JPH0648175Y2 - Integrated bearing cap for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial field of application) The present invention connects a plurality of bearing caps mounted on the lower surface of a cylinder block to rotatably support a crankshaft and the bearing caps. And an integrated bearing cap for an internal combustion engine having a beam portion.

(Prior Art) A conventional integrated bearing cap of this type is disclosed in, for example, Japanese Utility Model Laid-Open No. 57-71742. In the device described in this publication, the cap portion and the beam portion are integrally cast with cast iron made of the same material and relatively advantageous in terms of strength.

On the other hand, in recent years, engine components such as cylinder blocks and cylinder heads are made of aluminum alloy to reduce the weight of the engine. When a cast iron bearing cap is used for such an aluminum alloy cylinder block, the coefficient of thermal expansion differs greatly between the two materials.
In particular, the beam portion of the bearing cap cannot fully support the thermal expansion in the longitudinal direction of the cylinder block, and during operation of the engine, the bulk head portion and beam portion of the cylinder block to which the bearing cap is attached are distorted, which causes uneven bearing metal bearing contact. And uneven wear occur, which shortens the engine life.

On the other hand, if the bearing cap is made of an aluminum alloy like the cylinder block, the outer dimensions are inevitably large in order to obtain sufficient rigidity and strength, which is an obstacle to making the engine compact. Further, since the aluminum alloy has a large coefficient of thermal expansion, the inner diameter of the journal hole supporting the crankshaft expands due to the thermal expansion, resulting in a large expansion of the meta clearance and deterioration of the vibration and noise characteristics of the engine.

Therefore, the beam part of the bearing cap is made of an aluminum alloy similar to the cylinder block to prevent distortion between them, while the bearing cap part is made of cast iron to prevent the inner diameter of the journal hole from expanding and fastened with bolts. Is disclosed in Japanese Utility Model Publication No. 61-94615.

(Problems to be solved by the invention) However, in such a bearing cap, although the distortion due to the difference in thermal expansion can be prevented, since the bearing cap portion and the beam portion are connected by bolts,
Compared to the one that is cast integrally, it is inferior in terms of rigidity, the vibration around the bulkhead becomes large, and the beam part is still made of aluminum alloy,
In order to obtain sufficient rigidity and strength, the bearing cap and beam are made of aluminum alloy,
There is no choice but to increase the outer dimensions of the bearing cap.

The present invention has been made in view of the above problems, and has sufficient rigidity even though it has a structure in which the bearing cap portion and the beam portion are coupled with each other, and it is also possible to reduce engine noise and make it compact. It is an object of the present invention to provide an integrated bearing cap for a simple internal combustion engine.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention proposes that the bearing cap portion has a coefficient of thermal expansion of approximately half that of a cylinder block made of an aluminum alloy. While the beam part was made of ductile cast iron, the beam part was made of high-strength special cast iron having a thermal expansion coefficient substantially equal to that of aluminum alloy, and only one part of each joint part of the beam part was welded to the bearing cap part.

(Operation) Since the bearing cap is made of cast iron having a coefficient of thermal expansion smaller than that of the aluminum alloy cylinder block, expansion of the inner diameter of the journal hole of the crankshaft due to thermal expansion is suppressed and engine noise is reduced. Since the portion is made of special cast iron having a thermal expansion coefficient substantially equal to that of the cylinder block, it can cope with thermal expansion deformation of the cylinder block in the longitudinal direction and suppresses distortion of the cylinder block and the bearing cap. Further, since the bearing cap portion and the beam portion are joined by welding, the joint rigidity between them is high. Further, since the bearing cap portion and the beam portion are made of cast iron without using aluminum alloy, sufficient strength can be obtained without increasing the outer dimension.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 3 and 4 show a bearing cap 7 that rotatably supports the crankshaft 1 of the four-cylinder internal combustion engine shown in FIG. 1 and is attached to the lower surface of the bulkhead 5 of the aluminum alloy cylinder block 3. Bearing cap 7
Comprises a bearing cap portion 11 forming a journal hole 9 for rotatably supporting the journal portion of the crankshaft 1 on the bulkhead 5 side, and a beam portion 13 mounted on the lower surface of the bearing cap portion 11.

The bearing cap portion 11 is made of ordinary cast iron or ductile cast iron having a coefficient of thermal expansion (11 × 10 ⁻⁶ ) which is approximately half the coefficient of thermal expansion (20 to 22 × 10 ⁻⁶ ) of the aluminum alloy forming the cylinder block 3. Has been done. On the other hand, the beam section
13 is a thermal expansion coefficient (18 × 10
^-6 or more) and made of high-strength, high-strength special cast iron, both ends of the left and right beams 13a, 13b extending in the front-rear direction of the cylinder block 3 are connected by connecting portions 13c, 13d to be integrated. Has become.

The plurality of bearing cap portions 11 and the beam portion 13 are
Only the part indicated by the arrow in the figure, that is, the one side part on the outer side of each joint is welded. (Actually, as shown in Figure 3a, A,
It may be any one side portion of B, C and D. ) The bearing cap 7 integrated by welding is mounted on the bulkhead 5 of the cylinder block 3 by the bolt 15 shown in FIG.
Is attached to the underside of.

In such a bearing cap 7, since the bearing cap portion 11 is made of ordinary cast iron or ductile cast iron having a coefficient of thermal expansion approximately half that of the aluminum cylinder block 3, the crankshaft 1 is in operation during engine operation.
The excessive expansion of the metal clearance due to the thermal expansion of the inner diameter of the journal hole 9 for rotating and supporting is prevented, and the vibration and noise of the engine are reduced. On the other hand, since the beam portion 13 is made of high-rigidity and high-strength special cast iron having a thermal expansion coefficient substantially equal to that of the luminium alloy, it is possible to cope with thermal expansion in the longitudinal direction of the cylinder block 3. Therefore, distortion deformation of the bulkhead 5 and the beam portion 13 of the cylinder block 3 is prevented, the tilt vibration in the front-back direction is suppressed, and the vibration and noise of the engine are prevented.

Further, since the bearing cap portion 11 and the beam portion 13 are joined and integrated by welding, the joint rigidity is high and the vibration suppressing effect of the bearing cap 7 is further enhanced as compared with the case where both are bolted. Each of the welded portions of the plurality of bearing cap portions 11 and the beam portion 13 is spot-wise performed only on one side portion on the outer side, but when this is welded on two or more sides, the portion that gives heat is Since it is possible to form two or more in extremely close places, residual stress due to thermal stress is likely to occur, strain is generated by this residual stress, and if a force is applied from the main motion system in this state, cracks will occur in the strained portion. Because there is a fear. On the other hand, when welding is performed only on one side as in this embodiment,
Since there is only one part to which heat is applied, other parts can sufficiently absorb thermal stress, and strain is unlikely to occur. Moreover, even if strain occurs, there is no fear of developing cracks.

Since both the bearing cap 11 and the beam 13 of the bearing cap 7 are made of cast iron without using an aluminum alloy, it is not necessary to increase the size to obtain sufficient rigidity and strength, and to make the engine compact. Can contribute.

As described above, according to the present invention, the bearing cap portion is made of cast iron having a thermal expansion coefficient smaller than that of the cylinder block made of aluminum alloy,
Since the beam part is made of high-strength special cast iron having a thermal expansion coefficient almost equal to that of aluminum alloy, expansion of the inner diameter of the journal hole of the bearing cap part due to thermal expansion is suppressed, and the beam part extends in the longitudinal direction of the cylinder block. It is possible to cope with thermal expansion and suppress distortion of the cylinder block and the bearing cap, and as a result, effects such as reduction of engine noise and improvement of engine life can be obtained. Further, since one portion of each joint portion of the beam portion with respect to the plurality of bearing cap portions is welded and joined, the occurrence of strain between the both is suppressed, and the joint rigidity is improved. Furthermore, since cast iron is used for both the bearing cap portion and the beam portion, it is not necessary to increase the size to obtain sufficient rigidity, which can contribute to the compactness of the engine.

[Brief description of drawings]

The accompanying drawings relate to an embodiment of the present invention. FIG. 1 is a side view showing a coupled state of a cylinder block and a bearing cap, FIG. 2 is a front view of the same, and FIG. 3 is an exploded view of a bearing cap portion and a beam portion. FIG. 3 is a perspective view, FIG. 3a is an explanatory view of the welded portion, and FIG. 4 is a bottom view of the beam portion. 3 …… Cylinder block 7 …… Bearing cap 11 …… Bearing cap 13 …… Beam

Claims (1)

[Scope of utility model registration request] 1. An internal combustion engine having a plurality of bearing caps mounted on the lower surface of an aluminum alloy cylinder block, a beam connecting the bearing caps, and a bolt for fixing the bearing cap and the beam to the cylinder block. In the body-shaped bearing cap, the bearing cap portion is made of ordinary cast iron or ductile cast iron having a thermal expansion coefficient approximately half that of an aluminum alloy, while the beam portion has a high-strength special material having a thermal expansion coefficient approximately equal to that of an aluminum alloy. An integrated bearing cap for an internal combustion engine, which is made of cast iron and is welded to only one portion of each joint of the beam portion to the bearing cap portion.