JP3707147B2 - Crankcase structure of internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a crankcase structure for an internal combustion engine in which a crankcase at the lower part of a cylinder of an engine is divided into two parts, and the divided lower crankcase is integrated with a bearing cap that supports a crankshaft.
[0002]
[Prior art]
In an engine such as an automobile, the impact generated by the combustion pressure in the cylinder of the engine and the impact generated by the inertia of the piston, connecting rod and crank are repeatedly applied to the crankshaft. However, it is transmitted to the bearing cap portion that supports the crankshaft, and vibrates the partition wall portion of the lower crankcase integrated with the bearing cap.
[0003]
As shown in FIG. 8, the vibration of the partition wall 6 having the amplitude λ2 induces the vibration of the amplitude δ2 of the side wall 11 of the span L2 connected to the partition wall 6 and becomes one of the main sound sources of engine noise. It generates a loud noise.
[0004]
[Problems to be solved by the invention]
In order to reduce the noise caused by this vibration, it is effective to reinforce the partition wall portion 6 integrated with the bearing cap portion 5 that pivotally supports the crankshaft 4, and is indicated by a one-dot chain line in FIGS. As shown in the figure, the width B1 on the upper surface side which is the mounting side of the upper crankcase of the partition wall portion 6, the width B2 on the lower surface side which is the oil pan mounting surface 14 side, and the width b of the rib 6b are increased. In this case, in order to increase the rigidity of the partition wall 6 as a beam, it is effective to increase the cross-section secondary moment efficiently by increasing the width B1 on the upper surface side and the width B2 on the lower surface side. However, since the balancer 18 of the crankshaft 4 is arranged on both sides of each partition wall portion 6, there is a limit to the increase of B1 and B2, and the width b of the rib 6b that contributes little to the sectional moment of inertia. Must be increased. Therefore, there is a problem that the weight is remarkably increased for the effect of increasing the rigidity of the partition wall portion 6.
[0005]
In addition, as a measure for reducing vibration noise, the height H of the lower crankcase 3 may be increased, and the increased height portion on the lower surface side of the partition wall 6 may be thickened to reinforce the partition wall 6. However, in this case, there are problems that the total height of the engine becomes large and the weight of the engine increases.
In any case, it cannot be adopted from the viewpoint of reducing the weight of the engine as the weight increases.
[0006]
On the other hand, as a method for reinforcing the partition wall while suppressing an increase in the weight of the engine in an aluminum die cast crankcase such as a small engine, a cylinder block mounting surface 13 of the partition wall 6 is shown in FIGS. There is a method of adopting a double partition structure in which a groove portion 12 having an opening 12a is provided on the upper surface side which is the side.
However, in this double partition wall structure, since the partition wall portion 6 is composed of two opposing wall plates 6a whose upper surface side is opened by the opening 12a, the rigidity of the partition wall portion 6 as a whole is not sufficiently increased. In addition, since each wall plate 6a vibrates independently, there is a problem that the vibration of the partition wall portion 6 cannot be suppressed and the effect of reducing the vibration does not increase.
[0007]
The present invention has been made in order to solve the above-described problems. The object of the present invention is to increase the rigidity of the partition wall without increasing the weight in the lower crankcase integrated with the bearing cap. Another object of the present invention is to provide a crankcase structure for an internal combustion engine that can suppress vibration around the partition wall and reduce engine vibration and noise.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the crankcase portion of the engine is formed by dividing the crankcase portion into an upper crankcase and a lower crankcase from the center of the crank bearing portion, and the periphery of the lower crankcase is frame-shaped. Surrounding with a wall, connecting both side walls of the wall with a plurality of partition walls , and fastened to the upper crankcase with a main bolt at the center of the upper end of the partition , and pivotally supports the crankshaft provided by integrating the bearing cap, front SL surrounds the hollow portion in the side walls 11 with a double wall structure composed of the partition wall from Ryokabeban 6a having a hollow portion, further, the upper and lower surfaces of the partition Provided is a crankcase structure for an internal combustion engine in which a main bolt mounting hole communicating with the hollow portion is opened .
Further, in the partition portion of the lower crankcase, the two wall plates facing the hollow portion are connected by a connecting member provided integrally with the two wall plates .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.
In this embodiment, the crankcase portion is divided into two parts from the center C of the crank bearing portion 19 into an upper crankcase 2 and a lower crankcase 3, and the upper crankcase 2 is integrated with a cylinder 9 to form a cylinder block 1. are doing.
[0010]
On the other hand, the lower crankcase 3 is formed by surrounding the crank chamber 20 with a frame-like wall body, and connecting the both side walls 11 of the wall body with a plurality of partition walls 6. 5, a main bolt mounting hole 17, a block mounting surface 13, an oil pan mounting surface 14 and the like are provided, and the whole is integrally cast.
The partition wall portion 6 is connected to the side wall 11 of the wall body at an interval, and is integrated with a bearing cap portion 5 that pivotally supports the crankshaft 4. The bearing cap portion 5 has a main bolt mounting hole. The main bolt 10 inserted into the shaft 17 is fastened to the upper crankcase 2, and the crankshaft 4 is sandwiched and pivotally supported.
[0011]
And this partition part 6 is formed in the double-wall structure of the square-shaped cross section which has the hollow part 7, as shown in FIG.1 (b).
The partition wall portion 6 formed in this hollow shape is not only connected on the lower surface side, but also the upper surface side of the hollow portion 7 is connected to the wall plate 6a by the partition wall upper member 15, and has a large second moment of section. have.
[0012]
And in order to raise the cross-sectional secondary moment of the partition part 6, as shown in FIG.1 and FIG.2, between both the wall plates 6a of the hollow part 7 is connected with the connection member 8. FIG.
Further, in casting work, there is a concern that a work hole may be formed on the upper surface or the lower surface of the partition wall portion 6 in order to form the hollow portion 7, leading to a decrease in rigidity of the partition wall portion 6. By adopting a simple structure, during casting, the core for the hollow portion 7 is supported by a baseboard provided using a main bolt hole 17 for fastening the bearing cap portion 5, and further, sand removal of the core is performed. Since this hollow part 7 can be formed by performing from this main bolt hole 17, it is not necessary to provide a hole for coreboard or a hole for sand removal on the upper surface or the lower surface of the partition wall part 6, The rigidity of the partition wall 6 is not reduced.
[0013]
With the configuration described above, the following effects can be achieved.
Since the partition wall portion 6 of the lower crankcase 3 has a hollow shape having a hollow portion 7 and the partition wall portion 6 is firmly configured so that the cross-sectional shape becomes a square shape, the secondary cross section of the partition wall portion 6 The moment can be greatly increased, the rigidity of the partition wall portion 6 against bending and twisting can be improved, and the vibration of the partition wall portion 6 can be remarkably suppressed.
[0014]
As for the vibration of the side wall 11, as shown in FIG. 7, the vibration amplitude λ 1 of the partition wall 6 is reduced, the vibration itself transmitted to the side wall 11 is reduced, and the side wall span L 1 is further shortened. Since the rigidity of the side wall 11 itself can be increased, the vibration amplitude Δ1 of the side wall 11 can be made very small.
Further, as shown in FIG. 1 and FIG. 2, in the partition wall portion 6, the both wall plates 6 a of the hollow portion 7 are connected by the connecting member 8, thereby further increasing the sectional moment of the partition wall portion 6. The bending and torsional rigidity of the portion 6 can be improved, and vibration and noise can be further reduced.
[0015]
Accordingly, the vibration of the entire lower crankcase 3 can be remarkably reduced, and the vibration and noise of the engine can be greatly reduced.
On the other hand, by providing the hollow portion 7, even if the rigidity of the partition wall portion 6 is increased, an increase in weight can be substantially eliminated, so that an increase in the weight of the engine can be avoided.
[0016]
【The invention's effect】
As described above, according to the present invention, in the lower crankcase integrated with the bearing cap, the rigidity of the partition wall can be increased without increasing the weight, and the vibration around the partition wall can be suppressed. Thus, an internal combustion engine crankcase structure capable of reducing engine vibration and noise can be obtained.
In addition, when casting the partition wall, the core for the hollow portion is supported by a baseboard using the main bolt holes on the upper surface and the lower surface of the partition wall, and sand removal of the core is performed using the main bolt holes, Since the hollow portion can be formed, there is no need to newly provide a core base hole or a sand removal hole on the upper surface or the lower surface of the partition wall, so that the rigidity of the partition wall is not lowered.
Moreover, since both the wall plates of the hollow part of the partition part are connected by the connecting member, the cross-sectional secondary moment of the partition part can be further increased, and vibration noise can be further reduced.
[Brief description of the drawings]
FIG. 1 is a structural diagram of a cylinder block showing an embodiment of the present invention, and FIG. 1 (a) is a side view showing a lower crankcase portion in a step cross-sectional side view (XX step cross section in FIG. 2). (B) is a YY sectional view of a partition part.
2 is a plan sectional view of a lower crankcase showing a ZZ section in FIG. 1; FIG.
FIG. 3 is a structural diagram of a cylinder block showing an embodiment of the prior art, (a) is a side view showing a lower crankcase portion in a step cross-sectional side view (XX step cross section in FIG. 4). (B) is a YY sectional view of a partition part.
4 is a plan sectional view of the lower crankcase showing a ZZ section in FIG. 3; FIG.
FIG. 5 is a structural diagram of a cylinder block showing a second embodiment of the prior art, in which (a) is a side view showing a lower crankcase part in a stepwise sectional side view (XX sectional view in FIG. 6). It is a figure and (b) is YY sectional drawing of a partition part.
6 is a plan sectional view of the lower crankcase showing a ZZ section in FIG. 3; FIG.
FIG. 7 is a plan sectional view of a lower crankcase for explaining vibrations of the partition wall and the side wall according to the embodiment of the present invention.
FIG. 8 is a plan sectional view of a lower crankcase for explaining vibrations of the partition wall and the side wall according to the embodiment of the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Cylinder block 2 ... Upper crankcase 3 ... Lower crankcase 4 ... Crankshaft 5 ... Bearing cap part 6 ... Partition part 6a ... Wall board 7 ... Hollow part 8 ... Connecting member 9 ... Cylinder
10… Main bolt 11… Side wall
12… Opening 13… Block mounting surface
14… Oil pan mounting surface 15… Bulkhead member
17… Main bolt hole 18… Balancer
19… Journal receiving portion 20… Crank chamber H… Height L1, L2… Partition lengths δ1, δ2, λ1, λ2… Vibration amplitude

Claims (2)

An engine crankcase part is formed by dividing the crankcase part into an upper crankcase and a lower crankcase from the center of the bearing part of the crank, and the lower crankcase is surrounded by a frame-like wall body. while connected by a plurality of partition walls between, on the top center of the partition wall, provided by integrating the bearing cap portion for pivotally supporting the upper crankcase is fastened in the main bolt and the crankshaft, before Symbol The partition wall portion has a double wall structure composed of both wall plates 6a having a hollow portion, the hollow portion is surrounded by both side walls 11, and a main bolt mounting hole communicating with the hollow portion is opened on the upper and lower surfaces of the partition wall portion. A crankcase structure for an internal combustion engine. The crankcase structure for an internal combustion engine according to claim 1, wherein in the partition portion of the lower crankcase, the two wall plates facing the hollow portion are connected by a connecting member provided integrally with the two wall plates .

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