JPS62253908A - Valve lifter for overhead valve type internal combustion engine - Google Patents

Abstract

PURPOSE:To improve durability by specifying the orientation of eutectic carbide in metal structure extending from the tubular portion of a valve lifter interposed between a valve and a cam for reciprocating said valve and polishing the outer surface of tubular portion. CONSTITUTION:A valve mechanism 1 for opening and closing an intake-exhaust port 7 by reciprocating a valve 8 through a cam 5 interlocked rotatably with the movement of a piston 4 in a cylinder 3 has a valve lifter 21 interposed between the stem end 8a of valve 8 and the cam 5 and inserted slidably in a guide tube 14. Then, the valve lifter 21 is formed of hard tool steel having a large content of eutectic carbide oriented axially. And the eutectic carbide is oriented orthogonally to the thickness of longitudinal section of the valve lifter 21 from the tubular portion 22 to the upper end shoulder 21a on which larger bending moment acts, while the coarse eutectic carbide on the outer surface of tubular portion is adapted to be removed by barrel polishing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to technology applied to a valve mechanism portion of an overhead valve type internal combustion engine.

[Prior Art] As shown in FIG. 8, a valve mechanism 1 is installed in a cylinder head 2 of a four-cycle overhead valve type internal combustion engine. A cam 5 rotates at the timing (timing of 172 cycles of the piston) and a combustion chamber 6 is reciprocated by the cam 5.
The valve 8 is provided with a valve 8 (for intake or exhaust) that opens and closes a lower passage of fluid (for intake or exhaust) that communicates with the valve spring through a holder 9 attached to its stem end portion 8a. 10 applies a movement return force in the direction of closing the lower passage.

The stem end portion 8a of the valve 8 and the cam 5
A head 13 of the valve lifter 11 consisting of a cylindrical part 12 and a flat head 13 (a reinforcing plate 13a is fixed to the upper surface of the valve lifter 13 for preventing wear caused by the cam 5) is interposed between the valve lifter 11 and the cam 5. The valve lifter 11 is slidably guided in a guide tube 14 provided at the upper part of the cylinder head 2 at its cylindrical portion 12 .

Various external forces are applied to the valve lifter 11. That is, as shown in FIG. 7, the vertical pressing force FA from the cam 5 is applied to the upper center of the head 13 of the valve lifter 11, and the lateral reaction force from the wall surface of the guide cylinder 14 is applied to the cylindrical part 12. F3
is added from left and right. These external forces FA and FB cause a large bending moment to act on the valve lifter 11 from its cylindrical portion 12 to its upper shoulder, which may deform or crack that portion. There is. In order to prevent this, it is necessary to design with consideration to the strength of that part.

[Problems to be Solved by the Invention] However, it is not possible to attach a reinforcing plate to that part, and conventionally, as a means for providing strength, a reinforcing plate is inserted from the cylindrical part 12 of the valve lifter 11 to the shoulder at the upper end thereof. Since this method relies on increasing the wall thickness of the portion 11a, this increases the mass of the valve lifter 11, and as a result, the inertial mass of the moving part of the cam mechanism 1 increases, making it impossible to cope with higher speeds of the internal combustion engine. There was a problem.

This invention was made to solve these problems, and as a result of research, it was found that the orientation of eutectic carbides in the metal structure has a large effect on bending strength, and we focused on this. By carefully optimizing the orientation of the metal structure from the cylindrical part 12 of the valve lifter 11 to the shoulder at its upper end, the thickness of that part is suppressed and the required toughness is provided, thereby reducing the mass of the valve lifter 11 and the valve. It is an object of the present invention to provide a valve lifter that can reduce the inertial mass of the moving parts of a mechanism 1 and improve the sliding condition of the valve lifter 11 with respect to the guide tube 14 of the cylinder head 2, so as to be able to cope with higher speeds of internal combustion engines. do.

Means for Solving the L Problem] In order to solve the above problem, the valve lifter for the @1-valve internal combustion engine according to the present invention is composed of a head and a cylindrical part, and the head is made up of a combustion engine. The valve is interposed between a valve that opens and closes a fluid passageway leading to the chamber and a rotating cam that reciprocates the valve, and the cylindrical portion is attached to the cylinder head as the cam comes into rotational contact with the head. The valve lifter is made of a steel material containing dispersed eutectic carbide, and the eutectic carbide is transferred from the cylindrical part of the valve lifter to the upper end of the valve lifter. If the valve lifter is oriented in a direction perpendicular to the thickness direction of the longitudinal section of the valve lifter over the shoulder portion, the coarse eutectic carbide on the outer peripheral surface of the cylindrical portion is removed by barrel polishing.

[Function] The valve lifter has a structure in which the orientation of the eutectic carbide contained in its constituent metal structure is perpendicular to the direction of the thickness of the longitudinal section of the valve lifter, from the cylindrical part where bending moments are particularly likely to be applied to the upper shoulder part of the valve lifter. Since the metal structure itself is strong against the bending moment acting in that direction, the thickness of that part can be kept small while maintaining sufficient bending strength, and as a result, the thickness of the valve lifter is In addition, since the coarse eutectic carbide on the outer circumferential surface of the cylindrical part is removed by barrel polishing, the outer circumferential surface can be kept small while the valve lifter is sliding. The coarse eutectic carbide will not fall off and damage the sliding surfaces of the valve lifter and guide tube.

It is possible to maintain a smooth sliding state between the two at all times, thereby making it possible to cope with higher speeds of the internal combustion engine.

[Example] Fig. 1 is a partial vertical cross-sectional view of an overhead valve type internal combustion engine incorporating a valve lifter according to the present invention, Fig. 2 is an enlarged longitudinal cross-sectional view of the valve lifter according to the present invention, and Fig. 3 is a partial vertical cross-sectional view of an overhead valve type internal combustion engine incorporating a valve lifter according to the present invention. is a micrograph (50 times magnification) of the metallographic structure in a vertical cross-section of the cylindrical part of the valve lifter, and FIG. 4 shows the orientation of eutectic carbides in an explanatory partial vertical cross-section of the shoulder.

This valve lifter 21 is made of a round bar material of a certain length made of a hard tool steel with a high content of eutectic carbides and oriented in the axial direction (in particular, an alloy tool such as 5KDII). By cold forging so that the orientation of the carbide does not change, a closed-head cylindrical shape having a head 23 and a cylindrical part 22 is made (Fig. 2), and a cam is attached to the upper side of the head 23. 5 are in direct contact.

In this valve lifter 21, the cylindrical portion 22 on which a particularly large bending moment acts is also the shoulder portion 2 at the upper end of the valve lifter 21.
1a, eutectic carbides scattered in the structure of the constituent metals are oriented in a direction perpendicular to the thickness of the longitudinal section of the valve lifter so that they appear as white vertically elongated grains in FIG. The orientation of the eutectic carbides in the shoulder 21a is as illustrated in the partial longitudinal cross-sectional view of FIG.
It is oriented with a substantially constant curvature along 1a, and is oriented substantially perpendicular to the thickness direction of the longitudinal section.

Then, by performing barrel polishing on the outer peripheral surface of the cylindrical portion 22 of the valve lifter 21, coarse eutectic carbides on the surface are removed.

Incidentally, the manufacturing process of this valve lifter 21 will be explained as follows based on FIGS. 5 and 6.

That is, first, (1) a bar material 30 made of a steel material such as tool steel in which eutectic carbides are scattered along the axial direction in the metal structure (not shown) is cut into a required length to form a round bar. Material 3
1 is made, and (2) spheroidizing annealing is performed to smooth the corners of the eutectic carbide in the structure of the round bar material 31. Next, ■ the raw material 31 is cold forged without changing the orientation of the eutectic carbide on the circumferential side to form a cylindrical body 32 with a closed top end, and then ■ the end face is turned 6. , ■ Heat treatment to improve toughness.

Next, (1) polish its outer diameter and end face to make the surface smooth, and (2) perform surface hardening treatment (nitriding treatment).

Next, ■ Crowning is performed to make the outer shape of the cylindrical part barrel-shaped, and then ■ Barrel polishing is performed to remove coarse eutectic carbide on the surface of the cylindrical part 22. 5 Finally, the [phase] product is The valve lifter 2 is completed as a product through a series of inspection steps.

Valve lifter 21 (as a product made in this way)
2), as shown in FIG. 1, an intervening device is installed between the stem end portion 8a of the valve 8 and the cam 5 constituting the valve mechanism 1 of an internal combustion engine in substantially the same way as the conventional one. be done.

In addition, in the case of this embodiment, as shown in the figure, the valve 8
A small disk-shaped spacer 24 for adjusting the clearance between the small diameter portion 5a of the cam 5 and the valve lifter 21 is provided between the stem end portion 8a of the holder 9 and the inner bulging portion 21b of the bottom of the valve lifter 21. It is held in place so that it does not shift.

Since the other components are the same as those of the conventional example, the same reference numerals as in FIG. 8 showing the conventional example are given to avoid redundant explanation.

In the valve lifter 21 in this embodiment, the eutectic carbide in the constituent metal extends from the cylindrical part 22, which receives a particularly large bending moment, to the shoulder part 21a at the upper end in a direction perpendicular to the thickness direction of the longitudinal section of the valve lifter 21. Since the bending strength of that part is high due to the orientation, even if that part is made thinner to reduce weight, it can withstand the bending stress caused by the ultra-high speed rotation of an internal combustion engine. In addition, since the coarse eutectic carbide on the outer circumferential surface of the cylindrical part is removed by barrel polishing, the coarse eutectic carbide on the outer circumferential surface falls off while the valve lifter is sliding, and the sliding part of the valve lifter and guide tube without causing any damage.

A smooth sliding state between the two can be maintained at all times. In addition, since the entire pulp lifter 21 is integrally molded from a steel material with a high carbon content, even if the pulp lifter 21 is made thinner or smaller, there is almost no wear or deformation caused by contact with the cam 5 or the guide tube 14. There's nothing. In addition, since the eutectic carbide contained in the valve lifter 21 is spheroidized, the eutectic carbide is difficult to fall off.
Even if it falls off, it is unlikely to damage the sliding surfaces of the cam 5 or the guide tube 14, and even if an external force is applied to the valve lifter 21, it is unlikely that stress will be concentrated in its constituent metal structure and cause it to break. By using the valve lifter 21 in the embodiment, it is possible to cope with extremely high speed internal combustion engines.

[Effects of the Invention] According to the present invention, as described above, the shoulder at the upper end of the valve lifter, which is interposed between the valve and the cam that reciprocates the valve, is removed from the cylindrical part on which a particularly large bending moment acts. Part 21. The eutectic carbide in the constituent metal structure is oriented in the direction perpendicular to the thickness direction of the longitudinal section of the valve lifter in the area a, and the metal structure itself is strong against bending, so that part is made thinner to create a valve lifter. Even if the weight of the valve mechanism is reduced, the required bending strength can be obtained, and therefore, the inertial mass of the moving parts of the valve mechanism can be reduced. In addition, since the coarse eutectic carbide on the outer peripheral surface of the cylindrical part is removed by barrel polishing, the coarse eutectic carbide on the outer peripheral surface falls off while the valve lifter is sliding and becomes the sliding surface of the valve lifter and guide tube. without causing any damage,
A smooth sliding state between the two can be maintained at all times. Together, these can contribute to the ultra-high speed of the single overhead valve type internal combustion engine.

[Brief explanation of drawings]

1 to 6 show embodiments of the present invention. Among them, FIG. 1 is a partial longitudinal cross-sectional view showing a valve mechanism of an internal combustion engine in which the valve lifter of the present invention is incorporated, and FIG. A vertical cross-sectional view of a valve lifter. Figure 3 is a micrograph (50x magnification) showing the constituent metallographic structure in a longitudinal section of the cylindrical part of the valve lifter, and Figure 4 is an explanatory partial longitudinal section showing the orientation of eutectic carbides in the shoulder part of the valve lifter. FIG. 5 is an explanatory diagram showing the manufacturing process of the valve lifter, and FIG. 6 is an explanatory diagram showing an example of the manufacturing process. FIG. 7 is an explanatory diagram of external force acting on the valve lifter. FIG. 8 is a partial longitudinal sectional view showing a valve mechanism for an internal combustion engine incorporating a conventional valve lifter. 1... Valve mechanism, 2... Cylinder head. 5... Cam, 6... Combustion chamber, 7... Passage opening, 8... Valve, 8a... Stem end, 21
...Valve lifter. Figure 5 Figure 2 Figure 4 Bet 3 K

Claims (1)

[Claims] The valve is composed of a head and a cylindrical part, and the head is between a valve that constitutes a valve mechanism that opens and closes a fluid passageway leading to a combustion chamber of an overhead valve type internal combustion engine, and a rotating cam that reciprocates the valve. a valve lifter in which the cylindrical portion moves together with the valve by sliding on a guide tube provided in a cylinder head as the cam rotates in contact with the head; is made from a steel material containing dispersed eutectic carbides, and the eutectic carbides are oriented in a direction perpendicular to the thickness direction of the longitudinal section of the valve lifter, from the cylindrical part of the valve lifter to the shoulder at its upper end. A valve lifter for an overhead valve type internal combustion engine, characterized in that coarse eutectic carbide on the outer peripheral surface of the cylindrical portion is removed by barrel polishing.