourth through hole 454 to the upper side of the fourth gasket substrate 450. In particular, in the above embodiment, the second through hole 254 is located inside the third through hole 354, and the fourth through hole 454 is located inside the second through hole 254 in a plan view. Therefore, the liquid sealant S can be reliably moved above each of the gasket substrates 250, 350, 450 through each of the through holes 254, 354, 454.

[0066] In the above embodiment, the third through hole 354, the second through hole 254, and the fourth through hole 454 are set so that their hole diameters become smaller in this order. Accordingly, in the head gasket 50 according to the above embodiment, the lower surface 255 of the second gasket substrate 250 protrudes from the periphery of the third through hole 354 to the radially inner side of the third through hole 354 when viewed from below, and the lower surface 455 of the fourth gasket substrate 450 protrudes from the periphery of the second through hole 254 to the radially inner side of the second through hole 254. Therefore, a part of the liquid sealant S that has passed through the third through hole 354 moves along the lower surface 255 of the second gasket substrate 250 as shown by the arrow Y1 in FIG. 6, and is introduced between the second gasket substrate 250 and the third gasket substrate 350. 6, a portion of the liquid sealant S that has passed through the second through hole 254 moves along the lower surface 455 of the fourth gasket substrate 450 and is introduced between the fourth gasket substrate 450 and the second gasket substrate 250. In the above embodiment, the first gasket substrate 150 blocks the fourth through hole 454 from above. Therefore, a portion of the liquid sealant S that has passed through the fourth through hole 454 is restricted from moving further upward by the first gasket substrate 150, and is introduced between the first gasket substrate 150 and the fourth gasket substrate 450.

[0067] Here, each of the through holes 254, 354, 454 is provided near the first bead 151, the fourth bead 451, and the third bead 351, that is, near the bead line L1. This allows the liquid sealant S to be introduced between the gasket substrates 150, 250, 350, 450 and in the vicinity of the bead line L1.

[0068] As a result, in the above embodiment, as shown in FIG. 11, the middle part of the passage X3 is blocked by the liquid sealant S. When the middle part of the passage X3 is blocked by the liquid sealant S, as shown by the arrow Y21 in FIG. 11, the air passing through the passage X3 is prevented from moving toward the opening at its front end, and the amount of air pushed forward from the opening of the passage X3 is reduced. Therefore, according to the head gasket 50 according to the above embodiment, the liquid sealant S arranged in the gap X2 can be prevented from being blown away by the air in the passage X3, and the formation of a gap can be prevented in the liquid sealant S arranged in the gap X2 between the front end 51 of the head gasket 50 and the rear end surface 32 of the chain cover 30, thereby improving the sealing performance of the gap X2. In addition, the air moving forward through the passage X3 pushes the liquid sealant S introduced into the middle part of the passage X3 forward, that is, toward the gap X2. Therefore, according to the head gasket 50 of the above embodiment, the amount of liquid sealant S that is filled into the gap X2 as the liquid sealant S is extruded is ensured, thereby improving the sealing performance of the gap X2.

[0069] In particular, in the above embodiment, as described above, the centers of the second through hole 254, the third through hole 354, and the fourth through hole 454 are aligned, the lower surface 255 of the second gasket substrate 250 protrudes from the periphery of the third through hole 354 to the radially inward side of the third through hole 354 over the entire circumference, and the lower surface 255 of the fourth gasket substrate 450 protrudes from the periphery of the second through hole 254 to the radially inward side of the second through hole 254 over the entire circumference. Therefore, the liquid sealant S can be directed toward the radially outward side of each through hole 254, 354, 454 over the entire circumference of each through hole 254, 354, 454, and the liquid sealant S can be reliably introduced into the gap between each gasket substrate 150, 250, 350, 450. Therefore, the passage X3 can be reliably blocked, and the sealing property of the gap X2 can be reliably improved.

[0070] In the above embodiment, a guide portion 256 is provided around the periphery of the second through hole 254, which is bent downward and toward the inside in the radial direction of the second through hole 254. Therefore, the liquid sealant S can be guided along the guide portion 256 to the gap between the second gasket substrate 250 and the third gasket substrate 350, and a larger amount of liquid sealant S can be introduced into the gap therebetween, and further into the passage X3 between the second gasket substrate 250 and the third gasket substrate 350. can be blocked more reliably.

[0071] In the above embodiment, each of the through holes 254, 354, 454 is formed in a position close to the front end 51 of the head gasket 50, so that the liquid sealant S is filled in a region of the passage X3 from the middle of the passage X3 to the front end 51 of the head gasket 50, as shown in Fig. 11. This makes it possible to more reliably prevent the air in the passage X3 from blowing away the liquid sealant S in the gap X2. Even if the liquid sealant S is not filled up to the vicinity of the front end of the passage X3 due to the distance between each of the through holes 254, 354, 454 and the front end 51 of the head gasket 50, if the middle part of the passage X3 is blocked by the liquid sealant S, the amount of air blowing out from the front end of the passage X3 toward the gap X2 is kept small, so that the sealing performance of the gap X2 is improved.

[0072] (Modification) In the above embodiment, the first bead 151, the third bead 351 and the fourth bead 451 are inclined along the radial direction of the recess 59 and the chain accommodating portion 39, but these beads 151, 351, 451 may protrude upward or downward, and their specific structure is not limited to the above structure.

[0073] In the above embodiment, a case was described in which each through hole 254, 354, 454 was formed at a position radially inward of each bead 151, 351, 451 and bead line L1 of the recess 59 and the chain accommodating portion 39. However, each through hole 254, 354, 454 only needs to be near each bead 151, 351, 451 and bead line L1 in a planar view, and may be provided radially outward of the recess 59 (chain accommodating portion 39).

[0074] In the above embodiment, the case where the center positions of the through holes 254, 354, 454 are the same has been described, but these center positions do not have to be the same. Also, in the above embodiment, the case where the center positions of the through holes 254, 354, 454 are the same, the second through hole 254 is located inside the third through hole 354, and the fourth through hole 154 is located inside the second through hole 254 has been described, but it is sufficient that these through holes 254, 354, 454 are provided so that at least a portion of them overlap in a plan view.

[0075] In the above embodiment, the first gasket substrate 150 has a shape that blocks each of the through holes 254, 354, 454 from above. However, the first gasket substrate 150 may have holes that face each of the through holes 254, 354, 454.

[0076] In the above embodiment, the through holes 254, 354, 454 are circular holes, but the hole shape of these through holes 254, 354, 454 does not have to be circular.

[0077] In the above embodiment, the guide portion 256 is provided on the periphery of the second through hole 254, but this guide portion 256 can be omitted.

[0078] In the above embodiment, a case was described in which beads are formed on each of the first gasket substrate 150, the third gasket substrate 350, and the fourth gasket substrate 450, but the beads may be formed on any of the first gasket substrate 150, the second gasket substrate 250, and the third gasket substrate 350.

[0079] In the above embodiment, the thickness dimension of the second gasket substrate 250 is thinner than the thickness dimensions of the other gasket substrates 150, 350, and 450, and the second gasket substrate 250 does not have beads. However, the thickness of the second gasket substrate 250 may be the same as that of the other gasket substrates.

[0080] In the above embodiment, the head gasket 50 is a four-layer type gasket, but the head gasket may be a multi-layer type gasket having three or more gasket substrates, and the number of layers may be five or more.

[0081] The head gasket may also be configured as shown in Fig. 12. Specifically, in the head gasket 550 shown in Fig. 12, the fourth gasket substrate 450 is omitted, and the head gasket 550 is a three-layer type gasket. In the example of Fig. 12, similarly to the above embodiment, a guide portion 556 is formed on the periphery of the second through-hole 554 of the second gasket substrate 551, while the thickness dimension of the second gasket substrate 551 is set to be equal to the thickness dimensions of the first gasket substrate 150 and the third gasket substrate 350, and a bead 552 is formed on the second gasket substrate 551.

[0082] In the above embodiment, the engine body 2 is an in-line 6-cylinder engine, but the number of cylinders and the arrangement pattern of the cylinders of the engine body 2 are not limited to this. [Explanation of symbols]

[0083] 1 Engine 2 Engine body 10. Cylinder head 20 Cylinder block 30 Chain cover 32 Rear end surface (mating surface) 50 Head gasket 150 First gasket substrate (first substrate) 151 First bead (projection) 152 Ridgeline 153 Ridgeline 250 Second gasket board (second board) 254 Second Through Hole (Through Hole) 256 Information Department 350 3rd gasket board (3rd board) 351 3rd bead (projection) 352 Ridgeline 353 Ridgeline 354 3rd Through Hole (Through Hole) 450 4th gasket board (4th board) 451 4th bead (protrusion) 452 Ridgeline 453 Ridgeline 454 4th Through Hole (Through Hole)

Claims

1. A head gasket for an engine including a cylinder block and a cylinder head overlapping in a cylinder axial direction, and a cover member having mating surfaces that come into contact with end faces of the cylinder block and the cylinder head in a direction perpendicular to the cylinder axial direction, and in which lubricating oil is used inside the cover member, the head gasket being interposed between the cylinder block and the cylinder head, a first substrate having a thickness direction in the cylinder axial direction; a second substrate disposed on one side of the first substrate in the cylinder axial direction; a third substrate disposed on one side of the second substrate in the cylinder axial direction, At least one of the first to third substrates includes a protrusion that protrudes to one side or the other side in the cylinder axial direction and has a ridge line that extends toward the mating surface of the cover member as viewed in the cylinder axial direction, the second substrate and the third substrate each have a through hole formed at a position near the protrusion as viewed in the cylinder axial direction, the through hole passing through a front and rear surface of each substrate and overlapping with each other as viewed in the cylinder axial direction, A head gasket, wherein a diameter of the through hole of the second substrate is smaller than a diameter of the through hole of the third substrate.

2. 2. The head gasket according to claim 1, A head gasket, characterized in that the through hole of the second base plate is positioned inside the through hole of the third base plate when viewed in the cylinder axial direction.

3. The head gasket according to claim 2, A head gasket, characterized in that the through hole of the second substrate is positioned so that its center coincides with the center of the through hole of the third substrate.

4. The head gasket according to claim 2, a guide portion bent radially inwardly toward one side in the cylinder axial direction on a periphery of the through hole, the guide portion being bent radially inwardly toward one side in the cylinder axial direction.

5. 2. The head gasket according to claim 1, a first base plate having a shape that closes the through hole of the second base plate from the other side in the cylinder axial direction,

6. The head gasket according to any one of claims 1 to 5, Further comprising a fourth substrate disposed between the first substrate and the second substrate, A head gasket comprising: a fourth substrate having a through hole that passes through a front and a back surface of the fourth substrate and overlaps with the through hole of the second substrate when viewed in the cylinder axial direction.

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