JP2005325815A - Cylinder block of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder block of an engine which can prevent deformation of a cylinder liner resulting from the axial force of a bolt and deformation of the cylinder liner resulting from the force applied from the inner side of the cylinder, and which can reduce a temperature difference around a cylinder bore peripheral wall. <P>SOLUTION: In the cylinder block, a contact surface F1 between the cylinder 12 and the cylinder liner 13 includes a bottom wall inner-side contact surface FM where an outer peripheral surface 12 F of the cylinder positioned on the radially outer side is connected to a bottom wall 16, and a lower end inner-side contact surface FW positioned on the radially inner side of a lower end portion 14R of a water jacket 14 including a bottom surface 14B of the water jacket 14. An adhesion force between the cylinder 12 and the cylinder liner 13 at the bottom wall inner-side contact surface FM and the lower end inner-side contact surface FW is set to be smaller than an adhesion force between the cylinder 12 and the cylinder liner 13 at portions other than the bottom wall inner-side contact surface FM and the lower end inner-side contact surface FW. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cylinder block of an engine in which a cylinder liner is cast on the inner peripheral side of a cylinder.

  As a cylinder block of an engine, a cylinder block in which a cylinder liner is cast on the inner peripheral side of a cylinder has been put into practical use. In such a cylinder block, a water jacket is formed on the outer peripheral side of the cylinder.

Cylinder blocks are classified into the following open deck type and closed deck type depending on the formation mode of the water jacket.
In an open deck type cylinder block, the water jacket is formed with its top (cylinder head side) open. That is, the water jacket of the cylinder block includes an outer wall facing the outer peripheral surface of the cylinder with a predetermined interval, a bottom wall connecting the cylinder and the outer wall to form a bottom surface of the water jacket, and an outer peripheral surface of the cylinder. It is surrounded by

  In a closed deck type cylinder block, the water jacket is formed with its top closed. That is, the water jacket of the cylinder block includes an outer wall facing the outer peripheral surface of the cylinder with a predetermined interval, a bottom wall connecting the cylinder and the outer wall to form a bottom surface of the water jacket, and an outer peripheral surface of the cylinder. It is surrounded by

In addition, in an engine including a cylinder block and a cylinder head, including the engine including the cylinder block, the cylinder head and the cylinder block are fastened by bolts. In the cylinder block, the bolt is screwed into a screw hole formed in the outer wall of the water jacket.
Japanese Patent Laid-Open No. 8-100698

  Incidentally, in an engine having an open deck type cylinder block, the axial force of the bolt is transmitted to the cylinder through the bottom wall of the water jacket. In an engine having a closed deck type cylinder block, the axial force of the bolt is transmitted to the cylinder through the top wall and the bottom wall of the water jacket.

  For this reason, in the above engine, the cylinder may be deformed together with the cylinder by pulling the cylinder toward the bolt side through the axial force of the bolt. In this case, when the roundness of the cylinder bore deteriorates, for example, the sealing performance between the cylinder bore surface and the piston ring is lowered.

Patent Document 1 proposes the following cylinder block.
In this cylinder block, an air gap is formed between the outer peripheral surface of the lower end portion of the cylinder liner and the cylinder facing the outer peripheral surface. By adopting such a configuration, the axial force of the bolt transmitted from the cylinder to the cylinder liner is reduced, so that the deformation of the cylinder liner is suppressed.

  However, in the cylinder block of the above-mentioned patent document, since a gap is formed between the cylinder and the cylinder liner, the cylinder liner is moved outward in the radial direction by a force acting from the inside of the cylinder such as a combustion pressure or a thrust force of the piston. Deformation is also conceivable.

Moreover, in the engine provided with the said cylinder block, while the problem concerning the deformation | transformation of the cylinder liner mentioned above exists, we are also anxious about the following things.
During the operation of the engine, a temperature difference occurs in the cylinder bore and the cylinder circumferential direction on the peripheral wall (cylinder liner) of the cylinder bore. By the way, in the cylinder axial direction, the temperature of the peripheral wall increases as the distance from the cylinder head increases, whereas the temperature of the peripheral wall tends to decrease as the distance from the bottom surface of the water jacket increases. Further, in the cylinder circumferential direction, the temperature of the peripheral wall where the water jacket is present in the periphery is low, while the temperature of the peripheral wall where the water jacket is not present is high.

And since the size of a bore becomes non-uniform | heterogenous due to such a temperature difference of a cylinder bore peripheral wall, it can be considered that the increase of the friction of a piston etc. is caused, for example.
The present invention has been made in view of such circumstances, and a first object is to provide a cylinder liner caused by the deformation of the cylinder liner caused by the axial force of the bolt and a force caused from the inside of the cylinder. An object of the present invention is to provide an engine cylinder block capable of suppressing the deformation of a liner. A second object is to provide an engine cylinder block capable of reducing the temperature difference in the cylinder bore peripheral wall.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 includes a cylinder in which a cylinder liner is cast and a water jacket formed around the cylinder through an outer wall, and a screw hole of a bolt for fastening a cylinder head is formed in the outer wall. Among the contact surfaces between the cylinder and the cylinder liner, the contact force between the cylinder and the cylinder liner is applied to the contact force between the cylinder and the cylinder liner other than the contact surface. The gist of the invention is that it is smaller than the adhesion force between the cylinder and the cylinder liner.

  In the above configuration, since the contact force between the cylinder and the cylinder liner is reduced on the contact surface to which the axial force of the bolt is transmitted, the axial force of the bolt acting on the cylinder is difficult to be transmitted to the cylinder liner. Thereby, deformation of the cylinder liner caused by the axial force of the bolt can be suppressed.

  In addition, since the above-described configuration is realized in a state where the cylinder and the cylinder liner are in contact with each other without forming a gap, it is caused by a force from the inside of the cylinder such as a combustion pressure and a piston thrust force. It is possible to suppress the deformation of the cylinder liner that occurs.

  The invention according to claim 2 includes a cylinder in which a cylinder liner is cast, and a water jacket formed at the top of the cylinder so as to be opened around the cylinder, and the water jacket includes an outer peripheral surface of the cylinder. The cylinder head is surrounded by an outer wall facing with a predetermined interval, a bottom wall connecting the cylinder and the outer wall to form a bottom surface of the water jacket, and an outer peripheral surface of the cylinder. In the cylinder block of the open deck type engine in which the screw hole of the bolt for fastening is provided in the outer wall, of the contact surface between the cylinder and the cylinder liner, For the inner contact surface of the bottom wall whose outer peripheral surface is connected to the bottom wall, the adhesion force between the cylinder and the cylinder liner is That said cylinder other than touch surface is smaller than the adhesion between the cylinder liner has a gist.

  In the above configuration, since the adhesion force between the cylinder and the cylinder liner is reduced on the inner peripheral surface of the bottom wall, the axial force of the bolt that acts on the cylinder through the bottom wall of the water jacket is less likely to be transmitted to the cylinder liner. . Thereby, deformation of the cylinder liner caused by the axial force of the bolt can be suppressed.

  In addition, since the above-described configuration is realized in a state where the cylinder and the cylinder liner are in contact with each other without forming a gap, it is caused by a force from the inside of the cylinder such as a combustion pressure and a piston thrust force. It is possible to suppress the deformation of the cylinder liner that occurs.

  The invention according to claim 3 includes a cylinder in which a cylinder liner is cast, and a water jacket formed around the cylinder with its top closed, and the water jacket includes an outer peripheral surface of the cylinder. The outer wall which opposes with a predetermined space | interval, The bottom wall which connects the said cylinder and the said outer wall, and forms the bottom face of the said water jacket, The said cylinder and the said outer wall are connected, The top part of the said water jacket is obstruct | occluded. In a closed deck type engine cylinder block formed by being surrounded by a top wall and an outer peripheral surface of the cylinder, and a screw hole of a bolt for fastening a cylinder head provided in the outer wall, the cylinder and Of the contact surface with the cylinder liner, the outer peripheral surface of the cylinder located radially outward is the top wall. For top wall inner contact surfaces are Do therefore, is summarized in that the adhesion between the cylinder liner and the cylinder is made smaller than the adhesion between the cylinder liner and the cylinder other than the contact surface.

Incidentally, in the closed deck type cylinder block, the axial force of the bolt is transmitted to the cylinder through at least the top wall.
In the above configuration, since the contact force between the cylinder and the cylinder liner is reduced on the inner contact surface of the top wall, the axial force of the bolt acting on the cylinder is hardly transmitted to the cylinder liner through the top wall of the water jacket. Thereby, deformation of the cylinder liner caused by the axial force of the bolt can be suppressed.

  In addition, since the above-described configuration is realized in a state where the cylinder and the cylinder liner are in contact with each other without forming a gap, it is caused by a force from the inside of the cylinder such as a combustion pressure and a piston thrust force. It is possible to suppress the deformation of the cylinder liner that occurs.

  According to a fourth aspect of the present invention, in a cylinder block of an engine including a cylinder in which a cylinder liner is cast and a water jacket formed around the cylinder, a contact surface between the cylinder and the cylinder liner is provided. Among these, for the inner contact surface of the lower end portion including the bottom surface of the water jacket, which is located radially inward of the lower end portion of the water jacket, the cylinder and the cylinder liner have a close contact force between the cylinder and the cylinder liner. The gist is that it is smaller than the adhesion force between the cylinder liner and the cylinder liner.

  In the above configuration, since the adhesion between the cylinder and the cylinder liner is reduced on the inner contact surface of the lower end, the cylinder and the cylinder located radially inward of the lower end of the water jacket (the end including the bottom surface of the water jacket) For the liner, the thermal conductivity between these cylinders and the cylinder liner is reduced. Thereby, in the cylinder bore peripheral wall (cylinder liner), the degree of cooling on the lower side of the water jacket is reduced, so that the temperature difference in the cylinder axial direction can be reduced with respect to the peripheral wall.

  According to a fifth aspect of the present invention, there is provided a cylinder block of an engine including a cylinder in which a cylinder liner is cast and a water jacket formed around the cylinder, and includes a contact surface between the cylinder and the cylinder liner. The contact force between the cylinder and the cylinder liner is greater than the contact force between the cylinder and the cylinder liner other than the contact surface with respect to the jacket inner contact surface on which the water jacket is formed radially outward. The main point is to make it smaller.

  In the above configuration, since the contact force between the cylinder and the cylinder liner is reduced on the inner contact surface of the jacket, the heat between the cylinder and the cylinder liner is determined for the cylinder and the cylinder liner positioned radially inward of the water jacket. Conductivity is lowered. Thereby, in the cylinder bore peripheral wall (cylinder liner), the degree of cooling of the portion where the water jacket is formed radially outward is reduced, so that the temperature difference in the cylinder circumferential direction can be reduced with respect to the peripheral wall. Become.

  According to a sixth aspect of the invention, in the cylinder block of the engine according to any one of the first to fifth aspects, the cylinder liner and the cylinder liner are brought into close contact with each other by reducing the surface roughness of the cylinder liner. The gist is that the reduction of force was realized.

  According to a seventh aspect of the present invention, in the cylinder block of the engine according to any one of the first to fifth aspects, the cylinder, the cylinder liner, and the cylinder liner are coated by applying a lubricant to an outer peripheral surface of the cylinder liner. The gist is that a reduction in the adhesive strength of the material has been realized.

  According to the structure of these 6th and 7th, the fall of work efficiency and the raise of cost can be suppressed as much as possible, and the reduction | decrease of the said adhesive force can be implement | achieved.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS.
In this embodiment, the case where this invention is applied about the cylinder block of the engine provided with the some cylinder is assumed. Further, as the cylinder block, an open deck type cylinder block in which the top portion (cylinder head side) of the water jacket is opened is assumed.

First, the structure of the cylinder block will be described with reference to FIGS.
FIG. 1A shows a planar structure of the cylinder block 10 of the present embodiment.
FIG. 1B shows a cross-sectional structure of the cylinder block 10 taken along line D1-D1 of FIG.

The cylinder block 10 is integrally formed including a crankcase 11 and a plurality of cylinders 12. Further, it is formed using an aluminum alloy as a material.
In the cylinder block 10, each cylinder 12 is formed by connecting a part of adjacent cylinders 12.

  A cast iron cylinder liner 13 is cast on the inner peripheral side of each cylinder 12. The cylinder liner 13 is formed through casting. The cylinder 12 and the cylinder liner 13 are joined at the contact surface F1.

  Each cylinder 12 is formed with a cylinder bore 12B for accommodating a piston. In each cylinder 12, a cylinder bore 12 </ b> B is formed surrounded by the cylinder liner 13 and the inner peripheral surface of the cylinder 12. In the present embodiment, the cylinder liner 13 and the cylinder 12 correspond to the peripheral wall of the cylinder bore 12B.

A water jacket 14 is formed on the outer peripheral side of the cylinder 12.
The water jacket 14 connects the outer wall 15 facing the outer peripheral surface of the cylinder 12 (cylinder outer peripheral surface 12F) with a predetermined gap, and the bottom surface of the water jacket 14 (jacket bottom surface 14B) by connecting the cylinder 12 and the outer wall 15 to each other. The bottom wall 16 to be formed is surrounded by the cylinder outer peripheral surface 12F.

  At the top of the cylinder block 10, a deck surface 10T is formed through the top surface of the cylinder 12 (cylinder top surface 12T) and the top surface of the outer wall 15 (outer wall top surface 15T). A cylinder head is placed on the deck surface 10T via an appropriate seal member.

In the water jacket 14, the top (deck surface 10T side) is opened.
In the outer wall 15, a plurality of screw holes 17 are formed around the water jacket 14. Bolts for fastening the cylinder head to the cylinder block 10 are screwed into the screw holes 17.

FIG. 2 shows a perspective structure of the cylinder liner 13.
In the cylinder liner 13, an outer peripheral surface (liner outer peripheral surface 13F) includes a cast surface 13A having a surface roughness formed by casting, and a smooth surface 13B having a surface roughness smaller than the surface roughness of the cast surface 13A. And are provided.

FIG. 3 shows an enlarged view of a portion B in FIG.
The smooth surface 13B is formed in the region L in the cylinder axial direction of the liner outer peripheral surface 13F. The region L is divided into “region L1”, “region L2”, and “region L3” described below. In FIG. 3, the direction indicated by the arrow R1 indicates the outside of the cylinder in the radial direction. Further, the direction indicated by the arrow R2 indicates the radially inner side of the cylinder.

(A) “Region L1”
In the cylinder outer peripheral surface 12F, the outer peripheral surface 12F connected to the bottom wall 16 is defined as a bottom wall connecting surface 12FM. Of the contact surface F1 between the cylinder 12 and the cylinder liner 13, the contact surface F1 in which the bottom wall connecting surface 12FM is formed on the radially outer side (the radially outer side of the cylinder 12) is the bottom wall inner contact surface. FM.

The region L1 indicates a region including only the bottom wall inner contact surface FM in the cylinder axial direction.
The smooth surface 13B is formed including the region L1 in the cylinder axial direction of the liner outer peripheral surface 13F. That is, the liner outer peripheral surface 13 </ b> F is provided in a region where the bottom wall inner contact surface FM is formed together with the cylinder 12.

(B) “Region L2”
In the cylinder outer peripheral surface 12F, the outer peripheral surface 12F forming the lower end portion (jacket lower end portion 14R) of the water jacket 14 is defined as a lower end outer peripheral surface 12FW. Of the contact surface F1 between the cylinder 12 and the cylinder liner 13, a contact surface F1 in which a lower end outer peripheral surface 12FW is formed radially outward (radially outward of the cylinder 12) is used as the lower end inner contact surface. FW. The jacket lower end portion 14R corresponds to an end portion of the water jacket 14 including the jacket bottom surface 14B.

The region L2 indicates a region including only the lower end inner contact surface FW in the cylinder axial direction.
The smooth surface 13B is formed including the region L2 in the cylinder axial direction of the liner outer peripheral surface 13F. That is, the liner outer peripheral surface 13F is provided in a region where the lower end portion inner contact surface FW is formed together with the cylinder 12.

(C) “Region L3”
In the cylinder outer peripheral surface 12F, the outer peripheral surface 12F below the bottom wall connecting surface 12FM (on the crankcase 11 side in the cylinder axial direction) is defined as a lower portion outer peripheral surface 12FU. Of the contact surface F1 between the cylinder 12 and the cylinder liner 13, a contact surface F1 in which a lower outer peripheral surface 12FU is formed radially outward (radially outward of the cylinder 12) is defined as a lower inner contact surface. Let it be FU.

The region L3 indicates a region including only the lower portion inner contact surface FU in the cylinder axial direction.
The smooth surface 13B is formed including the region L3 in the cylinder axial direction of the liner outer peripheral surface 13F. That is, the liner outer peripheral surface 13 </ b> F is provided in a region that forms the lower portion inner contact surface FU together with the cylinder 12.

  As described above, the smooth surface 13B is formed in a region corresponding to the bottom wall inner contact surface FM, the lower portion inner contact surface FU, and the lower portion inner contact surface FU in the cylinder axial direction of the liner outer peripheral surface 13F. Hereinafter, in the contact surface F1 between the cylinder 12 and the cylinder liner 13, the contact surface F1 formed through the smooth surface 13B is referred to as a smooth contact surface FB. Moreover, let the contact surface F1 formed through the casting surface 13A be a casting surface contact surface FA. The smooth contact surface FB includes a lower end inner contact surface FW, a bottom wall inner contact surface FM, and a lower portion inner contact surface FU.

FIG. 4 shows an enlarged view of a portion A in FIG.
In FIG. 4, a region W indicates a region where the contact surface F1 and the screw hole 17 face each other in the cylinder circumferential direction.

  The smooth surface 13B is formed in the region W in the cylinder circumferential direction of the liner outer peripheral surface 13F. That is, it is formed so as to include a region where the contact surface F1 and the screw hole 17 face each other in the cylinder circumferential direction.

  The smooth surface 13B is formed by smoothing the casting surface 13A after the cylinder liner 13 is formed by casting. Although the cylinder liner 13 is processed on the casting surface 13A, the cylinder liner 13 has substantially the same thickness at both the portion where the casting surface 13A is formed and the portion where the smooth surface 13B is formed. That is, the cylinder liner 13 is formed so as to obtain substantially the same thickness throughout.

  Of the contact surface F1 between the cylinder 12 and the cylinder liner 13, in the casting surface contact surface FA, the cylinder 12 and the cylinder liner 13 are joined with high adhesion by the anchor action of minute irregularities present on the casting surface 13A. Become so.

  On the other hand, among the contact surfaces F1 between the cylinder 12 and the cylinder liner 13, the smooth contact surface FB is in a state where the smooth surface 13B and the cylinder 12 are in contact with each other, and therefore the adhesion force between the cylinder 12 and the cylinder liner 13 is reduced. It becomes smaller than the contact surface F1 formed through the casting surface 13A.

Next, the effect produced through the cylinder block 10 of this embodiment is demonstrated.
When the cylinder block 10 and the cylinder head are fastened and fixed with bolts, the axial force of the bolts acts around the screw holes 17 in the outer wall 15. Further, this axial force is transmitted to the cylinder 12 through the bottom wall 16. For this reason, the portion connected to the bottom wall 16 in the cylinder 12 is pulled toward the bolt side (the direction indicated by the arrow in FIG. 5A) by the action of the axial force of the bolt.

  In the cylinder block 10, a smooth contact surface FB is formed at a location where the axial force of the bolt acts by providing a smooth surface 13B on the liner outer peripheral surface 13F. Thereby, since the axial force of the bolt transmitted from the cylinder 12 to the cylinder liner 13 (force that pulls the cylinder liner 13 radially outward) is reduced, deformation of the cylinder liner 13 can be suppressed. .

  On the other hand, when the engine including the cylinder block 10 is in operation, combustion pressure and piston thrust force act on the cylinder liner 13 from the cylinder bore 12B side. As a result, the cylinder liner 13 is pressed outward in the cylinder radial direction (the direction indicated by the arrow in FIG. 5B).

  In the cylinder block 10, since the inner peripheral side of the cylinder 12 and the liner outer peripheral surface 13F are in contact with each other over the entire periphery, deformation of the cylinder liner 13 due to combustion pressure and piston thrust force can be suppressed. Become.

  By the way, in an engine cylinder, the temperature of the cylinder bore peripheral wall increases as the distance from the cylinder head increases, whereas the temperature of the cylinder bore peripheral wall tends to decrease as it approaches the bottom surface of the water jacket. Due to such a temperature difference, the degree of thermal expansion of the cylinder bore peripheral wall in the cylinder axial direction becomes different, and therefore the size of the cylinder bore becomes non-uniform. In this case, for example, it is conceivable to increase piston friction.

  In the cylinder block 10 of the present embodiment, by providing a smooth surface 13B on the liner outer peripheral surface 13F, the cylinder 12 and the cylinder liner 13 that are positioned radially inward of the lower end portion of the water jacket, The thermal conductivity between the two is reduced. This makes it difficult for the cylinder bore peripheral wall (cylinder liner 13) located radially inward of the lower end portion of the water jacket to be cooled, so that the temperature difference of the cylinder bore peripheral wall in the cylinder axial direction is reduced. Accordingly, the difference in the size of the cylinder bore in the cylinder axial direction is reduced.

  FIG. 6 shows the temperature distribution of the cylinder bore peripheral wall in the cylinder axial direction for each of an engine having a normal cylinder block (a cylinder block having a smooth outer surface on the liner outer surface) and an engine having the cylinder block 10. An example is shown. In FIG. 6, the solid line indicates the temperature distribution in the engine provided with the cylinder block 10. Moreover, a broken line shows the said temperature distribution in the engine provided with the normal cylinder block.

  As shown in the figure, the temperature difference Δt2 of the cylinder bore peripheral wall in the engine including the cylinder block 10 is smaller than the temperature difference Δt1 of the cylinder bore peripheral wall in the engine including the normal cylinder block.

As described above in detail, according to the present embodiment, the following effects can be obtained.
(1) According to the present embodiment, deformation of the cylinder liner 13 caused by the axial force of the bolt can be suppressed.

  (2) According to the present embodiment, it is possible to suppress deformation of the cylinder liner 13 caused by a force (combustion pressure or piston thrust force) acting from the inside of the cylinder 12.

(3) According to this embodiment, the difference in the size of the cylinder bore in the cylinder axis direction can be reduced.
(4) In the present embodiment, the smooth surface 13B is also formed in the region L2 and the region L3 located above (cylinder head side) and below (crankcase side) the region L1 in the cylinder axis direction. Thereby, the axial force of the bolt transmitted from the cylinder 12 to the cylinder liner 13 can be reduced more suitably.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIGS.
In the present embodiment, a closed deck type cylinder block in which the top of the water jacket is closed is assumed as the cylinder block. In this cylinder block, the portion other than the top of the water jacket has the same structure as the cylinder block of the first embodiment. In the following description, the same reference numerals are used for portions common to the first embodiment.

FIG. 7A shows a planar structure of the cylinder block 20 of the present embodiment.
FIG. 7B shows a cross-sectional structure of the cylinder block 20 along the line D2-D2 in FIG.

  A cast iron cylinder liner 23 is cast on the inner peripheral side of each cylinder 12. The cylinder liner 23 is formed through casting. The cylinder 12 and the cylinder liner 23 are joined at the contact surface F2.

  In each cylinder 12, a cylinder bore 12 </ b> B is formed surrounded by the cylinder liner 23 and the inner peripheral surface of the cylinder 12. In the present embodiment, the cylinder liner 23 and the cylinder 12 correspond to the peripheral wall of the cylinder bore 12B.

A water jacket 24 is formed on the outer peripheral side of the cylinder 12.
The water jacket 24 connects the outer wall 25 facing the outer peripheral surface (cylinder outer peripheral surface 12F) of the cylinder 12 with a predetermined distance, and the bottom surface (jacket bottom surface 24B) of the water jacket 24 by connecting the cylinder 12 and the outer wall 25 to each other. The bottom wall 26 to be formed, the top wall 27 that connects the cylinder 12 and the outer wall 25 to form the top surface of the water jacket 24 (jacket top surface 24C), and the cylinder outer peripheral surface 12F are surrounded.

  At the top of the cylinder block 20, the deck passes through the top surface of the cylinder 12 (cylinder top surface 12T), the top surface of the outer wall 25 (outer wall top surface 25T), and the top surface of the top wall 27 (top wall top surface 27T). A surface 20T is formed. A cylinder head is placed on the deck surface 20T via an appropriate seal member.

In the water jacket 24, the top portion (deck surface 20 </ b> T side) is closed by the top wall 27.
In the outer wall 25, a plurality of screw holes 28 are formed around the water jacket 24. Bolts for fastening the cylinder head to the cylinder block 20 are screwed into the screw holes 28.

FIG. 8 shows a perspective structure of the cylinder liner 23.
In the cylinder liner 23, an outer peripheral surface (liner outer peripheral surface 23F) includes a cast surface 23A having a surface roughness formed by casting and a smooth surface 23B having a surface roughness smaller than the surface roughness of the cast surface 23A. And are provided. The casting surface 23A and the smooth surface 23B are formed in the same manner as the casting surface 13A and the smooth surface 13B of the first embodiment.

FIG. 9 shows an enlarged view of a portion C in FIG.
The smooth surface 23B is formed in the previous region L (regions L1 to L3) and the region L4 in the cylinder axial direction of the liner outer peripheral surface 23F. In FIG. 9, the direction indicated by the arrow R1 indicates the outside of the cylinder in the radial direction. Further, the direction indicated by the arrow R2 indicates the radially inner side of the cylinder.

  Here, in the cylinder outer peripheral surface 12F, the outer peripheral surface 12F connected to the top wall 27 is defined as a top wall connecting surface 12FT. Of the contact surface F2 between the cylinder 12 and the cylinder liner 23, the contact surface F2 in which the top wall connecting surface 12FT is formed on the radially outer side (the radially outer side of the cylinder 12) is the top wall inner contact surface. FT.

The region L4 indicates a region including only the top wall inner contact surface FT in the cylinder axial direction.
The smooth surface 23B is formed including the region L4 in the cylinder axial direction of the liner outer peripheral surface 23F. That is, the smooth surface 23 </ b> B is provided in a region where the top wall inner contact surface FT is formed together with the cylinder 12.

  The smooth surface 23B is formed in the region W in the cylinder circumferential direction of the liner outer peripheral surface 23F (see FIG. 4). That is, the contact surface F2 and the screw hole 28 are formed so as to include a region facing each other in the cylinder circumferential direction.

Next, the effect produced through the cylinder block 20 of this embodiment is demonstrated.
When the cylinder block 20 and the cylinder head are fastened and fixed with bolts, the axial force of the bolts acts around the screw holes 28 in the outer wall 25. The axial force is transmitted to the cylinder 12 via the top wall 27 and the bottom wall 26. For this reason, the part connected with the top wall 27 and the bottom wall 26 in the cylinder 12 comes to be pulled to the bolt side by the axial force of such a bolt.

  In the cylinder block 20, the smooth outer surface 23F is provided on the liner outer peripheral surface 23F, so that the smooth contact surface FB is formed at a place where the axial force of the bolt acts. Thereby, since the axial force of the bolt transmitted from the cylinder 12 to the cylinder liner 23 (force that pulls the cylinder liner 23 radially outward) is reduced, deformation of the cylinder liner 23 can be suppressed. .

As described above in detail, according to the present embodiment, the same effects as the effects (1) to (4) according to the first embodiment can be achieved.
(Other embodiments)
Each said embodiment can also be changed as follows.

-In each said embodiment, the formation aspect of the smooth surfaces 13B and 23B can also be changed into either of the following (i)-(d).
(A) In the axial direction of the cylinder 12, the smooth surfaces 13B and 23B can be formed only in the region L1.
(B) In the axial direction of the cylinder 12, the smooth surfaces 13B and 23B can be formed only in the region L2.
(C) In the axial direction of the cylinder 12, the smooth surfaces 13B and 23B can be formed only in the regions L1 and L2.
(D) In the axial direction of the cylinder 12, the smooth surfaces 13B and 23B can be formed only in the regions L1 and L3.

-In the said 2nd Embodiment, the formation aspect of the smooth surface 23B can also be changed into any of the following (ii)-(ho).
(Ii) In the axial direction of the cylinder 12, the smooth surface 23B can be formed only in the region L4.
(B) In the axial direction of the cylinder 12, the smooth surface 23B can be formed only in the regions L4 and L1.
In the axial direction of the cylinder 12, the smooth surface 23B can be formed only in the regions L4 and L2.
(Ii) In the axial direction of the cylinder 12, the smooth surface 23B can be formed only in the regions L4, L1, and L2.
(E) In the axial direction of the cylinder 12, the smooth surface 23B can be formed only in the regions L4, L1, and L3.

  -In each said embodiment, if the length of the area | region L2 of the cylinder axial direction is a magnitude | size which can reduce the temperature difference of the cylinder axial direction of the cylinder 12, it will set to an appropriate magnitude | size in a cylinder lower end part. be able to. Even when the size is changed, it is formed so as to include at least the bottom surface of the cylinder.

  In each of the above-described embodiments, the surface roughness of the smooth surfaces 13B and 23B is set to an appropriate size that can suppress deformation of the cylinder liner 13 within a range smaller than the surface roughness of the casting surface 13A and 23A. Can be set.

  In each of the above embodiments, the smooth surface 13B is formed on the cylinder liner 13 so as to reduce the adhesion force between the cylinder 12 and the cylinder liner 13. However, for example, the following modifications can be made. That is, instead of the smooth surface 13B, the adhesion between the cylinder 12 and the cylinder liner 13 can be reduced by applying a lubricant (such as oil or grease) to a location where the smooth surface 13B is formed.

  In each of the above embodiments, the smooth surfaces 13B and 23B are formed in the region W in the circumferential direction of the cylinder 12, but the formation region in the cylinder circumferential direction is not limited to this. For example, the smooth surfaces 13B and 23B can be formed in the following [Modification 1] or [Modification 2].

  [Modification 1] FIG. 10A shows an example of the form of the smooth surfaces 13B and 23B. Fig.10 (a) shows the enlarged view of the A section of Fig.1 (a). As shown in the figure, of the contact surfaces between the cylinder 12 and the cylinder liners 13 and 23, the contact surface W1 is defined for the jacket inner contact surface W1 in which the water jackets 14 and 24 are formed radially outward. Smooth surfaces 13B and 23B may be provided on the outer peripheral surface 13F of the liner to be formed. In this case, the contact force between the cylinder 12 and the cylinder liners 13 and 23 can be made smaller than the contact force between the cylinder 12 and the cylinder liners 13 and 23 other than the jacket inner contact surface W1.

  In this case, since the contact force between the cylinder 12 and the cylinder liners 13 and 23 is reduced on the jacket inner contact surface W1, the cylinder 12 and the cylinder liners 13 and 23 positioned inward in the radial direction of the water jacket 14 are The thermal conductivity between the cylinder 12 and the cylinder liners 13 and 23 is lowered. As a result, in the cylinder bore peripheral wall (cylinder liners 13, 23), the degree of cooling of the portion where the water jacket 14 is formed radially outward is reduced, so that the temperature difference in the cylinder peripheral direction is reduced with respect to the peripheral wall. Will be able to.

  [Modification 2] FIG. 10B shows an example of how the smooth surfaces 13B and 23B are formed. FIG.10 (b) shows the enlarged view of the A section of Fig.1 (a). As shown in the figure, smooth surfaces 13B and 23B can be provided over the entire circumference WA of the liner outer circumferential surface 13F.

  10 shows the form of the smooth surface 13B in the open deck type cylinder block, the smooth surface 23B can be formed in the same way in the closed deck type cylinder block.

  In each of the above embodiments, the cylinder block of the in-line four-cylinder engine is illustrated, but the present invention is applied to any cylinder block as long as the cylinder liner is cast inside the cylinder. be able to. Even in such a case, the same effects as the effects of the above-described embodiments can be achieved.

FIG. 1 is a plan view (FIG. 1 (a)) / cross-sectional structure taken along line D1-D1 of FIG. 1 (a) showing a planar structure of a cylinder block in a first embodiment embodying a cylinder block of an engine according to the present invention. Sectional drawing which shows (FIG.1 (b)). The perspective view which shows the perspective structure of the cylinder liner which comprises the cylinder block of the embodiment. The enlarged view which shows the enlarged structure of the B section of FIG.1 (b) about the cylinder block of the embodiment. The enlarged view which shows the enlarged structure of the A section of Fig.1 (a) about the cylinder block of the embodiment. (A) (b) is sectional drawing which shows the partial cross-section along the D1-D1 line | wire of FIG. 1 about the cylinder block of the embodiment. The figure which shows the temperature distribution of the cylinder axial direction in engine operation about the cylinder block of the embodiment. FIG. 7 is a plan view (FIG. 7 (a)) / cross-sectional structure taken along line D2-D2 of FIG. 7 (a) showing a planar structure of a cylinder block in a second embodiment embodying a cylinder block of an engine according to the present invention. Sectional drawing which shows (FIG.7 (b)). The perspective view which shows the perspective structure of the cylinder liner which comprises the cylinder block of the embodiment. The enlarged view which shows the enlarged structure of the C section of FIG.7 (b) about the cylinder block of the embodiment. (A) (b) is an enlarged view which shows the enlarged structure of the A section of Fig.1 (a) about the cylinder block of other embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,20 ... Cylinder block, 10T, 20T ... Deck surface, 11 ... Crankcase, 12 ... Cylinder, 12B ... Cylinder bore, 12F ... Outer peripheral surface, 12FM ... Bottom wall connection surface, 12FT ... Top wall connection surface, 12FU ... Lower part Outer peripheral surface, 12FW ... Outer peripheral surface of lower end portion, 13, 23 ... Cylinder liner, 13A, 23A ... Cast surface, 13B, 23B ... Smooth surface, 13F, 23F ... Outer surface of liner, 14, 24 ... Water jacket, 14B ... Jacket Bottom surface, 14R ... jacket lower end, 15, 25 ... outer wall, 16, 26 ... bottom wall, 27 ... top wall, 17, 28 ... screw hole, F1, F2 ... contact surface, FA ... casting surface contact surface, FB ... smooth Contact surface, FM ... bottom wall inner contact surface, FT ... top wall inner contact surface, FU ... lower portion inner contact surface, FW ... lower end inner contact surface, W1 ... jacket inner contact surface.

Claims (7)

In a cylinder block of an engine provided with a cylinder in which a cylinder liner is cast, and a water jacket formed around the cylinder through an outer wall, and a screw hole of a bolt for fastening a cylinder head is provided in the outer wall.
Of the contact surfaces between the cylinder and the cylinder liner, with respect to the contact surface to which the axial force of the bolt is transmitted, the contact force between the cylinder and the cylinder liner is determined between the cylinder and the cylinder liner other than the contact surface. The cylinder block of the engine, characterized in that it is smaller than the adhesion force of the engine. A cylinder in which a cylinder liner is cast; and a water jacket formed at the top of the cylinder so as to be opened around the cylinder, the water jacket being opposed to the outer peripheral surface of the cylinder with a predetermined interval. A screw hole of a bolt for fastening a cylinder head, and being surrounded by an outer wall, a bottom wall connecting the cylinder and the outer wall to form a bottom surface of the water jacket, and an outer peripheral surface of the cylinder In the cylinder block of the open deck type engine provided on the outer wall,
Of the contact surfaces between the cylinder and the cylinder liner, the cylinder and the cylinder liner are in close contact with each other on the inner contact surface of the bottom wall where the outer peripheral surface of the cylinder located radially outward is connected to the bottom wall. A cylinder block for an engine, wherein the force is made smaller than the adhesion force between the cylinder and the cylinder liner other than the contact surface. A cylinder in which a cylinder liner is cast; and a water jacket formed around the cylinder with a top portion thereof closed, the water jacket being opposed to the outer peripheral surface of the cylinder with a predetermined interval. An outer wall, a bottom wall connecting the cylinder and the outer wall to form a bottom surface of the water jacket, a top wall connecting the cylinder and the outer wall to close the top of the water jacket, and an outer peripheral surface of the cylinder In a cylinder block of a closed deck type engine in which a screw hole of a bolt for fastening a cylinder head is provided in the outer wall.
Of the contact surfaces of the cylinder and the cylinder liner, the cylinder and the cylinder liner are in close contact with each other on the inner contact surface of the top wall where the outer peripheral surface of the cylinder located radially outward is connected to the top wall. A cylinder block for an engine, wherein the force is made smaller than the adhesion force between the cylinder and the cylinder liner other than the contact surface. In an engine cylinder block including a cylinder in which a cylinder liner is cast, and a water jacket formed around the cylinder,
Of the contact surfaces between the cylinder and the cylinder liner, the lower end portion inner contact surface located radially inward of the lower end portion of the water jacket including the bottom surface of the water jacket, the cylinder and the cylinder liner An engine cylinder block, wherein an adhesion force is smaller than an adhesion force between the cylinder and the cylinder liner other than the contact surface. In an engine cylinder block comprising a cylinder in which a cylinder liner is cast, and a water jacket formed around the cylinder,
Of the contact surfaces of the cylinder and the cylinder liner, the contact force between the cylinder and the cylinder liner other than the contact surface with respect to the jacket inner contact surface on which the water jacket is formed radially outward. An engine cylinder block characterized by having a smaller contact force between the cylinder and the cylinder liner. In the cylinder block of the engine according to any one of claims 1 to 5,
A cylinder block of an engine characterized in that a reduction in the adhesion between the cylinder and the cylinder liner is realized by reducing the surface roughness of the cylinder liner. In the cylinder block of the engine according to any one of claims 1 to 5,
A cylinder block of an engine characterized in that a reduction in adhesion between the cylinder and the cylinder liner is realized by applying a lubricant to the outer peripheral surface of the cylinder liner.

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