JP2005315115A - Cylinder block - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reliability with respect to strength around the center between cylinder bores. <P>SOLUTION: A cylinder block 11 is equipped with a cylinder liner 13 and a cylinder block body 12 having an outside wall 19. A through hole 26 is provided in an upper deck part 22 of the cylinder liner 13. A screw hole 23 is provided in the outside wall 19. In an unfastened state of the upper deck part 22, the center line L2 of the screw hole 23 is offset from the center line L3 of the through hole 26 toward the center C side between cylinder bores 21. By inserting a positioning part 27 provided in the through hole 26 into the screw hole 23, compressive stress F toward the center C between cylinder and bores 21 is generated in a surface which is perpendicular to the arrangement direction of the cylinder bore 21 with respect to the cylinder liner 13 and passes between neighboring cylinder bores 21 prior to the fastening of the upper part 22. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cylinder block that forms the main part of an engine.

  As one form of the engine, a mixture of fuel and air is burned in a cylinder, the piston is reciprocated linearly by the energy generated by the combustion, and the movement is converted into rotational movement by a crank mechanism to output shaft (crank There is a so-called reciprocating engine in which a shaft is driven to rotate. The main part of such a reciprocating engine is constituted by a cylinder block having a cylinder bore. In a cylinder block of a multi-cylinder engine, a plurality of cylinder bores are arranged close to each other.

In addition, the following patent document 1 is mentioned as a prior art document concerning this invention.
JP 2002-195126 A

  As described above, in a cylinder block in which a plurality of cylinder bores are arranged in a row, a portion sandwiched between adjacent cylinder bores is thinner than other portions. Since the cylinder block adopts such a configuration, a stress (tensile stress) is generated between the cylinder bores in a direction perpendicular to the arrangement direction of the cylinder bores toward the side away from the center between the cylinder bores.

  There are various possible causes for such tensile stress. For example, in a cylinder block manufactured by casting, when the molten metal poured into the mold is cooled, a tensile stress called residual stress (strain) is generated inside the cylinder block, particularly around the center between the cylinder bores. To do. Also, tensile stress is generated when the engine is assembled. Further, during operation of the engine, heat and pressure generated when the air-fuel mixture burns are transmitted between the cylinder bores, and tensile stress is generated. If the sum of these tensile stresses becomes large, there is a risk that stress exceeding the allowable stress may occur between the cylinder bores.

  Therefore, it is necessary to take measures to prevent an excessive tensile stress from acting around the center between the cylinder bores. Patent Document 1 describes a technique that absorbs the difference in elongation between the cylinder head and the fuel pipe due to a temperature difference or the like and suppresses twisting of the injector and unnecessary deformation of the fuel pipe. No. 1 does not solve the above-described problem of tensile stress.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a cylinder block capable of improving the reliability of the strength around the center between the cylinder bores.

In the following, means for achieving the above object and its effects are described.
In the first aspect of the present invention, a cylinder block having a cylinder liner having a plurality of cylinder bores and having an upper deck portion at an end on the cylinder head side, and an outer wall surrounding a portion of the cylinder liner excluding the upper deck portion. A cylinder block in which the upper deck portion is fastened to the cylinder head and the outer wall by a screw member, and when the upper deck portion is fastened to the outer wall, the arrangement direction of the cylinder bores with respect to the cylinder liner And a compressive stress generating means for generating a compressive stress toward the center between the cylinder bores on a plane passing between adjacent cylinder bores.

  According to the above configuration, when the cylinder block is assembled, the portion of the cylinder liner excluding the upper deck portion is first disposed in the space surrounded by the outer wall, and the upper deck portion is placed on the outer wall. By means of the compressive stress generating means, the cylinder liner is caused to generate a compressive stress toward the center between the cylinder bores in a plane perpendicular to the arrangement direction of the cylinder bores and passing between the adjacent cylinder bores. Since this compressive stress is a force in the opposite direction to the stress (tensile stress) generated during the production of the cylinder liner, the tensile stress is weakened by the amount of this compressive stress. In this state where the tensile stress is reduced, the upper deck portion is fastened to the cylinder head and the outer wall by the screw member. Therefore, even if heat and pressure generated when the fuel / air mixture burns during operation of the engine is transmitted between the cylinder bores and tensile stress is generated, the average stress, which is a heavy factor in fatigue strength, is small. As a result, the reliability of the strength around the center between the cylinder bores is improved.

  According to a second aspect of the present invention, in the first aspect of the present invention, the compressive stress generating means is provided in the upper deck portion, and is provided in a through hole through which the screw member is inserted, and in the outer wall. And a screw hole into which the screw member is screwed, and in a state before the upper deck portion is fastened, the center line of the screw hole is offset to the center side between the cylinder bores than the center line of the through hole Suppose that

  According to said structure, when an upper deck part is fastened by a screw member, the centerline of the through-hole of an upper deck part and the centerline of the screw hole of an outer side wall are made to correspond. For this match, for example, the cylinder liner is compressed toward the center between the cylinder bores, the cylinder block body is expanded away from the center between the cylinder bores, or both are performed. . As described above, when both center lines are matched or a screw member inserted through the through hole is screwed into the screw hole, the cylinder liner is subjected to compressive stress toward the center between the cylinder bores. Occur.

  According to a third aspect of the present invention, in the second aspect of the present invention, the through hole is provided with a tubular positioning portion that protrudes from the upper deck portion to the side opposite to the cylinder head and through which the screw member can be inserted. Suppose that

  According to said structure, when an upper deck part is fastened by a screw member, the centerline of a screw hole has shifted | deviated to the center side between cylinder bores rather than the centerline of a positioning part (through-hole). From this state, the cylinder liner is subjected to compressive stress toward the center between the cylinder bores by matching the center line of the positioning part with the center line of the screw hole or by inserting the positioning part into the screw hole. Occur. In this state, when the screw member is inserted into the cylinder head and the positioning portion and screwed into the screw hole, the upper deck portion is fastened to the cylinder head and the outer wall.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, a taper-shaped guide portion whose diameter decreases as the distance from the cylinder head increases is formed at the end of the positioning portion on the side opposite to the cylinder head. And

  According to said structure, the outer diameter is smaller in the guide part in a positioning part than the other location of the positioning part. In addition, the guide portion has a tapered shape with a reduced diameter as the distance from the cylinder head increases. The outer diameter of the positioning portion is the smallest at the tip of the guide portion. Therefore, the tip of the guide can be positioned at the opening of the screw hole without compressing the cylinder liner toward the center between the cylinder bores or expanding the cylinder block body away from the center. is there. When the upper deck portion is further brought closer to the outer wall from this state, the guide portion enters the screw hole. In this process, a force toward the center between the cylinder bores acts on the positioning portion. This force is transmitted to the cylinder liner through the upper deck portion, and a compressive stress toward the center between the cylinder bores is generated in the cylinder liner. When the guide part is completely inserted into the screw hole, the center line of the positioning part (through hole) matches the center line of the screw hole, so that the screw member is inserted into the positioning part (through hole) and the screw hole is inserted. It becomes possible to screw in.

  According to a fifth aspect of the present invention, in the second aspect of the present invention, the shaft portion of the screw member has a large-diameter portion that fits into the through-hole while the upper deck portion is fastened to the outer wall. It is assumed that a taper-shaped guide portion whose diameter decreases as the distance from the cylinder head is increased is formed at the end of the same large diameter portion on the side opposite to the cylinder head.

  According to said structure, when an upper deck part is fastened with a screw member, the centerline of a screw hole has shifted | deviated to the center side between cylinder bores rather than the centerline of a screw member (through-hole). From this state, the large-diameter portion of the screw member is fitted into the through hole, and the portion of the shaft portion on the side opposite to the cylinder head than the large-diameter portion is inserted into the screw hole.

  Here, the outer diameter of the guide portion in the large-diameter portion is smaller than in other portions of the large-diameter portion. In addition, the guide portion has a tapered shape with a reduced diameter as the distance from the cylinder head increases. The outer diameter of the large-diameter portion is the smallest at the position farthest from the cylinder head in the guide portion. Therefore, even if the cylinder liner is not compressed to the side toward the center between the cylinder bores, and the cylinder block body is not expanded to the side away from the center, the minimum diameter part of the guide part should be positioned at the opening of the screw hole. Is possible. When the upper deck portion is further brought closer to the outer wall from this state, the guide portion enters the screw hole. In this process, a force toward the center between the cylinder bores acts on the screw member. This force is transmitted to the cylinder liner through the upper deck portion, and a compressive stress toward the center between the cylinder bores is generated in the cylinder liner. When the guide portion is completely inserted into the screw hole, the center line of the screw member (through hole) matches the center line of the screw hole, so that the screw member can be screwed into the screw hole.

  According to a sixth aspect of the present invention, in the first aspect of the present invention, the compressive stress generating means includes a positioning recess provided at a location corresponding to one of the cylinder bores of the outer wall and the upper deck portion. And a positioning protrusion provided on the other and fitted in the positioning recess, and provided on the outer wall of the positioning recess and the positioning protrusion in a state before the upper deck portion is fastened. It is assumed that the center line of the thing is offset to the center side between the cylinder bores than the center line of the thing provided in the upper deck portion.

  According to the above configuration, when the upper deck portion is fastened by the screw member, the center line of the positioning recess and the center line of the positioning protrusion are displaced on a plane orthogonal to the arrangement direction of the cylinder bores. More precisely, the center line of the positioning recess and the positioning protrusion provided on the outer wall is shifted to the center side between the cylinder bores than the center line of the positioning recess provided on the upper deck.

  From this state, the cylinder liner is compressed toward the center between the cylinder bores by matching the center line of the positioning protrusion with the center line of the positioning recess or by inserting the positioning protrusion into the positioning recess. Stress is generated. In this state, the upper deck portion is fastened by the screw member.

(First embodiment)
Hereinafter, a first embodiment in which the present invention is embodied in a cylinder block for a reciprocating engine will be described with reference to FIGS.

  As shown in FIGS. 1 and 2, the cylinder block 11 is a main part of the engine and includes a cylinder block body 12 and a cylinder liner 13. A cylinder head 15 is placed on the cylinder block 11 via a cylinder head gasket 14.

  The cylinder block main body 12 includes a skirt portion 17 that forms the lower portion thereof, and an outer wall 19 that forms the upper portion and surrounds a portion that serves as a water jacket 18. The cylinder block body 12 is integrally formed by a casting method such as die casting, medium pressure casting, or low pressure casting using a metal material having a relatively small specific gravity such as an aluminum alloy or a magnesium alloy.

  The cylinder liner 13 is made of a metal material having excellent wear resistance such as cast iron. The cylinder liner 13 is formed with a plurality of cylinder bores 21 each having a cylindrical shape whose upper and lower ends are opened. Adjacent cylinder bores 21 are close to each other. In a state where the cylinder liner 13 is incorporated in the cylinder block 11, a piston (not shown) is accommodated in each cylinder bore 21 so as to be able to reciprocate. In each cylinder bore 21, the space above the piston is a combustion chamber (not shown) for burning a mixture of fuel and air.

  An upper deck portion 22 is integrally formed at an end portion of the cylinder liner 13 on the cylinder head 15 side (upper end portion in FIGS. 1 and 2). The upper deck portion 22 is a portion disposed between the cylinder block body 12 and the cylinder head 15 and has a plate shape.

  The cylinder block 11 employs the following structure for fastening the upper deck portion 22 to the cylinder head 15 and the outer wall 19. In the outer wall 19, screw holes 23 are provided at a plurality of locations around each cylinder bore 21. More specifically, the screw holes 23 are provided at locations facing each other across the center C in a plane orthogonal to the arrangement direction of the cylinder bores 21 and passing between the adjacent cylinder bores 21. Here, the center C refers to an intermediate position in the width direction (left-right direction in FIG. 2) on the surface.

  Each screw hole 23 opens at the upper surface of the outer wall 19 and extends parallel to the center line L1 of the cylinder bore 21. A female thread is formed at least at the lower part of the inner peripheral surface of each screw hole 23. In the cylinder head 15, the cylinder head gasket 14, and the upper deck part 22, through holes 24, 25, and 26 through which head bolts 16 as screw members can be inserted are provided at positions facing the screw holes 23 ( (See FIG. 3). And the upper deck part 22, the cylinder head gasket 14, and the cylinder head 15 are mounted in order on the outer side wall 19. FIG. The head bolts 16 inserted into the through holes 24 and 25 of the cylinder head 15 and the cylinder head gasket 14 are screwed into the screw holes 23 through the through holes 26 of the upper deck portion 22, thereby the cylinder head gasket 14 and the upper deck portion. 22 is fastened to the cylinder head 15 and the outer wall 19.

  By the way, in the cylinder block 11 having the above-described configuration, when the molten metal poured into the mold is cooled when the cylinder liner 13 is cast, the molten metal gradually cools from the outside toward the inside. Therefore, a temperature gradient is generated in the course of cooling, and tensile stress called residual stress (strain) is generated inside the cylinder block 11, particularly around the center C between the cylinder bores 21 when it is cooled to room temperature. The tensile stress is also generated when the cylinder liner 13 and the like are fastened to the cylinder block body 12 and the cylinder head 15, that is, when the engine is assembled. Further, during operation of the engine, heat and combustion pressure generated when the air-fuel mixture burns are transmitted between the cylinder bores 21, and tensile stress is generated. In particular, the tensile stress due to the combustion pressure varies around the value A as shown in FIG. And what added various tensile stress mentioned above becomes the stress (average stress) which generate | occur | produces on average between the cylinder bores 21 of the cylinder liner 13 when an engine is operate | moving. Further, the amplitude of the tensile stress that varies depending on the combustion pressure is called a stress amplitude as shown in FIG.

  The relationship shown in FIG. 5 is generally observed between these average stresses and stress amplitudes. The characteristic line in FIG. 5 shows the fatigue limit line. If the point corresponding to the average stress and the stress amplitude is in the region Z1 below the fatigue limit line in FIG. 5, it can be said that the strength between the cylinder bores 21 is sufficiently high. On the other hand, if the point is in the region Z2 above the fatigue limit line, the strength between the cylinder bores 21 is low.

  Therefore, in the present embodiment, when the upper deck portion 22 is fastened by the head bolt 16, a compressive stress generating means is provided for generating the compressive stress F toward the center C between the cylinder bores 21 with respect to the cylinder liner 13.

  As shown in FIG. 3, the upper deck portion 22 is provided with a through hole 26 through which the head bolt 16 is inserted, and the outer wall 19 is provided with a screw hole 23 into which the head bolt 16 is screwed. As described above, the center line L2 of the screw hole 23 is offset from the center line L3 of the through hole 26 by a predetermined amount toward the center C between the cylinder bores 21. In FIG. 3, this offset amount is emphasized, but is actually about several hundred microns. The offset through holes 26 and the screw holes 23 constitute the compressive stress generating means. Further, a pipe is press-fitted and fixed in each through hole 26, and a lower end portion of the pipe protrudes downward from the upper deck portion 22, which is the side opposite to the cylinder head 15. The protruding portion constitutes a circular tubular positioning portion 27 through which the head bolt 16 can be inserted.

  In assembling the cylinder block 11 configured as described above, for example, a portion of the cylinder liner 13 excluding the upper deck portion 22 is first disposed in a space surrounded by the outer wall 19, and the upper deck portion 22 is placed in the outer wall 19. Place on top. In this state, the center line L2 of the screw hole 23 is shifted to the center C side between the cylinder bores 21 with respect to the center line L3 of the positioning portion 27 (through hole 26).

  Next, the cylinder head gasket 14 and the cylinder head 15 are placed in order on the upper deck portion 22, and the upper deck portion 22 and the cylinder head gasket 14 are fastened to the cylinder head 15 and the outer wall 19 by the head bolts 16. At this time, the center line L3 of the positioning portion 27 (through hole 26) and the center line L2 of the screw hole 23 are matched. For this matching, for example, the cylinder liner 13 is compressed toward the side toward the center C between the cylinder bores 21, the cylinder block body 12 is expanded away from the center C, and both are performed.

  And the positioning part 27 is inserted in the screw hole 23 in the state which matched both centerline L2, L3. As a result of the compression or insertion of the positioning portion 27, a compressive stress F toward the center C between the cylinder bores 21 is generated in the cylinder liner 13 as indicated by an arrow in FIG. Since this compressive stress F is a force in the opposite direction to the stress (tensile stress due to residual stress) generated during manufacture of the cylinder liner 13, the tensile stress is weakened by this compressive stress F. Further, by the insertion, the upper deck portion 22 and the cylinder block main body 12 are held in a state where the center lines L2 and L3 are aligned, that is, in a state where the upper deck portion 22 is positioned. In this state, when the head bolt 16 inserted into the through holes 24 and 25 of the cylinder head 15 and the cylinder head gasket 14 is passed through the positioning portion 27 and screwed into the screw hole 23, the upper deck portion 22 and the cylinder head gasket 14 are moved. Fastened to the cylinder head 15 and the outer wall 19.

  Therefore, even when heat or combustion pressure generated when the air-fuel mixture burns during operation of the engine is transmitted between the cylinder bores 21 and tensile stress is generated, the average stress, which is a heavy factor in fatigue strength, is reduced. At this time, the stress amplitude does not change. As a result, even if the point corresponding to the average stress and the stress amplitude is in the region Z2 above the fatigue limit line before the upper deck portion 22 is fastened, as shown by the arrow in FIG. The reliability of strength is improved.

  In the state where the upper deck portion 22 is fastened as described above, at least the lower surface of the cylinder liner 13 abuts on the boundary portion between the outer wall 19 and the skirt portion 17 as shown in FIG. Further, although not shown, the lower end portion of the outer wall surface 13A of the cylinder liner 13 may abut on the lower end portion of the inner wall surface 19A of the outer wall 19. At least the upper part of the outer wall surface 13 </ b> A of the cylinder liner 13 is separated from the upper part of the inner wall surface 19 </ b> A of the outer wall 19. A space surrounded by the outer wall surface 13 </ b> A, the inner wall surface 19 </ b> A, and the upper deck portion 22 serves as a water jacket 18 that is a cooling water passage for cooling the cylinder block body 12 and the cylinder liner 13.

According to the first embodiment described in detail above, the following effects can be obtained.
(1) In a state before the upper deck portion 22 is fastened by the head bolt 16, the center line L2 of the screw hole 23 provided in the outer wall 19 is located between the cylinder bores 21 more than the center line L3 of the through hole 26 provided in the upper deck portion 22. Offset to the center C side. Further, a tubular positioning portion 27 protruding downward from the upper deck portion 22 is provided in the through hole 26. By matching both the center lines L2 and L3, or by further inserting the positioning portion 27 into the screw hole 23, when the upper deck portion 22 is fastened by the head bolt 16, the compression stress F toward the center C is applied to the cylinder liner 13. Can be generated. The compressive stress F can weaken the tensile stress due to the residual stress generated between the cylinder bores 21 when the cylinder liner 13 is manufactured. To reduce the average stress, which is an important factor in fatigue strength, and to assign the point corresponding to the average stress and stress amplitude to the region Z1 below the fatigue limit line, and to improve the reliability of the strength around the center C Can do.

  (2) By inserting the positioning portion 27 into the screw hole 23, the center lines L2 and L3 are matched. Therefore, it becomes easy to insert the head bolt 16 into the through hole 26 and screw it into the screw hole 23.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, a tapered guide portion whose diameter decreases toward the lower end outer peripheral surface of the positioning portion 27 that protrudes from the upper deck portion 22 to the side opposite to the cylinder head (lower side) as it moves away from the cylinder head 15 (lower side). 28 is formed. Other configurations are the same as those in the first embodiment. Therefore, the same members and portions as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  According to the second embodiment having the above-described configuration, the outer diameter of the guide portion 28 in the positioning portion 27 is smaller than that of other portions of the positioning portion 27. In addition, the guide portion 28 has a tapered shape with a diameter decreasing toward the lower side. The outer diameter of the positioning portion 27 is the smallest at the lower end of the guide portion 28. Therefore, depending on the offset amount of both center lines L2 and L3, the cylinder liner 13 is compressed toward the side toward the center C (right side in FIG. 6), or the cylinder block body 12 is away from the center C (left side in FIG. 6). It is possible to position the lower end of the guide portion 28 at the opening portion of the screw hole 23 without expanding to).

  When the upper deck portion 22 is further brought closer to the outer wall 19 from this state, the guide portion 28 enters the screw hole 23. In this process, a force toward the center C acts on the positioning portion 27. This force is transmitted to the cylinder liner 13 through the upper deck portion 22, and a compressive stress F toward the center C is generated in the cylinder liner 13. When the guide portion 28 is completely inserted into the screw hole 23, the center line L3 of the positioning portion 27 (through hole 26) matches the center line L2 of the screw hole 23, and the head bolt 16 is moved to the positioning portion 27 ( It can be inserted into the through hole 26) and screwed into the screw hole 23.

Therefore, according to the second embodiment, in addition to the effects (1) and (2) in the first embodiment described above, the following effects can be obtained.
(3) A tapered guide portion 28 is formed at the lower end portion of the positioning portion 27. For this reason, only by performing a simple operation of bringing the upper deck portion 22 close to the outer wall 19, the guide portion 28 and thus the entire positioning portion 27 are inserted into the screw hole 23, and the compressive stress toward the center C is applied to the cylinder liner 13. F can be generated. Work such as compressing the cylinder liner 13 toward the center C or expanding the cylinder block body 12 away from the center C becomes unnecessary. As a result, the assembling property of the cylinder liner 13 to the cylinder block body 12 is improved.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. In the third embodiment, the shaft portion 31 of the head bolt 16 has an outer diameter substantially the same as that of the through hole 26 and is fitted into the through hole 26 in a state where the upper deck portion 22 is fastened to the outer wall 19. A large diameter portion 32 is formed. In addition, a tapered guide portion 33 is formed at the lower end of the large-diameter portion 32 on the side opposite to the cylinder head. The tapered guide portion 33 decreases in diameter toward the lower side, that is, as it moves downward from the cylinder head 15. In addition, the positioning part 27 is not provided. This is because the large diameter portion 32 described above exhibits the same function as the positioning portion 27. The configuration other than the above is the same as that of the first embodiment. Therefore, the same members and portions as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the cylinder block 11 having the above configuration, in the state immediately before the upper deck portion 22 is fastened by the head bolt 16, the center line L2 of the screw hole 23 is closer to the center C side than the center line L3 of the head bolt 16 (through hole 26) ( The right side of FIG. At the time of fastening, from the above state, the large-diameter portion 32 of the head bolt 16 is fitted into the through hole 26, and the portion of the shaft portion 31 below the large-diameter portion 32 is inserted into the screw hole 23.

  Here, the outer diameter of the guide portion 33 in the large diameter portion 32 is smaller than that of other portions of the large diameter portion 32. Moreover, the guide portion 33 has a tapered shape with a diameter decreasing toward the lower side. The outer diameter of the large diameter portion 32 is the smallest at the lower end of the guide portion 33. Therefore, depending on the offset amount of both center lines L2 and L3, the cylinder liner 13 is compressed to the side toward the center C (right side in FIG. 7) or the cylinder block body 12 is separated from the center C (in FIG. 7). It is possible to position the lower end of the guide portion 33 at the opening of the screw hole 23 without spreading it to the left side. In this state, when the upper deck portion 22 is further brought closer to the outer wall 19, the guide portion 33 enters the screw hole 23. In this process, a force toward the center C acts on the head bolt 16. This force is transmitted to the cylinder liner 13 through the upper deck portion 22. A compressive stress F toward the center C is generated in the cylinder liner 13. When the guide portion 33 is completely inserted into the screw hole 23, the center line L3 of the head bolt 16 (through hole 26) matches the center line L2 of the screw hole 23. Further, when the head bolt 16 is screwed into the female screw of the screw hole 23, the upper deck portion 22 is fastened to the cylinder head 15 and the cylinder block body 12.

Therefore, according to the third embodiment, the following effect can be obtained in addition to the above-described effect (1).
(4) A large diameter portion 32 having substantially the same outer diameter as the through hole 26 is formed in the shaft portion 31 of the head bolt 16, and a tapered guide portion 33 is formed at the lower end portion of the large diameter portion 32. ing. The large diameter portion 32 of the head bolt 16 having such a guide portion 33 exhibits the same function as the positioning portion 27 having the guide portion 28. For this reason, the assembly property with respect to the cylinder block main body 12 of the cylinder liner 13 can be improved like (3) mentioned above. In addition, the positioning part 27 is not necessary, and the number of parts can be reduced.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIG. In the fourth embodiment, apart from the through hole 26 and the screw hole 23, a positioning projection 35 and a positioning recess 36 for positioning the upper deck portion 22 with respect to the outer wall 19 are provided on the upper deck portion 22 and the outer wall 19. ing. Here, a positioning recess 36 is provided at a location corresponding to the space between the cylinder bores 21 on the upper surface of the outer wall 19, and a positioning projection 35 is provided at a location corresponding to the positioning recess 36 on the lower surface of the upper deck portion 22. The location corresponding to the space between the cylinder bores 21 is a surface that is orthogonal to the arrangement direction of the cylinder bores 21 and passes between adjacent cylinder bores 21. In the present embodiment, the positioning protrusion 35 is constituted by a pin press-fitted and fixed to the upper deck portion 22. A tapered guide portion 37 is formed on the outer peripheral surface of the lower end portion of the positioning projection 35 so as to decrease in diameter as it moves away from the cylinder head 15 (lower side).

  In a state before the upper deck portion 22 is fastened, the center line L5 of the positioning recess 36 is offset by a predetermined amount from the center line L4 of the positioning projection 35 to the center C side between the cylinder bores 21 (right side in FIG. 8). This offset amount is the same as the offset amount of the center line L2 of the screw hole 23 with respect to the center line L3 of the through hole 26. The positioning portion 27 is not provided in the through hole 26. Other configurations are the same as those in the first embodiment. Therefore, the same members and portions as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the cylinder block 11 configured as described above, the center line L5 of the positioning recess 36 is displaced from the center line L4 of the positioning protrusion 35 toward the center C before the upper deck portion 22 is fastened by the head bolt 16. Further, the center line L2 of the screw hole 23 is shifted to the center C side from the center line L3 of the through hole 26.

  Here, the outer diameter of the positioning projection 35 is the smallest at the tip of the guide portion 37 (the lower end in FIG. 8). Therefore, when the upper deck portion 22 is fastened, the cylinder liner 13 is not compressed toward the side toward the center C (right side in FIG. 8), and the cylinder block body 12 is not expanded toward the side away from the center C (left side in FIG. 8). In addition, the lower end of the guide portion 37 can be positioned at the opening of the positioning recess 36.

  When the upper deck portion 22 is further brought closer to the outer wall 19 from this state, the guide portion 37 enters the positioning recess 36. In this process, a force toward the center C acts on the positioning protrusion 35. This force is transmitted to the cylinder liner 13 through the upper deck portion 22, and a compressive stress F toward the center C is generated in the cylinder liner 13. When the guide portion 37 is completely inserted into the positioning recess 36, the center line L 4 of the positioning projection 35 coincides with the center line L 5 of the positioning recess 36. In this state, the center line L3 of the through hole 26 matches the center line L2 of the screw hole 23. Therefore, when the head bolt 16 is screwed into the screw hole 23 through the through hole 26, the positioning protrusion 35 is completely inserted into the positioning recess 36 as shown by a two-dot chain line in FIG. Can be fastened to the cylinder head 15 and the outer wall 19.

Therefore, according to the fourth embodiment, the same effects as the effects (1), (3), and (4) described above can be obtained.
Note that the present invention can be embodied in another embodiment described below.

-About the large diameter part 32 in 3rd Embodiment, and the positioning protrusion 35 in 4th Embodiment, you may omit at least one guide part 33,37.
The positioning portion 27 in the first and second embodiments and the positioning protrusion 35 in the fourth embodiment may be integrally formed on the upper deck portion 22.

In contrast to the fourth embodiment, a positioning recess 36 may be provided in the upper deck portion 22 and a positioning protrusion 35 may be provided on the outer wall 19 of the cylinder block body 12.
-You may form the positioning protrusion 35 in 4th Embodiment in the shape of a tube.

  -This invention is applicable not only to the cylinder block 11 mentioned above but to the site | part to which tensile stress acts by the thermal expansion and vibration between members about the mechanical joining between metal members. Also in this case, the compressive stress is generated by the compressive stress generating means for the portion where the tensile stress acts. For example, a through hole through which a screw member such as a bolt is inserted is provided in a member on which a tensile stress is easily applied, and a screw hole into which the screw member is screwed is provided in a member on which a tensile stress is not easily applied. . The center line of the screw hole is offset with respect to the center line of the through hole. Then, the compression stress is generated by screwing the screw member inserted through the through hole into the screw hole in a state where both center lines are matched.

  An example of the member on which the tensile stress easily acts is an exhaust manifold 41 that collects the exhaust discharged from the combustion chamber of each cylinder and sends it to the exhaust pipe as shown in FIG. The exhaust manifold 41 is fastened to the cylinder head by a bolt or the like inserted through the through hole 42.

  Another member that easily generates tensile stress is an oil pan for storing engine lubricating oil. FIG. 10 shows an example. In this example, the oil pan includes a first oil pan 43 and a second oil pan 44, and a baffle plate 45 disposed therebetween. The first oil pan 43 is fastened to the cylinder block with bolts or the like, and the baffle plate 45 and the second oil pan 44 are fastened to the first oil pan 43 with bolts or the like. Both of these oil pans 43 and 44 and the baffle plate 45 correspond to the members where the tensile stress is easily generated.

  Another member includes a bracket for attaching a part attached to the engine. FIG.11 and FIG.12 has shown the example. FIG. 11 shows an engine side bracket 47 for attaching the engine mount 46 to the engine, and a body side bracket 48 for attaching the engine mount 46 to the body of the automobile. The engine side bracket 47 is fastened to the engine by bolts or the like, and the body side bracket 48 is fastened to the body by bolts 49 or the like. In FIG. 11, 51 is a through hole through which a bolt or the like is inserted.

  FIG. 12 shows a first bracket 53 and a second bracket 54 for attaching the alternator 52 to the engine. The first bracket 53 is fastened to the engine with a bolt or the like. The alternator 52 is rotatably supported by a shaft 56 with respect to the first bracket 53 at a lower portion thereof. Therefore, the tension of the belt 57 can be adjusted by rotating the alternator 52 with the shaft 56 as a fulcrum. On the other hand, the second bracket 54 is fastened to the engine by a bolt 55. The second bracket 54 is formed with an arc-shaped long hole 58 centered on the shaft 56, and a bolt 59 inserted through the upper portion of the alternator 52 is passed through the long hole 58. When the bolt 59 is tightened, the alternator 52 is fastened to the second bracket 54, and the belt 57 is held in a state of being pulled with a predetermined tension.

  Among the brackets 47, 48, 53, and 54 described above, in particular, tensile stress is likely to act on the engine-side bracket 47 in FIG. 11 and the second bracket 54 in FIG. 12, and thus compressive stress is generated as described above. It is effective.

The partial exploded perspective view of a cylinder liner and a cylinder block main part about a 1st embodiment of the present invention. Sectional drawing which shows the state which fastened the cylinder liner to the cylinder block. The fragmentary sectional view which shows the relationship between the centerline of a through-hole, and the centerline of a screw hole in the state before fastening of a cylinder liner. The diagram which shows the aspect from which the stress which generate | occur | produces between cylinder bores changes in steps. The diagram which shows the fatigue limit line prescribed | regulated in the relationship between average stress and stress amplitude. The fragmentary sectional view which shows the state before the fastening of a cylinder liner about 2nd Embodiment of this invention. The fragmentary sectional view which shows the state before the fastening of a cylinder liner about 3rd Embodiment of this invention. The fragmentary sectional view which shows the state before fastening of a cylinder liner about 4th Embodiment of this invention. The partial front view which shows the other application site | part (exhaust manifold) of this invention. The disassembled perspective view which shows the other application part (oil pan) of this invention. The perspective view which shows the other application site | part (bracket) of this invention. The partial front view which shows the other application site | part (bracket) of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Cylinder block, 12 ... Cylinder block main body, 13 ... Cylinder liner, 15 ... Cylinder head, 16 ... Head bolt (screw member), 19 ... Outer wall, 21 ... Cylinder bore, 22 ... Upper deck part, 23 ... Screw hole, 26 DESCRIPTION OF SYMBOLS ... Through-hole, 27 ... Positioning part, 28, 33 ... Guide part, 31 ... Shaft part, 32 ... Large diameter part, 35 ... Positioning protrusion, 36 ... Positioning recessed part, C ... Center between cylinder bores, F ... Compression stress, L2... Center line of screw hole, L3... Center line of through hole, L4... Center line of positioning protrusion, L5.

Claims (6)

A cylinder liner having a plurality of cylinder bores and having an upper deck portion at an end on the cylinder head side;
A cylinder block body having an outer wall surrounding a portion excluding the upper deck portion of the cylinder liner, and a cylinder block in which the upper deck portion is fastened to the cylinder head and the outer wall by a screw member.
When the upper deck portion is fastened to the outer wall, the cylinder liner is caused to generate a compressive stress toward the center between the cylinder bores in a plane perpendicular to the arrangement direction of the cylinder bores and passing between adjacent cylinder bores. A cylinder block comprising compressive stress generating means. The compressive stress generating means includes a through hole provided in the upper deck portion and through which the screw member is inserted, and a screw hole provided in the outer wall and into which the screw member is screwed.
2. The cylinder block according to claim 1, wherein a center line of the screw hole is offset toward a center side between the cylinder bores with respect to a center line of the through hole in a state before the upper deck portion is fastened. 3. The cylinder block according to claim 2, wherein the through hole is provided with a tubular positioning portion that protrudes from the upper deck portion to the side opposite to the cylinder head and through which the screw member can be inserted. 4. The cylinder block according to claim 3, wherein a taper-shaped guide portion whose diameter decreases as the distance from the cylinder head is increased is formed at an end of the positioning portion on the side opposite to the cylinder head. The shaft portion of the screw member is formed with a large-diameter portion that fits into the through-hole in a state where the upper deck portion is fastened to the outer wall, and an end portion of the large-diameter portion on the side opposite to the cylinder head The cylinder block according to claim 2, wherein a tapered guide portion having a diameter reduced as the distance from the cylinder head increases. The compressive stress generating means includes a positioning recess provided at a position corresponding to one of the cylinder bores on the outer wall and the upper deck portion, and a positioning protrusion provided on the other and fitted in the positioning recess. With
In the state before the upper deck portion is fastened, the center line of the positioning recess and the positioning protrusion provided on the outer wall is closer to the center side between the cylinder bores than the center line provided on the upper deck portion. The cylinder block according to claim 1, wherein the cylinder block is offset.

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