Patent Application
20120319361
The present invention relates to a method for manufacturing a metal gasket for a cylinder head that is interposed between a cylinder block and a cylinder head in an internal combustion engine to seal a joint surface between the cylinder block and the cylinder head, as well as such a metal gasket for a cylinder head.
In internal combustion engines, a metal gasket is interposed on a joint surface between a cylinder block and a cylinder head, and the metal gasket is fastened by head bolts for sealing of fuel gas, coolant, and lubricating oil. In particular, sealing of cylinder holes is crucial, because insufficient sealing of the cylinder holes can cause unwanted leakage flows of the fuel gas between adjacent cylinders, which might lead to a decrease in engine power. The leaked fuel gas can also flow into coolant holes circumferentially formed around the cylinder holes, resulting in malfunctions such as overheat, or in the worst case, engine seizure.
In an attempt to avoid the above phenomena, Patent Literatures 1, 2 disclose a metal gasket including a resilient metal layer in which annular beads are provided around the cylinder holes, for example. The metal gasket for a cylinder head disclosed in Patent Literatures 1 and 2 includes: a metal substrate made of a metal layer and having cylinder holes formed in correspondence with cylinder bores in a cylinder block of an internal combustion engine, annular beads formed around peripheries of the cylinder holes, coolant holes formed along peripheries of the annular beads in correspondence with a cooling water jacket of the cylinder block and coolant holes of the cylinder head; and an annular step adjustment plate provided to face the annular beads of the substrate. The step adjustment plate is provided with claw-shape portions, and these claw-shape portions are inserted into fastening holes formed in the substrate and folded over to one side so that the step adjustment plate is integrated with the substrate. Due to a thickness difference created by the step adjustment plate provided between the annular beads and outer beads, surface pressure is appropriately adjusted.
However, one problem with the technologies disclosed in Patent Literatures 1 and 2 is that, as shown in
In view of the above problems, the present inventors conducted studies and they revealed that, as shown in
Patent Literature 1: Japanese Patent Application Publication No. 2002-286141
Patent Literature 2: Japanese Patent Application Publication No. H10-281289
Nevertheless, it has been found out that, when a material for deep drawing (e.g. SUS304 or SUS430) is used in the above step adjustment plate 3, due to a low tensile strength and a high elongation of the material, the step adjustment plate 3 is weakened in resistance to expansion and contraction of a cylinder head and a cylinder block during a cold temperature operation of an engine, and can be deformed in an exhaust direction, an intake direction, and other directions, as shown in
One of the measures to cope with the deformation of the step adjustment plate 3 is to increase a thickness of the plate so as to enhance the strength. However, as a result of this method, a strain is increased in the cylinder head and the cylinder block, thereby causing other problems such as increased oil consumption and abnormal noise heard from various components, although this method improves deformation resistance, along with sealing performance against the fuel gas. From the requirement of compatibility between the seal performance of the gasket and the above problems due to the distortion of the cylinder head and the cylinder block, an applicable thickness of a metal foil constituting the step adjustment plate 3 should generally be limited to a range from 0.05 mm to 0.15 mm, and this range restriction in thickness is one of the foremost causes of the deformation. In particular, when an extremely thin metal foil having a thickness of 0.05 mm is utilized to define a slight step, such a deformation must be addressed, which emphasizes the demand for measures to prevent the deformation of the step adjustment plate 3.
Since the aforementioned anti-deformation method of increasing the thickness of the metal foil cannot be adopted to prevent the deformation of the step adjustment plate 3 in view of the above problems, a resilient material such as a stainless steel strip for a spring (e.g. SUS301-1/2H, SUS301-3/4H, and SUS304-3/4H) was used as the metal foil constituting the step adjustment plate 3, and thus formed step adjustment plate 3 was fastened with the substrate 2. However, in this case, the following additional problems emerged.
More particularly, in the circular prepared hole 3c provided in the protruding piece 3b of the step adjustment plate 3, the tubular portion 3d having the circular cross section was formed with use of the die including the cylindrical punch, and the tubular portion 3d was inserted through the fastening hole 2h of the substrate 2. Subsequently, the tubular portion 3d was folded over to an outside of the substrate 2 (i.e. bending process) and flattened out. In this case, as shown in
In light of the above, an objective of the present invention is to provide a method for manufacturing a metal gasket for a cylinder head that is capable of establishing a firmly engaged state between the substrate and the step adjustment plate without suffering the aforementioned occurrence of cracks and deficiency due to loss. Another objective of the present invention is to provide a metal gasket for a cylinder head that is capable of improving the engaging force between the substrate and the step adjustment plate while obtaining an appropriate contact pressure balance by providing the thickness difference between the annular beads and the outer beads by means of a slight step utilizing the metal foil.
Thus, the objective of the present invention is to advantageously solve the aforementioned problems, and the present invention provides a method for manufacturing a metal gasket for a cylinder head according to the present invention, the metal gasket including: at least one substrate made of a resilient metal layer and having cylinder holes formed in correspondence with cylinder bores in a cylinder block to be mounted with the cylinder head in an engine, annular beads each formed around a different one of the cylinder holes, coolant holes formed around an outer periphery of each of the annular beads in correspondence with coolant holes of the cylinder head and a cooling water jacket or coolant holes of the cylinder block, and an outer bead formed and positioned to entirely enclose the annular beads and the coolant holes; and a step adjustment plate made of a metal layer and having a plurality of annular portions each disposed over and around an outer periphery of a different one of the cylinder holes of the substrate; and a plurality of protruding pieces formed integrally with each annular portion at a peripheral edge thereof, each protruding piece of the step adjustment plate engaged through the substrate, the method comprising the steps of: forming a prepared hole in each protruding piece of the step adjustment plate; forming a tubular portion including a plurality of projecting segments by inserting a die including a polygonal pyramidal punch into the prepared hole so as to bend up a peripheral portion around the prepared hole while cutting the peripheral portion into segments; forming in the substrate an fastening hole in correspondence with a position of the tubular portion formed in the step adjustment plate; and engaging the protruding piece through the substrate by inserting the tubular portion of the step adjustment plate through the corresponding fastening hole formed in the substrate, and subsequently folding the plurality of projecting segments of the tubular portion over to an outside of the substrate and flattening out the projecting segments. Note that the “polygonal pyramidal shape” herein encompasses the meaning of a truncated polygonal pyramidal shape in which a tip of the punch is flattened or rounded.
According to the above method for manufacturing a metal gasket for a cylinder head, since the die including the polygonal pyramidal punch is used for bending up the peripheral portion around the prepared hole formed in the protruding piece of the step adjustment plate into the tubular shape, a sidewall of the bent-up tubular portion is cut into a plurality of projecting segments having a substantially uniform size by angled edges (joining adjacent conical surfaces and serving as blades) of the punch. Accordingly, by folding the plurality of projecting segments over to the outside and flattening out the projecting segments, a state where the flattened projecting segments are uniformly distributed in a petaloid shape is achieved, whereby the firmly engaged state is established between the substrate and the step adjustment plate. As a result, even when fretting (relative surface motion in a direction parallel to deck surfaces of the cylinder head and the cylinder block) occurs in the deck surfaces in the presence of repeated heating and cooling of the cylinder head and the cylinder block, disengagement of the step adjustment plate from the substrate is prevented. The present invention is particularly advantageous when the resilient material (e.g. stainless steel strip for a spring) is used as a material for the step adjustment plate.
In the above method for manufacturing a metal gasket for a cylinder head, it is preferable that the polygonal pyramidal punch of the die comprises a pentagonal pyramidal punch, and that the plurality of projecting segments of the tubular portion comprises five projecting segments. With the above structure, the plurality of projecting segments of the tubular portion which have been flattened in the petaloid shape are each assured to have a sufficient size to establish the firmly engaged state with respect to the substrate.
Furthermore, in the above method for manufacturing a metal gasket for a cylinder head, it is preferable the punch of the die has a cone angle θ ranging from 20 to 40 degrees. Note that the “cone angle of the punch” herein refers to an angle that the angled edges, which are located in boundaries between adjacent conical surfaces of the polygonal pyramidal punch and serve as blades, form with respect to an axis line of the punch. If the cone angle of the punch is greater than 40 degrees, some parts of the tubular portion cannot be cut into a plurality of segments simultaneously with formation thereof, and discrepancy might occur in number and angle (i.e. an inclination angle of the projecting segments with respect to a plane in which the step adjustment plate extends). On the other hand, if the cone angle of the punch is less than 20 degrees, a press stroke is lengthened, and the tip of the die is thinned, and therefore the die is exposed to increased risk of break-off at the tip during process, although this case presents no problems in terms of forming the tubular portion.
Moreover, in the above method for manufacturing a metal gasket for a cylinder head, it is preferable that a shape of the prepared hole formed in the step adjustment plate is circular. Although it is no problem to form the prepared hole in a polygonal shape in concordance with the shape of the punch, such a polygonal prepared hole in combination with the similarly polygonal punch adversely affects workability in terms of securing positional precision and angular positional precision of the hole and the punch. If the prepared hole is formed in a circular shape, the need for positional alignment and angular positional alignment is omitted, and therefore a favorable quality is maintained while workability is improved.
Moreover, in the above method for manufacturing a metal gasket for a cylinder head, it is preferable that a shape of the fastening hole formed in the substrate is circular. Although it is no problem to form the fastening hole in a polygonal shape in concordance with the cross section of the tubular portion, such a polygonal fastening hole, in combination with the similarly polygonal tubular portion to be inserted into the fastening hole, adversely affects workability in terms of securing the positional precision and the angular positional precision of the fastening hole and the tubular portion. Furthermore, when the fastening hole of the substrate is formed in the polygonal shape, the folding die used for folding the projecting segments of the tubular portion over to the outside and flattening the projecting segments out needs to be formed in the polygonal shape, and workability is adversely affected in terms of securing the positional precision and the angular positional precision of the folding die and the projecting segments. On the other hand, when the fastening hole is formed in the circular shape, the need for the positional alignment and the angular positional alignment is omitted both between the fastening hole and the tubular portion and between the folding die and the projecting segments. Consequently, the favorable quality is maintained while workability is improved.
The present invention also provides a metal gasket for a cylinder head, the metal gasket including: at least one substrate made of a resilient metal layer and having cylinder holes formed in correspondence with cylinder bores in a cylinder block to be mounted with the cylinder head in an engine, annular beads each formed around a different one of the cylinder holes, coolant holes formed around an outer periphery of each of the annular beads in correspondence with coolant holes of the cylinder head and a cooling water jacket or coolant holes of the cylinder block, and an outer bead formed and positioned to entirely enclose the annular beads and the coolant holes; and a step adjustment plate made of a metal layer and having a plurality of annular portions each disposed over and around an outer periphery of a different one of the cylinder holes of the substrate; and a plurality of protruding pieces formed integrally with each annular portion at a peripheral edge thereof, each protruding piece of the step adjustment plate engaged through the substrate, wherein a prepared hole is formed in each protruding piece of the step adjustment plate, and a tubular portion including a plurality of projecting segments is formed by inserting a die including a polygonal pyramidal punch into the prepared hole so as to bend up a peripheral portion around the prepared hole while cutting the peripheral portion into segments, and an fastening hole is formed in the substrate in correspondence with a position of the tubular portion formed in the step adjustment plate, and the protruding piece is engaged through the substrate by inserting the tubular portion of the step adjustment plate through the corresponding fastening hole formed in the substrate, and subsequently folding the plurality of projecting segments of the tubular portion over to an outside of the substrate and flattening out the projecting segments.
In the above metal gasket for a cylinder head according to the present invention, it is preferable that an outer edge surface of each annular portion of the step adjustment plate located closer to the coolant holes is situated outward from an outer edge forming a bead profile of the annular beads. It is also preferable that the outer edge surface is inward from an inner edge of the outer bead formed and positioned to entirely enclose the cooling water jacket or the coolant holes of the cylinder block and the coolant holes.
According to the present invention, a method for manufacturing a metal gasket for a cylinder head that is capable of establishing a firmly engaged state between a substrate and a step adjustment plate, as well as a metal gasket for a cylinder head that is capable of improving an engaging force between the substrate and the step adjustment plate, is provided.
The following describes an embodiment according to the present invention in detail with reference to the drawings.
In the present embodiment, a metal gasket 1 for a cylinder head (referred to below simply as the “metal gasket 1”) is a three-layer lamination type that includes three metal layers, inclusive of a step adjustment plate, as well as two substrates 2 as resilient metal layers made of stainless steel, stacked on each other as shown in
Outside the outer bead 2d, each substrate 2 also includes: a plurality of lubricating oil holes 2e; a plurality (eight in the drawing) of bolt holes 2f in each of which a head bolt is to be inserted for tightly fastening the cylinder head to the cylinder block; and eyelet holes 2g. The annular beads 2b of the two substrates 2 are aligned in a thickness direction of the gasket 1 and externally protruded to face opposite directions. Similarly, the outer beads 2d of the two substrates 2 are aligned in the thickness direction of the gasket 1 and externally protruded to face opposite directions.
Furthermore, as shown in
Moreover, as shown in
Note that, as
According to the metal gasket 1 of the above two embodiments, owing to the plurality of projecting segments 3d1 folded over across a corresponding fastening hole 2h and flattened out, the firmly engaged state is established between the substrate 2 and the step adjustment plate 3. As a result, even when the fretting (relative surface motion in the direction parallel to the deck surfaces) occurs in the deck surfaces in the presence of repeated heating and cooling of the cylinder head and the cylinder block, the disengagement of the step adjustment plate from the substrate is prevented.
Furthermore, according to the metal gasket 1 of the above two embodiments, as shown in
Moreover, according to the metal gasket 1 of the above two embodiments, since the fastening holes 2h for insertion of the tubular portions 3d are formed along the peripheries of the annular beads in correspondence with the coolant holes of the cylinder head, and the cooling water jacket or the coolant holes of the cylinder block, a portion of each tubular portion that are folded over to the outside and flattened out can enter a corresponding coolant or a corresponding cooling water jacket without sandwiched between the deck surface of the cylinder head and that of the cylinder block.
Consequently, the folded and flattened portion is prevented from becoming an obstacle to an increase in the surface pressure in the annular beads 2b.
Moreover, according to the metal gasket 1 of the above two embodiments, since the number of the projecting segments 3d1 formed in each protruding piece 3b is five, when flattened into the petaloid shape with a plurality of petals, the projecting segments 3d1 of the tubular portion 3d surely have a sufficient size to establish the firmly engaged state with respect to the substrate 2.
Moreover, according to the metal gasket 1 of the above two embodiments, the number of the fastening holes 2h formed in the substrate 2 for engagement of the protruding pieces 3b is set to be four or five in correspondence with each cylinder bore, the engaging force of the step adjustment plate 3 to the substrate 2 is sufficiently enhanced so that the disengagement of the step adjustment plate 3 from the substrate 2 is prevented even when the fretting occurs in the deck surfaces of the cylinder head and the cylinder block.
Next, a description is given of a method for manufacturing the metal gasket 1 according to the above embodiments.
To begin with, as shown in an enlarged manner in
Subsequently, the drawing processing is applied to the peripheral portion around the prepared hole 3c formed in each protruding piece 3b by inserting a die 4 including a polygonal pyramidal (pentagonal pyramidal in this example) punch 4a. By doing so, as shown in
Subsequently, the step adjustment plate 3 in which the tubular portion 3d has been bent up in each protruding piece 3b as described above is disposed on the lower substrate 2 shown in
Subsequently, as shown in
Then, the petaloid-shaped projecting segments 3d1 of the tubular portion 3d are flattened out with use of the die (not shown) including a punch having a flat tip, for example. As a result, as shown in
In this way, the step adjustment plate 3 engages with the lower substrate 2 via the tubular portions 3d of the protruding pieces 3b, and then, as shown in
According to the method for manufacturing the metal gasket 1, since the die 4 including the polygonal pyramidal punch 4a is used for bending up the peripheral portion around each prepared hole 3c formed in the protruding piece 3b of the step adjustment plate 3 into the tubular shape, the sidewall of the bent-up tubular portion 3d is cut into the plurality of projecting segments 3d1 having the substantially uniform size by the blades 4d (i.e. angled edges joining adjacent conical surfaces) of the punch 4a. By folding the above plurality of projecting segments 3d1 to the outside and flattening out the projecting segments 3d1, the state where the projecting segments 3d1 are flattened in the petaloid shape in a uniformly distributed manner is achieved, whereby the firmly engaged state is established between the substrate 2 and the step adjustment plate 3. As a result, even when the fretting (relative surface motion in the direction parallel to the deck surfaces) occurs in the deck surfaces in the presence of repeated heating and cooling of the cylinder head and the cylinder block, the disengagement of the step adjustment plate 3 from the substrate 2 is prevented. The present manufacturing method is particularly advantageous when the resilient material (e.g. stainless steel strip for a spring) is used as the material for the step adjustment plate 3.
In the method for manufacturing the metal gasket 1, it is preferable that the polygonal pyramidal punch 4a of the die 4 comprises a pentagonal pyramidal punch, and the plurality of projecting segments 3d1 of the tubular portion 3d comprises five projecting segments. With the above structure, the projecting segments 3d1 of the tubular portion 3d which have been flattened into the petal shape are each assured to have a sufficient size to establish the firmly engaged state with respect to the substrate 2.
Furthermore, in the above method for manufacturing a metal gasket 1, it is preferable that the punch 4a of the die 4 has a cone angle θ ranging from 20 to 40 degrees. Note that the “cone angle θ of the punch” herein refers to an angle that the angled edges, which are located in boundaries between adjacent conical surfaces of the polygonal pyramidal punch and serve as blades, form with respect to an axis line S of the punch. If the cone angle θ of the punch is greater than 40 degrees, some parts of the tubular portion 3d cannot be cut into a plurality of segments simultaneously with formation thereof, and discrepancy might occur in number and angle (i.e. an inclination angle of the projecting segments 3d1 with respect to a plane in which the step adjustment plate 3 extends). On the other hand, if the cone angle θ of the punch is less than 20 degrees, a press stroke is lengthened, and the tip of the die is thinned, and therefore the die is exposed to increased risk of break-off at the tip during the process, although this case presents no problems in terms of forming the tubular portion 3d.
Moreover, in the above method for manufacturing the metal gasket, it is preferable that a shape of the prepared hole 3c formed in the step adjustment plate 3 is circular. Although it is no problem to form the prepared hole 3c in a polygonal shape in concordance with the shape of the punch, as shown in
Moreover, in the above method for manufacturing the metal gasket, it is preferable that a shape of the fastening hole 2h formed in the substrate 2 is circular.
Although it is no problem to form the fastening hole 2h in a polygonal shape in concordance with the cross section shape of the tubular portion 3d, such a polygonal fastening hole 2h, in combination with the similarly polygonal tubular portion 3d to be inserted into the fastening hole 2h, adversely affects workability in terms of securing the positional precision and the angular positional precision of the fastening hole 2h and the tubular portion 3d. Furthermore, when the fastening hole 2h in the substrate 2 is formed in the polygonal shape, the folding die used for folding the projecting segments 3d1 of the tubular portion 3d over to the outside and flattening out the projecting segments 3d1 needs to be in the polygonal shape, and workability is adversely affected in terms of securing the positional precision and the angular positional precision of the folding die and the projecting segments 3d1. On the other hand, when the fastening hole 2h is formed in the circular shape, the need for the positional alignment and the angular positional alignment is omitted both between the fastening hole 2h and the tubular portion 3d and between the folding die and the projecting segments 3d1. Consequently, the favorable quality is maintained while workability is improved.
As shown in
The manufacturing method of Example 1 comprises, for engaging the step adjustment plate 3 with the substrate 2, the steps of: forming the pentagonal prepared hole 3c in each protruding piece 3b of the step adjustment plate 3; forming the tubular portion 3d including five projecting segments 3d1 by inserting the die 4 including the pentagonal pyramidal punch 4a into the prepared hole 3c; forming in the substrate 2 a pentagonal fastening hole 2h in correspondence with the position of the tubular portion 3d formed in the step adjustment plate 3; and inserting the tubular portion 3d of the step adjustment plate 3 through the corresponding fastening hole 2h formed in the substrate 2, and subsequently folding the projecting segments 3d1 of the tubular portion 3d to the outside and flattening out the projecting segments 3d1 with use of the pentagonal folding die.
The manufacturing method of Example 2 comprises, for engaging the step adjustment plate 3 with the substrate 2, the steps of: forming the circular prepared hole 3c in each protruding piece 3b of the step adjustment plate 3; forming the tubular portion 3d including five projecting segments 3d1 by inserting the die 4 including the pentagonal pyramidal punch 4a into the prepared hole 3c; forming in the substrate 2 a pentagonal fastening hole 2h in correspondence with the position of the tubular portion 3d formed in the step adjustment plate 3; and inserting the tubular portion 3d of the step adjustment plate 3 through the corresponding fastening hole 2h formed in the substrate 2, and subsequently folding the projecting segments 3d1 of the tubular portion 3d to the outside and flattening out the projecting segments 3d1 with use of the pentagonal folding die.
The manufacturing method of Example 3 comprises, for engaging the step adjustment plate 3 with the substrate 2, the steps of: forming the circular prepared hole 3c in each protruding piece 3b of the step adjustment plate 3; forming the tubular portion 3d including five projecting segments 3d1 by inserting the die 4 including the pentagonal pyramidal punch 4a into the prepared hole 3c; forming in the substrate 2 a circular fastening hole 2h in correspondence with the position of the tubular portion 3d formed in the step adjustment plate 3; and inserting the tubular portion 3d of the step adjustment plate 3 through the corresponding fastening hole 2h formed in the substrate 2, and subsequently folding the projecting segments 3d1 of the tubular portion 3d to the outside and flattening out the projecting segments 3d1 with use of the pentagonal folding die.
The portions around where the substrate and the step adjustment plate are engaged with each other were collected with respect to the respective gaskets manufactured according to the aforementioned three types of manufacturing methods, and the tensile tests were carried out as shown in
Accordingly, from the above test results, it was found out that the metal gasket 1 capable of improving the engaging force between the substrate 2 and the step adjustment plate 3 was manufacturable at low cost and in a stable manner as long as the manufacturing method of Example 3 is used, i.e. the tubular portion 3d is formed from the peripheral portion around the prepared hole 3c with use of the die 4 including the pentagonal pyramidal punch 4a, and that there is no need to adopt the manufacturing methods of Examples 1 and 2 which are inferior in terms of workability because of the importance of the positional precision and the angular positional precision of the hole.
Next, a description is given of work tests on the tubular portion 3d carried out by varying the cone angle θ (blade angle) of the pentagonal pyramidal punch. In the work tests, five dies 4 in which the cone angles θ of the punches 4a of 10 degrees, 20 degrees, 30 degrees, 40 degrees, and 60 degrees were used.
Although the present invention has been described based on the example shown in the drawings, the present invention is not limited to the example described above. For example, the shape of the prepared hole 3c formed in each protruding piece 3b may be any other polygon such as square and hexagon. Furthermore, the fastening holes 2h may be formed in the upper substrate 2 for engagement of the tubular portions 3d of the step adjustment plate 3. Moreover, as shown in
Thus, according to the present invention, the method for manufacturing a metal gasket for a cylinder head that is capable of establishing the firm engaged state between the substrate and the step adjustment plate, as well as the metal gasket for a cylinder head that is capable of improving the engaging force between the substrate and the step adjustment plate made of the resilient metal foil having the thickness ranging from 0.05 mm to 0.15 mm, is provided.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-036530 | Feb 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/000962 | 2/21/2011 | WO | 00 | 8/21/2012 |
