JP2759856B2 - Camshaft - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camshaft.

[0002]

2. Description of the Related Art A camshaft forming a valve operating mechanism of an engine opens and closes an intake valve and an exhaust valve at a predetermined timing. A sprocket or a pulley is attached to an end of the camshaft. The rotation of the shaft is transmitted and driven. FIG. 1 shows an example of a camshaft. The camshaft 1 includes a shaft 2, a journal 3, a shaft 4, a cam 5, a shaft 6, a cam 7, a shaft 8, a cam 9,
The shaft 10, the journal 11, etc. are formed integrally, the diameter of the journal 3, 11 is the largest, and the shafts 2, 4, 6,
8, 10 have the same diameter. A pulley 15 is attached to the end surface 2a of the shaft 2, the journals 3 and 11 are supported by bearings of a cylinder head, and the cams 5, 7, and 9 abut against corresponding rocker arms (not shown).
A timing belt (neither is shown) is wound between the pulley 5 and a pulley attached to the crankshaft.

[0003]

When a load is applied to the pulley 15 in the camshaft 1, a bending moment as shown in FIG. 2A is generated, and the vicinity of the journal 3 closest to the pulley 15 becomes maximum. . That is, the pulley 15
When a load F, the distance from the end face 2a of the shaft 2 to the center of the journal 3 (P ₀ to P ₂₎ and L applied to the bending moment it becomes F × L. For this reason, the camshaft 1
The margin of strength near the journal 3 is reduced, and the horizontal axis of the journal 3 with respect to the diameter of the journal 3, ie,
When the shafts 2 and 4 connected to both end faces 3a and 3b (FIG. 1) are thin, these shafts 2 and 4 are particularly weak portions. still,
FIG. 2B schematically shows the section modulus of each part of the camshaft 1.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has a camshaft to which a pulley or a sprocket is attached and driven by a chain or a belt. It is an object to provide a camshaft adapted to effectively deal with moments.

[0005]

According to the present invention, there is provided a camshaft to which a sprocket or a pulley is attached and which is driven by a chain or a belt. The structure is such that a portion close to a close journal is thick and becomes thinner as the distance from the journal increases.

[0006]

When a load is applied to the pulley of the camshaft, a large bending moment is generated near the journal closest to the pulley. Since the camshaft is formed so that the shaft close to the journal is thick and becomes thinner as the distance from the journal increases, the section modulus near the journal increases and the strength increases. This increases the strength of the camshaft in the portion beside the journal where the margin of strength is the least.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the accompanying drawings. In FIG. 3, the camshaft 20 has shafts 21, 22, a journal 23, a shaft 24, a cam 25, a shaft 26, a cam 27, a shaft 28, a cam 29, a shaft 30, a journal 31, and the like formed integrally from the left side. End surface 21a of shaft 21
A screw hole is drilled in the shaft center of
It is attached by. Camshaft 20, the largest diameter D ₃ of the journal 23. The shaft of the cam shaft 20 on the side of the pulley 35 with respect to the journal 23 is not uniform, and is divided into a shaft 21 and a shaft 22. If the diameters are D ₁ and D ₂ , respectively, these shafts 21, 22
Are set so that D ₃ > D ₂ > D ₁ for the journal 23.

Further, the camshaft 20 is connected to the journal 2
3, the shafts 24, 26, 28 on the side opposite to the pulley have different diameters across the cams 25, 27, and the shaft diameters are D ₄ , D
_6, when D _8, there is a _{D 3> D 4> D 6} > D 8. The shafts 28 and 29 far from the journal 23 are shown in FIG.
And the shaft 21 has the same diameter as the shaft 2 of the camshaft 1. The conventional shaft diameters are drawn by thin lines on the shafts 22, 24 and 26 in the figure.

That is, the camshaft 20 is connected to the end face 23a of the journal 23 closest to the pulley 35 on the pulley side.
The diameter of the shaft 22 connected to the journal 23 is larger than the diameter of the journal 23, the shaft 24 connected to the opposite pulley side end surface 23 b of the journal 23 is larger than the shaft 22, and the diameter of the shaft 26 is Next, it is set to be thick. For example, the journal 23 has D ₃ = D ₈ + about 20 mm, and the shaft 22 has
D ₂ = D ₈ +14 mm, the shaft 24 is set to D ₄ = D ₈ +2 mm, and the shaft 26 is set to D ₆ = D ₈ +1 mm.

The operation will be described below. Camshaft 20
When a load is applied to the pulley 35 attached to the end face of the shaft 21, a large bending moment is generated near the journal 23 closest to the pulley 35 as shown in FIG. This bending moment is applied to the pulley 35 as described above.
Is F × L, where F is the load applied to, and L is the distance from the pulley 35 to the center of the journal 23. As shown in FIG. 4B, the shaft shafts 22, 24, and 26 near the journal 23 have a large section diameter and a large cross-sectional modulus, so that the strength margin is increased. The conventional section modulus is indicated by a thin line at a position corresponding to the shafts 22, 24, 26 in FIG. 4B.

As a result, the camshaft 20 is connected to the pulley 3
Even if a large load is applied to 5 and a large bending moment is generated near the journal 23 closest to the pulley, the strength of each part of the shafts 22, 24, 26 on both sides of the journal 23 is improved. FIG. 5 shows another embodiment of the present invention. The camshaft 20 'is gradually tapered as the shaft 22' of the journal 23 'on the pulley 35 side is separated from the journal 23', and is tapered. 21 '. The diameter of the joint portion between the 'journal 23' the shaft 22 is the same diameter as the diameter of the shaft 22 of the cam shaft 20 (FIG. 3) (D _2). It should be noted that there is no problem even if the shaft 21 'has a portion far from the journal 23', for example, the tip 21a 'has a larger diameter than the shaft 21'.

In the above embodiment, the type in which the pulley 35 is attached to one end of the camshaft 20 has been described. However, the present invention is not limited to this, and the type in which the pulley or sprocket is attached near the center of the camshaft. It is needless to say that the present invention can be applied to the camshaft.

[0013]

As described above, according to the present invention, it is possible to increase the strength of the portion having the smallest strength margin beside the sprocket or pulley and the journal closest to the sprocket or the pulley without significantly increasing the weight of the camshaft. This has the effect of improving the durability of the camshaft.

[Brief description of the drawings]

FIG. 1 is a partial front view of a conventional camshaft.

FIG. 2 is a graph showing an outline of a bending moment and a section modulus acting on the camshaft of FIG.

FIG. 3 is a partial front view showing an embodiment of the camshaft according to the present invention.

FIG. 4 is a graph showing an outline of a bending moment and a section modulus acting on the camshaft of FIG. 3;

FIG. 5 is a partial front view showing another embodiment of the camshaft according to the present invention.

[Explanation of symbols]

 20, 20 'Camshaft 21, 22, 24, 26, 28, 30 Shaft 23, 31 Journal 25, 27, 29 Cam 35 Pulley

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F01L 1/04

Claims (1)

(57) [Claims] 1. A camshaft to which a sprocket or a pulley is attached and driven by a chain or a belt is formed such that a portion close to a journal closest to the sprocket or a pulley is thicker and narrower as the distance from the journal increases. A camshaft characterized by being made.