JP2811991B2 - Camshaft for internal combustion engine and processing method thereof - 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 for an internal combustion engine, which is used as a valve mechanism component of an internal combustion engine as a prime mover of an automobile or the like, and a method of machining the same.

[0002]

2. Description of the Related Art A conventional camshaft used as a valve mechanism component of an internal combustion engine, which is a prime mover of an automobile or the like, includes:
The camshaft material is manufactured by casting, hot forging-heat treatment, or the like, and then manufactured by a process of grinding the cam journal, shaft end and cam so as to have a predetermined size or profile.

By the way, in the case of an internal combustion engine for an automobile,
There is a demand for higher performance than before, that is, further improvements in fuel efficiency, durability and output, and for the camshaft, it is also desired to lower the friction of the sliding portion of the cam and improve the wear resistance. ing.

[0004]

However, in conventional camshafts, the camshaft material itself is changed to a material suitable for reducing friction or a material having excellent wear resistance, or a material such as nitriding or coating is used. However, there is a problem that it is not very advantageous to perform such a surface treatment because the cost increases.

Further, by incorporating a needle bearing on the rocker arm, there is also an internal combustion engine having a valve train with reduced friction of the sliding portion between the cam and the cam follower, equivalent inertia of valve train components by incorporating a needle bearing There is a problem that it is not suitable for a high-speed high-performance engine due to an increase in weight.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. The sliding portion between the cam and the cam follower has low friction, and the wear resistance of the cam portion is low. It is an object of the present invention to provide a camshaft for an internal combustion engine which is excellent in performance.

[0007]

As a result of various investigations to achieve the above object, the present inventors have found that after the cam grinding step, a cross-hatched processing mark is left on the cam surface. It has been found that by finishing, friction at a sliding contact portion between a cam and a cam follower is reduced and wear resistance is also improved.

That is, the camshaft for an internal combustion engine according to the present invention is ground so as to have a predetermined cam profile.
Sliding contact with cam follower formed by processing
A camshaft for an internal combustion engine having a cam surface,
The cam surface has a cross-hat
It has fin-shaped processing streaks and the surface roughness is center line average roughness.
0.15μm or less in Ra and 1μm or less in undulation height
The configuration is below.

Further, the processing method for an internal combustion engine camshaft in accordance with the present invention, when processing the cams surfaces of the cam shaft example Bei the cam shaft, after performing the grinding so as to have a predetermined cam profile The cam surface is finished by the finishing tool while the cam shaft and the finishing tool are relatively moved in the circumferential direction of the cam and also in the cam axis direction. It is configured to form a mark .

[0010]

In order to complete the present invention, as shown in FIG. 4, a sliding test was performed using a test machine simulating a cam and a cam follower.

In this tester, a ring test piece 11 made of the same material as a camshaft and simulating a cam was attached to a rotating shaft 12, and a rocker arm tip was made of the same material as a cam follower material attached to a holder 13. the ring test piece 11 to rotate the disc test piece 14 in the arrow a ₁₀ pressing direction by the repulsive force of the spring 15, the torque detector 17 which is coupled between the rotary shaft 12 and the motor 16 between both the test pieces 11 and 14 It is configured to measure the generated friction torque.

Therefore, the ring test piece 11 of Comparative Example 1 subjected to only the normal grinding and the finish processing using a wrapping tape after the grinding were performed, and as shown in FIG. As shown in FIG. 6, the ring test piece 11 of Comparative Example 2 in which the processing streak 18 is left and the ring test piece 11 are rotated in the direction of arrow A ₁₁ and the arrow A
While oscillating in ₁₂ directions, the finishing process was sufficiently performed by the wrapping tape 20 backed up by the backup roller 19, and the test piece 11 of the application example of the present invention in which the cross-hatched processing streak 21 was left. When the friction coefficient was measured, the results were as shown in FIG. In addition, when the amount of wear after the 50-hour test was measured, the results shown in Table 1 were obtained.

[0013]

[Table 1]

As shown in FIG. 7 and Table 1, a test piece 11 according to the application example of the present invention finished so that a processing streak 21 remains in a cross hatch shape by a lapping tape 20 after grinding.
It can be seen that the friction coefficient and the amount of wear of are smaller than those of the test pieces 11 of the other comparative examples 1 and 2.

Therefore, after performing a grinding process so as to have a predetermined cam profile, a finishing process such as a wrapping tape is performed to finish the cam surface so as to leave working streaks in a cross hatch shape. Friction between the shaft and the cam follower is reduced, and wear is suppressed.

[0016]

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

FIG. 1 is a diagram showing an embodiment of the present invention.

As shown in FIG. 1, a cam 1 ground on a shaft 1a so as to have a predetermined cam profile.
camshaft direction which is the arrow A ₁ direction camshaft 1 with b, i.e. the case shown in FIG. 1 was fixed to a chuck 2 which can be oscillating in the lateral direction, the cam circle is an arrow A ₂ direction camshaft 1 while oscillating in the direction along the cam shaft is an arrow a ₁ direction is rotated in the circumferential direction, moves in the arrow a ₃ direction and backup rollers 3
Arrow by A ₄ wrapping tape 4 is pressed a finishing tool direction finishing operation the surface of the cam 1b, it was processed finish to leave the cross-hatched machining streaks 6 the cam surface by.

At this time, it is preferable that the surface roughness of the cam surface is Ra 0.15 μm or less in terms of center line average roughness.

[0020] In this example, the arrow _{A 1} direction Oscillating cycle 1000 Hz, the stroke 2 mm, polishing time 60 sec, alumina particle size of lapping tape 4 15.mu.
m, surface pressure of 12kg pressed by backup roller 3
f / mm ² , tape peripheral speed of wrapping tape 4 50 m /
When the shaft torque of the camshaft 1 was measured for the camshaft 1 on which the finishing of the cam 1b was performed under the conditions of min, the results shown in FIG. 2 were obtained. Also, when the wear amount of the camshaft after the wear resistance evaluation for 100 hours was examined,
The results are shown in Table 2.

As shown in FIG. 2, the camshaft according to the embodiment of the present invention, in which the finishing process is performed so that the cross-hatched processing streak 6 remains as compared with the camshaft finished only by the conventional grinding process. It can be seen that shaft torque is smaller and friction is smaller. In addition, as shown in Table 2, the amount of wear of the camshaft after the 100-hour wear resistance evaluation test is small.

[0022]

[Table 2]

FIG. 3 shows another embodiment of the present invention. As shown in FIG. 3, a camshaft having a cam 1b ground on a shaft 1a so as to have a predetermined cam profile. 1 was fixed to a chuck capable of oscillating in the direction along the cam shaft is an arrow a ₁ direction, the cam axis is the arrow a ₁ direction to rotate the cam shaft 1 in the cam circumferential direction is the arrow a ₂ direction while oscillating, by pressing the grinding wheel 7 which is working tool finish having a fine finishing grindstone surface 7a of rotation and the particle size of the arrow a ₅ direction finish to leave the machining streaks crosshatch shape cam surface processing The following shows the case where is performed.

Even in such a case, it is possible to provide a camshaft for an internal combustion engine having a low friction at the sliding portion between the cam and the cam follower and having excellent wear resistance.

When the undulation shape of the cam surface of the camshaft according to the embodiment of the present invention was measured, the height difference of the undulation was about 2.5 in the conventional ground camshaft.
In contrast, the height difference of the waviness is as small as about 1 μm or less in the camshaft according to the embodiment of the present invention, whereas the height difference is generated between the cam and the cam follower in the initial operation. It was possible to suppress a certain abnormal noise.

[0026]

In an internal combustion engine camshaft according to the present invention, the grinding so as to have a predetermined cam profile
A cross hatch-like processing streak is provided on the cam surface which is formed by sliding contact with the cam follower .
Surface roughness Ra 0.15μm or less and high and low undulation
By setting the difference to 1 μm or less, and in the method for processing a camshaft for an internal combustion engine according to the present invention, after performing a grinding process so as to have a predetermined cam profile, the camshaft and the finishing tool are separated by a cam circle. The finishing surface of the cam is finished by the finishing tool while being relatively moved in the circumferential direction and also in the cam axis direction, so that a cross-hatched processing streak is formed on the cam surface .
Between the cam that makes sliding contact and the cam follower.
It is possible to efficiently reduce the resistance due to sliding friction.
And sliding friction on the cam surface due to reduced sliding friction.
Abrasion resistance on the cam surface
The reduction of noise reduces the occurrence of abnormal noise and improves sound and vibration performance.
Up. Also, cross-hatched processing streaks on the cam surface
It can be formed efficiently and productivity is improved.

[Brief description of the drawings]

1 shows an embodiment of the present invention, wherein FIG. 1 (a) is a partial front view, FIG. 1 (b) is a partial cross-sectional view, and FIG. 1 (c) is a cam surface of a camshaft. FIG.

FIG. 2 is a graph illustrating a result of measuring a shaft torque of a camshaft;

3A and 3B show another embodiment of the present invention. FIG. 3A is a partial front view, and FIG. 3B is a partial cross-sectional view.

FIG. 4 is an explanatory view showing an example of a wear tester.

5A and 5B show a comparative example in which circumferential processing marks are left on the cam surface. FIG. 5A is a front view, and FIG. 5B is a side view.

6A and 6B show an application example of the present invention in which a cross-hatched processing streak is left on a cam surface. FIG.
6B is an explanatory sectional view, and FIG. 6C is an explanatory front view of a cam surface.

FIG. 7 is a graph illustrating a result of measuring a wear coefficient of each test piece;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Camshaft 1a Shaft 1b Cam 4 Wrapping tape (finishing tool) 6 Cross-hatch-shaped processing streak 7 Grindstone (finishing tool) A ₁ Cam axis direction A ₂ Cam circumferential direction

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-78507 (JP, A) JP-A-3-60968 (JP, A) JP-A-1-167021 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) F01L 1/04 F16H 53/02

Claims (2)

(57) [Claims] (1) A grinding method for obtaining a predetermined cam profile.
Formed by grinding to make sliding contact with the cam follower.
A camshaft for an internal combustion engine having a cam surface , wherein the cam surface is a cross shaft formed by finishing.
It has a stitch-like processing streak and the surface roughness is center line average
0.15μm or less in roughness Ra, 1μm
A camshaft for an internal combustion engine , which is as follows . 2. The method of claim 1] of the cam shaft example Bei the cam shaft
Upon processing the cams surfaces, after performing the grinding so as to have a predetermined cam profile, while also move relative to the cam axis causes relative movement between machining tool finishing the camshaft cam circumferential direction the by processing finish the cam surface by finishing tool, the cam surface, the processing method for an internal combustion engine cam shaft and forming processed striations cross Ha pitch shape.