JP3109344B2 - Camshaft bearing structure for valve train - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a camshaft bearing structure constituting a valve train of an internal combustion engine.

[0002]

2. Description of the Related Art Journal bearings for supporting a camshaft with an oil film formed between the camshaft and the bearing are widely used as a camshaft bearing for driving a valve gear of an internal combustion engine. As shown in FIGS. 5 (A) and 5 (B), such a camshaft bearing has a semi-circular bearing which is in sliding contact with a camshaft (not shown) on the inner periphery of a half-shaped bearing 90 formed in an arch shape. A surface 91 is formed and this bearing surface 9
Through holes 92, 92 through which bolts are inserted are formed in the legs 90A, 90A, which contact the bearings of the cylinder head (not shown) on both sides of the bearing 1, and the bearing 90 is inserted through the through holes 92. It is fastened to the joint surface of the cylinder head with no bolt. These legs 90A, 90A
In order to supply lubricating oil to the bearing surface 91, lubricating oil passages 93, 93 each having a substantially U-shape are formed at a predetermined depth on the bottom surface of the camshaft. Discharge passages 93A, 93A opened to the bearing surface 91 so as to be orthogonal to the axis of the shaft, and a passage 93B connecting these discharge passages is disposed parallel to the camshaft axis and between the bearing surface 91 and the through hole 92. Is done.

[0003] A lubricating oil supply hole is opened corresponding to a lubricating oil passage 93 on a joint surface (not shown) of the cylinder head with which the leg portion 90A of the bearing 90 abuts. Lubricating oil is pumped from the supply hole to the lubricating oil passage 93. The lubricating oil is discharged from the discharge passages 93A, 93A opened to the bearing surface 91 via the passage 93B in a direction orthogonal to the camshaft axis, and forms an oil film having a predetermined thickness necessary to support the camshaft. Note that such a camshaft bearing structure is disclosed in
The one disclosed in JP 23712 is also known.

[0004]

In order to reduce the size and weight of the bearing 90, the distance L between the axis of the camshaft and the through hole 92 is reduced.
And the leg 9 surrounded by the lubricating oil passage 93
There is a method of shortening the island portion 90B, which is the bottom surface of 0A, in the entire length direction (interval L direction) of the bearing 90, and shortening the interval between the through holes 92, 92 to reduce the size.

However, in the conventional camshaft bearing structure of the valve train, when the island portion 90B is shortened in the entire length direction of the bearing 90 to shorten the interval L, the lubricating oil passage 93 forms the leg portion 90A. Not only does the rigidity of the island portion 90B separated from the bottom surface decrease, but also there is a problem that the island portion 90B is galling when the bearing surface 91 is processed, while the rigidity of the island portion 90B is secured. Therefore, when the discharge passage 93A of the lubricating oil passage 93 is inclined, the lubricating oil is not supplied in the direction orthogonal to the axis, flows out in the axial direction of the camshaft, and a predetermined oil film is not formed on the bearing surface 91. May cause.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a camshaft bearing structure for a valve train capable of promoting the miniaturization and weight reduction of a bearing while ensuring lubrication performance and rigidity. With the goal.

[0007]

According to the present invention, a half-split type bearing main body for supporting a cam shaft is provided in a pair with a bearing portion on a cylinder head side, and the bearing main body has a bearing surface for supporting the cam shaft. Are formed on both sides of the bearing surface, and a through hole is formed in the leg to insert a fastening member with the cylinder head.The through hole is formed on the joint surface of the leg with the cylinder head. In a camshaft bearing structure of a valve gear, a lubricating oil passage is formed between the bearing surface and a lubricating oil supplied from the cylinder head side through the lubricating oil passage to the bearing surface. The opening at both ends of the lubricating oil passage is opened in the bearing surface from a direction orthogonal to the camshaft, and a curved portion is formed in the lubricating oil passage connecting these openings so as to avoid the through hole. .

[0008]

Therefore, the connection between the two ends of the lubricating oil passage formed in the leg of the bearing is curved so as to avoid the through hole provided in the leg of the bearing body, and both ends of the lubricating oil passage are connected to the camshaft. Because the bearing surface is opened in a direction perpendicular to the bearing surface, the area between the camshaft shaft and the through hole is reduced without reducing rigidity by securing the area of the bottom surface of the bearing legs surrounded by the lubricant passage. The total length can be shortened, and the lubricating oil fed into the lubricating oil passage is discharged from the opening in the bearing surface in the direction orthogonal to the axis of the camshaft, and the hydraulic pressure in the radial direction is almost applied to the camshaft. An oil film having a predetermined thickness is formed on the bearing surface, so that the camshaft can be smoothly supported.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a cylinder head 1 of an OHC engine.
A camshaft (not shown) is supported by a cam bracket 2 and a cam bracket 82 as a bearing body fastened to the cylinder head 1 and slides freely in the valve hole 11. A supported intake valve (not shown) is driven by a camshaft.

As shown in FIG. 2, a cam bracket 2 for supporting a cam shaft is a half-split type formed in an arch shape.
A semicircular bearing surface 20 that slides on a camshaft (not shown) is formed on the inner periphery.

The cam bracket 2 sandwiching the bearing surface 20
2A, 2A, which contact the cylinder head 1
Is provided. Through holes 21 and 22 are formed in the legs 2A and 2A, respectively, which penetrate the legs 2A of the cam bracket 2 in the vertical direction for inserting bolts, and the bottom surfaces of the legs 2A as joint surfaces and the cylinder head 1 are formed. The cam bracket 2 is fastened to the cylinder head 1 by a bolt (not shown) serving as a fastening member inserted into the through holes 21 and 22, respectively, while making contact with an end face (not shown).

The cam bracket 2 is disposed in a direction perpendicular to the axis of the camshaft. The through hole 21 is inside the cylinder head 1 (left side in FIG. 1), and the through hole 22 is outside the cylinder head 1 (see FIG. 1). (Right side of No. 1). Although not shown, a half-shaped bearing surface is also formed on the cylinder head 1 facing the cam bracket 2, and the camshaft is supported between the cam bracket 2 and the cylinder head 1.

As shown in FIGS. 3 and 4, lubricating oil passages 3 are formed in the bottom surface of the leg 2A having the through holes 22 in a groove shape having a predetermined depth. Form openings 31, 31 opened in the bearing surface 20, and these openings 31,
Reference numeral 31 denotes a predetermined interval in the axial direction of the camshaft and a through hole 2.
They are arranged symmetrically with respect to a center line connecting the first and the second 22.

The lubricating oil passage 3 has openings 31 at both ends.
And a bent portion 32 which is bent in a direction along the bearing surface 20 after moving toward the inner periphery of the leg portion 2A, and a curved portion formed between the through hole 22 and the bearing surface 20 by connecting the bent portions 32, 32. An island portion 2B is formed on a part of the bottom surface of the leg portion 2A which is constituted by the portion 33 and is partitioned by the lubricating oil passage 3.

The lubricating oil passage 3, which has once been directed from the opening 31 to the inner periphery of the leg 2A, is bent from the inner periphery of the leg 2A in a direction along the bearing surface 20 by an arc-shaped bent portion 32, and then the opening is formed. 3
At the approximate center of the first and the first 31, a curved portion 33 curved toward the bearing surface 20 is formed so as to move away from the through hole 22, and the opening 31 at the other end is formed from the curved portion 33 through the bent portion 32.
Connected to.

The opening 31 opens from the arcuate bent portion 32 in a direction perpendicular to the axis of the camshaft (not shown), and the lubricating oil fed to the lubricating oil passage 3 is perpendicular to the bearing surface 20, that is, as shown in FIG. Not discharged in the radial direction of the camshaft.

The operation will be described next.

The cam bracket 2 is fastened to the cylinder head 1 by bolts (not shown) inserted through the through holes 21 and 22, and slidably contacts a cam shaft (not shown) on the bearing surface 20.

As shown in FIG. 1, the lubricating oil is discharged to a predetermined position facing the bent portion 32 of the lubricating oil passage 3 on the end surface of the cylinder head 1 where the bottom surface of the leg 2A of the cam bracket 2 abuts. The supply hole 12 opens.

The lubricating oil pumped by a pump (not shown) with the start of the engine is supplied from the supply hole 12 to the bent portion 32 of the lubricating oil passage 3.

The lubricating oil is discharged from the bent portion 32 to the camshaft (not shown) through the opening 31 at one end of the lubricating oil passage 3, and from the opening 31 at the other end through the curved portion 33 and the bent portion 32. It is also discharged toward the camshaft.

The lubricating oil discharged from the opening 31 is discharged at right angles to the bearing surface 20, that is, in a direction perpendicular to the axis of the camshaft.
Is supported by an oil film of a predetermined thickness formed according to the oil pressure of the lubricating oil. Since the discharge of the lubricating oil from the opening 31 is performed in the direction orthogonal to the axis of the camshaft, it is possible to suppress the outflow of the lubricating oil in the axial direction of the camshaft and to form a good oil film.

The curved portion 33 provided in the middle of the lubricating oil passage 3 not only connects the bent portions 32, 32 smoothly, but also curves the lubricating oil passage 3 toward the bearing surface 20 so that the through hole 22 and the lubricating oil passage The through hole 22 can be made as close as possible to the bearing surface 20 while avoiding interference with the through holes 21, 2, and 3.
2 can be reduced, and the cam bracket 2 forming the bearing body can be reduced in size.

Further, the thickness of the island portion 2B separated from the bottom surface of the leg portion 2A by the lubricating oil passage 3 (through holes 21, 22)
Is the thinnest on the center line connecting the through-holes 21 and 22, but the thickness of the island portion 2 increases toward the opening 31 and increases in accordance with the curved portion 33.
B can obtain a predetermined rigidity by securing a predetermined area while having a thin-walled portion, so that it does not generate galling when cutting the bearing surface 20 and improves workability. Can be.

After the lubricating oil passage 3 formed in the leg portion 2A of the cam bracket 2 is opened in the bearing surface 20 in a direction orthogonal to the axis of the camshaft, the arcuate bent portion 32 follows the bearing surface 20. Bend in the direction, and further bending part 3
3 is curved so as to be close to the bearing surface 20 so as to avoid the through-hole 22, so that the interval between the through-holes 21 and 22 can be shortened, and the cam bracket 2 can be downsized. The island portion 2B constituting a part of the bottom surface of the leg portion 2A partitioned by the above can secure a predetermined rigidity, and does not generate galling when cutting the bearing surface 20, etc. Since the discharge of the lubricating oil from the opening 31 is performed in a direction orthogonal to the axis of the camshaft, a good oil film is formed on the bearing surface 20 to suppress the flow of the lubricating oil in the axial direction of the camshaft. The lubrication of the shaft can be performed smoothly.

In the above embodiment, the lubricating oil passage 3
Is formed on the leg 2A on the side of the through hole 22, but can be formed on the leg 2A having the through hole 21.

Further, the curved portion 33 and the openings 31, 3 at both ends are provided.
The connection with the camshaft 1 is made by an arcuate bent portion 32, but the shape is not limited to the arcuate shape, and the lubricating oil passage 3 in the opening 31 may be arranged in a direction perpendicular to the axis of the camshaft. I just need.

[0029]

As described above, according to the present invention, the lubricating oil passage formed in the leg of the bearing body is opened in the bearing surface in a direction perpendicular to the axis of the camshaft, and then the through hole provided in the leg is formed. Since it is curved so as to avoid holes, the distance between the through holes formed on both sides of the bearing surface can be shortened, and the miniaturization of the bearing body can be promoted. The bottom surface can secure a predetermined rigidity, so that it does not generate galling when cutting the bearing surface, etc., and discharge of lubricating oil from the opening is performed in the direction orthogonal to the camshaft axis. Therefore, lubricating oil flowing out in the axial direction of the camshaft can be suppressed, and a good oil film can be formed on the bearing surface to smoothly lubricate the camshaft.

[Brief description of the drawings]

FIG. 1 is a sectional view of a bearing body showing an embodiment of the present invention.

FIG. 2 is a front view of a cam bracket.

FIG. 3 is a view taken on line AA of FIG. 2;

FIG. 4 is a sectional view taken along the line BB in FIG. 3;

FIG. 5 is a front view and a bottom view of a bearing showing a conventional example.

[Explanation of symbols]

 Reference Signs List 2 cam bracket 2A leg 3 lubricating oil passage 20 bearing surface 21, 22 through hole 31 opening 32 bent portion 33 curved portion

Claims (1)

(57) [Claims] 1. A half-split bearing body for supporting a camshaft is provided in pair with a bearing portion on a cylinder head side, and a bearing surface for supporting a camshaft is formed on the bearing body.
Legs are provided on both sides of the bearing surface, and a through-hole for inserting a fastening member with the cylinder head is formed in the leg, and the through-hole and the bearing surface are formed on the joint surface of the leg with the cylinder head. A camshaft bearing structure of a valve gear configured to form a lubricating oil passage positioned between the lubricating oil passages and guide the lubricating oil supplied from the cylinder head side through the lubricating oil passage to the bearing surface; Both ends of the passage are open to the bearing surface in a direction perpendicular to the camshaft, and a curved portion is formed in the middle of the lubricating oil passage connecting these openings so as to avoid the through hole. Camshaft bearing structure of the valve train.