JP2011256716A - Valve lifter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem with a conventional technique for forming fine grooves in a radial shape from the center of the top to reduce the friction between a valve lifter and the cam, wherein the friction can not be effectively reduced because the grooves and parallel to the sliding direction of the cam in the peripheral fringe of the top are increased in the fine grooves formed in the radial shape.SOLUTION: The friction can be effectively reduced in the center and also the peripheral fringe by forming the grooves having parts linearly extended from the center to the peripheral fringe and parts curbed or bent and going parallel to the peripheral fringe or going to the peripheral fringe along the peripheral fringe in the top of the valve lifter.

Description

  The present invention relates to a valve lifter that is a component of an engine valve system.

  In order to increase the efficiency of an internal combustion engine (hereinafter also referred to as “engine”) and improve fuel efficiency, it is necessary to reduce a loss caused by a member moving inside the engine, so-called mechanical loss. In particular, various improvements have been made regarding the valve train. For example, a valve that sends intake air into the combustion chamber and exhausts the gas after combustion has evolved from an OHV system having a long push rod to an OHC system in which a camshaft is arranged at the upper part of the combustion chamber. In the OHC system, the camshaft is driven by a rotational motion by a chain from the crankshaft, and therefore it is easier to reduce the loss than when the push rod having mass is linearly moved.

  Even in the OHC system, a system in which the cam directly drives the valve (direct system) can reduce the weight of the cam and valve, and can easily realize high engine speed and low loss. On the other hand, sliding friction (friction) between the cam and the valve lifter that transmits the power from the cam to the valve causes mechanical loss. Conventionally, the friction has been reduced by finishing the top surface of the valve lifter into a mirror surface.

  By the way, in recent years, tribology that deals with friction, wear, and lubrication collectively has been actively researched and applied to practical aspects in many cases. Application to sliding parts in engines can also be seen. Patent Document 1 discloses a technique for reducing friction on a sliding surface between a valve lifter (valve lifter) and a cam.

  Here, a radial streak is formed by cutting on the cam sliding portion of the valve lifter. The reason for the reduction of wear due to the streak is explained as follows. First, the friction between parts made of metal such as alloy cast iron is proportional to the minimum oil film thickness formed between them, and the minimum oil film thickness is the sliding direction of the minute recesses formed on the sliding surface. Depends on the ratio of length to width r. When r is smaller, the minimum oil film thickness is larger, which is advantageous for lubrication between parts. That is, by forming a narrow groove that intersects at right angles to the sliding direction of the cam, the minimum oil film thickness is increased and friction is reduced.

  Therefore, if a streak is formed radially from the center of the cam lift of the valve lifter, even if the valve lifter rotates around the valve shaft, the cam will always be in the center where there is a lot of opportunity to slide with the cam. There are numerous striations in the direction transverse to the sliding direction, which can reduce friction.

Japanese Patent Laid-Open No. 06-280509

  However, in the technique introduced in Patent Document 1, a large number of striations can exist in the direction crossing the sliding direction of the cam at the central portion of the valve lifter, but the peripheral portion of the valve lifter is parallel to the sliding direction of the cam. There was a problem that only the streak was caused and the effect of reducing friction was reduced.

  The present invention has been conceived in view of the above problems, and an object of the present invention is to provide a valve lifter that can reduce friction between a cam and a valve lifter even at the peripheral portion of the valve lifter.

Specifically, the present invention provides:
A valve lifter disposed between an intake valve or an exhaust valve of an internal combustion engine and a valve drive cam and having a groove formed on the top surface;
The groove has a portion that extends linearly from the center of the top surface toward the periphery, and a portion that is curved or bent and extends in a direction parallel to or along the periphery of the periphery. A valve lifter is provided.

  Since the groove formed on the top surface of the valve lifter of the present invention has a radial shape near the center of the top surface, there are many grooves in the direction crossing the sliding direction of the cam. In addition, since the groove is formed in the direction parallel to the periphery or along the periphery toward the periphery near the periphery of the top surface, the groove also exists in the direction crossing the sliding direction of the cam. Accordingly, it is possible to reduce the friction at the central part and the peripheral part of the valve lifter.

It is a figure which shows the outline of a valve operating part. It is a figure which illustrates the pattern of the groove | channel on the top surface of the valve lifter of this invention. It is a figure which illustrates the pattern of the groove | channel on the top surface of the valve lifter of this invention. It is a figure explaining the relationship between rotation of a valve and a sliding locus. It is a figure explaining a mode that friction reduces by dynamic pressure and a Rayleigh step effect by a slot.

  FIG. 1 shows an outline of the valve mechanism. The valve mechanism is disposed at the intake or exhaust port of the internal combustion engine and operates when intake or exhaust is taken in or out of the combustion chamber. The dish-shaped valve 100 is connected to a rod-shaped valve stem 102. The other end of the valve stem 102 is in contact with the valve lifter 1 via a shim 104. A valve spring retainer 106 is disposed between the valve stem 102 and the shim 104. The valve spring 108 is inserted into the valve stem 102 and is disposed between a predetermined wall surface 110 in the cylinder head and the valve spring retainer 106. Then, the valve spring retainer 106 is biased upward (in the direction in which the valve closes).

  The valve lifter 1 has a cylindrical shape with one opening, and is crowned so that the valve spring 108 and the valve stem 102 are placed inside. A cam 2 is disposed on the top surface 4 of the valve lifter 1. When the cam 2 pushes down the valve lifter 1, the valve overcomes the urging force of the valve spring 108 and opens.

  An oil hole for oil supply (not shown) is provided in the base circle of the cam 2, and lubricating oil is supplied between the cam 2 and the top surface 4 of the valve lifter 1.

  FIG. 2A shows the top surface 4 of the valve lifter 1 of the present invention. On the top surface 4 of the valve lifter 1 of the present invention, a groove 6 is formed from the center toward the periphery. In the central portion 8 of the top surface, the groove is linearly formed from the center toward the peripheral edge, and the entire groove has a radial shape.

  On the other hand, in the peripheral portion 10, each groove is formed so as to bend the forming direction at a point away from the center of the top surface by a predetermined distance, and asymptotically approach the peripheral edge along the peripheral edge. Thus, by changing the groove forming direction from the radial direction of the top surface to the circumferential direction, the groove is formed in a direction crossing the sliding direction with the cam at the peripheral edge portion 10.

  The number of times the groove is curved need not be one. FIG. 2B shows a groove shape in which the groove forming direction is bent twice (reference numerals 12 and 14) from the center toward the periphery. By changing the forming direction a plurality of times, the number of grooves crossing the sliding direction with the cam at the peripheral edge increases. In this case, it is necessary to form the grooves in the same manner for all the grooves. This is because if there are grooves with different bending directions, the grooves intersect when formed densely. In addition, although the case where it curved is shown here, you may bend linearly.

  FIG. 2 (c) shows one groove 6 in FIG. 2 (b). A portion linearly extending from the center toward the periphery is denoted by reference numeral 5. A portion that is curved or bent and extends in the direction toward the periphery along the periphery is denoted by reference numeral 7. As described above, the number of times of bending or bending may be plural. As shown in FIG. 2 (c), the portion 7 extending in the direction toward the periphery along the periphery is curved or bent from the linearly extending portion 5 and asymptotically approaches the periphery of the top surface. It is a groove formed in the approaching direction.

  FIG. 3A shows another groove shape of the present invention. The grooves are basically formed radially from the center of the top surface. Accordingly, the groove density is high in the portion close to the center, but the groove density is low in the peripheral portion. It can be said that the distance between adjacent grooves is increased. Therefore, in the groove structure of the top surface shown in FIG. 3A, the branch portion 16 is formed in the groove 6 at the periphery of the top surface. FIG. 3B shows one groove 6. Although the case where two branches (16a, 16b) are formed is shown in the drawing, it is of course not limited to this example.

  Moreover, a groove | channel may be formed in the peripheral part parallel to the peripheral part, and may have a branch part. A specific example is shown in FIG. The groove 6 extends linearly from the center to the periphery, and bends in parallel to the periphery at the end of the region where the groove is formed. As long as the direction of bending does not intersect with adjacent grooves, both the left and right sides may be bent. As a result, the groove may be T-shaped at the peripheral portion. Since the portion parallel to the peripheral edge of the groove is actually formed very short, it may be said that it is parallel to the peripheral edge even if it is formed by a straight line that is not an accurate arc.

  In addition, a plurality of branch portions may be formed in the groove. The length is not limited as long as the branch portion does not intersect with the branch portion of the adjacent groove. By forming the branch portion, the number of grooves crossing the sliding direction of the cam at the peripheral portion can be increased.

  FIG. 3D shows one groove 6. A groove 18 bent in parallel to the periphery is formed at the end of the region where the groove is formed, and a branch 20 is formed from the groove 6 to the groove 18. FIG. 3D shows an example in which the left and right branches (20a, 20b) are formed alternately. This is because adjacent branches do not cross each other.

  The shape of the groove is not particularly limited, but a width of about several to several tens of μm is preferable. This is because the valve lifter is a member having a diameter of about several centimeters, so that the width is just right for forming many grooves on the top surface. In addition, the density formed on the top surface of the valve lifter is not particularly limited, but the strength of the groove portion is lower than that of the portion without the groove in terms of supporting the load. The cam and valve lifter have a metal contact portion, and it is not necessary to form a large number of grooves. Furthermore, the sliding between the valve lifter and the cam varies depending on the engine specifications, and therefore is appropriately determined by design.

  The groove as described above can be obtained by grinding, but can also be obtained by dry etching using a sputtering method, wet etching using chemicals, laser machining, electric discharge machining, or the like.

  As described above, the valve lifter according to the present invention includes a portion that extends linearly from the center to the periphery on the top surface, and a portion that is curved or bent and is parallel to the periphery or along the periphery toward the periphery. Is formed.

  Next, the effect of the valve lifter 1 of the present invention will be described. FIG. 4 is a diagram outlining the contact between the cam 2 and the valve lifter 1. FIG. 4 (e) shows a sliding locus on the top surface. Referring to FIG. 4A, at the base position of cam 2, cam 2 and valve lifter 1 are not in contact. Referring to FIG. 4B, when the cam 2 rotates, the cam 2 contacts the valve lifter 1 at a certain position on the top surface (reference numeral 24 in FIG. 4E). Thereafter, when the rotation of the cam 2 proceeds, the contacted portion is directed toward the periphery of the valve lifter 1 (reference numeral 25 in FIG. 4 (e)).

  Then, referring to FIG. 4C, after the tip of the cam crest contacts, the contact portion goes to the center of the valve lifter (reference numeral 26 in FIG. 4E). After the center of the top surface has been moved away from the top surface of FIG. 4 (d), the contact portion moves toward the center of the top surface (reference numeral 27 in FIG. 4 (e)), and again. The cam leaves.

  FIG. 5 shows the sliding locus 30 with the above cam superimposed on the top surface of the valve lifter of the present invention. As described above, the sliding portion of the cam moves from the central portion of the valve lifter toward the peripheral portion, and the cam is folded at a predetermined portion of the peripheral portion, passes through the central portion, and is folded again at the other peripheral portion.

  Since the groove formed on the top surface of the valve lifter of the present invention has a radial shape near the center of the top surface, there are many grooves in the direction crossing the sliding direction of the cam. In addition, since the groove is formed in the direction parallel to the periphery or along the periphery toward the periphery near the periphery of the top surface, the groove also exists in the direction crossing the sliding direction of the cam.

  FIG. 5B shows a cross section perpendicular to the groove 6. Reference numeral 42 indicates the sliding direction of the cam. Before and after the cam moves over the groove 6, the pressure increases and decreases. However, when the lubricating oil is an incompressible solution such as oil, the pressure is not lower than the vapor pressure of the liquid, and the gas dissolved in the liquid is saturated. Does not drop below atmospheric pressure. For this reason, when the pressure is reduced at the portion over the groove, the bubbles 46 are formed by the gas dissolved in the lubricating oil, and as a result, a force for supporting the applied load is generated. This is an effect called the Rayleigh step effect.

  That is, in the central portion 34 of the top surface 4, there are a large number of grooves that cross the cam due to the radially formed grooves, so that the pressure that supports the load from the cam 2 is generated by the Rayleigh step effect, and friction is reduced. Further, in the peripheral portion 36 of the top surface 4, friction can be reduced by the Rayleigh step effect generated by the groove formed by the curved or bent portion of the groove.

  As can be understood from the above description, since the Rayleigh step effect occurs for each groove, it is easier to obtain the effect when the grooves crossing the sliding direction of the cam are dense. That is, it can be said that the groove configuration as shown in FIGS. 3A and 3C in which many grooves can be formed in the direction perpendicular to the sliding direction of the cam also in the peripheral portion is a preferred embodiment.

  Further, it is preferable that the groove does not reach the edge of the valve lifter top surface. This is because if the groove is formed up to the edge of the top surface of the valve lifter, the oil tends to spill onto the side surface of the valve lifter. In other words, if the groove does not reach the edge of the valve lifter top surface, the oil is unlikely to spill onto the side surface of the valve lifter.

  As described above, the valve lifter according to the present invention includes a portion formed linearly from the center toward the periphery on the top surface that slides with the cam, and is bent or bent from there to asymptotically approach the periphery along the periphery. Therefore, the friction reduction effect due to the dynamic pressure can be obtained at the central portion, and the friction reduction effect due to the Rayleigh step effect can be obtained at the peripheral portion.

  The valve lifter of the present invention can be suitably used for an intake / exhaust valve of an engine employing an OHC direct method.

DESCRIPTION OF SYMBOLS 1 Valve lifter 2 Cam 4 Top face of valve lifter 5 Linearly extended portion of groove 6 Groove 7 Curved portion extending in the direction toward the peripheral edge along the peripheral edge 8 Center part 10 Peripheral part 12 First Bending portion 14 Second bending portion 16 Branch portion 16a, 16b Branch portion 18 Groove parallel to the peripheral edge 20 Branch portion 20a, 20b Branch portion 24-27 Sliding locus 30 Sliding locus 34 Central portion 36 Perimeter portion 42 Cam sliding Movement direction 46 Bubble 47 Pressure

Claims (1)

A valve lifter disposed between an intake valve or an exhaust valve of an internal combustion engine and a valve drive cam and having a groove formed on a top surface thereof;
The groove has a portion that extends linearly from the center of the top surface toward the periphery, and a portion that is curved or bent and extends in a direction parallel to or along the periphery of the periphery. A valve lifter characterized by