JP2011132851A - Cylinder block structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder block structure suppressing deformation of a cylinder block and also securing the axial force of a head bolt. <P>SOLUTION: In the aluminum cylinder block, cast iron cylinder liners 41, 42 are buried in the cylinder bore portion 13 of the cylinder block 1, the cylinder bore portion 13 is surrounded by a cylinder outer wall portion 16 through a water jacket 15, and the cylinder outer wall portion 16 is integrally formed with head bolt bosses 17, 18 having head bolt holes 19. The rigidity of the head bolt axial direction Z2 of a water jacket bottom in a portion surrounded by the head bolt holes 19 and the tangents 22b and 22c, 26b and 26c of the peripheral surfaces of the cylinder liners 41, 42, projected in a cylinder axial direction Z1, is increased. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cylinder block structure, and more particularly to an open deck type cylinder block structure in which a cylinder bore portion is surrounded by a water jacket.

  For example, in an automobile engine, tightening of the head bolt is improved by improving the rigidity around the head bolt hole into which the head bolt for fixing the cylinder head to the cylinder block via a head gasket with high output is screwed. There is a demand to increase the force, that is, the axial force of the head bolt, to secure the surface pressure between the head gasket and the top deck to suppress the combustion pressure leakage, the cooling water leakage, and the like. In particular, in order to reduce the weight of the engine, the cylinder block formed of an aluminum alloy has lower rigidity than the conventional cast iron cylinder block, and various improvements are made in the head bolt axial direction around the head bolt hole. There is a cylinder block structure.

  An example of a cylinder block structure for improving the rigidity around this type of head bolt hole will be described with reference to FIGS. 6 is a plan view of a principal part of a cylinder block of a horizontally opposed engine projected from the cylinder axial direction, FIG. 7 is a schematic cross-sectional view taken along the line VII-VII of FIG. 6, and FIG. 8 is a schematic view of VIII of FIG. FIG.

  The cylinder block 100 is an open deck type made of an aluminum alloy, and has a cylinder bore portion 102 in which a cylinder bore 101 in which a pair of cylinder liners 109 are embedded is provided with a partition wall portion 103 therebetween. The outer periphery of the cylinder bore portion 102 is surrounded by a cylinder outer wall portion 105 with a war jacket 104 interposed therebetween, and the cylinder outer wall portion 105 is integrally coupled to the cylinder bore portion 102 via a crankcase portion 108 constituting the bottom portion 104b of the water jacket 104. .

  The water jacket 104 is formed in a deep groove shape opening to the top deck 100 a in an arc shape surrounding each cylinder bore 101 via the cylinder bore portion 102, and is connected by connecting portions 104 a that are curved in the vicinity of the partition wall portion 103.

  A head bolt hole 107 is formed in which a head bolt for fixing a cylinder head (not shown) is screwed and fastened to a head bolt boss 106 formed to swell in a predetermined shape on the cylinder outer wall portion 105.

  The head bolt bosses 106 are formed in the vicinity of the connecting portion 104a of the water jacket 104 and in the vicinity of the corners of the cylinder block 100 around the water jacket 104. Head bolt holes 107 are formed in the head deck bosses 106 in the head deck bosses 106a. A threaded portion 107a is formed on the front end portion 106a side of the head bolt boss 106 that is opened and perforated and spaced from the top deck 100a.

  The water jacket 104 is formed so that the bottom 104b is shallower than the threaded portion 107a of the bolt hole 107 over the entire circumference. As a result, a thick portion is formed in an annular shape along the bottom 104b of the water jacket 104, and the rigidity around the threaded portion 107a of the bolt hole 107 is increased.

  A cylinder block structure according to Patent Document 1 will be described with reference to FIGS. 9 is a plan view of the cylinder block 110 of the V-type engine projected from the cylinder axial direction, FIG. 10 is a cross-sectional view taken along line XX of FIG. 9, and FIG. 11 is a cross-sectional view taken along line XI-XI of FIG.

  The cylinder block 110 has a cylinder bore portion 112 in which three cylinder bores 111 into which a cylinder liner 119 is cast with a partition wall portion 113 interposed therebetween are arranged side by side. The outer periphery of the cylinder bore portion 112 is surrounded by a cylinder outer wall portion 115 with a war jacket 114 therebetween, and the cylinder outer wall portion 115 is integrally coupled to the cylinder bore portion 112 via a crankcase portion 118 that constitutes the bottom portion of the water jacket 114. The water jacket 114 is formed in a deep groove shape that opens to the top deck 110 a and extends in an arc shape surrounding each cylinder bore 111 via the cylinder bore portion 112, and is connected to each other in the vicinity of the partition wall portion 113 by the connecting portion 114 a.

  A head bolt hole 117 is formed in a head bolt boss 116 formed at a predetermined position on the cylinder outer wall 115. Specifically, the head bolt boss 116 is formed in the vicinity of the connecting portion 114 a of the water jacket 114 and in the vicinity of the corner of the cylinder block 110 around the water jacket 114.

  A rib 114b (shown by hatching in FIG. 9) is formed at the bottom of the water jacket 114 at a position in the vicinity of each head bolt boss 116. That is, the bottom of the water jacket 114 is formed so that the periphery of the head bolt boss 6 is shallower than the threaded portion 117a of the head bolt hole 117 by the rib 114b. As a result, the rigidity in the head bolt axial direction around the screw portion 117a of the head bolt hole 117 is improved, and the periphery of the screw portion 117a of the head bolt hole 117 is cooled by the cooling water flowing in the water jacket 114. Thermal expansion is suppressed, and a decrease in tightening force due to thermal expansion is suppressed.

JP 2006-194159 A

  According to the cylinder block structure shown in FIGS. 6 to 8, the head bolt axial direction around the screw portion 107a to which the head bolt is screwed and fastened by making the water jacket 104 shallower than the screw portion 107a of the head bolt hole 107. This increases the rigidity of the head bolt and increases the tightening force of the head bolt.

  However, since the water jacket 104 is made shallower than the threaded portion 107a of the head bolt hole 107 over the entire circumference, the coupling rigidity between the cylinder bore portion 102 and the cylinder outer wall portion 105 increases over the entire circumference. As a result, the reaction force of the axial force of the head bolt due to the tightening of the head bolt is applied to the tip portion 106a of the head bolt boss 106 where the screw portion 107a to which the head bolt is fastened is formed as shown by the arrow F1 in FIGS. At the same time, the cylinder bore 102 and the cylinder outer wall 105 are dispersedly transmitted as indicated by the arrow F2 and further transmitted to the partition 103 as indicated by F4 in FIG.

  The reaction force of the axial force of the head bolt is distributed over a wide range of the cylinder bore portion 102 and the cylinder outer wall portion 105 including the partition wall portion 103, the axial force of the head bolt is reduced, and the clamping force of the cylinder head by the head bolt is reduced. Is concerned. As the tightening force of the cylinder head by the head bolt decreases, there is a concern that the surface pressure of the head gasket with respect to the top deck 100a decreases and the occurrence of combustion pressure leakage, cooling water leakage, and the like is induced. On the other hand, when the tightening force of the head bolt is increased in order to increase the axial force of the head bolt, the reaction forces F2 and F4 exerted on the cylinder bore portion 102 and the partition wall portion 103 increase as the axial force increases, and the cylinder bore 101 is deformed. It becomes a factor to induce. There is a concern that the cylinder liner 109 may be deformed by the deformation of the cylinder bore 101 to cause a reduction in fuel consumption due to an increase in frictional resistance of a piston or the like, or to cause separation between the cylinder liner 109 and the cylinder bore portion 102. Moreover, there is a concern that the cylinder outer wall 105 may be deformed, that is, collapsed due to an excessive reaction force F3 on the cylinder outer wall 105.

  On the other hand, according to Patent Document 1, the rib 114b is formed in the lower part of the water jacket 114 in the vicinity of the head bolt boss 116, and the bottom is locally shallowed to increase the rigidity around the screw portion 117a of the head bolt hole 117. Thus, the tightening force of the head bolt can be increased to some extent.

  However, since the head bolt boss 116 and the cylinder bore portion 112 are locally coupled by the rib 114b and the rigidity of the head bolt axial direction of the portion is enormous, the reaction force of the axial force of the head bolt due to the tightening of the head bolt is Distributed transmission is also performed to the cylinder bore portion 112 including the outer wall portion 115 and the partition wall portion 113. As the reaction force is dispersed, it is difficult to secure the axial force of the head bolt, the tightening force of the cylinder head by the head bolt is reduced, the surface pressure of the head gasket against the top deck 110a is reduced, combustion pressure leakage, cooling water There is a concern of inducing the occurrence of leakage.

  Further, when the tightening force by the head bolt is increased, the reaction force exerted on the cylinder bore portion 112 including the partition wall portion 113 is increased, and the reaction force is locally applied to the cylinder bore portion 112 by the rib 114b formed on the bottom portion of the water jacket 114. It is transmitted unevenly and becomes a factor that induces deformation of the cylinder bore 111.

  In addition, the position of the rib 114b locally formed at the bottom of the water jacket 114 needs to be set in consideration of the cooling efficiency by the cooling water, and may not be set at a necessary part in terms of strength.

  Accordingly, an object of the present invention is to provide a cylinder block structure that can suppress deformation of the cylinder block and secure the axial force of the head bolt.

  According to a first aspect of the present invention for achieving the above object, a cylinder liner made of a metal having a rigidity higher than that of the aluminum alloy is embedded in a cylinder bore portion of a cylinder block made of aluminum alloy, and the cylinder bore portion is provided with a water jacket so that a cylinder outer wall is interposed. A head bolt boss having a head bolt hole into which the head bolt is screwed is integrally formed with the cylinder outer wall portion, and the cylinder outer wall portion, the head bolt boss and the cylinder bore portion are connected by the bottom portion of the water jacket. In the open deck type cylinder block structure, the rigidity in the head bolt axial direction at the bottom of the water jacket in the portion surrounded by the tangent line between the head bolt hole projected in the cylinder axial direction and the outer peripheral surface of the cylinder liner, The bottom of the jacket Characterized by being higher than the stiffness of Doboruto axis.

  According to this, the rigidity in the head bolt axial direction of the bottom portion of the water jacket in the portion surrounded by the tangent line between the head bolt hole projected in the axial direction of the cylinder and the outer peripheral surface of the cylinder liner, the head bolt in the bottom portion of the water jacket. Since it is higher than the rigidity in the axial direction, the reaction force of the axial force caused by tightening the head bolt is intensively distributed and received in the cylinder bore part where the rigidity is secured by the cylinder liner, so that the axial force of the head bolt can be secured. .

  On the other hand, the reaction force in the head bolt axial direction at the head bolt boss is reduced, and the reaction force transmitted to the cylinder outer wall is extremely reduced. By securing the axial force by the head bolt, the surface pressure of the head gasket with respect to the top deck is obtained, and combustion pressure leakage, cooling water leakage, and the like can be avoided. Further, the reaction force is distributed and transmitted over a wide range of the cylinder bore portion, so that local deformation of the cylinder bore portion is prevented, and peeling between the cylinder liner and the cylinder bore portion is avoided, thereby improving durability. Further, by reducing the reaction force exerted on the cylinder outer wall portion, deformation of the cylinder outer wall portion, so-called collapse deformation, is suppressed, and deformation of the cylinder block can be suppressed.

  According to a second aspect of the present invention, in the cylinder block structure according to the first aspect of the present invention, the rigidity of the head bolt boss on the cylinder bore portion side is opposite to the cylinder bore portion side with respect to the rigidity in the head bolt axial direction. The rigidity in the head bolt axial direction is equal or smaller.

  According to this, the rigidity in the head bolt axis direction on the cylinder bore side of the head bolt boss is equal to or smaller than the rigidity in the head bolt axis direction on the opposite side to the cylinder bore side, so that it is distributed to the cylinder outer wall. The transmitted reaction force is suppressed and the invention of claim 1 is efficiently executed.

  According to a third aspect of the present invention, in the cylinder block structure according to the first or second aspect, the difference in rigidity is set by the thickness of the bottom portion of the water jacket.

  According to this, invention of Claim 1 can be implemented by setting the thickness of a water jacket bottom part according to required rigidity.

  According to the present invention, the rigidity in the head bolt axial direction at the bottom portion of the water jacket surrounded by the tangent line between the head bolt hole projected in the cylinder axial direction and the outer peripheral surface of the cylinder liner is determined. By making it higher than the rigidity in the axial direction, the reaction force of the axial force due to tightening of the head bolt is intensively distributed and transmitted to the cylinder bore part to secure the axial force of the head bolt and obtain the surface pressure of the head gasket against the top deck. It is done. On the other hand, by reducing the reaction force in the head bolt axial direction at the head bolt boss, the reaction force transmitted to the cylinder outer wall is extremely reduced, and deformation of the cylinder block can be suppressed.

It is the top view projected from the cylinder axial direction of the cylinder block of the horizontally opposed engine which shows the outline | summary of embodiment of the cylinder block structure by this invention. It is the II-II sectional view taken on the line of Drawing 1 shown typically. It is the III-III sectional view taken on the line of FIG. It is the A section enlarged view of FIG. 1 which shows the stiffening range of a head bolt axial direction. It is the top view projected from the cylinder axial direction of the cylinder block which shows the stiffening range of a head bolt axial direction. It is a principal part top view projected from the cylinder axial direction of the cylinder block which shows the outline | summary of the conventional cylinder block structure. It is the VII-VII sectional view taken on the line of FIG. It is the VIII-VIII sectional view taken on the line of FIG. 6 shown typically. It is a principal part top view of the cylinder block which shows the outline | summary of the conventional cylinder block structure. FIG. 10 is a sectional view taken along line XX in FIG. 9. It is the XI-XI sectional view taken on the line of FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  1 is a plan view projected from the cylinder axial direction of a cylinder block in a horizontally opposed engine, FIG. 2 is a schematic cross-sectional view taken along the line II-II of FIG. 1, and FIG. It is III sectional drawing. FIG. 4 is an enlarged view of part A in FIG. 1 for explaining the stiffening range in the head bolt axial direction.

  The cylinder block 1 is an open deck type made of an aluminum alloy, and is formed continuously with a cylinder block body 10 forming a cylinder row portion and a base end side of the cylinder block body 10 to form a crankshaft storage space 31 therein. It is comprised from the crankcase part 30 which carries out.

  As shown in FIGS. 1 to 3, the cylinder block body 10 is made of a pair of metal liners 41 and 42 embedded in a metal having a higher rigidity than an aluminum alloy with a partition wall portion 14 interposed therebetween, in the present embodiment, cast iron. The cylinder bores 11 and 12 have a cylinder bore portion 13 arranged in parallel. The outer periphery of the cylinder bore portion 13 is surrounded by a cylinder outer wall portion 16 with a water jacket 15 therebetween, and the cylinder outer wall portion 16 is integrally coupled to the cylinder bore portion 13 via a crankcase portion 30 that forms a bottom portion 15b of the water jacket 15.

  The water jacket 15 is formed in a deep groove shape opened to the top deck 10 a in an arc shape surrounding the cylinder bores 11 and 12 via the cylinder bore portion 13, and is connected by a connecting portion 15 a that is curved in the vicinity of the partition wall portion 14. .

  Head bolt bosses 17, 18 extending from the top deck 10 a side to the crankcase portion 30 side are formed at predetermined positions on the cylinder outer wall portion 16 so as to swell axially toward the water jacket 15, and each head bolt boss 17 and 18 are formed with head bolt holes 19 into which head bolts (not shown) for fixing the Linder heads are screwed.

  Specifically, a head bolt hole 19 is formed in a head bolt boss 17 formed in a shaft shape from the cylinder outer wall portion 16 toward the partition wall portion 14 in the vicinity of the connecting portion 15a of the water jacket 15, and the water jacket 15 is formed. A head bolt hole 19 is formed in a head bolt boss 18 that is bulged and formed on the cylinder outer wall 16 in the vicinity of the corner of the cylinder block body 10 around 15. A head bolt hole 19 formed in each of the head bolt bosses 17 and 18 is formed by perforating the top deck 10a with the base end opened, and has a depth substantially the same as the bottom 15b of the water jacket 15, and is separated from the top deck 10a. A screw portion 19a serving as a fastening portion having a predetermined length is formed on the tip end side of the head bolt boss 17.

  The bottom 15b of the water jacket 15 in the vicinity of each head bolt boss 17 has a thickness of the bottom 15b of the water jacket 15 so as to protrude from the bottom 15b and connect the tip 17a of the head bolt boss 17 and the cylinder bore 13 to each other. A stiffening portion 20 formed to increase the thickness is provided.

  The stiffening portion 20 has a thickness of the bottom portion 15 b that substantially corresponds to the entire range of the screw portion 19 a of the head bolt hole 19, and the top portion 20 a is at a position that substantially corresponds to the base end of the screw portion 19 a of the head bolt hole 19. As shown in FIG. 4, one end 20 b that protrudes from the bottom 15 b along the tangent line 22 b between the outer edge 19 b of the head bolt hole 19 formed in the head bolt boss 17 and the outer peripheral surface 41 a of the cylinder liner 41. Is formed, and the other end portion 20c that protrudes from the bottom portion 15b along the tangent line 22c between the outer edge 19b of the head bolt hole 19 and the outer peripheral surface 42a of the cylinder liner 42 is formed.

  That is, the stiffening portion 20 is projected from the cylinder axial direction Z1 of the outer edge 19b of the head bolt hole 19, the outer peripheral surface 41a of the cylinder liner 41, the tangent line 22b, the outer edge 19b of the head bolt hole 19, and the outer peripheral surface 42a of the cylinder liner 42. And the outer end 20d on the opposite side of the cylinder bore 13 side is connected only to the head bolt boss 17, while the inner end of the water jacket 15 is increased in thickness over the range of the tangent line 22c. The side end 20e is connected over a wide range of the cylinder bore portion 13, and is formed in a taper shape whose width gradually increases as it moves from the head bolt boss 17 side to the cylinder bore portion 13 side. As a result, the rigidity in the head bolt axial direction Z2 on the cylinder bore 13 side of the head boss 17 is set equal to or smaller than the rigidity in the head bolt axial direction Z2 on the cylinder outer wall 16 side.

  Further, as shown in FIG. 3, a concave unconnected portion 21 is formed between the partition wall portion 14 and the head bolt boss 17 so as to enter the stiffening portion 20 from the crankshaft accommodating portion 31 of the crankcase portion 30. In addition, by setting the thickness of the stiffening portion 20 small, the rigidity of the head bolt boss 17 and the partition wall portion 14 in the head bolt axial direction Z2 is suppressed, and load transmission from the head bolt boss 17 to the partition wall portion 14 is interrupted. Or suppress.

  The same stiffening part 20 is formed although the detailed description is abbreviate | omitted by attaching | subjecting the same code | symbol to the part corresponding also to the bottom part 15b of the water jacket 15 in the position near the other head bolt boss | hub 17.

  In the vicinity of each corner of the cylinder block body 10, the bottom 15 b of the water jacket 15 in the vicinity of the head bolt boss 18 bulging and formed on the cylinder outer wall 16 protrudes from the bottom 15 b to the head bolt boss 18 and the cylinder bore 13. Are formed.

  For example, as shown in FIG. 4, the stiffening portion 25 has a top portion 25 a at a position substantially corresponding to the base end of the screw portion 19 a of the head bolt hole 19, and the head bolt hole 19 formed in the head bolt boss 18. One end portion 25b is formed to protrude from the bottom portion 15b along one tangent line 26b between the outer edge 19b and the outer peripheral surface 41a of the cylinder liner 41, and the outer edge 19b of the head bolt hole 19 and the outer peripheral surface of the cylinder liner 41 are formed. An end portion 25c protruding from the bottom portion 15b is formed along the other tangent line 26c with 41a.

  That is, the reinforcing portion 25 is projected from the cylinder axial direction Z 1, one tangent line 26 b between the outer edge 19 b of the head bolt hole 19 and the outer peripheral surface 41 a of the cylinder liner 41, the outer edge 19 b of the head bolt hole 19, and the cylinder liner 41. While the thickness of the bottom 15b of the water jacket 15 is increased between the outer tangent 12a and the other tangent 26c, the outer end 25d is connected only to the head bolt boss 18 only, while the inner end 25e is connected over a wide range of the cylinder bore 13 and is formed in a tapered shape whose width gradually increases as it moves from the head bolt boss 18 side to the cylinder bore 13 side. As a result, the rigidity in the head bolt axial direction Z2 on the cylinder bore 13 side of the head boss 18 is set to be equal to or smaller than the rigidity in the head bolt axial direction Z2 on the cylinder outer wall 16 side.

  The same stiffening portion 25 is formed although the detailed description is omitted by attaching the same to the portion corresponding to the bottom portion 15b of the water jacket 15 in the vicinity of the other head bolt boss 18.

  By setting the thickness of the bottom portion 15b of the water jacket 15 by the stiffening portion 20 and the stiffening portion 25, the head bolt hole 19 projected in the cylinder axial direction and the tangent lines 22b of the outer peripheral surfaces 41a and 42a of the cylinder liners 41 and 42, The rigidity in the head bolt axial direction Z2 of the bottom portion 15b of the water jacket 15 in the portion surrounded by 22c, 26b, and 26c can be set higher than the rigidity in the head bolt axial direction Z2 of the bottom portion 15b of the water jacket 15 in the other portion. A stiffening range in which the rigidity is increased by the stiffening portion 20 and the stiffening portion 25 and the rigidity in the head bolt axial direction is high is shown in FIGS. 4 and 5 by hatching.

  That is, the rigidity of the head bolt boss 17 and the cylinder bore portion 13 in the head bolt axial direction Z2 is increased by the stiffening portion 20 without increasing the rigidity of the head bolt boss 17 and the cylinder outer wall portion 16 in the head bolt axial direction Z2. Further, the stiffening portion 25 increases the rigidity of the head bolt boss 18 and the cylinder bore portion 13 in the head bolt axial direction Z2 without increasing the rigidity of the head bolt boss 18 and the cylinder outer wall portion 16 in the head bolt axial direction Z2. On the other hand, the rigidity in the head bolt axial direction Z <b> 2 between the head bolt boss 17 and the partition wall portion 14 is extremely reduced by forming the non-connecting portion 21 formed between the head bolt boss 17 and the partition wall portion 14. In other words, the thickness of the bottom portion 15b of the water jacket 15 in the portion indicated by hatching surrounded by the tangent line between the head bolt hole 19 projected in the axial direction of the cylinder and the outer peripheral surfaces 41a and 42a of the cylinder liners 41 and 42 is set in another range. By setting the thickness larger than the thickness of the bottom portion 15b of the water jacket 15, the rigidity in the head bolt axial direction Z2 in this range is made higher than the rigidity in the head bolt axial direction Z2 of the bottom portion 15b of the water jacket 15 in the other portion. Is set.

  In the cylinder block 1 configured as described above, the axial force of the head bolt that is screwed into the screw portion 19a of the head bolt hole 19 formed in the head bolt boss 17 is fastened by the head bolt as shown in FIG. The screw 19a of the head bolt hole 19 to be screwed acts on the tip 17a of the head bolt boss 17, and the reaction force is generated at the tip 17a.

  The reaction force of the tip portion 17a is distributed and transmitted over a wide range of the cylinder bore portion 13 as indicated by an arrow F2 through a stiffening portion 20 that is connected to the tip portion 17a and has excellent rigidity in the head bolt axial direction Z2. . As a large amount of reaction force F2 is distributed and transmitted from the distal end portion 17a to the cylinder bore portion 13 via the stiffening portion 20, the reaction force F1 at the distal end portion 17a decreases. Further, there is no stiffening portion between the tip portion 17a and the cylinder outer wall portion 16, and the reaction force that is distributed and transmitted from the tip portion 17a to the cylinder outer wall portion 16 becomes extremely small. Further, the reaction force transmitted from the distal end portion 17a to the partition wall portion 14 via the stiffening portion 20 by the non-connecting portion 21 formed between the distal end portion 17a of the head bolt boss 17 and the partition wall portion 14 is blocked or greatly reduced. Reduced.

  That is, the reaction force in the head bolt axial direction Z2 generated at the front end portion 17a of the head bolt boss 17 in which the threaded portion 19a of the head bolt hole 19 into which the head bolt is screwed is mainly applied to the cylinder bore via the stiffening portion 20. It is distributed and transmitted to the part 13 as a reaction force F2 in the head bolt axial direction Z2, and is received by the cylinder bore part 13 whose rigidity is secured by the cylinder liners 41 and 42. On the other hand, the reaction force F1 at the head bolt boss 17 is greatly reduced by largely dispersing and transmitting the reaction force in the head bolt axial direction Z2 from the tip end portion 17a of the head bolt boss 17 to the cylinder bore portion 13. Further, the reaction force transmitted from the tip end portion 17a of the head bolt boss 17 to the cylinder outer wall portion 16 and the partition wall portion 14 is cut off or greatly reduced.

  Similarly, the axial force of the head bolt that is screwed and tightened to the screw portion 19a of the head bolt hole 19 formed in each head bolt boss 18 forms the screw portion of the head bolt hole 19 into which the head bolt is screwed. Acting on the tip of the head bolt boss 18, a reaction force in the head bolt axial direction Z <b> 2 is generated at the tip of the head bolt boss 18. The reaction force generated at the tip of the head bolt boss 18 is distributed and transmitted over a wide range of the cylinder bore 13 mainly through the stiffening portion 25 connected to the tip of the head bolt boss 18.

  On the other hand, the reaction force in the head bolt boss 18 is greatly reduced because a large amount of reaction force in the head bolt axial direction generated at the tip of the head bolt boss 18 is distributed and transmitted to the cylinder bore 13. Further, the reaction force distributed and transmitted to the cylinder outer wall portion 16 in which the head bolt boss 18 is formed becomes extremely small.

  Accordingly, the head bolt bosses 17 and 18 are connected to a wide range of the cylinder bore portion 13 via the stiffening portions 20 and 25, and the cylinder axial direction in the range of the stiffening portions 20 and 25 of the head bolt bosses 17 and 18 and the cylinder bore portion 13 is achieved. The head bolt bosses 17 and 18, the cylinder outer wall 16 and the head bolt in a range other than the range of the stiffening portions 20 and 25 projected from the cylinder axis direction Z1 with a high rigidity in the head bolt axis direction Z2 projected from Z1. By setting the rigidity of the boss 17 and the partition wall portion 14 in the head bolt axial direction Z2 low, the cylinder bore portion 13 in which the reaction force of the axial force caused by tightening the head bolt is secured by the cylinder liners 41 and 42 made of cast iron. The axial force of the head bolt can be secured by being distributed and received in a concentrated manner. On the other hand, by reducing the reaction force in the head bolt axial direction Z2 at the head bolt bosses 17 and 18, the reaction force transmitted to the cylinder outer wall portion 16 becomes extremely small, and the reaction force transmitted to the partition wall portion 14 becomes extremely small.

  By securing the axial force by each head bolt, a tightening force of the head bolt is obtained, the surface pressure of the head gasket with respect to the top deck 10a is obtained, and combustion pressure leakage, cooling water leakage, and the like can be avoided. Further, the reaction force in the head bolt axial direction Z2 due to the tightening of the head bolt is dispersed over a wide range of the cylinder bore portion 13, and local deformation of the cylinder bore portion 13 is suppressed, and local portions of the cylinder bores 11 and 12 and the cylinder liners 41 and 42 are suppressed. Deformation is prevented, and peeling between the cylinder liners 41 and 42 and the cylinder bore 13 is avoided to improve durability, and frictional resistance between the cylinder liners 41 and 42 and pistons is reduced to improve fuel efficiency. can get. Furthermore, the deformation of the cylinder outer wall portion 15, that is, the so-called collapse deformation is suppressed by the reduction of the reaction force exerted on the cylinder outer wall portion 15, and the deformation of the cylinder block 1 can be suppressed.

  Further, the stiffening portions 20 and 25 can be configured with a simple configuration due to the difference in thickness of the bottom portion 15b of the water jacket 15, so that the shape of the existing cylinder block does not need to be changed greatly, and the quality of the cylinder bracket is maintained. .

DESCRIPTION OF SYMBOLS 1 Cylinder block 11, 12 Cylinder bore 13 Cylinder bore part 14 Partition part 15 Water jacket 15b Bottom part 16 Cylinder outer wall part 17, 18 Head bolt boss 19 Head bolt hole 19a Screw part 19b Outer edge 20 Stiffening part 21 Unconnected part 22b, 22c Tangential 25 Stiffening part 26b Tangent line 26c Tangent line 30 Crankcase part 41, 42 Cylinder liner 41a, 42a Outer peripheral surface

Claims (3)

A cylinder liner made of a metal having a rigidity higher than that of the aluminum alloy is embedded in the cylinder bore portion of the cylinder block made of aluminum alloy, the cylinder bore portion is surrounded by a cylinder outer wall portion with a water jacket interposed, and a head bolt is attached to the cylinder outer wall portion. In an open deck type cylinder block structure in which a head bolt boss having a head bolt hole to be screwed is integrally formed, and the cylinder outer wall portion and the head bolt boss and the cylinder bore portion are connected by a bottom portion of the water jacket,
The rigidity of the head bolt axial direction at the bottom of the water jacket surrounded by the head bolt hole projected in the cylinder axial direction and the tangent line of the outer peripheral surface of the cylinder liner, and the rigidity of the other portion of the water jacket bottom at the head bolt axial direction Cylinder block structure characterized by higher height.   2. The cylinder according to claim 1, wherein the rigidity in the head bolt axial direction on the opposite side of the cylinder bore portion is equal to or smaller than the rigidity in the head bolt axial direction on the cylinder bore portion side of the head bolt boss. Block structure.   The cylinder block structure according to claim 1 or 2, wherein the difference in rigidity is set by a thickness of a bottom portion of the water jacket.

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