JPH03105004A - Tappet structure - Google Patents

Abstract

PURPOSE:To improve abrasion resistance by utilizing a hardened layer of a crown surface without polishing and eliminating the hardened layer by forming, on the crown surface of a tappet, a projecting shape part contacting with a company cam at an offset position from the tappet center. CONSTITUTION:The crown surface 1a of abrasion resistance is provided on a tappet 1 without polishing a layer hardened by heat treatment. In a crown surface 1a, projecting shape parts 1c, 1b formed by heat treatment are formed respectively on the circumference and the center of the tappet 1 in order to rotate the tappet 1 in accordance with the rotation of a cam 2a, by contacting the cam 2a of a cam shaft 2 at an offset position from a tappet center C. A shaft part 1d is connected to the crown surface 1a. It is thus possible to improve abrasion resistance by utilizing the hardened layer of the crown surface 1a without polishing and eliminating the hardened layer.

Description

[Detailed description of the invention] [Purpose of the invention]

(Industrial Application Field) The present invention relates to a mushroom-type or cap-type tappet structure used in an engine valve mechanism. (Prior Art) Engine valve mechanisms have various structures, but for example, a camshaft is rotated in synchronization with the rotation of the engine crankshaft, and the rotation of the camshaft causes the tappet to reciprocate. There is a structure in which the engine valve is reciprocated through one end of the plunger of the hydraulic mechanism part of the tappet. FIG. 5 partially shows an example of a valve operating mechanism for an engine, and shows a valve operating mechanism using hydraulic tappets. In FIG. 5, 51 is a camshaft having a shaft 51a and a plurality of cams 51b, and 52 is the cam 51b.
The tappet crown 52a, the tappet shaft 52b, and the plunger one end 5, which is a part of the tappet hydraulic mechanism, are in contact with the
2c is a tappet, 53 is a tappet guide, and 54 is an engine valve (stem). In such a valve operating mechanism, power transmission for opening and closing the valve is performed by transmitting the rotation of the camshaft 51 from the cam 51b to the tappet crown surface 52a, and to the engine valve (stem) 54 via the plunger end 52c of the hydraulic mechanism. It is done. In this case, the cam 51b of the camshaft 51 usually has
A small inclination angle 0 of about 2 to 7' is provided, and it is in contact with the tappet crown surface 52a which has been finished with a spherical surface. Therefore, the contact point IA between the inclined cam 51b and the spherically finished tappet crown surface 52a is offset by the offset amount D with respect to the tappet center C, and as the camshaft 51 rotates, the tappet 52 rotates,
The tappet crown surface 52a is designed to wear uniformly. Conventionally, the tappet 52 having such a structure uses tappet-shaped tappet material obtained by cold forging and machining of the tappet material, and this tappet material is subjected to high-concentration carburizing or carbonitriding treatment and Manufactured by quenching and tempering, finishing the inner and outer surfaces of the tappet shaft 52b, and then polishing the tappet crown surface 52a to a spherical finish, and assembling it with the hydraulic mechanism and its plunger shaft 52c, etc. It was used as a hydraulic tappet. In addition, the tappet crown surface 52a is often polished to a flat surface instead of being polished to a spherical surface, and in this case, the material is generally made of a higher quality material in consideration of the disadvantage of wear caused by rotation. It is true. (Problem to be Solved by the Invention) However, in such conventional tappets for valve train mechanisms, spherical finish polishing is performed to make the tappet crown surface 52a spherical, and the tappet crown surface 52a is not made spherical. Even if the surface is polished, the surface finish is polished, so the distortion during heat treatment is added, and at least 30 JLm is removed by the polishing allowance. The tappet crown surface 52 has reduced wear resistance because the carbide layer is scraped off.
It had to be a. Therefore, when used under high surface pressure, there was a problem that scuffing wear and pitting wear were likely to occur. In addition, in terms of manufacturing, there was a problem in that spherical finish polishing and flat finish polishing required polishing of a hard layer of precipitated carbide, which resulted in an increase in cost. Furthermore, when polishing a flat surface, which is easier than polishing a spherical surface, there is a risk of scuffing wear due to the corner edges of the cam portion of the camshaft. (Purpose of the Invention) The present invention has been made in view of the above-mentioned conventional problems. As a material with better wear resistance, it reduces the occurrence of scuffing wear and pitting wear on the tappet crown surface, avoids the increase in cost due to spherical finish polishing and flat finish polishing, and also reduces the occurrence of scuffing wear and pitching wear on the tappet crown surface. By forming a convex portion that contacts the mating cam in an offset manner through heat treatment, the tappet rotates on its own axis, thereby eliminating the need for final polishing on the tappet crown surface and evening out wear on the tappet crown surface. The purpose is to do so.

[Structure of the invention]

(Means for Solving the Problems) A tappet structure according to the present invention has a wear-resistant tappet crown surface in which the hardened surface by heat treatment is left as it is without substantially polishing, and the tappet crown surface has the above-mentioned The tappet is shaped by heat treatment and has a convex portion that contacts the mating cam at an offset from the center of the tappet, thereby causing the tappet to rotate along with the rotation of the mating cam. The structure is used as a means to solve the conventional problems mentioned above. The tappet according to the present invention has the above-mentioned structure, and is made by cold forging #4 wire rod, machining it to obtain a rough tappet material, and then subjecting it to heat treatment such as surface hardening treatment and heat refining treatment. By doing so, at least the surface of the tappet crown surface is hardened and, at the same time, a convex portion is intentionally formed on the tappet crown surface. In this case, the influence on the formation of the convex portion is as shown in Table 1. Therefore, when obtaining the required convex shape, consider the shape, wall thickness, and heat treatment conditions (especially the cooling rate during quenching) of the tappet rough material. The tappet, in which the convex portion is intentionally formed on the tappet crown surface in this way, rotates on its own axis along with the rotation of the inclined cam due to its combination with the inclined cam. Since the surface pressure received between the inclined cam and the convex cam is averaged over the entire circumference of the convex part, polishing the convex part is no longer necessary. By forming it in an offset manner, it can rotate more easily than a general polished spherical surface (the radius of curvature of the sphere is after 2000 mm Q), and the distribution of lubricating oil is better. In addition, as a more preferable embodiment of the present tappet manufacturing method, the thickness of the tappet crown surface is 3.5 to 4.5 mm, and the heating rate during carburizing and quenching is 900 mm for 10 to 30 minutes.
It is possible to raise the temperature to ℃, perform the carburizing treatment for 1.5 to 3.0 hours, and perform oil quenching. (Operation of the invention) The tappet structure according to the present invention is as described above, and the tappet crown surface, which has been hardened by heat treatment, is used as is without polishing, so it has excellent wear resistance. In addition, the tappet crown surface is intentionally formed with a convex portion that contacts the mating cam at an offset from the center of the tappet, so that the tappet rotates on its axis due to the rotation of the mating cam, and the tappet crown surface contacts the mating cam. The smooth contact with the cam provides the same effect as a polished finish, and even if wear occurs, it becomes smooth, and the rotation of the tappet increases the ability to distribute the lubricating oil and improves the cam. The wear resistance is improved by increasing the contact area. (Example) Example 1 Fig. 1 shows an example of a tappet structure according to the present invention.This tappet 1 constitutes a mushroom-shaped hydraulic tappet, and the hardened surface is hardened by heat treatment. It has a wear-resistant tappet crown surface 1a that is left as is without polishing, and the tappet crown surface 1a is formed by the heat treatment and has a tappet center C with respect to the cam 2a of the camshaft 2 which is the mating material. A west-shaped portion 1b near the peripheral portion that causes the tappet 1 to rotate together with the rotation of the cam 2a by contacting with a more offset position.
It has a convex portion IC at the center, and a tappet shaft portion 1d is connected to the tappet crown surface 1a. The tappet 1 of this embodiment 1 is made of chromium molybdenum steel (JIS SCM420).
Tappet rough material is made of wire rod, and is made into a tappet shape by cold forging and machining.
Carburizing this tappet a material at 920'C→
Surface hardening heat treatment was performed by oil quenching at 820°C and then tempering at 160°C. Then, depending on a combination of the shape, wall thickness, heat treatment conditions, etc. of the tappet rough material, an annular convex portion 1b is formed in the peripheral portion (near the thick portion that is continuous with the tappet shaft portion 1d). A convex portion IC is also formed in the center portion. In this case, the positional error of the convex portions 1b and lc is 0. 2m
m, and its outer shape is a parabola. The height of the convex portion 1b near the periphery is a maximum of 6, wm, a minimum of 2 pm, and an average of 3.9 gm, and the height of the convex portion 1C in the center is a maximum of 10 gm.
gm, minimum 7 gm, average 7.7pm. Furthermore, the radius of curvature at the top of the convex portion 1b near the periphery is a minimum of 500 mm, and the radius of curvature at the top of the convex portion IC at the center is a minimum of 760 mm, which makes the surface much smaller than that of the conventional finish polished one. There is no pressure burden. Furthermore, the contact position A between the cam 2b of the camshaft 2 and the tappet crown surface 1a of the tappet 1 is at the convex portion 1b near the peripheral portion, and the offset }ffiD for causing the tappet 1 to rotate is as follows. The inclination angle θ of the cam 2b is 2
~7', D=9.8mm±0.2m
m, which is sufficient for this type of offset}M. Next, the tappet 1 obtained here was incorporated into the engine valve mechanism as a hydraulic tappet, and an engine wear durability test by motoring was conducted under the conditions shown in Table 2.
The results are shown in the table. As shown in Table 2 and Table 3, in the tappets of Comparative Example 1, which had a spherical finish polished, not all of the tappets rotated on their own axis, and the wear pattern was relatively good. In the case of polished tappets, not only did rotational failure occur, but there was also a large amount of wear. On the other hand, in the tappet of Example 1, all the tappets rotate,
The amount of wear was small and the wear pattern was normal. In addition, in the tappet of the example, the increase in surface pressure at the initial stage of use due to the formation of the convex portion is not so large, but rather increases the durability due to the increased circulation of lubricating oil due to high-speed rotation and the increased contact area with the cam. It was recognized that this was advantageous in improving abrasion resistance. It was also found to be superior to those polished to a flat finish, which places stress on corner edges. Embodiment 2 FIG. 2 shows another embodiment of the tappet structure according to the present invention, and this tappet 11 has a wear-resistant tappet crown surface 11a in which the hardened surface by heat treatment is fixed without polishing. In addition, the tappet crown surface 11a has a convex-shaped portion 1lb near the periphery that is shaped by the heat treatment and contacts the cam 2a of the camshaft 2, which is a mating member, with an offset from the tappet center C, The tappet shaft portion lid has a continuous structure on the tappet crown surface 11a. The tappet 11 of this embodiment 2 is JIS SCM
A tappet rough material made of 420 steel and having the same shape as in Example 1 was used, and the tappet rough material was plasma carburized at 930°C.
r r), quenched with oil at 820°C and 16
The tappet 11 of Example 2 was subjected to surface hardening treatment and heat treatment by tempering at 0''C.As a result, the tappet 11 of Example 2
The tappet 1 has almost the same shape except that there is almost no convex portion IC at the center, and convex portions 1lb are similarly formed near the periphery. In this case, the height of the convex portion 11b near the peripheral portion is 12 gm at the maximum, 5 tom at the minimum, and 9.5I1 on the average. m, and the offset }fitD with respect to the tappet center C at the contact position A with the cam 2a was 9.8 mm. Further, when the same abrasion durability test as in Example 1 was conducted, all of the tappets 11 were rotating on their own axis, and the tappet 11 was in a state of normal wear. Embodiment 3 FIG. 3 shows still another embodiment of the tappet structure according to the present invention, and this tappet 21 is of a solid mushroom type and is generally used in ○HV engines. This tappet 21 has a wear-resistant tappet crown surface 21a in which the hardened surface by heat treatment is left as is without polishing, and the tappet crown surface 21a is
1a has a convex shaped part 21b near the peripheral part which is formed by the heat treatment and comes into contact with the cam 2a of the camshaft 2 which is the mating material at an offset from the tappet center C, The tappet shaft 21d
has a continuous structure. The tappet 21 of this embodiment 3 is JIS SUJ 2
Using a solid tappet material made of steel, the tappet material is quenched at 830"C with oil and 160°C.
It has been heat treated to be tempered. As a result, in the tappet 21 of this third embodiment, a convex portion 21b is formed near the peripheral portion, and this convex portion 21b is formed in the vicinity of the peripheral portion.
The height of 1b is maximum 4pm, minimum 2 JLm, average 3
．． 2JLm, the tappet of Example 1.2}1.11
It was slightly smaller than the . Then, when the same abrasion durability test as in Example 1 was conducted,
It was observed that all of the tappets 21 were rotating, and the type of wear was normal wear. Embodiment 4 FIG. 4 shows still another embodiment of the tappet structure according to the present invention. This tappet 31 is of a cap type and has a shape that can also be used as a hydraulic tappet. This tappet 31 has a wear-resistant tappet crown surface 31a in which the hardened surface by heat treatment is left as it is without polishing, and the tappet crown surface 31a has a hardened surface without polishing.
a has a convex shaped part 31b near the peripheral part which has been shaped by the heat treatment and comes into contact with the cam 2a of the camshaft 2 which is the mating material at an offset from the tappet center C, and the tappet crown surface 31a has The tappet shaft portion 31d has a continuous structure. The tappet 31 of this embodiment 4 is. JIS SCM
Using tappet rough material made of 420 steel, this tappet rough material is carburized at 720°C in an atmosphere containing 30% NH3 scum in an endothermic gas, and then quenched by oil cooling at the same temperature of 720°C. and surface hardening treatment and heat treatment by tempering at 180°C. As a result, a relatively small convex portion 31b is formed near the periphery of the tappet 31. In this case, the height of the convex portion 31b near the peripheral portion is 3.1 pm at maximum! Since the offset amount D from the tappet center C at the contact position A with the cam 2a is large, the assembly offset amount E between the cam 2b and the tappet 31 is set to be large. Then, when the same abrasion durability test as in Example 1 was conducted,
It was observed that all of the tappets 31 had rotated, and the wear pattern was normal wear.

【Effect of the invention】

The tappet according to the present invention has a wear-resistant tappet crown surface in which the hardened surface by heat treatment is left as is without polishing, and the tappet crown surface is formed by the heat treatment and is offset from the center of the tappet with respect to the mating cam. The tappet crown has a structure with a convex part that comes in contact with the tappet crown, so by utilizing the hardened layer on the tappet crown surface that has been shaped by surface treatment without polishing it, the tappet crown can be made with superior wear resistance. In addition to reducing the occurrence of wear in the process and avoiding the increase in costs caused by spherical finish polishing and flat finish polishing,
A convex part is intentionally formed on the tappet crown surface by heat treatment so that it contacts the mating cam at an offset from the center of the tappet, so the rotation of the cam causes the tappet to rotate, which allows the lubricating oil to flow through the tappet. The wear resistance is significantly improved due to the increase in the contact area with the cam and the increase in the contact area with the cam, thereby eliminating the conventional spherical polishing of the tappet crown surface. In addition, compared to conventional tappets with polished spherical surfaces, the amount of offset from the center of the tappet at the contact position with the cam is greater, so the rotation speed of the tappet increases even more, and the rolling rate of the contact increases, causing this part to The tappet of this invention is better against adhesion and scuffing wear, which cause damage, and even when conventional tappets were used with a flat surface, the tappet of this invention can rotate on its own axis without finishing polishing. This has the excellent effect of improving wear resistance and reducing costs.

[Brief explanation of drawings]

FIG. 1, FIG. 2, FIG. 3, and FIG. 4 are partial explanatory diagrams of a valve mechanism using tappets having structures in Embodiment 1, Embodiment 2, Embodiment 3, and Embodiment 4 of the present invention, respectively; FIG. 5 is an explanatory diagram of a conventional valve operating mechanism using tappets. 1, 11, 21. 31... tappet, la, lla,
21a, 31a... Tappet crown surface, lb, llb, 2lb, 31b... Convex shaped portion.

Claims (1)

[Claims] (1) It has a wear-resistant tappet crown surface with a surface hardened by heat treatment without polishing, and the tappet crown surface is formed by the heat treatment and contacts the mating cam offset from the center of the tappet. A tappet structure characterized by having a convex portion.