JP2638910B2 - Camshaft bearing support device for 4-cycle engine - Google Patents

Description

The present invention relates to a camshaft bearing support device for an overhead cam type four-stroke engine.

(Prior Art) The valve train of an overhead cam type four-stroke engine is usually installed on the upper surface of a cylinder head and covered with a head cover. The camshaft that drives the valve mechanism is mounted directly or via a bearing in a bearing hole in which a lower half bearing hole formed in a cylinder head and an upper half bearing hole formed in a bearing housing are combined.

If the bearing is a needle bearing, it is common to press the bearing into the camshaft and fix it,
In the case where there is a journal portion between the cams, a split type is used, and fixing means by press fitting cannot be employed.

When a split type bearing is used or a metal bearing is used as described above, it is necessary to position the bearing (to prevent rotation) or to prevent the bearing from falling off. A circlip or a pin is used for positioning. If such a bearing positioning device is provided on the cylinder head side, a circlip groove and a pin hole will be formed in the lower half bearing hole, but a rocker arm and a rocker arm shaft are arranged near the journal portion. For this reason, there is a difficulty in processing due to space, which tends to increase the size of the cylinder head.

In particular, for cylinder heads that directly support the camshaft without using bearings, a large oil reservoir for oil lubrication is attached to the lower half bearing hole, so a cylinder head was added to improve engine performance. When a bearing is interposed by machining, there is a problem that there is often no room to arrange a positioning device.

(Problems to be Solved by the Invention) As described above, in the four-cycle engine that supports the camshaft via the bearing, there is a problem that it is difficult to install the bearing positioning device on the cylinder head.

The present invention has been made in consideration of the above-described circumstances, and allows a bearing to be positioned without machining a cylinder head, and a camshaft of a four-cycle engine that is easily modified by modifying an existing cylinder head that does not use a bearing. It is an object to provide a bearing support device.

[Configuration of the invention]

(Means for Solving the Problems) A camshaft bearing support device for a four-stroke engine according to the present invention has the following features.
The lower half bearing hole formed in the upper surface of the cylinder head and the upper half bearing hole formed in the bearing housing are aligned to clamp the camshaft bearing, and the above bearing is composed of a split type bearing. An oil passage is formed in the cylinder head to form an oil passage communicating the bearing with the cylinder head, and a locking member for positioning the split type bearing is provided in the bearing housing, a split surface of the bearing, an installation position of the locking member and The positions of the oil holes are balanced at substantially equal intervals in the circumferential direction of the bearing.

(Operation) This camshaft bearing support device for a four-cycle engine does not require bearing positioning processing in the lower half bearing hole of the cylinder head, simplifies the layout of the cylinder head in the lower half bearing hole portion, and enables manufacturing processing. It will be easier.

The lower half bearing hole of an existing cylinder head that does not use a bearing can be enlarged and the bearing can be interposed without difficulty, so that it is easy to improve the performance of the engine.

Further, since the shape of the bearing housing is small, machining and additional processing of the bearing positioning device are easy, and even if the shape needs to be changed, an increase in cost such as mold cost can be minimized.

(Embodiment) A description will be given below with reference to the drawings showing an embodiment of the present invention.

On the upper surface of the cylinder head 1, a lower half bearing hole 2 of the camshaft is arranged on both sides, and a valve stem support hole 3, a bearing housing fastening screw hole 4 and the like are arranged therearound. Further, a spark plug insertion hole 5, a stud bolt insertion hole 6, a cam chain chamber 7, and the like are formed, and the shape is extremely complicated and mixed with the mating surfaces 8, 9 with the head cover.

A bearing housing 10 is mounted on the lower half bearing hole 2 with a fastening bolt.
11, a bearing hole is formed in combination with the upper half bearing hole 12 of the bearing housing 10. The camshaft 13 is rotatably supported in the bearing hole via a bearing 14. The bearing 14 is composed of a vertically split bearing.

Lower half bearing hole 2 of cylinder head 1, bearing housing 10
The upper half bearing hole 12 is originally set so as to support the camshaft without a bearing, and the inner diameter of each bearing hole 2, 12 is enlarged so that the bearing 14 can be interposed. Therefore, a large oil reservoir 15 remains in the lower half bearing hole 2.

A rocker arm support shaft 16 is mounted below the lower half bearing hole 2. The inner hole 17 of the rocker arm support shaft 16 is used as an oil passage, and the oil sump 15 is supplied with lubricating oil from the oil passage, and normally passes through an oil hole 18 below the bearing 14 to lubricate the inner surface of the bearing 14. Supply oil.

Next, the upper half bearing hole 12 and the bearing 14 of the bearing housing 10
Blind holes 19 and 20 are respectively formed at upper relative positions, and a locking pin 21 is held as a locking member. As a result, the bearing 14 is positioned and fixed, the operation of the camshaft 13 is stabilized, and the communication between the oil reservoir 15 and the oil hole 18 is stabilized.

The bearing 14 may be a split needle bearing. Further, the circlip can be used for positioning in the thrust direction instead of the locking pin. In this case, since the outer peripheral side of the upper half bearing of the split bearing 14 is locked and positioned by the locking pin 21 or the circlip, which is a locking member mounted on the bearing housing 10, the ball of the split bearing 14 is positioned. The locking member can be arranged without affecting the needle and the needle, and the bearing 14 can be made compact.

In addition, since the split surface of the split type bearing 14, the installation position of the locking pin (locking member) 21, and the oil hole 18 are arranged at substantially equal intervals (central angle 90 degrees) in the circumferential direction of the bearing 14, Bearing 14 has good rigidity balance, bearing
14 is advantageous in terms of durability and deformation resistance.

In this manner, the bearing 14 is positioned on the bearing housing 10 side, which facilitates processing, and does not require processing of a positioning hole on the cylinder head 1 side. Therefore, regardless of the presence of a large oil sump, the structure of this part is reduced. This has the effect of simplifying and preventing the cylinder head from becoming large.

〔The invention's effect〕

As described above, the camshaft bearing support device of the four-stroke engine according to the present invention holds the camshaft bearing by aligning the lower half bearing hole formed in the upper surface of the cylinder head with the upper half bearing hole formed in the bearing housing. The bearing is composed of a split bearing, an oil hole is formed in the cylinder head side of the bearing to form an oil passage communicating with the bearing in the cylinder head, and the bearing for positioning the divided bearing in the bearing housing. A member is provided, and the split surface of the bearing, the installation position of the locking member, and the oil hole position are arranged at substantially equal intervals in the circumferential direction of the bearing, without machining the bearing positioning hole in the cylinder head. The bearing interposed on the camshaft can be positioned and the bearing can be used. Not equipped with bearings to an existing cylinder head, it is possible to easily the performance of the engine.

Also, since the positioning and fixing of the split type bearing can be performed by the locking member mounted on the bearing housing side,
While the bearing can be designed compactly, the split surface of the bearing, the installation position of the locking member and the oil hole can be arranged in a well-balanced manner in the circumferential direction of the bearing at almost equal intervals, so that the rigidity balance of the bearing is good, the durability of the bearing,
It is advantageous in that a highly reliable camshaft bearing support device having excellent deformation resistance can be provided.

[Brief description of the drawings]

FIG. 1 is a vertical side view of a camshaft bearing support device showing an embodiment of the present invention, FIG. 2 is a vertical front view of the camshaft bearing support device of FIG. 1, and FIG. 3 is a plan view of a cylinder head. . 1 ... Cylinder head, 2 ... Lower half bearing hole, 10 ... Bearing housing, 12 ... Upper half bearing hole, 13 ... Camshaft,
14 ... Bearing, 15 ... Puddle, 21 ... Locking pin.

Claims (1)

(57) [Claims] 1. A camshaft bearing is sandwiched by aligning a lower half bearing hole formed in an upper surface of a cylinder head with an upper half bearing hole formed in a bearing housing, and the bearing is constituted by a split type bearing. An oil hole is formed in the cylinder head side to form an oil passage communicating with the bearing in the cylinder head, and a locking member for positioning the split type bearing is provided in the bearing housing. A camshaft bearing support device for a four-stroke engine, wherein the positions of the members and the positions of the oil holes are balanced at substantially equal intervals in the circumferential direction of the bearing.