JPH04127849U - Internal combustion engine cylinder block structure - Google Patents

Abstract

(57) [Abstract] [Purpose] In the cylinder block structure of an internal combustion engine, which is divided into two parts at the crankshaft axis into an upper block and a lower block, the durability of the main bearing can be improved by reducing the amount of thermal expansion of the block. improve. [Structure] Upper and lower blocks 3 and 4 are fastened and fixed to each other from below by a first stud bolt 5 and a second stud bolt 6. The diameter φD ₅ of the first stud bolt 5 is made smaller than the diameter φD 6 of the second stud bolt ₆ to bring the fastening position 5c as close as possible to the axis of the crankshaft.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention is an internal combustion engine in which the cylinder block is divided into upper and lower parts around the crankshaft axis. Regarding the cylinder block structure.

0002

[Conventional technology]

In automotive internal combustion engines, the cylinder block is generally formed as one piece. , multiple bearing caps are connected to the center of the lower end, and the bearing cap The oil pan is connected so as to cover the bottom surface of the cylinder block including the top. Ru.

0003 However, as shown above, if the bearing cap is connected to the integrated cylinder block, In this structure, the main effect of the combustion gas pressure and inertia force is to increase the output of the engine. It is difficult to sufficiently increase the rigidity of the bearing cap and cylinder block skirt. Yes. Therefore, as described in, for example, Japanese Utility Model Application Publication No. 64-26456, multiple A lower block is formed by integrally connecting the bearing caps, and this is Tighten to the upper block with tad bolts to essentially clamp the cylinder block. It has a structure that is divided into upper and lower halves at the center of the shaft.

0004

[Problem that the idea aims to solve]

By the way, after starting the internal combustion engine, the temperature of the block body rises to approximately 100 degrees Celsius. Therefore, thermal expansion also occurs in the upper block and the lower block. Here, the cylinder tab An internal combustion engine in which the lock is divided into two parts, an upper block and a lower block, at the center of the crankshaft. In the cylinder block structure, the lower block is connected to the upper block by stud bolts. Since the configuration is fastened to the lock, the amount of thermal expansion is the stud at the fastening position. When the bolt is a fixed point, thermal expansion occurs in an amount proportional to the distance from the fixed point. Furthermore, the expansion occurs in the direction of the main bearing surface using the stud bolt as a fixing point.

[0005] On the other hand, to fasten the lower block to the upper block using stud bolts. In this case, the lower block is provided with a reamed part and the upper block is provided with a female threaded part. It is necessary. By the way, when providing the reamed part or female thread part, there are a few It must have a wall thickness that can at least withstand the fastening force generated by the stud bolt. Therefore, a certain wall thickness is required.

[0006] Therefore, the predetermined wall thickness is the maximum that can withstand the fastening force generated by the stud bolt. Even if the wall thickness is set to a low value, if the stud bolt is thick, the specified wall thickness will be thicker. , so that the amount of thermal expansion proportional to the predetermined wall thickness expands the stud bolt as described above. Occurs in the direction of the main bearing surface as a fixed point. Therefore, the metal clearance of the main bearing This may cause metal scuffing or fretting, and the durability of the main bearing may deteriorate. There is a risk that this will decrease.

[0007] Furthermore, due to the recent need for weight reduction, internal combustion engines are also made of aluminum alloy. Nowadays, a steel lower block is fastened to an aluminum alloy upper block. However, in this case, the linear expansion coefficient of aluminum is approximately twice that of iron. Therefore, even for the same temperature rise, the upper block has a temperature increase of about 2 compared to the lower block. Double the amount of thermal expansion will occur, which will cause the upper block and lower block to There is also a risk that the metal may get caught in the crankshaft due to the uneven surface.

[0008] Therefore, in view of the above-mentioned conventional circumstances, the present invention has been developed to In the cylinder block structure of an internal combustion engine, which is divided into two parts: a block and a lower block, The durability of the main bearing is improved by reducing the amount of thermal expansion related to the block. The porpose is to do.

[0009]

[Means to solve the problem]

Therefore, in this invention, the cylinder block is connected to the upper block at the center of the crankshaft. In the cylinder block structure of an internal combustion engine that is divided into two parts, the upper and Of the stud bolts that fasten both the upper and lower blocks, the one closest to the crankshaft axis The diameter of the first stud bolt located on the side is located on the side far from the axis of the crankshaft. The diameter was made smaller than that of the second stud bolt.

0010

[Effect]

In such a configuration, the first stud bolt located on the side closer to the crankshaft axis The diameter is made smaller than the diameter of the second stud bolt located on the side far from the crankshaft axis. Therefore, it is necessary to reduce the wall thickness to withstand the fastening force generated by stud bolts. This makes it possible to move the first stud bolt closer to the crankshaft axis. can be attached to the crankshaft from the fastening position of the first stud bolt. The distance to the bearing surface of the main bearing section becomes shorter.

[0011] Therefore, when the temperature of the block body increases, The amount of thermal expansion with the fastening position of the first stud bolt as the fixing point becomes smaller, and the main Even if the metal clearance of the bearing part is subjected to thermal expansion, it will remain within the allowable value, and the metal clearance will be maintained within the allowable value. It can prevent fretting and fretting.

0012

【Example】

Hereinafter, an example in which the present invention is applied to a V-type internal combustion engine will be explained based on the drawings. do. In addition, since it is symmetrical, only one side of the bank is shown in the diagram. There is. A cylinder block 1 of an internal combustion engine has a main bearing hole through which a crankshaft (not shown) passes. The upper block 3 and the lower block It is divided into four blocks. The upper block 3 has the same weight as the main body of the V-type internal combustion engine. It is made of aluminum alloy in order to reduce the It has a plurality of bearing support parts 3c extending perpendicularly to the longitudinal direction so as to be connected. Ru. In addition, the lower block 4 is made of iron because it requires strength, and each bearing A bearing cap portion 4a is provided at a position corresponding to the support portion 3c.

These upper and lower blocks 3 and 4 are connected to each other by first stud bolts 5 and second stud bolts 6 which are arranged at symmetrical positions across the main bearing hole 2 at the position of each bearing cap portion 4a. It is fastened and fixed from the bottom. Here, as a configuration according to the present invention, the diameter φD 5 of the first stud bolt 5 located on the side close to the main bearing hole 2, that is, the crankshaft axis, is changed to the diameter φD ₅ of the first stud bolt 5 located on the side far from the crankshaft axis. The diameter of the stud bolt 6 is smaller than φD ₆ (φD ₅ <φD ₆ ). In addition, the effective fastening force of the first stud bolt 5 can exert the wall thickness t ₃ of the upper block 3 on the main bearing hole 2 side of the first stud bolt 5 and the wall thickness t ₄ of the lower block 4 of the first stud bolt 5. The fastening position 5c is configured to be as close as possible to the crankshaft axis, so that the upper and lower blocks 3, 4 have the minimum thickness that does not cause deformation when fastening is performed using the effective fastening force.

[0014] Next, the operation of this configuration will be explained. First, to generally explain the amount of thermal expansion ξ related to length x, the amount of thermal expansion ξ is When the coefficient of linear thermal expansion is α and the temperature rise is t, ξ=α×x×t It is expressed as

[0015] Therefore, when the temperature of the block body increases by t, the amount of thermal expansion of the first stud bolt 5 with the fastening position 5c of the first stud bolt as the fixed point is: The distance from the fastening position 5c of the stud bolt to the bearing surface of the main bearing of the crankshaft is ξ ₃ =α ₃ ×L ×t for the upper block 3 made of aluminum alloy, and for the lower block made of iron 4, ξ ₄ =α ₄ ×L×t. However, α ₃ is the thermal linear expansion coefficient of the aluminum alloy, and α ₄ is the thermal linear expansion coefficient of iron, and α ₃ is approximately twice as large as α ₄ . That is, the upper block 3 extends at least by ξ ₃ in the direction of the main bearing with the fastening position 5c as a reference, and the lower block 4 extends at least in the direction of the main bearing with the fastening position 5c as a reference. Stretch by ξ ₄ . Therefore, an expansion difference δ=ξ ₃ −ξ ₄ occurs between the upper block 3 and the lower block 4.

Here, since the diameter φD ₅ of the first stud bolt 5 is made smaller than the diameter φD 6 of the second stud bolt ₅ , the diameter φD 5 of the first stud bolt 5 is made smaller than the diameter φD 6 of the second stud bolt 5. It becomes possible to reduce the effective thickness. Furthermore, since the fastening position 5c of the first stud bolt is brought closer to the crankshaft axis, the distance L from the fastening position 5c of the first stud bolt to the bearing surface of the main bearing portion of the crankshaft is reduced. It is made as short as possible, so that ξ ₃ and ξ ₄ become small, and as a result, δ also becomes small.

Therefore, the metal clearance of the metal (not shown) fitted into the main bearing hole 2 that pivotally supports the crankshaft remains within the allowable value even when subjected to thermal expansion, preventing metal scuffing and fretting. The durability of the parts is improved. In this embodiment, a case has been described in which the upper block 3 and the lower block 4 are made of different materials, causing an expansion difference δ, but even when both blocks 3 and 4 are made of the same material, the same structure as in this embodiment can be applied. By doing so, the amounts of thermal expansion ξ ₃ and ξ ₄ are reduced, the roundness of the metal is maintained, and the bearing performance can be improved.

[0018]

[Effect of the idea]

As explained above, according to the present invention, the cylinder block is aligned with the crankshaft axis. The cylinder block structure of an internal combustion engine is divided into two parts: an upper block and a lower block. the diameter of the first stud bolt located on the side closer to the crankshaft axis. The diameter of the second stud bolt located on the far side from the axis of the shaft is made smaller than that of the second stud bolt. It becomes possible to bring the fastening position of the stud bolt 1 closer to the axis of the crankshaft. , the amount of thermal expansion related to the first stud bolt is reduced, and the metal of the main bearing portion is Cuffing and fretting can be prevented, improving bearing performance.

[Brief explanation of drawings]

[Fig. 1] A sectional view of a main part of a cylinder block showing an embodiment of the present invention.

[Figure 2] Action diagram for explaining the action of the present invention

[Explanation of symbols]

1 cylinder block 2 Main bearing hole 3 Upper block 3d Female thread part 4 Lower block 4d Reamer part 5 First stud bolt 6 Second stud bolt

Claims (1)

[Scope of utility model registration request] Claims: 1. A cylinder block structure for an internal combustion engine in which a cylinder block is divided into two parts, an upper block and a lower block, at the crankshaft axis; A cylinder block structure for an internal combustion engine, characterized in that the diameter of a first stud bolt located closer to the crankshaft axis is smaller than the diameter of a second stud bolt located further away from the crankshaft axis.