JPH058337Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a bearing structure applied to support a main journal of a crankshaft.

[Conventional technology]

As internal combustion engines become lighter, their vibrations and
Noise reduction is becoming more and more important, and various countermeasures have been taken in the past. For example, in the main journal bearing of a crankshaft, the oil groove on the inner circumferential surface of the bearing on the cap side, that is, the lower side, is eliminated to reduce the surface pressure on the bearing surface.
51211), the peak value of the lubricating oil pressure is lowered by increasing the shaft diameter of the main journal to reduce the surface pressure on the bearing surface, or by reducing the oil clearance. In other words, by taking these measures, the lubrication state between the crankshaft and the bearings is improved, and the effect of damping the vibrations of the crankshaft due to the lubricating oil film is obtained.

[Problem that the invention attempts to solve]

However, if the bearing sliding surface is increased by eliminating the oil groove, the shaft diameter is increased, or the oil clearance is decreased, a problem arises in that friction loss between the crankshaft and the bearing increases. In other words, when attempting to reduce noise by suppressing crankshaft vibrations, friction loss in the bearings increases.
It was not possible to achieve both noise reduction and friction loss reduction.

[Means for solving problems]

In order to solve the above-mentioned problems, the crankshaft bearing structure according to the present invention has grooves extending in the circumferential direction and capable of retaining lubricating oil formed on the inner circumferential surface of the bearing. It is characterized in that the pitch of the striations on the upper bearing member located on the block side is larger than the pitch of the striations on the lower bearing member forming the bearing and located on the cap side.

〔Example〕

The present invention will be explained below with reference to the illustrated embodiments.

1 and 2 show a first embodiment of the present invention, which is an example in which the present invention is applied to a bearing that supports a main journal 11 of a crankshaft. The bearing 21 is held between a cylindrical support surface 13 formed on the cylinder block 12 and a cylindrical support surface 15 formed on the cap 14, and the main journal 11 is rotated within the bearing 21 with a clearance 16. freely supported. An oil passage 17 is bored in the cylinder block 12 and the bearing 21, and lubricating oil discharged from an oil supply section (not shown) passes through the oil passage 17, and enters the oil groove 22 formed on the inner peripheral surface of the bearing 21, and the main oil passage 17. The oil is supplied to the clearance 16 through an oil hole 23 formed in the journal 11.

The bearing 21 consists of an upper bearing member 24, a lower bearing member 25, and back metals 26, 27 provided on the outer peripheral sides of these bearing members 24, 25. The bearing members 24 and 25 are both formed into a semi-cylindrical shape from an aluminum alloy, and are joined together to form a cylindrical shape.
The back metals 26 and 27 also have a semi-cylindrical shape and are closely fixed to the outer circumferential sides of the upper and lower bearing members 24 and 25, respectively.

An oil groove 22 and a groove 31 extending in the circumferential direction are formed on the inner peripheral surface of the upper bearing member 24 .
The oil groove 22 is carved in the center of the inner peripheral surface, and has a diameter of about 4 mm, for example.
With a width of mm and a depth of about 0.1-0.2 mm. On the other hand, the streaks 31 are 0.15 to 0.3 mm on both sides of the oil groove 22.
It is formed with a pitch of, for example, about 4μ in depth. These oil grooves 22 and grooves 31 are formed by boring, and after the boring, a cylindrical sliding surface 32 is formed on the inner peripheral surface of the bearing member 24 by broaching. On the other hand, grooves 33 extending in the circumferential direction are also formed on the inner circumferential surface of the lower bearing member 25. The grooves 33 of the lower bearing member 25 are also formed by boring and have a depth of about 4 μm, but the pitch is larger than that of the upper bearing member 24, for example, 0.3 to 0.5 mm. After the lower bearing member 25 is also bored, a sliding surface 34 is formed by broaching.

Since such streaks 31 and 33 do not communicate with the oil passage 17 and have a small depth, they can retain lubricating oil, thereby ensuring that a good lubricating oil film is always formed on the sliding surfaces 32 and 34. It is formed. Since these grooves 31 and 33 extend in the circumferential direction, the lubricating oil does not flow laterally, that is, in the axial direction of the main journal 11 and escape from the clearance 16, so that the oil retention function is high. Further, the pitch of the striations 33 on the lower bearing member 25 is set larger than the pitch of the striations 31 on the upper bearing member 24. This is because the lower bearing member 25 receives a larger engine explosion load than the upper bearing member 24, so if the lower bearing member 25 is made to have the same pitch as the upper bearing member 24, the sliding surface 34 will easily wear out. Therefore, the sliding surface 34 of the lower bearing member 25 has a larger area than the sliding surface 32 of the upper bearing member 24.

As described above, since this embodiment has the streaks 31 and 33, a stable oil film can always be formed on the sliding surfaces 32 and 34. Therefore, the bearing 21
The vibration of the main journal 11 can be reduced without increasing wear loss between the main journal 11 and the main journal 11. Furthermore, since the pitch of the grooves 33 on the lower bearing member 25, which has a relatively large bearing load, is set roughly, the sliding surface 34 is less likely to wear out, and the durability of the bearing 21 is improved.

The bearing members 24 and 25 are manufactured by boring and broaching the inner circumferential surface of the cylindrical member to form oil grooves and finely pitched grooves, and then cutting the inner peripheral surface of the cylindrical member at a plane including the axis. Similarly, the inner peripheral surface of another cylindrical member is bored and broached to form rough pitched grooves, and then cut to form two lower bearing members. 25, one set of bearing members 24,
25 may be joined. Of course, the above-described processing may be applied to a member that has been previously formed into a semi-cylindrical shape.

FIG. 3 shows a second embodiment. This embodiment has a structure in which the outer peripheral surfaces of back metals 26 and 27 are coated with thin film layers 28 and 29 made of tetrafluoroethylene resin, respectively. The thin film layers 28 and 29 are in close contact with the cylinder block 12 or the cap 14, respectively, and absorb vibrations between these and the back metals 26 and 27, thereby enhancing the vibration damping effect of the main journal 11.

Note that when the bearing 21 is used to support a crank pin, the oil groove 22 of the upper bearing member 24 is unnecessary.

[Effect of idea]

As described above, according to the present invention, friction loss can be minimized, crankshaft vibration can be effectively reduced, and a bearing with excellent durability can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line - in FIG. 1, and FIG. 3 is a sectional view showing a second embodiment. 16... Clearance, 31, 33... Streak.

Claims (1)

[Scope of utility model registration request] In a crankshaft bearing structure in which a crankshaft is rotatably supported with a clearance within the bearing, and lubricating oil is supplied within the clearance to form a lubricating oil film on the inner peripheral surface of the bearing, the inner peripheral surface of the bearing is At the same time, the pitch of the grooves on the upper bearing member that constitutes the bearing and is located on the cylinder block side is formed on the cap side that constitutes the above-mentioned bearing. A crankshaft bearing structure characterized in that the pitch of the grooves is larger than that of the lower bearing member.