Bearing structure for internal combustion engine

#The present invention relates to a bearing structure for an internal combustion engine, and in particular to a bearing structure for an internal combustion engine in which a rotational shaft of the internal combustion engine is supported by a radial plain bearing via lubricating oil, and the radial plain bearing is retained by a bearing retaining unit.

#Patent Document 1 discloses a technique related to a bearing structure in which a rotational shaft of an internal combustion engine is supported by a radial plain bearing via lubricating oil. In Patent Document 1, a PTC heater is provided opposing an outer peripheral surface of a radial plain bearing mounted on a cylinder block and a bearing cap of an engine, and a thermal insulation material is provided on a side, of the PTC heater, opposite (outer peripheral side) to the side opposing the outer peripheral surface of the radial plain bearing. During a cold start of the engine, the radial plain bearing is heated by the PTC heater such that the lubricating oil filled between the radial plain bearing and a crank shaft is heated. With this configuration, viscosity of the lubricating oil filled between the radial plain bearing and the crank shaft is reduced, and a viscous frictional loss when the crank shaft is rotated is reduced.

#[Patent Document 1] JP 2010-127375 A

#FIG. 1A is a diagram schematically showing a configuration of a bearing structure for an internal combustion engine according to a preferred embodiment of the present invention.

#FIG. 1B is a diagram schematically showing a configuration of the bearing structure for an internal combustion engine according to the preferred embodiment of the present invention.

#FIG. 2 is a diagram schematically showing another configuration of the bearing structure for an internal combustion engine according to the preferred embodiment of the present invention.

#A preferred embodiment of the present invention (hereinafter referred to as “embodiment”) will now be described with reference to the drawings.

#FIGS. 1A and 1B are diagrams schematically showing a configuration of a bearing structure for an internal combustion engine according to an embodiment of the present invention. FIG. 1A is a cross-sectional diagram of the bearing structure viewed from a rotational shaft direction of the bearing structure, and FIG. 1B is an internal structural diagram of the bearing structure viewed from a direction perpendicular to the rotational shaft direction. In the bearing structure for an internal combustion engine according to the present embodiment, a crank journal 18 of a crank shaft which is a rotational shaft of the internal combustion engine is supported by a radial plain bearing (which is also called a journal plain bearing) 30 via lubricating oil, and the radial plain bearing 30 is retained by a bearing retaining unit 13. In the figures including FIGS. 1A and 1B, a thickness of the radial plain bearing 30 and the size of the gap between the radial plain bearing 30 and the crank journal 18 or the like are shown larger than the actual size for the purpose of explanation.

#The bearing retaining unit 13 comprises a bearing retaining unit body 20 formed by a portion of a cylinder block of the internal combustion engine, and a cap 21 which is fastened to the bearing retaining unit body 20. For the bearing retaining unit 13 (the bearing retaining unit body 20 and the cap 21), a metal material such as iron and aluminum is used. A volume of the bearing retaining unit body 20 is larger than a volume of the cap 21, and a thermal capacity of the bearing retaining unit body 20 is larger than a thermal capacity of the cap 21. In the bearing retaining unit body 20, a bearing mounting surface 13A which is a concave curved surface having an approximately semi-cylindrical shape is formed, and on the cap 21, a bearing mounting surface 13B which is a concave curved surface having an approximately semi-cylindrical shape is formed. The cap 21 is fastened to the bearing retaining unit body 20 by a bolt 15 which is a fastening member so that a through hole through which the crank journal 18 is inserted is formed between the bearing mounting surfaces 13A and 13B. More specifically, a bolt through hole 16 having a slightly larger diameter than a diameter of a shaft portion 15B of the bolt 15 is formed on the cap 21, and a male screw 15A of the bolt 15 inserted through the bolt through hole 16 is screw-engaged with a female screw 20A formed on the bearing retaining unit body 20 so that a head 15C of the bolt 15 contacts the cap 21 and the cap 21 is fastened to the bearing retaining unit body 20. The radial plain bearing 30 having a halved structure is mounted on the bearing mounting surfaces 13A and 13B and is retained on the bearing retaining unit 13.