JP4088269B2 - Cylinder block fastening structure - Google Patents

Description

  The present invention relates to a cylinder block fastening structure in which a cylinder head is fastened to a deck surface of a cylinder block by a head bolt.

Conventionally, a cylinder head is fastened to a cylinder block of an engine via a gasket on a deck surface by a so-called head bolt (see, for example, Patent Document 1).
2. Description of the Related Art Conventionally, engine cylinder blocks and cylinder heads are formed by die casting with a light alloy as the weight is reduced. The cylinder block and the cylinder head are fastened by inserting a steel head bolt into a bolt hole drilled in the cylinder head and gasket and screwing the head bolt into the bolt hole of the cylinder block. .
Japanese Unexamined Patent Publication No. 2000-240502 (paragraphs 0019 to 0026, FIGS. 1 to 5)

However, the cylinder block described in Patent Document 1 is made of a light alloy such as an aluminum (Al) alloy or a magnesium (Mg) alloy having a higher thermal expansion coefficient than a steel head bolt. For this reason, when the engine becomes hot due to the operation of the engine, the head bolt has a larger axial extension of the bolt hole of the cylinder block into which the head bolt is inserted. A phenomenon occurs in which the tightening axial force increases.
As a result, the guaranteed axial force of the head bolt needs to take into account the increase in the tightening axial force. If a high tightening axial force is required for the head bolt, select a head bolt with a higher strength category. I had to.
For this reason, the head bolt has to have a large diameter in order to increase the strength of the increase in the tightening axial force, which has been a problem in terms of engine layout and the like.

  In addition, when an aluminum alloy cylinder block having a high coefficient of thermal expansion due to the heat associated with engine operation is expanded or contracted, there is a problem that the tightening axial force of the head bolt is greatly changed and the sealing performance of the deck surface is impaired. .

  For this reason, it is desired that the head bolt has a tightening axial force that is not affected by the temperature even at low temperatures and at high temperatures.

  Accordingly, the present invention has been made to solve the problems of the prior art, and an object of the present invention is to reduce the increase in the head bolt tightening axial force due to engine temperature changes. It is to provide a fastening structure.

In order to solve the above-described problem, the cylinder block fastening structure according to claim 1 is a cylinder block fastening structure in which a cylinder head is fastened to a deck surface of the cylinder block by a head bolt. The cylindrical body provided in the cylinder block is inserted into the female screw portion formed in the cylinder block , and a cylindrical portion is formed around the opening end side of the female screw portion of the cylinder block. The cylinder has a three-dimensional network structure composed of a plurality of spherical cells (void portions of the ceramic molded body) and communication holes (also referred to as windows) that allow the adjacent spherical cells to communicate with each other. From a metal matrix composite (MMC) in which the spherical cells of a ceramic molded body (also called a preform) are filled with metal In addition , the cylindrical body has a large-diameter portion having a diameter larger than the inner diameter on the opening end side of the cylindrical body, and the large-diameter portion of the cylindrical body is fitted and integrally formed with the cylindrical portion of the cylinder block. It is characterized by that.

According to the first aspect of the present invention, the ceramic molded body constituting the cylindrical body is composed of a metal matrix composite member having a spherical cell filled with metal. When this metal matrix composite member is manufactured, the molten metal is filled in each spherical cell, and the metal spreads through the communication holes. For this reason, the metal matrix composite member is provided with high rigidity, high thermal conductivity, and low expansion.
That is, since the ceramic molded body is in a state in which the metal is constrained by the spherical cell having higher rigidity, the ceramic molded body has high rigidity that increases the rigidity improvement effect. In addition, since the ceramic compact is a ceramic (spherical cell) with higher thermal conductivity than metal, high heat conductivity can be achieved by increasing the overall thermal conductivity when heat flows preferentially to ceramics. Have Furthermore, since the ceramic molded body is in a state of being constrained by a spherical cell having a lower thermal expansion coefficient than that of a metal, it has a low thermal expansion property that increases the thermal expansion coefficient reduction effect.
Further, in this metal matrix composite member, the metal is restrained in the spherical cell, and the thermal expansion of the metal filled in the spherical cell becomes uniform. Therefore, the cylinder has a coefficient of thermal expansion that is uniformly reduced in the metal matrix composite member, and can reduce an increase in the tightening axial force of the head bolt. The head bolt is inserted into the cylindrical body made of the ceramic molded body and is screwed into a female screw portion formed in the cylinder block.
Thereby, it becomes possible to make the said cylindrical body equivalent to the thermal expansion coefficient of a head bolt, and it becomes possible to reduce the increase in the tightening axial force of a head bolt when an engine becomes high temperature.

The fastening structure of the cylinder block according to claim 2 is the fastening structure of the cylinder block according to claim 1, wherein a volume fraction (Vf: Volume Fraction) of the ceramic molded body in the metal matrix composite member is It is characterized by being 10 to 40%.
Here, the “volume fraction” indicates the ratio of the ceramic molded body to the volume of the metal matrix composite member. For example, when the volume fraction of the ceramic molded body is 25%, the ceramic molded body occupies a quarter of the volume of the metal matrix composite member, and the metal is contained in the remaining three quarters.

  According to the second aspect of the present invention, since the cylindrical body is manufactured using the ceramic molded body in which the spherical cells are arranged in the close-packed structure, the volume of the ceramic molded body in the metal matrix composite member The rate is smaller than that of a conventional metal matrix composite member. As a result, the molten metal is easily impregnated into the voids of the spherical cells, and the mechanical strength and impact resistance of the ceramic molded body are improved. The volume fraction is preferably 15 to 30%.

The fastening structure of the cylinder block according to claim 3 is the fastening structure of the cylinder block according to claim 1 or 2, wherein the ceramic molded body is made of silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ) Any one of alumina (Al ₂ O ₃ ) and aluminum nitride (AlN) is included.

According to the third aspect of the present invention, for example, when the ceramic molded body is made of silicon carbide, a cylindrical body having high thermal conductivity, high strength, high rigidity, wear resistance and low thermal expansion is obtained. be able to.
Further, when the ceramic molded body is made of silicon nitride, a cylindrical body having high strength, high rigidity, wear resistance and low thermal expansion can be obtained.
When the ceramic molded body is made of alumina, a cylindrical body having high strength, high rigidity, wear resistance and low thermal expansion can be obtained.
When the ceramic molded body is made of aluminum nitride, a cylindrical body having high thermal conductivity, high strength, high rigidity, wear resistance, and low thermal expansion can be obtained.

  The fastening structure of the cylinder block according to claim 4 is the fastening structure of the cylinder block according to any one of claims 1 to 3, wherein a shaft portion of the head bolt is provided on the deck surface. A bolt hole to be inserted is formed, and the bolt hole is formed at the opening end side by the cylindrical body, and the back side is formed by the female screw portion, and the inner diameter of the cylindrical body is 10 % Or more is formed.

According to the fourth aspect of the present invention, the bolt hole into which the shaft portion of the head bolt is inserted has the opening end formed of the cylindrical body and the back side formed of the female screw portion. As a result, when the head bolt is thermally expanded by the heat of the engine, the bolt hole is inserted into the cylindrical body made of the ceramic molded body, so that the head bolt and the cylindrical body perform substantially the same thermal expansion. . For this reason, the head bolt and the cylinder into which the head bolt is inserted are subjected to substantially the same thermal expansion, so that the axial extension due to heat is the same and the increase in the tightening axial force can be reduced.
For example, even if the cylinder block expands / contracts due to the heat generated by the operation of the engine, the tightening axial force of the head bolt does not change greatly, so that the sealing performance of the deck surface can be maintained.
In addition, by forming the inner diameter of the cylindrical body to be 10% or more larger than the diameter of the valley of the female threaded portion, it is possible to easily form the female threaded portion on the inner side of the cylindrical body made of a metal matrix composite member having poor workability Will be able to.

In addition, as for the said cylinder, it is preferable that the outer peripheral surface comprises a part of inner wall of a water jacket.
By doing so, the tightening axial force that is not affected by the temperature is suppressed by preventing the cylinder from becoming hot due to the heat of the engine, thermal expansion, and increasing the tightening axial force of the head bolt. It becomes possible to provide the fastening structure of the cylinder block which has these.

  According to the cylinder block fastening structure of the present invention, it is possible to reduce an increase in the tightening axial force of the head bolt due to a change in engine temperature, so that the fastening is not affected by the temperature even at a low temperature or a high temperature. A cylinder block fastening structure having an axial force can be provided.

Hereinafter, an embodiment of a fastening structure of a cylinder block according to the present invention will be described in detail with reference to the accompanying drawings.
The cylinder block fastening structure according to the present invention is not limited to the type and type of the internal combustion engine as long as the cylinder block and the cylinder head are fastened by a head bolt. A type gasoline engine will be explained.

  FIG. 1 is a drawing showing a fastening structure of a cylinder block according to an embodiment of the present invention, and a sectional view showing a fastening state of a head bolt. FIG. 2 is a perspective view of a cylinder block having a partial cross section, illustrating a fastening structure of a cylinder block according to an embodiment of the present invention. FIG. 3 is a view showing a fastening structure of the cylinder block according to the embodiment of the present invention, and is a plan view of a main part of the cylinder block having a partial cross section.

≪Engine≫
As shown in FIG. 1, the engine E includes a cylinder block 1 and a cylinder head 4 fastened by a plurality of head bolts 3 with a gasket 2 interposed between the upper deck surface 1 a of the cylinder block 1. I have.
In addition, the engine E has a head cover (not shown) disposed above the cylinder head 4 shown in FIG. 1 and an oil pan disposed below the cylinder block 1 via a lower case (not shown).

≪Cylinder block≫
As will be described later, the cylinder block 1 has a cylinder liner 5 and a ceramic molded body 7 (see FIG. 5) constituting the base material of the cylindrical body 6 embedded in the cylinder block 1 in a mold. A metal 11 such as an aluminum alloy (see FIG. 5) is cast into the molded body 7 and is integrally formed with the cylindrical body 6. Bolts formed on the deck surface 1a of the cylinder block 1 are, for example, four continuous barrel holes 1b in which a cylinder liner 5 is provided, and ten cylindrical bodies 6 that are formed around the barrel holes 1b. The hole 6a and the water jackets 1e and 1f provided in the peripheral part of the barrel hole 1b are arranged flush with each other (see FIGS. 2 and 3).

<Water jacket>
The water jackets 1e and 1f are provided with cooling water in the cylinder block 1 and the cylinder head 4 around the cylinder liner 5 in order to prevent the piston (not shown) from being seized by heat on the cylinder liner 5 (see FIG. 2). Are connected to one in the cylinder block 1.
The water jackets 1 e and 1 f are flow paths for flowing cooling water for cooling the cylinder block 1, the cylinder liner 5, and the cylindrical body 6, and are arranged around the cylinder liner 5 at substantially equal intervals.
The water jacket 1e has a triangular shape in plan view, and is disposed on the left and right between the cylinder liners 5 arranged in a row at a relatively small interval, and the wall surface of the water jacket 1e. A cylinder liner 5 and a cylindrical body 6 are formed in part.
The water jacket 1 f has an oval shape in plan view, and is disposed around the cylinder liner 5.
A through hole 1c is formed on the outside of the water jacket 1f to allow the oil circulated through the cylinder head 4 to flow downward.

≪Gasket≫
As shown in FIG. 1, the gasket 2 is a seal member called a cylinder head gasket for preventing gas from leaking from a joint portion between the cylinder block 1 and the cylinder head 4. For example, the gasket 2 is formed by stacking a plurality of steel plates in order to obtain cushioning properties, and has holes 2a that respectively match the bolt holes 4a and 6a and the water jackets 1e and 1f.

≪Head bolt≫
The head bolt 3 is made of a commonly used steel hexagon bolt, and is formed in a cylindrical shape with a hexagonal head 3c and a thread formed between the head 3c and the male screw 3b. The shaft portion 3a and a male screw portion 3b in which a screw thread is formed.
The male screw part 3b of the head bolt 3 is inserted into the bolt hole 4a of the cylinder head 4 through the metal washer W, the gasket 2 and the bolt hole 6a of the cylindrical body 6, and the female screw part 1d formed in the cylinder block 1 is formed. Screwed on. The head bolt 3 may be a seated bolt in which the washer W is integrated with the head 3c.

≪Cylinder head≫
As with the cylinder block 1, the cylinder head 4 shown in FIG. 1 is also formed by die casting of a metal 11 (see FIG. 5) that is light and has good heat dissipation, for example, an aluminum alloy. The cylinder head 4 is placed on the deck surface 1a of the cylinder block 1 via the gasket 2, the shaft portion 3a of the head bolt 3 is inserted through the bolt holes 4a and 6a and the gasket 2, and the male screw portion 3b is inserted into the bolt. It is firmly fixed to the cylinder block 1 by being screwed into a female screw portion 1d formed on the inner side of the hole 6a.
The cylinder head 4 is provided with a combustion chamber (not shown) and a plug and a valve mechanism.

≪Cylinder liner≫
As shown in FIG. 2, the cylinder liner 5 is a cylindrical member into which a piston (not shown) is slidably inserted, and is also called a cylinder sleeve. In the cylinder liner 5, a cast product having high rigidity or a cylindrical body 6 to be described later is integrally formed on the cylinder block 1 with the same metal 11 (see FIG. 5). The cylinder liner 5 is formed with a cylindrical portion 5a having a constant outer diameter in the axial direction, and a step portion 5b formed at the upper end and the central portion of the cylindrical portion 5a.

<Cylinder>
As shown in FIG. 1, the cylindrical body 6 is a so-called bolt housing. The male screw portion 3b of the head bolt 3 is inserted therethrough, the bolt hole 6a into which the shaft portion 3a is inserted, and the open end of the female screw portion 1d. A cylindrical ceramic molded body 7 (see FIG. 5) having a large diameter portion 6b formed in a state of being fitted to a cylindrical portion 1g formed around the side is used as a base material. The cylindrical body 6 is formed by placing a cylindrical ceramic molded body 7 constituting the base material of the cylindrical body 6 in a mold as a filling, and casting a metal 11 such as an aluminum alloy into the ceramic molded body 7. It is integrally formed with the block 1 (see FIG. 5). The cylindrical body 6 has an inner diameter D1 that is approximately 10% larger than an inner diameter D2 of the female screw portion 1d. The cylindrical body 6 is disposed between the water jacket 1e and the water jacket 1f, and has a lower end portion adjacent to the receiving side of the female screw portion 1d and an upper end portion that is flush with the deck surface 1a. The cylinder 6 is made of a composite material having a thermal expansion coefficient equivalent to that of the steel head bolt 3 and lower than that of the cylinder block 1. The cylindrical body 6 prevents an increase in the tightening axial force of the head bolt 3 by preventing the periphery of the shaft portion 3a of the head bolt 3 from expanding due to thermal expansion when the engine E reaches a high temperature. (See FIG. 1). In this cylindrical body 6, metal 11 is filled in spherical cells 8 of a ceramic molded body 7 having a three-dimensional network structure 10 constituted by spherical cells 8 to be described later and communication holes 9 that allow adjacent spherical cells 8 to communicate with each other. The metal matrix composite member 16 is formed (see FIG. 5).
The cylindrical body 6 (metal-based composite member 16) is referred to as a “cylindrical body” for the sake of convenience. In practice, however, the metal 11 is applied to the ceramic molded body 7 of the cylindrical base material as described later. Since it is cast and integrally formed with the cylinder block 1, there is no boundary surface between the cylinder 6 and the cylinder block 1 (see FIG. 5).

≪Ceramic molded body≫
FIG. 4 is a schematic view of a ceramic molded body forming a cylinder used in the cylinder block fastening structure according to the embodiment of the present invention.
The ceramic molded body 7 is made of the material of the three-dimensional network structure 10 that forms the base material of the cylindrical body 6 (see FIG. 2), and is formed in the same shape as the cylindrical body 6 shown in FIG. As shown in FIG. 4, the ceramic molded body 7 has a plurality of spherical cells 8 formed therein. The ceramic molded body 7 is made of, for example, silicon carbide, but may be an engineering ceramic such as alumina, silicon nitride, or aluminum nitride.

<Spherical cell>
FIG. 5 is a conceptual diagram of a metal matrix composite member produced using a ceramic molded body.
As shown in FIG. 5, the spherical cell 8 is a portion filled with the metal 11 when the metal matrix composite member 16 to be described later is manufactured using the ceramic molded body 7, and the spherical cell 8 has a substantially uniform inner diameter. It is formed with bubbles. For example, since the spherical cells 8 are arranged in a close-packed structure in the ceramic molded body 7, the spherical cells 8 are densely and uniformly arranged in the ceramic molded body 7.

<Communication hole>
As shown in FIG. 5, when the metal matrix composite member 16 is manufactured using the ceramic molded body 7, the communication hole 9 is a metal melted in each spherical cell 8 by communicating each spherical cell 8. 11 is for spreading. The inner diameter of the communication hole 9 is set according to the inner diameter of the spherical cell 8 set, and the ratio of the median (M _d ) of the inner diameter of the communication hole 9 to the median (M _D ) of the inner diameter of the spherical cell 8 (M _d / M _D ) is preferably less than 0.5. By setting the inner diameter of the communication hole 9 in this manner, the thermal expansion coefficient of the cylindrical body (metal matrix composite member 16) 6 is further reduced by the ceramic molded body 7.

<Metal matrix composite member>
As shown in FIG. 5, the metal matrix composite 16 is a material that forms the cylindrical body 6 (see FIG. 2) in which the spherical cells 8 and the communication holes 9 of the ceramic molded body 7 are filled with the metal 11. In the metal matrix composite member 16, the metal 11 in each spherical cell 8 is formed in a spherical shape having a uniform outer diameter and is restrained in the spherical cell 8. The spherical metals 11 are distributed in the metal matrix composite member 16 so as to form the close-packed structure. In addition, the volume fraction (Vf) of the ceramic molded body 7 in the metal matrix composite member 16 is 10 to 40%.

<Metal>
The metal 11 is a material for forming the cylinder block 1 while being cast into the base ceramic molded body 7 of the cylinder 6 to complete the cylinder 6 (see FIG. 2). As shown in FIG. 5, the metals 11 filled in the spherical cell 8 spread in the metal matrix composite member 16.
In the metal matrix composite member 16 manufactured using the ceramic molded body 7 having a median (M _d ) ratio (M _d / M _D ) of less than 0.5, the metal filled in the spherical cell 8 is used. The ratio of the median of the outer diameter of the metal 11 filled in the communication hole 9 to the median of the outer diameter of 11 is equal to the M _d / M _D and is less than 0.5.
The metal 11 used for the metal matrix composite member 16 is made of, for example, an aluminum alloy, but may be aluminum, silicon (Si), silicon alloy, copper (Cu), copper alloy, magnesium, magnesium alloy, or the like. Good.

≪Cylinder block manufacturing method≫
Next, a manufacturing method of the cylinder block will be described mainly with reference to FIG.
In the cylinder block fastening structure according to the embodiment of the present invention, the manufacturing method of the metal matrix composite member 16 made of the ceramic molded body 7 of the three-dimensional network structure 10 forming the cylindrical body 6 is not particularly limited. As an example, a case where the metal 11 is an aluminum alloy will be described.

<Manufacture of cylindrical ceramic molded body>
FIG. 6 is a process explanatory diagram of a cylinder and cylinder manufacturing method used in the cylinder block fastening structure according to the present embodiment.
As shown in FIG. 6, the manufacturing step S1 of the ceramic molded body 7 of the cylindrical body 6 includes a step of preparing microspheres that vaporize at a preset temperature (microsphere preparation step S2), a microsphere and ceramic particles. Is mainly composed of a step of filling the mold (filling step S3), a step of vaporizing the microspheres (vaporization step S4), and a step of sintering the ceramic particles (sintering step S5). Next, those steps S2 to S5 will be described in more detail.

<Preparation process of microsphere>
The microspheres prepared in the microsphere preparation step S2 are composed of true spherical particles having a standard deviation of the outer diameter of a predetermined value or less. The microsphere is made of, for example, a resin such as poly (meth) methyl acrylate or polystyrene.

<Filling process>
FIG. 7 is a conceptual diagram of “microspheres coated with ceramic particles” manufactured in a filling process when manufacturing a cylindrical body.
In the filling step S3, as shown in FIG. 7, ceramic particles 13 made of true spherical fine particles having a uniform outer diameter, and microspheres 12 covered with the ceramic particles 13 and having a uniform outer diameter are formed in the mold. Filled. In the filling step S3, the surface of the microsphere 12 is covered with the ceramic particles 13 before the microsphere 12 is filled into the mold. The ceramic particles 13 and the ceramic powder 14 (see FIG. 8) described below are made of, for example, silicon carbide, and are fired in a sintering step S5 described later to form a skeleton of the ceramic molded body 7.
The ceramic particles 13 and the ceramic powder 14 (see FIG. 8) may be engineering ceramics such as alumina, silicon nitride, and aluminum nitride.

  Next, a mixture of the microspheres 12 coated with the ceramic particles 13 and the ceramic slurry is prepared. This ceramic slurry is obtained by dispersing ceramic powder 14 in a dispersion medium such as water, and is obtained by mixing ceramic powder 14 (see FIG. 8) and dispersion medium using a ball mill or the like. . By adjusting the viscosity of the ceramic slurry to about 0.05 Pa · s to 5 Pa · s, the ceramic slurry (that is, the ceramic powder 14) is sufficiently provided between the microspheres 12 coated with the ceramic particles 13. Go around.

FIG. 8 is a conceptual diagram of a molded body material manufactured in a filling process when manufacturing a cylindrical body.
Next, the mixture is poured into a dewaterable mold made of, for example, gypsum, and filtered under reduced pressure through the mold. Then, the dispersion medium in the ceramic slurry which is a liquid component of this mixture escapes from the mixture. As a result, as shown in FIG. 8, “microspheres 12 coated with ceramic particles 13” which are solids in the mixture are close to each other and between “microspheres 12 coated with ceramic particles 13”. Thus, a molded body material 15 filled with the ceramic powder 14 is obtained. And this molded object material 15 is processed by the following vaporization process S4, after drying.

<Vaporization process>
FIG. 9 is a conceptual diagram of a sintered compact produced in the vaporization step when producing a cylinder.
In this vaporization step S4, when the molded body material 15 shown in FIG. 8 is heated in the furnace at a predetermined temperature increase rate, the microspheres 12 in the molded body material 15 are vaporized. Then, as shown in FIG. 9, the portion of the molded body material 15 (see FIG. 8) where the microspheres 12 (see FIG. 8) existed is hollowed out to form spherical cells 8. On the other hand, the ceramic particles 13 covering the microspheres 12 are released by the gas pressure generated when the microspheres 12 are vaporized. At this time, the ceramic particles 13 where the adjacent spherical cells 8 are close to each other are preferentially removed. As a result, as shown in FIG. 9, a communication hole 9 for communicating the spherical cells 8 is formed.
The molded body material 15 (see FIG. 8) in which the spherical cells 8 and the communication holes 9 are thus formed becomes a sintered molded body 17 used in the next sintering step S5.
In the sintered compact 17, a plurality of spherical cells 8 are arranged in the above-described close-packed structure in the sintered compact 17, and as shown in FIG. A three-dimensional network structure 10 is formed.

<Sintering process>
In the sintering step S5, the sintered compact 17 (see FIG. 9) obtained in the vaporization step S4 is fired. In the sintering step S5, the sintered compact 17 (see FIG. 9) is fired, so that the ceramic particles 13 and the ceramic powder 14 surrounding the spherical cell 8 are sintered and united. As a result, the sintered compact 17 becomes a ceramic compact 7 as shown in FIG. 5, and is formed in the shape of a cylindrical cylinder 6 as shown in FIG.

<Manufacturing process of cylinder block and cylinder>
Next, the manufacturing process S6 of the cylinder block 1 and the cylinder 6 in which the cylinder block 1 is integrally formed with the ceramic molded body 7 of the cylinder 6 manufactured in this way and the cylinder liner 5 as a filling will be described.
The manufacturing process S6 of the cylinder block 1 and the cylinder 6 is performed by casting the ceramic molded body 7 and the cylinder liner 5 which are the base materials of the cylinder 6 as a filling metal, and the cylinder 6 and the cylinder with an aluminum alloy (metal 11). This is a process of casting the block 1 at the same time. As shown in FIG. 6, the area around the head bolt 3 is compounded by the installation process S7 in the block mold, the complex casting process S8, and the machining process S9. A cylinder block 1 is formed. Next, those steps S7 to S9 will be described in more detail.

<Installation process in block mold>
In the installation step S7 in the block mold, the ceramic molded body 7 (see FIG. 5) of each cylindrical body 6 shown in FIG. 2 manufactured by the manufacturing process S1 of the ceramic molded body 7 of the cylindrical body 6, and the ceramic Each cylinder liner 5 formed of the same material as the molded body 7 or a cast product with high rigidity is set at a predetermined position in the mold.

<Composite casting process>
In the next composite casting step S8, the metal that forms the main body of the cylinder block 1 in the mold and the aluminum 11 that is the metal 11 filled in the spherical cells 8 of the ceramic molded body 7 that is the base material of the cylindrical body 6. An alloy is poured to form the cylinder block 1 in which the cylindrical body 6 and the cylinder liner 5 are cast. Thereby, in the cylinder block 1, the cylinder body 6 in which the spherical cell 8 was filled with the aluminum alloy (metal 11) and the cylinder liner 5 are integrally formed. Since the cylindrical body 6 manufactured in this way has no boundary surface between the cylindrical body 6 and the cylinder block 1, high strength, high rigidity, wear resistance, and low thermal expansion can be obtained.

<Processing process>
Next, after removing the cylinder block 1 formed in the composite casting step S8 from the mold and cooling, in the processing step S9, tapping to form the female screw portion 1d is performed, and burrs formed at the time of casting are deleted. Then, the final grinding process is performed. Note that when the internal thread portion 1d is formed in the cylinder block 1, the inner diameter D1 of the cylindrical body 6 is formed to be 10% or more larger than the valley diameter D2 of the internal thread portion 1d. The female screw portion 1d can be easily formed on the back side of the cylindrical body 6 made of the member 16. Thereby, the cylinder block 1 which compounded the circumference | surroundings of the head bolt 3 is completed.

≪Assembly≫
As shown in FIG. 1, the completed cylinder block 1 has the cylinder head 4 mounted on the deck surface 1 a via the gasket 2, and the cylinder block 1 and the cylinder head 4 are fastened by the head bolt 3. To do. At this time, the head bolt 3 is inserted into the shaft portion 3 a through the bolt hole 4 a of the cylinder head 4, the gasket 2, and the bolt hole 6 a of the cylinder 6, and the male screw portion 3 b is screwed to the female screw portion 1 d of the cylinder block 1. Is done. Then, a head cover (not shown) is attached on the cylinder head 4 and an oil pan is attached below the cylinder block 1 via a lower case (not shown), whereby the assembly of the engine E is completed.

≪Action≫
When the engine E thus completed is operated, heat is generated with the operation. The heat of the cylinder block 1, the cylinder 6, the head bolt 3, and the cylinder head 4 is heated by the coolant flowing through the water jackets 1 e and 1 f formed by the cylinder block 1, the cylinder 6, and the cylinder head 4. It is cooled and rises to a predetermined temperature.

The cylindrical body 6 is composed of the ceramic molded body 7 having the three-dimensional network structure 10, so that the distribution of the spherical cells 8 is high, and the thermal expansion coefficient of the cylinder block 1 is high. It is lower than the aluminum alloy forming the main body, is equivalent to the steel head bolt 3, and has a low thermal expansion. Moreover, since the cylindrical body 6 has good thermal conductivity, the heat easily escapes and is excellent in heat sinkability.
For this reason, the head bolt 3 is inserted into the cylindrical body 6 and screwed into the female thread portion 1 d of the cylinder block 1, whereby the shaft portion 3 a and the cylindrical body 6 have the same thermal expansion. For this reason, the cylindrical body 6 has the same axial extension as that of the head bolt 3 due to heat, and can reduce an increase in the tightening axial force of the head bolt 3 when the engine E reaches a high temperature.
Since the tightening axial force of the head bolt 3 does not change significantly in the gasket 2, the tightening force by the cylinder block 1 and the cylinder head 4 does not change, so that the sealing performance of the deck surface 1a can be maintained.

<Effects of the present embodiment>
The cylinder 6 (see FIG. 2) formed in the steps S2 to S9 has the following effects.
(1) As shown in FIG. 5, since the metal 11 filled in the spherical cell 8 is spherical, anisotropy does not occur in the thermal expansion of the metal 11.
(2) In the cylinder 6, the metal 11 is constrained in the spherical cell 8, and the metal 11 is distributed so as to form the three-dimensional network structure 10 in the metal matrix composite member 16. The thermal expansion of the metal 11 filled therein becomes uniform. Therefore, the cylinder 6 has a smaller coefficient of thermal expansion than the conventional metal matrix composite member. For example, since the cylinder 6 has a lower coefficient of thermal expansion than the aluminum alloy forming the cylinder block 1, the cylinder 6 can be made equal to the coefficient of thermal expansion of the head bolt 3 made of a metal having a lower coefficient of thermal expansion than the aluminum alloy. Thus, an increase in the axial force of the head bolt 3 when the engine E is at a high temperature can be reduced.
(3) Since the metal matrix composite member 16 forming the cylindrical body 6 has the metal 11 filled in the spherical cells 8 arranged in a close-packed structure, the mechanical strength and impact resistance of the ceramic molded body 7 Is improved, and the mechanical strength of the cylindrical body 6 is improved. As a result, it is possible to reduce the volume fraction Vf of Sera Mi click molded body 7, the metal matrix composite 16, the metal 11 was molten in the gap of the spherical cell 8 is easily impregnated.
(4) In the metal matrix composite member 16, the ratio (M _d / M _D ) of the median (M _d ) of the inner diameter of the communication hole 9 to the median (M _D ) of the inner diameter of the spherical cell 8 is less than 0.5. The cylindrical body 6 manufactured using the ceramic molded body 7 has a smaller thermal expansion coefficient of the metal matrix composite member 16 and is smaller. Even when the head bolt 3 having the same strength is used, the axial force higher than that of the related art is obtained. It becomes possible to conclude with.
(5) Since the inner diameter D1 of the cylindrical body 6 is 10% or more larger than the valley diameter D2 of the female screw portion 1d, the cylindrical body 6 is formed on the inner side of the cylindrical body 6 made of the metal matrix composite member 16 having poor workability. The internal thread portion 1d can be easily formed.
(6) The cylindrical body 6 has a boundary surface between the cylindrical body 6 and the cylinder block 1 by pouring the metal 11 into the ceramic molded body 7 of the cylindrical base material and integrally forming it with the cylinder block 1. Therefore, it has high rigidity, high thermal conductivity, and low expansion.

  Note that the present invention is not limited to the above-described embodiment, and various modifications and changes can be made within the scope of the technical idea, and the present invention extends to these modifications and changes. Of course.

≪Modification≫
For example, in the above-described embodiment, the spherical cells 8 are arranged so as to form a face-centered cubic lattice and are arranged in a face-centered close-packed structure. Or the spherical cell 8 may be arrange | positioned in the body center close-packed structure shape. Further, they may be arranged randomly such as amorphous.
Moreover, in the said embodiment, although the ceramic molded body 7 is a substantially cube shape, this invention can be changed suitably according to the shape of the metal matrix composite member 16 to manufacture.

  In the above-described embodiment, as shown in FIGS. 1 and 2, it has been described that the cylinder body 6 is cast into the cylinder block 1. However, the cylinder body 6 is not limited thereto, for example, The bolt hole 4 a may be formed by the cylinder 6 by being installed in the cylinder head 4.

The cylindrical body 6 is made of a metal matrix composite member 16 (see FIG. 5) formed by filling the ceramic molded body 7 with a metal 11 such as an aluminum alloy by the same processes as the manufacturing steps S2 to S9 described above. After the finished product is formed, the cylindrical body may be inserted into a mold for forming the cylinder block 1 and the metal 11 may be poured into the mold to integrally form the cylinder block 1.
Even when the cylinder block 1 is manufactured in this manner, the cylinder is formed by the metal matrix composite member 16 and then integrally cast into the cylinder block 1, so that high strength, high rigidity, and high heat conduction are obtained. , Low expansibility, abrasion resistance and low thermal expansibility.

It is drawing which shows the fastening structure of the cylinder block which concerns on embodiment of this invention, and is sectional drawing which shows the fastening state of a head bolt. It is drawing which shows the fastening structure of the cylinder block which concerns on embodiment of this invention, and is a perspective view of the cylinder block which has a partial cross section. It is drawing which shows the fastening structure of the cylinder block which concerns on embodiment of this invention, and is a principal part top view of the cylinder block which has a partial cross section. It is a schematic diagram of the ceramic molded body which forms the cylinder used for the fastening structure of the cylinder block which concerns on embodiment of this invention. It is a conceptual diagram of the metal matrix composite member manufactured using the ceramic molded body. It is process explanatory drawing of the manufacturing method of the cylinder and cylinder which are used for the fastening structure of the cylinder block which concerns on this Embodiment. It is a conceptual diagram of the microsphere coat | covered with the ceramic particle manufactured at the filling process when manufacturing a cylinder. It is a conceptual diagram of the molded object material manufactured at the filling process when manufacturing a cylinder. It is a conceptual diagram of the molded object for sintering manufactured at the vaporization process when manufacturing a cylinder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder block 1a Deck surface 1d Female thread part 3 Head bolt 3a Shaft part 3b Male thread part 4 Cylinder head 4a, 6a Bolt hole 6 Cylindrical body 7 Ceramic molded body 8 Spherical cell 9 Communication hole 10 Three-dimensional network structure 11 Metal 16 Metal matrix composite Element

Claims (4)

In the cylinder block fastening structure in which the cylinder head is fastened to the deck surface of the cylinder block by a head bolt,
The male screw portion of the head bolt is inserted into a cylinder provided in the cylinder block and screwed to a female screw portion formed in the cylinder block.
A cylindrical portion is formed around the opening end side of the female screw portion of the cylinder block ,
The cylindrical body is a metal-based composite in which a metal is filled in the spherical cells of a ceramic molded body having a three-dimensional network structure that includes a plurality of spherical cells and communication holes that allow the adjacent spherical cells to communicate with each other. The cylindrical body has a large-diameter portion having a diameter larger than the inner diameter on the opening end side of the cylindrical body, and the large-diameter portion of the cylindrical body is fitted and integrally formed with the cylindrical portion of the cylinder block. Cylinder block fastening structure characterized by 2. The cylinder block fastening structure according to claim 1, wherein a volume fraction of the ceramic molded body in the metal matrix composite member is 10 to 40%. 3. The cylinder block fastening structure according to claim 1, wherein the ceramic molded body includes any one of silicon carbide, silicon nitride, alumina, and aluminum nitride. A bolt hole into which the shaft portion of the head bolt is inserted is formed on the deck surface,
The bolt hole has an opening end side formed of the cylindrical body, and a back side formed of the female screw portion,
The cylinder block fastening structure according to any one of claims 1 to 3, wherein an inner diameter of the cylindrical body is formed to be 10% or more larger than a diameter of a valley of the female screw portion.

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