Crankshaft support structure of internal combustion engine

1. A crankshaft support structure of an internal combustion engine, comprising:

a cylinder block;

a crankshaft having journal portions assembled to a lower portion of the cylinder block;

wall-shaped journal support bases formed in the lower portion of the cylinder block and extending along a direction crossing with an axis of the crankshaft;

semi-circular bearing portions respectively formed to undersurfaces of the journal support bases, the bearing portions accommodating half parts of each of the journal portions; and

saddle-shaped bearing caps respectively mounted on the undersurfaces of the journal support bases in such a manner as to straddle the journal portions being accommodated in the bearing portions, whereby the journal portions are rotatably supported,

wherein, each undersurface has a recessed portion that opposes a mount surface of the saddle-shaped bearing cap, and the undersurface, including the recessed portion, is provided with a thick portion thicker than other portion of the undersurface, the mount surface also has a thickness that corresponds to a thickness of the thick portion.

2. A crankshaft support structure of an internal combustion engine, according to claim 1 , wherein the thick portion is formed to a journal support base which supports a journal portion disposed in a center of a direction of the axis of the crankshaft.

3. A crankshaft support structure of an internal combustion engine, comprising:

a cylinder block;

a crankshaft having journal portions assembled to a lower portion of the cylinder block;

wall-shaped journal support bases formed in the lower portion of the cylinder block and extending along a direction crossing with an axis of the crankshaft;

semi-circular bearing portions respectively formed to undersurfaces of the journal support bases, the bearing portions accommodating half parts of each of the journal portions; and

saddle-shaped bearing caps respectively mounted on the undersurfaces of the journal support bases in such a manner as to straddle the journal portions being accommodated in the bearing portions, whereby the journal portions are rotatably supported,

wherein, each undersurface has a portion that opposes a mount surface of a saddle-shaped bearing cap, and the undersurface, including said portion, is provided with a thick portion thicker than other portion of the undersurface, the mount surface also has a thickness that corresponds to a thickness of the thick portion,

wherein the thick portion is formed in a manner that, a rib extending along sidewalls of each of the journal support bases is formed in a region of each of edges on both sides of each of the journal supports bases, wherein the region has a predetermined length from an inner side to outer side of each of the bearing caps with respect to a site set as reference, the site overlapping with the edge portion of each of the end faces on both sides of each of the bearing caps.

4. A crankshaft support structure of an internal combustion engine, according to claim 3 , wherein the rib linearly extends to the vicinity of a cylinder bore formed in the cylinder block.

5. A crankshaft support structure of an internal combustion engine, comprising:

a cylinder block;

a crankshaft having journal portions assembled to a lower portion of the cylinder block;

wall-shaped journal support bases formed in the lower portion of the cylinder block and extending along a direction crossing with an axis of the crankshaft;

semi-circular bearing portions respectively formed to undersurfaces of the journal support bases, the bearing portions accommodating half parts of each of the journal portions; and

saddle-shaped bearing caps respectively mounted on the undersurfaces of the journal support bases in such a manner as to straddle the journal portions being accommodated in the bearing portions, whereby the journal portions are rotatably supported,

wherein, each undersurface has a portion that opposes a mount surface of a saddle-shaped bearing cap, and the undersurface, including said portion, is provided with a thick portion thicker than other portion of the undersurface, the mount surface also has a thickness that corresponds to a thickness of the thick portion,

wherein the thick portion is formed to a journal support base which supports a journal portion disposed in a center of a direction of the axis of the crankshaft, and

wherein the thick portion is formed in a manner that, a rib extending along sidewalls of each of the journal support base is formed in a region of each of edges on both sides of each of the journal supports bases, wherein the region has a predetermined length from an inner side to outer side of each of the bearing cap with respect to a site set as reference, the site overlapping with the edge portion of each of the end faces on both sides of each of the bearing caps.

6. A crankshaft support structure of an internal combustion engine, comprising:

a cylinder block having wall-shaped journal support bases formed in the lower portion of the cylinder block and extending along a direction crossing with an axis of a crankshaft; and

semi-circular bearing portions respectively formed to undersurfaces of the journal support bases, the bearing portions accommodating half parts of each of a journal portions of the crankshaft; and

wherein, each undersurface has a recessed portion that opposes a mount surface of a bearing cap, and the undersurface, including the recessed portion, is provided with a thick portion thicker than other portion of the undersurface.

7. A crankshaft support structure of an internal combustion engine, according to claim 1 , wherein the mount surface also has a thickness that corresponds to a thickness of the thick portion.

8. A crankshaft support structure of an internal combustion engine, according to claim 1 , wherein the recessed portion makes direct contact with the mount surface of the bearing cap.

9. A crankshaft support structure of an internal combustion engine, according to claim 6 , wherein the recessed portion makes direct contact with the mount surface of the bearing cap.