WO2015107837A1

WO2015107837A1 - Valve lifter

Info

Publication number: WO2015107837A1
Application number: PCT/JP2014/083831
Authority: WO
Inventors: 明男吉元; 正之佐藤
Original assignee: 株式会社リケン
Priority date: 2014-01-15
Filing date: 2014-12-22
Publication date: 2015-07-23
Also published as: JPWO2015107837A1; JP6419727B2

Abstract

[Problem] To provide a valve lifter that can reduce the friction between the edge on the top and bottom ends of a valve lifter and a cylinder head bore. [Solution] This valve lifter (100) has a crown section (110) on which a cam slides, and a skirt section (120) that extends down from the crown section. A first texture groove (132) for retaining lubricating oil is formed in the circumferential direction in a top end region (130) on the skirt section (120), and a second texture groove (152) for retaining the lubricating oil is formed in the circumferential direction in the bottom end region (150) separated by an intermediate region (140) adjacent to the top end region (130).

Description

Valve lifter

The present invention relates to a valve lifter used in a direct-acting valve operating mechanism, and more particularly to a surface structure of a skirt portion of the valve lifter.

∙ Reduction of friction loss in internal combustion engines is an important issue in order to improve fuel efficiency in response to energy and environmental problems. Examples of main sliding parts of the internal combustion engine include a valve system, a piston system, and a crankshaft system. Friction loss accounts for 75 to 90% of these main sliding parts, and the ratio of piston rings, pistons and connecting rods is high in the middle and high speed rotation range, and the ratio of friction in the valve system is high in the low speed rotation range. There are various technologies for reducing these friction losses, basically reducing the surface roughness of the sliding surface to lower the frictional resistance, and providing a surface structure with improved oil retention from the viewpoint of lubrication. Improvements have been made.

One of the typical valve systems of internal combustion engines is the valve lifter. The valve lifter is a member that is disposed between the cam and the valve, and converts the rotational movement of the cam into the opening / closing movement of the valve (

Patent Documents

1, 2, etc.). The valve lifter has a valve lifter body including a crown part and a skirt part, and the valve lifter body slides in a bore formed in the cylinder head in accordance with the rotational movement of the cam. Therefore, it is desirable to reduce the frictional resistance between the outer peripheral surface of the skirt portion of the valve lifter body and the bore inner peripheral surface of the cylinder head. In the valve lifter of Patent Document 3, the concave portion is formed by shot blasting or sand blasting in the entire outer peripheral surface of the skirt portion of the valve lifter or in the entire inner peripheral surface of the bore into which the valve lifter is inserted (valve lifter accommodating portion). Lubricating oil is held between the skirt and the bore inner peripheral surface to reduce friction. In the valve lifter of Patent Document 4, the sliding resistance in the vertical direction is reduced by alternately forming textured grooves and non-textured grooves in the vertical direction of the outer peripheral surface of the skirt portion of the valve lifter.

JP 2008-240601 A JP 2008-215172 A JP 2008-75591A JP 2011-256715 A

1A is a schematic sectional view of a valve lifter valve operating system, FIG. 1B is a sectional view when the valve lifter is raised and the valve is closed, and FIG. 1C is a valve lifter lowered and the valve is It is sectional drawing when it opens. A valve lifter 14 is disposed in a bore 12 formed in the cylinder head 10 so as to be movable up and down with an appropriate clearance. A cam 16 that slides on the crown of the valve lifter 14 is attached to a camshaft 18, and the camshaft 18 is rotated by a drive system 20 such as a chain. The lubricating oil supplied to the space 18A in the camshaft 18 is supplied to the cam journal portion 24 and the cam journal cap 26 through the holes 22, and the lubricating oil that has further lubricated the cam journal portion 24 is indirectly outer periphery thereof. Part is used for lubrication of the valve lifter 14.

2A is a schematic cross-sectional view when the valve lifter is lowered, and FIG. 2B is a schematic cross-sectional view when the valve lifter is raised. A curved upper surface 32 is formed on the outer peripheral portion (opening end) of the bore 12 of the cylinder head 10 so as to collect the lubricating oil 30 dispersed from the camshaft or the like. The upper surface 32 needs to be formed with a relief so as not to come into contact with the tip of the cam. As a result, a sharp edge 34 is formed between the upper surface 32 and the inner wall of the bore 12. The lubricating oil 30 stored on the upper surface 32 is also used for sliding between the outer peripheral surface of the skirt portion 14 </ b> A of the valve lifter 14 and the inner peripheral surface of the bore 12.

The cam 16 slides in a fixed direction on the valve lifter crown surface, but the center of the cam width is slightly offset from the center of the valve lifter 14, so when the cam 16 slides on the crown surface, A rotational moment is applied, and the valve lifter 14 is rotated in the bore 12 together with the lift operation. Since a clearance is set between the valve lifter 14 and the bore 12, the valve lifter 14 is slightly inclined in the bore 12 when moving up and down as shown in FIGS. 2 (A) and 2 (B). Will repeat the reciprocating motion.

Fig. 3 shows an example of calculation of the tilt angle (cocking amount) in the bore of the valve lifter. As shown in FIG. 3, the operation Y with a rectangular inclination is performed immediately after the start of the lift operation and immediately before the maximum lift, and immediately after the maximum lift has elapsed and immediately before the end of the lift. When the cam 16 rotates clockwise, a right-turning moment is generated in the valve lifter 14 immediately after the lift starts, and the valve lifter 14 tilts to the right as shown in FIG. 2A, and the right upper end S1 and the left lower end of the skirt portion 14A. S2 contacts the inner wall of the bore and receives moment reaction forces F1 and F2. Since the direction of this moment does not change until immediately before the maximum lift, the valve lifter 14 performs the lowering operation while always tilting to the right. At this time, in particular, the supply of the lubricating oil to the lower end S2 is reduced, and the bore inner wall is scraped off by the lower end S2.

Also, in the process of turning the valve lifter 14 from immediately after the maximum lift to just before opening and closing, the valve lifter is always tilted to the left as shown in FIG. The upper and lower ends S1 and S2 on the side receive moment reaction forces F1 and F2. Since the direction of this moment does not change until just before the end of the lift, the valve lifter 14 always moves upward while tilting to the left. At this time, in particular, the supply of lubricating oil to the upper end S1 is reduced, and the bore inner wall is scraped off. Further, since the valve lifter crown surface rises beyond the edge 34 to the point of lift 0, if the upper end S1 slides with the edge 34 and the lubrication state is insufficient, the frictional resistance there increases, and the edge 34 wears out.

Thus, the posture of the valve lifter is tilted while moving up and down, and therefore, the main contact portion between the valve lifter 14 and the bore is limited to the upper and lower end portions S1 and S2 of the skirt portion 14A. Due to the structure of the two, since they are in contact and sliding at the edges of each other, the oil film easily breaks at this portion, and there is a concern of increased friction loss and local wear. In particular, when the edge 34 is worn, the diameter of the upper end portion of the bore increases, and abnormal noise is generated when the valve lifter is cocked (operation Y in FIG. 3). Further, when the diameter of the upper end portion of the bore is increased, the inclination angle of the valve lifter is also increased, the optimum clearance between the valve lifter and the bore is gradually lost, and the sliding performance is also lowered due to local contact.

An object of the present invention is to provide a valve lifter that can solve such problems of the prior art and reduce the frictional resistance between the upper and lower ends of the valve lifter and the bore of the cylinder head.

The valve lifter according to the present invention is disposed between the valve and the cam and converts the rotational operation of the cam into the lift operation of the valve. The valve lifter includes a crown surface on which the cam slides, and the crown surface. A first texture groove for holding lubricating oil in an upper end region defined by a first distance in the axial direction from the crown surface of the skirt portion. A second texture groove for holding lubricating oil is formed in the circumferential direction in the lower end region defined by a second distance in the axial direction across an intermediate region adjacent to the upper end region. Formed.

Preferably, the first and second texture grooves are formed by laser processing. Preferably, the axial distance of the upper end region is larger than the axial distance of the lower end region. Preferably, an amorphous hard carbon coating is formed on the outer peripheral surface of the skirt portion, and the first and second texture grooves are formed in the amorphous hard carbon coating. Preferably, after the surface roughness of the outer peripheral surface of the skirt portion is polished to Ra 0.3 μm or less, the first and second texture grooves are formed by laser processing. Preferably, the upper end region includes a chamfered edge region, and a first texture groove is formed in the edge region. Preferably, the lower end region includes a chamfered edge region, and a second texture groove is formed in the edge region. Preferably, the first and second texture grooves are herringbone patterns. Preferably, a plurality of grooves extending in a circumferential direction orthogonal to the axial direction are formed in the intermediate region. An internal combustion engine according to the present invention includes a valve lifter having the above characteristics and a cylinder head in which a bore for slidably inserting the valve lifter is formed.

According to the present invention, the first and second texture grooves are formed in the upper end region and the lower end region of the valve lifter, respectively, so that the edges of the upper end portion and the lower end portion of the valve lifter slide with the bore inner peripheral surface of the cylinder head. Friction when moving can be reduced. Thereby, expansion of the clearance between the valve lifter and the bore due to wear of the bore inner peripheral surface can be suppressed, and generation of abnormal noise during operation of the valve lifter can be suppressed.

1A is a cross-sectional view schematically showing a valve lifter valve operating system, FIG. 1B is a cross-sectional view when the valve lifter is raised and the valve is closed, and FIG. 1C is a view showing the valve lifter being lowered. It is sectional drawing when a valve opens. 2A is a schematic cross-sectional view for explaining the operation when the valve lifter is lowered, and FIG. 2B is a schematic cross-sectional view for explaining the operation when the valve lifter is raised. It is a graph which shows the example of calculation of the rotation angle of a cam, and the inclination angle of a valve lifter. 4A is a front view of the valve lifter according to the embodiment of the present invention, and FIG. 4B is a longitudinal sectional view of FIG. 4A. FIG. 5A is a cross-sectional view illustrating another configuration example of the skirt portion according to the embodiment of the present invention, and FIG. 5A illustrates an example in which texture grooves are formed on the chamfers of the upper end portion and the lower end portion of the skirt portion. FIG. 5B shows an example in which an amorphous hard carbon film is formed on the skirt portion. It is a figure which shows an example of the texture groove | channel formed in the skirt part of the valve lifter of a present Example. It is a figure which shows an example of the texture groove | channel formed in the skirt part of the valve lifter of a present Example. FIG. 8 is a diagram showing the configuration of the skirt portion of the valve lifter according to the second embodiment of the present invention.

The valve lifter according to the present invention will be described below with reference to the drawings. It should be noted that the scale of the drawings is emphasized for easy understanding of the features of the invention, and is not necessarily the same as the scale of actual devices and parts.

The valve lifter according to the present embodiment is disposed between the valve stem and the cam in the direct stroke type valve operating mechanism of the internal combustion engine and has a function of transmitting the lift operation of the cam to the valve. Further, the valve lifter may be provided with a pausing mechanism for pausing or operating the lift operation of the valve stem by controlling the hydraulic ON / OFF. For example, when the internal combustion engine is operated at a low speed, the cam lift operation is stopped so as not to be transmitted to the valve, and when the internal combustion engine is operated at a medium or high speed, the cam lift operation is transmitted to the valve.

4A is a front view of the valve lifter according to the present embodiment, and FIG. 4B is a longitudinal sectional view of the valve lifter of FIG. 4A. The valve lifter 100 according to the present embodiment has a generally inverted cup-shaped valve lifter body, and the valve lifter body has a circular crown portion 110 and a cylindrical skirt portion 120 extending in the vertical direction from the crown portion 110. A boss 122 is formed on the back surface of the valve lifter crown 110 to be in contact with a valve stem or the like. Although not shown in detail here, the valve pausing mechanism can be arranged in the space inside the skirt portion 120.

In the valve lifter 100 of the present embodiment, the first texture groove 132 is formed in the upper end region 130 of the outer peripheral surface of the skirt portion 120, and the second lower region 150 is separated by the intermediate region 140 adjacent to the upper end region 130. The texture groove 152 is formed. That is, the first texture groove 132 is formed in the upper end region 130 defined by the distance L1 in the axial direction from the upper end surface or the crown surface of the skirt portion 120 as a reference. Further, the second texture groove 152 is formed in the lower end region 150 defined by the lower end surface from the distance L3, with the intermediate region 140 defined by the distances L1 and L2 being separated.

The texture groove is a groove with regular irregularities and fine irregularities. Due to the irregular periodic structure, the texture groove has a function of effectively retaining the lubricating oil in the groove and improving the oil retaining property of the lubricating oil. In a preferred embodiment, the axial distance L1 of the upper end region 130 is set larger than the axial distance (L3-L2) of the lower end region 150 (L1> (L3-L2)). The reason for this is that, as shown in FIG. 2A, when the valve lifter is in the lift 0 (when it is in the uppermost position), the edge of the upper end region 130 is located above the edge 34, and the edge of the upper end region 130 Since the sliding distance by any one of the edges 34 is effectively increased, the distance L1 is increased accordingly. On the other hand, in the lower end region 150, it is sliding between the edge of the lower end region 150 and the bore inner peripheral surface, and it is sufficient that the lubricating oil can be supplied to at least the edge of the lower end region. (L3-L2) may be small.

In a preferred embodiment, the first and

second texture grooves

132 and 152 are formed by laser processing after the surface roughness of the outer peripheral surface of the skirt portion 120 is polished to Ra 0.3 μm or less. Laser processing makes it possible to form texture grooves with fine and complex patterns on the outer peripheral surface of the skirt portion by optically scanning with laser light. The depth of the groove can be arbitrarily adjusted by the output of the laser beam. The texture grooves have a depth of about 300 nm, for example, and are formed at a pitch of 0.1 to 0.2 mm, for example. Further, the first and

second texture grooves

132 and 152 may have the same configuration or different configurations. The structure of the texture groove is specified from, for example, a pattern, depth, pitch, size, area ratio, cross-sectional shape, and the like.

As described in FIGS. 2A and 2B, the valve lifter moves up and down in an inclined posture due to the action of the rotational moment. At this time, the edges of the upper end S1 and the lower end S2 of the valve lifter are in contact with the bore inner peripheral surface, and the intermediate region between the upper end S1 and the lower end S2 is not substantially in contact with the bore inner peripheral surface. For this reason, a large surface pressure is generated at the edges of the upper end S1 and the lower end S2 of the valve lifter, the oil retaining properties of the upper end S1 and the lower end S2 are weakened, the frictional resistance is increased, and the wear proceeds.

In the present embodiment, in order to solve such a problem, the first texture groove 132 is formed in the upper end region 130 of the skirt portion 120 and the second texture groove 152 is formed in the lower end region 150. By forming the first texture groove 132, the lubricating oil supplied from the gap between the crown 110 and the bore is held by the first texture groove 132, and between the upper end region 130 and the bore inner peripheral surface. Friction is reduced. Further, by forming the second texture groove 152, the oil retaining property of the lower end region 150 of the skirt portion 120 is improved, and the friction between the lower end region 150 and the bore inner peripheral surface is reduced. Since the oil retaining properties of the upper end region 130 and the lower end region 150 are improved, wear on the bore inner peripheral surface due to the edges of the upper end region 130 and the lower end region 150 is suppressed. In particular, the wear of the edge 34 connecting the upper surface 32 of the cylinder head and the bore shown in FIG. 2A is suppressed, and the spread of the diameter of the upper end of the bore is suppressed. As a result, an increase in the clearance between the valve lifter and the bore is suppressed, and the generation of noise during the operation of the valve lifter is also suppressed.

Also, the texture grooves formed by laser processing have different performance from the grooves formed by shot blasting, sand blasting, or the like. Shot blasting and sand blasting form random grooves, and complex patterns and patterns with periodicity and regularity cannot be formed unlike laser processing. Further, in the case of laser processing, as shown in FIG. 4B, the area ratio of the groove irregularities can be accurately determined. The convex surface P is a region that slides with the inner peripheral surface of the bore, and since the surface pressure is determined by the area of the convex surface P, the area ratio of the texture groove is a very important factor.

Furthermore, in this embodiment, the intermediate region 140 is not substantially in contact with the inner peripheral surface of the bore during the vertical movement of the valve lifter, so that it is not necessary to form a texture groove here. In other words, by forming the texture groove only in a necessary region of the skirt portion 120 by laser processing, the cycle time of laser processing can be increased, productivity can be improved, and cost can be reduced.

Next, another preferred embodiment of the valve lifter of this embodiment will be described. FIG. 5A shows an example in which R chamfering is formed at each edge of the upper end region 130 and the lower end region 150 of the skirt portion. As described above, during the vertical movement of the valve lifter, the valve lifter is inclined, and the edge of the upper end region 130 and the edge of the lower end region 150 abut against the bore inner peripheral surface. For this reason, it is desirable to perform R chamfering on the edge E1 of the upper end region 130 and the edge E2 of the lower end region 150 to reduce the surface pressure of the edges E1 and E2 and further suppress the frictional resistance. The R chamfering can be performed by, for example, shot blasting or sand blasting in addition to lace processing. In a more preferred embodiment, the

texture grooves

132 and 152 are formed on the edges C1 and E2 which are chamfered. Thereby, the lubrication by the edges E1 and E2 is further improved, and the frictional resistance and wear can be further reduced. Although an example of R chamfering is shown here, C chamfering may be formed at the edges E1 and E2 instead of R chamfering. Or the combination of R chamfering and C chamfering may be sufficient. By forming the C chamfer, it is possible to expect the same effect as that of the R chamfer.

FIG. 5B shows a configuration example of the skirt portion of a further preferable aspect of the present embodiment. An amorphous hard carbon film (hereinafter referred to as a DLC (Diamond-like carbon film)) 160 is formed on the surface of the skirt portion 120. The DLC film 160 may be formed directly on the substrate surface, but may be formed through an intermediate layer of a metal such as Cr or a metal nitride thereof in order to improve adhesion. The base material on which the DLC film 160 is formed is subjected to hardening heat treatment such as carburizing treatment or quenching treatment on steel materials such as SCM415 material according to JIS standard, iron alloys, or the steel materials or iron alloys, and the surface hardness is HRC53 or more. It is preferable to use what was done. The DLC film 160 can be formed by a PVD method, a CVD method, a PACVD method, or the like. For example, it is preferable in terms of hardness and wear resistance that the hydrogen content formed by PVD method, particularly arc ion plating method is 0.5 atomic% or less. The film thickness of the DLC film 160 is, for example, 0.3 to 1.5 μm, preferably 1.0 μm or less in the PVD method. If it is CVD method, it can have a film thickness of about 20 micrometers.

The first and

second texture grooves

132 and 152 are formed on the DLC film 160. Thereby, since the convex surface P (refer FIG. 4 (B)) of the 1st and

2nd texture grooves

132 and 152 becomes a DLC film, the further sliding performance is improved combined with the oil retention property improvement of lubricating oil.

Next, a preferred pattern example of the texture groove of this embodiment will be described. 6A to 6D show a part of the first and

second texture grooves

132 and 152 in the upper end region 130 and the lower end region 150. FIG. The

texture grooves

132 and 152 in FIG. 6A are formed by forming rectangular grooves in the horizontal direction perpendicular to the sliding direction of the valve lifter. By forming the groove in a direction perpendicular to the sliding direction, the lubricating oil is more easily retained.

Textures

132 and 152 in FIG. 6 (B) are obtained by forming a mountain-shaped rectangular herringbone groove. Each of the grooves is substantially V-shaped, and the V-shape is directed toward the crown surface, and a plurality of sets are arranged in the circumferential direction and in the radial direction. The herringbone has a groove that intersects the sliding direction of the valve lifter at a certain angle, and this is continuous in the circumferential direction, so that the lubricating oil is easily held in the groove. Further, the lubricating oil is easily supplied to the lower end region of the skirt portion by the V-shaped direction. FIG. 6C is a modification of FIG. 6B, and is a herringbone groove in which V-shaped grooves are continuous in the circumferential direction. Oil retention in the circumferential direction is further improved by the continuous grooves in the circumferential direction. The

texture grooves

132 and 152 in FIG. 6D are formed by continuously forming diamond-shaped cross hatch grooves in the circumferential direction. Lubricating oil easily flows in the circumferential direction and the axial direction.

FIG. 7 (E) shows an example in which 45 ° and 135 ° oblique grooves are alternately set to form a continuous V-shaped groove in the radial direction. The groove is configured to be continuously connected in the axial direction of the skirt portion. FIG. 7F is a diagram in which the continuity in the radial direction of each hatched groove in FIG. FIG. 7 (G) shows a continuous herring bone formed vertically in the circumferential direction of FIG. 6 (C) and the pitch changed by the upper and lower grooves. FIG. 7H shows a herringbone formed in the chamfered portion of the upper end region and the lower end region.

Preferably, the pattern, depth, pitch, size, area ratio, cross-sectional shape, and the like of the first and

second texture grooves

132 and 152 are optimized according to the compatibility with the material on the cylinder head side.

Next, a second embodiment of the present invention will be described. In the second embodiment, texture grooves are formed in the intermediate region 140. The intermediate region 140 is substantially non-contact with the inner peripheral surface of the bore during the vertical movement of the valve lifter, but forms a texture groove in the intermediate region 140. Preferably, a pattern is formed so that the lubricating oil is easily retained. An example of the texture groove 142 formed in the intermediate region 140 is shown in the specification 8 of FIG. The texture groove 142 shown in the figure is formed by forming a plurality of continuous grooves in the circumferential direction in the pattern of the

texture grooves

132 and 152 shown in FIG. As a result, the oil retaining property is improved in the intermediate region 140, and as a result, the retained lubricating oil flows to the upper end region 130 and the lower end region 150. The texture groove formed in the intermediate region 140 may be a combination with FIGS. 6B to 7H.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to such embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. Is possible.

100: valve lifter 110: crown 120: skirt 122: boss 130: upper end region 132: first texture groove 140: intermediate region 142: texture groove 150: lower end region 152: second texture groove

Claims

A valve lifter that is disposed between the valve and the cam and converts the rotational operation of the cam into the lift operation of the valve,
The valve lifter has a crown surface on which the cam slides and a skirt portion extending downward from the crown surface,
A first texture groove for holding lubricating oil is formed in a circumferential direction in an upper end region defined by a first distance in the axial direction from the crown surface of the skirt portion, and is adjacent to the upper end region. A valve lifter in which a second texture groove for retaining lubricating oil is formed in the circumferential direction in a lower end region defined by a second distance in the axial direction across the intermediate region.
The valve lifter according to claim 1, wherein the first and second texture grooves are formed by laser processing.
The valve lifter according to claim 1 or 2, wherein an axial distance of the upper end region is larger than an axial distance of the lower end region.
The amorphous hard carbon film is formed on the outer peripheral surface of the skirt portion, and the first and second texture grooves are formed in the amorphous hard carbon film. The valve lifter described.
5. The valve lifter according to claim 1, wherein the first and second texture grooves are formed by laser processing after the surface roughness of the outer peripheral surface of the skirt portion is polished to Ra 0.3 μm or less.
6. The valve lifter according to claim 1, wherein the upper end region includes a chamfered edge region, and a first texture groove is formed in the edge region.
The valve lower lifter according to any one of claims 1 to 6, wherein the lower end region includes a chamfered edge region, and a second texture groove is formed in the edge region.
The valve lifter according to any one of claims 1 to 7, wherein the first and second texture grooves have a herringbone pattern.
The valve lifter according to any one of claims 1 to 8, wherein a plurality of grooves extending in a circumferential direction orthogonal to the axial direction are formed in the intermediate region.
An internal combustion engine having the valve lifter according to any one of claims 1 to 9, and a cylinder head formed with a bore for slidably inserting the valve lifter.