KR20060049014A - Valve lifter and forming and processing method therefor - Google Patents

Abstract

A method of forming and processing a valve lifter is disclosed. The forming and processing method includes the steps of forming a hole in the valve lifter at a site where the cam is in sliding contact, and forming a diameter increase portion along an edge of the valve lifter, the edge defining a part of the hole, and also the cam Forming the diameter increasing portion, which is located on the sliding contact side, and performing a surface treatment on the entire surface of the valve lifter, which is a surface on the sliding contact side of the cam.

Valve lifter, internal combustion engine, intake valve, exhaust valve

Description

VALVE LIFTER AND FORMING AND PROCESSING {VALVE LIFTER AND FORMING AND PROCESSING METHOD THEREFOR}

1 is a partial cross-sectional view of the essential components of a first embodiment of a valve lifter according to the present invention;

FIG. 2 is a longitudinal sectional view of the valve lifter of FIG. 1; FIG.

3 is a plan view of the valve lifter of FIG.

4 is a partial cross-sectional view of the essential components of the valve lifter used in the durability test for comparison purposes.

Fig. 5 is a sectional view of the valve operating system of the internal combustion engine to which the valve lifter according to the first embodiment is applied.

6 is a partial cross-sectional view of the essential components of a second embodiment of a valve lifter according to the present invention;

Fig. 7A is a longitudinal sectional view of the valve lifter and cam with the valve lifter and cam in mutual contact;

FIG. 7B is a cross-sectional view taken along the line A-A of FIG. 7A;

8 is a longitudinal sectional view of a fourth embodiment of a valve lifter according to the present invention;

Fig. 9 is a partial enlarged view of a portion around the diameter increasing portion of the valve lifter according to the prior art, showing peeling of the diamond-like carbon layer at the diameter increasing portion due to the conventional forming process.

<Explanation of symbols for the main parts of the drawings>

1: cylinder head

4: camshaft

5, 6: drive cam

7, 8: valve lifter

14: crown part

14a: crown surface

15: skirt part

16: lubricant supply hole

17: surface treatment layer

The present invention relates to a valve lifter of an internal combustion engine and an improvement in a method of forming and processing the valve lifter, and more specifically, to a crown or core portion of a valve lifter in which the cam formed on the camshaft is in sliding contact ( It relates to an improvement in the surface treatment method for the upper surface of the shim).

In the direct drive valve lifter of an internal combustion engine, high frictional resistance is generated between the lower surface protrusion of the crown portion and the stem of the intake valve during engine driving. In view of this, a technique as disclosed in Japanese Patent Laid-Open No. 2001-342810 has been proposed, that is, a lubricant supply hole penetrates the crown portion of the valve lifter in order to reliably supply lubricant between the protrusion and the stem end. It is formed.

In addition, with respect to the core fitting into the recess formed in the upper surface of the crown portion of the valve lifter, some techniques have been proposed, ie an air hole for blowing air between the bottom of the recess and the bottom of the core through the core. It is formed. When removing the core from the recess to exchange the core, air leaks through the air hole.

Although a lubricant supply hole or air hole is formed on the outer circumferential side of the upper surface of the crown portion or the core portion, the cam formed on the cam shaft slides with the entire upper surface in the radial direction of the crown portion or the core portion to ensure a high lift amount of the intake valve. In contact, the cam is in sliding contact with an edge defining a lubricant supply or air hole. As a result, there is a fear that the bearing pressure applied to the edge forming the lubricant supply hole or the air hole becomes high when the cam is in sliding contact with the edge.

Therefore, a method for reducing the bearing pressure is carried out in such a manner as to chamfer the edge defining the upper end of the lubricating oil supply hole or the air hole to form a diameter increasing portion or a flared portion.

In addition, in view of the fact that the cam is excessively slid and rotated on the upper surface of the crown or core, the crown or core is formed so as to form a hard surface treatment layer to lower sliding frictional resistance and also ensure wear resistance. The upper surface is surface-treated.

However, in connection with the above-mentioned prior art which forms a high hardness surface treatment layer on the upper surface of the crown portion or the core portion, after the surface treatment is carried out, the diameter increasing portion opens the opening of the upper end of the lubricating oil supply hole or the air hole. Since formed along the defining edge, the surface treatment layer on the diameter increasing portion inevitably becomes thinner.

Therefore, as shown in Fig. 9, under the condition that the cam is in continuous sliding contact with the upper surface of the disc-shaped core portion 21 provided to fit into the recess formed in the upper surface of the crown portion, the surface treatment layer 23 There is a possibility of being partially peeled from the diameter increasing portion 22a of the lubricating oil supply hole 22.

As a result, abrasion originating from the peeling part 24 of the surface treatment layer 23 arises, and the durability of a valve lifter undesirably falls.

It is therefore an object of the present invention to provide a conventional valve lifter and an improved valve lifter and its processing method which can effectively overcome the drawbacks encountered in its formation and processing method.

One aspect of the present invention provides a method for forming a hole in a valve lifter at a site where a cam is in sliding contact, and (b) forming a diameter increase along an edge of the valve lifter, the edge of Forming the diameter increasing portion, which defines a part and is located on the side where the cam is in sliding contact, and (c) surface treatment of the entire surface of the valve lifter, which is the surface on the side where the cam is in sliding contact. A method of forming and processing a valve lifter comprising the steps of performing.

Another aspect of the invention resides in a valve lifter having a hole formed at the site where the cam is in sliding contact and comprising a crown having an edge of the valve lifter. The edge defines part of the hole. The diameter increasing portion is formed along the edge. The skirt portion is formed integrally with the outer peripheral edge of the crown portion. The surface treatment layer includes a surface treatment layer formed on an area extending from the diameter increasing portion to the inside of the hole on the entire surface in which the cam is in sliding contact.

Another aspect of the invention is a valve lifter comprising a crown portion with an oil hole and a circular recess formed in communication with the recess to penetrate the crown portion. The skirt portion is formed integrally with the outer peripheral edge of the crown portion. The shim is formed with a hole penetrating the core and is received inside the recess. The diameter increasing portion is formed along an edge defining a portion of the hole. The surface treatment layer is formed on an area extending from the diameter increasing portion to the inside of the hole on the entire surface to which the cam is in sliding contact.

The above and other objects and features of the present invention will be understood from the following description in connection with the accompanying drawings.

1 to 3 and 5, a first embodiment of a valve lifter according to the present invention is shown by reference numerals 7 and 8. The valve lifters 7, 8 form part of the valve actuation system of the internal combustion engine for automobiles.

The valve actuation system is shown in FIG. 5 and has an intake valve 2 and an exhaust valve 3 which open or close the open ends of the intake port 1a and the exhaust port 1b, the intake port and the exhaust The port communicates with the combustion chamber (not shown) and is formed in the cylinder head 1. The camshafts 4 and 4 provided on the intake side and the exhaust side are rotatably supported by bearings (not shown) with respect to the upper end of the cylinder head 1. The drive cams 5 and 6 are integrally formed on the outer circumferential surfaces of the cam shafts 4 and 4. The valve lifters 7 and 8, which are sliding members, convert the rotational motion of the drive cams 5 and 6 into reciprocating motions and transmit the reciprocating motions to the intake valves 2 and the exhaust valves 3. The valve lifters 7 and 8 are slidably held on the inner walls of the small bore 1c and 1d respectively formed inside the cylinder head 1.

The intake valve 2 and the exhaust valve 3 are biased in the direction of closing the open ends of the intake port 1a and the exhaust port 1b by valve springs 12 and 13, respectively, each valve valve being a valve. It is elastically disposed between each of the spring retainers 11 provided at the upper end of the stem and the bottom face of each of the small diameter bores 1c and 1d. The intake valve 2 and the exhaust valve 3 are slidably supported through the cylindrical valve guides 9 and 10 fixed to the cylinder head 1, respectively.

The rotational driving force of the internal combustion engine is transmitted from the crankshaft to the camshafts 4 and 4 on the intake and exhaust sides, though not shown in the figure, by means of a timing chain. That is, the drive cams 5 and 6 rotate together with the cam shafts 4 and 4 to open the open ends of the intake port 1a and the exhaust port 1b and the intake valve 2 and the exhaust valve ( 3) Push or operate

Each of the drive cams 5 and 6 is formed in a teardrop shape and made of a chilled casting or the like. Cam surfaces 5a and 6a respectively formed on the outer circumferential surfaces of the drive cams 5 and 6 slide on the crown surface or the upper surface 14a of the crown portion 14 of the valve lifters 7 and 8. In addition, the cam surfaces 5a, 6a are polished to high precision and then shot blasted to have a predetermined surface roughness to provide a smooth surface.

With respect to the valve lifters 7 and 8, only the intake side valve lifter 7 will be described for convenience. As shown in Figs. 2 and 3, the valve lifter 7 is made of an iron-based metal material as a single member, and has a crown portion 14 and a cylindrical skirt portion 15 as main components. Crown portion 14 is a circular top wall portion. The cylindrical skirt 15 is integrally formed with the outer peripheral edge of the crown 14.

Crown portion 14 is a top surface of crown portion 14 and also has a smooth spherical or round crown surface 14a. In other words, the crown surface 14a is part of the surface of a large sphere. The crown surface 14 has a protrusion 14b, which is in contact with the stem end of the intake valve 2 and is formed in a substantially cylindrical shape. The protrusion 14b is located at the bottom center of the crown portion 14. In order to inject lubricating oil sticking on the crown surface 14a into the valve lifter 7 through the cam surface 5a of the drive cam 5, the crown portion 14 is passed through the crown portion 14. Lubricating oil supply holes 16 are formed at predetermined positions in the circumferential direction of the valve lifter on the outer periphery side of the head). In addition, a diameter reducing portion or flared portion 16a (chamfered portion) is formed in the annular portion or edge (of the crown portion 14) that defines the upper open end of the lubricating oil supply hole 16.

In addition, a high hardness surface treatment layer 17 is formed on the entirety of the crown surface 14a using diamond-like carbon treatment. After the diamond-like carbon treatment, a lapping treatment is performed on the surface treatment layer 17.

Hereinafter, a method of forming and processing the valve lifter 7 will be described.

First, the base metal is formed into a basic shape of the valve lifter 7 by cold forging using iron-based metal as a base material, and the basic shape is a cylindrical shape with the bottom closed.

The upper and lower surfaces of the crown portion 14 and the inner and outer peripheral surfaces of the skirt portion 15 are subjected to surface processing. Moreover, in order to form the lubricating oil supply hole 16, the process for forming a hole in the predetermined position on the outer peripheral surface side of the crown surface 14a of the crown part 14 is performed. The lubricating oil supply hole 16 may be formed during the above-mentioned cold forging process.

Thereafter, the valve lifter 7 is subjected to heat treatment such as carburizing, carbonitriding, nitriding, and the like. Thereafter, the outer diameters of the protrusions 14b and the skirt 15 are matched to the outer diameter of the stem end and the inner diameter of the bore 1c so as to ensure precise sliding movement on the outer circumferential surfaces of the protrusions 14b and the skirt 15. Polishing is performed.

After that, ultra-fine finishing is performed on the whole so that the crown surface 14a has a surface roughness of about 0.1 μm (according to Japanese Industrial Standard JIS B0601). In addition, so-called R-machining (rounding processing) by lapping, barrel polishing, shot blasting, etc., so that the outer circumferential surface side of the crown surface 14a has a surface roughness of about 0.2 μm. ). Naturally, the surface treatment may be performed during the above-described polishing processing. At this time, the upper open end of the lubricating oil supply hole 16 in such a manner that the rounded surface (cross section or vertical plane including the axis of the lubricating oil supply hole 16) has a radius of curvature R in the range of about 0.05 to 0.2 mm. On the annular portion or the edge defining the diameter increasing portion or flare (16a) is formed. In addition, the surface of the diameter increasing portion 16a is polished to have a surface roughness of about 0.2 μm. The diameter increasing portion 16a may be formed during the polishing process.

After that, the valve lifter 7 is placed in an oven and washed inside. Then, diamond-like carbon treatment is performed on the entirety of the crown surface 14a to form a high hardness surface treatment layer or diamond-like carbon layer on the entirety of the crown surface 14a. This diamond-like carbon treatment is performed not only on the entire crown surface 14a but also on the inner side of the lubricating oil supply hole 16 through the surface of the diameter increasing portion 16a of the lubricating oil supply hole 16.

Thereafter, brush-lapping is performed on the surface of the surface treatment layer 17 using diamond abrasive particles and a brush to remove a predetermined amount of fine particles or molecules from the surface of the surface treatment layer 17. Thereby, a number of fine recesses are formed in the surface treatment layer 17 such that the total area of the fine recesses is about 5-30% of the total area of the crown surface 14a. Naturally, such surface processing can be replaced by barrel polishing, shot blasting, and the like.

In order to measure the durability of the annular portion or the edge defining the upper open end of the lubricant supply hole 16 in which the surface treatment layer 17 is formed, the lubricant supply hole 16 of the lubricant supply hole 16 is operated under the conditions in which the internal combustion engine operates at a high speed. Durability tests were conducted in such a way that the cam surface 5a of the cam 5 was slid for 100 hours on an annular portion or edge defining the upper open end. For a valve lifter 7 of the type whose surface has a rounded diameter increasing portion 16a as shown in FIG. 1 and the lubricant supply hole 16 has a diameter of the lubricant supply hole 16 as shown in FIG. A durability test was performed on the valve lifter 7 of the type having no increase 16a. With respect to the valve lifter of the type in which the lubricating oil supply hole 16 has the diameter increasing portion 16a, the radius of curvature R (in cross section) of the rounded surface of the diameter increasing portion 16a is changed.

As a result of the test, with respect to a valve lifter of the type in which the lubricant supply hole 16 does not have a diameter increasing portion 16a, for example, the surface of the crown surface 14a of the crown portion 14 due to an increase in bearing pressure. This was worn out.

On the other hand, for the valve lifter of the type in which the lubricating oil supply hole 16 has the diameter increasing portion 16a, there was little wear. Especially with regard to valve lifters of the type with a rounded surface in which the radius of curvature R ranges from 0.05 to 0.2 mm, there is no wear. In consideration of this, it is preferable that the rounded surface of the diameter increasing portion 16a has a radius of curvature R falling within the range of 0.05 to 0.2 mm. According to this, the surface treatment layer or the treatment film is difficult to peel off while the bearing pressure may be reduced.

In the first embodiment, the surface treatment layer 17 is subjected to diamond-like carbon treatment after a diameter increasing portion 16a having a rounded surface is formed in an annular portion or edge defining the upper open end of the lubricating oil supply hole 16. Since it is formed over the entire crown surface 14a, the surface treatment layer 17 formed on the diameter increasing portion 16a is prevented from decreasing in thickness. As a result, the surface treatment layer 17 on the diameter increasing portion 16a is prevented from being peeled off even if the sliding movement of the cam surface 5a is continued, so that the wear resistance of the diameter increasing portion 16a is improved.

In addition, since diamond-like carbon treatment is performed on the region extending from the entire crown surface 14 to the inside of the lubricating oil supply hole 16, even if a shearing force is applied from the cam 5 to the surface treatment layer 17, the surface treatment is performed. Peeling of the layer 17 is sufficiently suppressed. In addition, in the first embodiment, since the diameter increasing portion 16a is formed to have a rounded surface, that is, it is formed so as not to have a square portion, it is high when the cam surface 5a slides on the valve lifter 7. The generation of bearing pressure is suppressed.

Further, in the first embodiment, after the high hardness surface treatment layer 17 is formed on the crown surface 14a by diamond type carbon treatment, the total area is about 5 to 30 of the total area of the crown surface 14a. A fine recess is formed by the lapping process to be%. With the fine recess, the frictional resistance between the crown surface 14a and the cam surface 5a can be reduced. Thus, when the cam surface 5a slides on the valve lifter 7, a significant amount of lubricant is always present in the many fine recesses so that an oil film can be formed between the crown surface 14a and the cam surface 5a. Is retained. As a result, the wear resistance of the valve lifter 7 is improved, and the frictional resistance between the crown surface 14a of the valve lifter 7 and the cam surface 5a of the cam 5 can be further lowered.

Fig. 6 shows a second embodiment of the valve lifter according to the present invention, in which the diameter increasing portion 16a is tapered instead of the rounded surface at the annular portion or the edge defining the upper open end of the lubricating oil supply hole 16. Similar to the first embodiment except that it has a surface or a truncated conical surface.

That is, the tapered diameter increasing portion 16a of the second embodiment is formed with an inverted cone having a substantially flat surface having a straight cross section. After the tapered diameter increasing portion 16a is formed, diamond-like carbon treatment is performed on the crown surface 14a and the surface of the tapered diameter increasing portion 16a.

Therefore, according to the second embodiment, the same effects as in the first embodiment are obtained. In addition, since the diameter increasing portion 16a is formed in a tapered or truncated cone shape, the forming and machining is easier as compared with the first embodiment in which the diameter increasing portion 16a is rounded in cross section.

7A and 7B show a third embodiment of the valve lifter according to the present invention, except that the crown portion 14 of the valve lifter 7 is formed into a sphere having a large radius of curvature in cross section. Similar to the first embodiment. On the spherical crown surface 14a, a high hardness surface treatment layer 17 is formed by diamond carbon treatment.

Therefore, according to the third embodiment, since the cam surface 5a is in contact with the surface treatment layer 17 in the state of forming the contact point P, sliding between the cam surface 5a and the surface treatment layer 17 is caused. Resistance decreases. In addition, since the normal at the contact point P can be almost equal to the axis X by adjusting the inclination of the cam 5 or the axis inclination of the camshaft 4 as shown in Fig. 7B, the valve The sliding resistance between the lifter 7 and the inner wall of the small bore 1c can be reduced.

Figure 8 shows a fourth embodiment of the valve lifter according to the present invention, which is similar to the first embodiment except that the body of the valve lifter 7 is made of aluminum alloy for weight reduction, and the crown portion 14 A circular recess 19 is formed on an upper surface of the disk, and the disc-shaped core 20 is received inside the circular recess 19.

An oil groove 19a is formed in an annular shape at a predetermined position on the outer peripheral side of the circular recess 19. In addition, an oil hole 19b through which lubricating oil passes is formed at a predetermined position in the circumferential direction of the oil groove 19a, and the oil hole communicates with the oil groove 19a and the Penetrate the top wall. The core 20 is formed of an iron metal. The lubricating oil supply hole 16 is formed at a predetermined position of the core 20, which corresponds to the oil hole 19b in communication with the oil groove 19a for penetrating the core 20. In addition, a diameter increasing portion 16a having a rounded surface is formed at the annular portion or the edge defining the upper open end of the lubricating oil supply hole 16. Moreover, the surface treatment layer 17 is formed in the upper surface of the core part 20 by which the cam 5 slides by diamond-like carbon processing. The surface treatment layer 17 is formed by diamond carbon treatment after the lubricating oil supply hole 16 and the diameter increasing portion 16a are formed in a predetermined machining process. The surface treatment layer 17 which extends the inner branch of the lubricating oil supply hole 16 from the diameter increasing part 16a is formed.

Therefore, according to the fourth embodiment, since the surface treatment layer 17 is formed after the lubricating oil supply hole 16 and the diameter increasing portion 16a are formed, the same effect as in the first embodiment can be obtained.

The entire contents of Japanese Patent Application No. P2004-226230, filed August 3, 2004, are incorporated herein by reference.

While the invention has been described with reference to some embodiments and examples of the invention, the invention is not limited to the embodiments and examples described above. Modifications and variations of the embodiments and examples described above will occur to those skilled in the art in light of the above teachings. For example, the through lubricating oil supply hole 16 of the valve lifter may also be used as an air hole. The principles of the present invention may be applied to a valve lifter on the side of the exhaust valve. In addition, although the diamond-like carbon treatment has been described at least after the formation of the diameter increasing portion 16a, the forming and machining processes are not limited to the above.

The scope of the invention is defined with reference to the following claims.

According to the present invention, since the surface treatment layer is formed throughout the crown surface by diamond-like carbon treatment after the diameter increasing portion having a rounded surface is formed in the annular portion or the edge defining the upper open end of the lubricating oil supply hole, The surface treatment layer formed on the increase portion is prevented from decreasing in thickness. As a result, the surface treatment layer on the diameter increasing portion is prevented from peeling off even if the sliding movement of the cam surface continues, thus improving the wear resistance of the diameter increasing portion.

In addition, since diamond-like carbon treatment is performed on the entire area of the crown surface extending to the inner side of the lubricating oil supply hole, peeling of the surface treatment layer is sufficiently suppressed even when a shearing force is applied from the cam to the surface treatment layer. In addition, in the first embodiment, since the diameter increasing portion is formed to have a rounded surface, that is, is formed so as not to have a square portion, generation of high bearing pressure is suppressed when the cam surface slides on the valve lifter.

Further, after the high hardness surface treatment layer is formed on the crown surface by diamond-like carbon treatment, fine recesses are formed by lapping so that the total area is about 5 to 30% of the total area of the crown surface. With the fine recess, the frictional resistance between the crown surface and the cam surface can be reduced. Thus, when the cam surface slides on the valve lifter, a significant amount of lubricant is always retained in the many fine recesses so that an oil film can form between the crown surface and the cam surface. As a result, the wear resistance of the valve lifter is improved, and the frictional resistance between the crown surface of the valve lifter and the cam surface of the cam can be further lowered.

Claims (20)

Method of forming and processing valve lifter, Forming a hole in the valve lifter at the site where the cam is in sliding contact; Forming a diameter increasing portion along the edge of the valve lifter, the edge defining a portion of the hole and located on the side where the cam is in sliding contact; And surface-treating the entire surface of the valve lifter, wherein the cam is a surface on the side in sliding contact. The method of claim 1, wherein the surface treatment is performed in an area where the cam extends from the entire surface in sliding contact with the inside of the hole through the diameter increasing portion formed along the annular edge of the valve lifter. The method of claim 1, wherein the diameter increasing portion is formed in a rounded cross-sectional shape of the valve lifter. The method for forming and processing a valve lifter according to claim 3, wherein the rounded surface of the diameter increasing portion has a radius of curvature with a cross-sectional shape in a range of 0.05 to 0.2 mm. The method of claim 1, wherein the diameter increasing portion is tapered. The method of claim 1, wherein the surface treatment is diamond carbon treatment. The method for forming and processing a valve lifter according to claim 6, wherein the valve lifter is subjected to the lapping treatment after the diamond-like carbon treatment. The method of claim 1, wherein the crown surface of the valve lifter is formed into spheres. The method of claim 1, wherein the hole forming step is performed after surface treatment of the inner and outer circumferential surfaces of the crown and skirt portions of the valve lifter. The method for forming and processing a valve lifter according to claim 1, wherein the hole is a lubricant supply hole, which is formed during cold forging of the valve lifter. The method of claim 1, wherein the diameter increasing portion is formed after heat treatment and surface polishing performed after the hole is formed. The method of claim 1, wherein the surface treatment is performed after valve lifter cleaning performed after the diameter increase is formed. A crown portion formed at a portion where the cam is in sliding contact, having an edge of a valve lifter defining a portion of the aperture, and having a diameter increasing portion formed along the edge; A skirt portion integrally formed with an outer peripheral edge of the crown portion, And a surface treatment layer formed on an area extending from the diameter increasing portion to the inside of the hole on the entire surface in which the cam is in sliding contact. The valve lifter according to claim 13, wherein the crown portion and the skirt portion are formed of ferrous metal. 15. The valve lifter of claim 14, wherein a fine recess is formed in the surface treatment layer. A crown portion having a circular recess and an oil hole, wherein the oil hole is formed to communicate with the recess so as to pass through the crown portion; A skirt portion integrally formed with an outer peripheral edge of the crown portion, A shim portion housed in the recess, the shim having a hole formed therein, the diameter increasing portion being formed along an edge defining a portion of the hole; And a surface treatment layer formed on an area extending from the diameter increasing portion to the inner side of the hole on the entire surface in which the cam is in sliding contact. 17. The valve lifter of claim 16, wherein a fine recess is formed in the surface treatment layer. The valve lifter of claim 16, wherein the crown portion and the skirt portion are formed of an aluminum alloy, and the core portion is formed of an iron-based metal. 17. The method of claim 16, wherein the annular oil groove is formed to communicate with the inside of the recess, the oil hole is formed to communicate with the first position of the oil groove to penetrate the crown portion, the hole in the core portion corresponding to the oil groove A valve lifter formed at the second position. 17. The valve lifter of claim 16, wherein the aperture is an aperture through which air flows.

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