JPH0627762Y2 - Valve drive for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of use) The present invention relates to a valve operating system for an internal combustion engine of integrated bearing type.

(Prior Art) As a conventional valve operating system for an internal combustion engine, there is, for example, a type shown in FIG. 4 or a type shown in FIG.

FIG. 4 (a) is a sectional view of the valve operating device, and FIG. 4 (b) is an exploded view for explaining the bearing portion. However, FIG. 4 shows each of the bearing portions 2 of the camshaft 1. The bearing ring 3 is divided into upper and lower parts, and the cam bracket 4 is fixed to the cylinder head 6 by a nut 5.

In this model, the cam bracket 4,
Since the nut 5 is required and the tightening work thereof is required, the cost is increased in terms of both the number of parts and man-hours.

Therefore, an integrated bearing type as shown in FIG. 5 has been proposed. (A) is a sectional view of the valve train, (b)
The figure is an exploded view for explaining the bearing part, which is formed integrally with the cylinder head 6 without dividing the bearing 3 of the bearing part 2 into upper and lower parts, and the camshaft 1 is inserted from one side of the cylinder head 6. It is something that is done (Shokai Sho 55
-92005, Japanese Utility Model Laid-Open No. 60-167103, etc.). (Problems to be Solved by the Invention) However, in such a conventional integral type bearinging type valve operating device for an internal combustion engine, the cylinder head 6
Since the camshaft 1 is sequentially inserted into the bearing 3 from one end side of the bearing, the diameter of the journal 7 of the bearing portion 2 and the diameter of the bearing 3 are inevitably larger than those of the cam portion 8 as shown in FIG. As a result, the peripheral speed of the bearing 2 becomes faster than the engine speed. Therefore, in order to prevent seizure during high rotation, it is necessary to give the oil clearance 9 much larger than the split type bearing structure of FIG. 4 described above from the relationship of the clearance ratio to the journal diameter.

Therefore, as the crankshaft rotates, the camshaft 1 is largely displaced in response to the reaction force from the valve spring within the diameter of the bearing 3 of the bearing 2, and the displacement is expanded by the rocker arm, so that the valve opening / closing timing and the valve overlap amount are increased. However, there is a problem that the values are likely to vary.
In particular, the displacement is small on the timing belt side because the camshaft 1 is always pulled downward, and is large on the opposite side, and therefore varies depending on the cylinder position. Therefore, the overlap angle varies greatly depending on the valve opening / closing timing depending on the cylinder, and the residual ratio of intake and exhaust varies depending on the cylinder. there were.

The present invention has been made for the purpose of solving such a conventional problem.

(Means for Solving the Problem) Therefore, according to the present invention, a plurality of beer rings forming a camshaft bearing portion are integrally formed on a cylinder head without being divided, and a camshaft is provided with the plurality of beer rings from one end side of the cylinder head. In a valve operating system for an internal combustion engine that is sequentially inserted into the interior of the bearing, the bearing diameter and oil clearance of the bearing that is the most advanced in the camshaft insertion direction among the plurality of bearings are set to the bearing diameters of other bearings. It is characterized in that it is set smaller than the oil clearance and that a belt pulley around which a timing belt is wound is arranged at the end of the camshaft which is the rear end in the insertion direction.

(Function) By reducing the bearing ring diameter at the most distal end in the camshaft insertion direction, the oil clearance required due to the clearance ratio is reduced, and movement of the camshaft in the direction perpendicular to the axis is restricted.

At the opposite end, the tension of the timing belt acts on the cam shaft to press the cam shaft in the direction perpendicular to the axis.

That is, the movement in the direction perpendicular to the axis is restricted at both ends of the camshaft.

(Example) Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the present invention.

Since the drawing shows the bearing portion in detail, the same components as those in FIG. 6 showing the conventional example are designated by the same reference numerals, and the description thereof will be omitted.

This embodiment is an example of a valve train for a 4-cylinder engine.
It is provided with five bearing portions 1 to # 5. The camshaft 1 is inserted from the left side to the right side of the drawing with respect to the cylinder head integrally formed with the bearing ring 3, that is, the right side of the drawing is the leading end in the insertion direction. Also, the camshaft 1
A belt pulley (not shown) is attached to the left end of the figure.

Further, in this embodiment, the diameters of the four journals 7 of the # 1 to # 4 bearing portions 2, the inner diameter of the bearer ring 3, and the respective oil clearances 9 are the same as those in the conventional example. For example, the diameter of the journal 7 and the bearing 3 is about 47 mm, and the oil clearance 9 thereof is 100 μm. On the other hand, for the # 5 bearing portion 2, the diameter of the journal 7a is 20 ± 5 mm and the oil clearance 9a is 3 mm.
It is set to 0 ± 5 μm. The oil clear lance 9b on the lower side of the # 1 bearing portion 2 is extremely small because the camshaft 1 is always pulled downward by the tension of the timing belt (not shown) as in the conventional case.

Next, the operation of the above configuration will be described with reference to FIGS. 2 and 3.

If the oil clearance 9a of the journal 7a of the # 5 bearing 2 located at the rear end of the camshaft 1 (the tip in the inserting direction of the camshaft 1) is reduced to about 30 ± 5 μm as described above, the camshaft 1 is The movement in the direction perpendicular to the axis of is restricted. Further, since the other end of the camshaft 1 is constantly pulled downward by the timing belt as described above, the oil clearance 9b below the # 1 bearing 2 becomes extremely small, and the camshaft 1 in the direction orthogonal to the axis of the camshaft 1 also becomes extremely small. Movement is restricted. In other words, the # 1 journal 7b and the # 5 journal 7a at each end of the camshaft 1 restrict the movement of the camshaft 1 in the direction perpendicular to its central axis.

For this reason, the oil clearance 9 of the # 2 to # 4 journals 7 between the # 1 journal 7b and the # 5 journal 7a.
Is about 100 μm, the displacement of the camshaft 1 is very small.

Figure 2 shows the relationship between oil clearance and idle stability.
It can be seen that the idle operation is always in a stable state when the thickness is 5 μm.

FIG. 3 shows the relationship between the journal diameter and the clearance ratio. In the # 5 journal 7a, not only the oil clearance 9a is simply reduced, but the journal diameter itself is also reduced. Therefore, the gap ratio required for lubrication can be secured within an appropriate range. In the above example, the gap ratio is 0.030 / 20 = 1.50 × 10 ⁻³ , which is a generally required gap ratio 1 × 10 ^{−3 to} 2.5 × 10 ^3.
-3 can be satisfied and the oil clearance is small, but there is no fear of seizure.

(Effect of the Invention) As described above, according to the present invention, the movement of the camshaft in the direction perpendicular to the axis can be restricted at two positions on both ends of the camshaft, and the case of the integrated bearinging type It is possible to suppress the increase in the displacement of the cam shaft when opening and closing the valve or the variation in the displacement of each cylinder, which is a problem. At the same time, a sufficient clearance ratio necessary for lubrication can be secured, and seizure of each journal can be prevented. That is, the displacement of the camshaft can be suppressed without lowering the lubrication performance, and the idle stability can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a crankshaft bearing portion showing an embodiment of the present invention, FIG. 2 is a diagram showing a relationship between oil clearance and idle stability, and FIG. 3 is a diagram showing a relationship between a journal diameter and a clearance ratio. 4 to 6 show a conventional example, and FIG. 4 (a) is a sectional view of a split type bearinging type valve operating device,
(B) is an exploded view for explaining the bearing portion, FIG. 5 (a)
Is a cross-sectional view of the integrated bearinging type valve operating device, (b) is an exploded view for explaining the bearing portion, and FIG. 6 is an explanatory view of the crankshaft bearing portion. 1 ... Cam shaft, 2 ... Bearing part, 3 ... Beering, 7 ... Journal, 7a ... # 5 journal, 8 ...
… Cam section, 9 …… Oil clearing, 9a …… # 5 Journal oil clearing, 9b …… # 1 Journal oil clearing.

Claims (1)

[Scope of utility model registration request] 1. An internal combustion engine in which a plurality of bearings forming a camshaft bearing portion are integrally formed on a cylinder head without being divided, and a camshaft is sequentially inserted into the plurality of bearings from one end side of the cylinder head. In this valve operating system, the bearing diameter and oil clearance of the bearing, which is the most distal end in the camshaft insertion direction among the bearings, should be set smaller than the bearing diameter and oil clearance of other bearings. A valve train for an internal combustion engine, wherein a belt pulley around which a timing belt is wound is arranged at a camshaft end portion which is a rear end in the insertion direction.