JP5495959B2 - Valve lifter - Google Patents

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 a vehicle 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 a 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 that can be applied to all sliding receiving members. In particular, application to a valve lifter is also disclosed.

  Here, a large number of circular depressions are formed in the annular band portion located at least at the center C of the crown surface (top surface) of the tappet (valve lifter), and at least one central portion of the crown surface There is disclosed a configuration in which a large number of concentric rectangular recesses are formed in which the opposing sides are perpendicular to the sliding direction (of the cam) and the other opposing sides are along the sliding direction.

  In Patent Document 1, the sliding speed of the sliding member is slow and the lubricating oil film thickness between the two is thin, and at the turn-around point of the sliding member or in the vicinity of the sliding end in the vicinity thereof, the circular shape is more than the rectangular recess. Indentations are more effective in reducing friction, while rectangular indentations are more effective in reducing friction than circular indentations where the sliding speed of the sliding member is high. Teaches.

  Further, in Patent Document 1, as a reason for this, metal contact occurs in a region where the lubricant film thickness is thin, so that a circular recess is easier to get over a recess step than a rectangular recess, and slides. In the high speed region, the lubricant film thickness is sufficiently thick so that the number of metal contacts is reduced, and the more the sides perpendicular to the sliding direction are, the more the depression effect can be obtained due to the hydraulic amplification effect when riding on the depression step. As it is easy, rectangular depressions are good.

JP 2007-46660 A

  Various attempts and studies have been made to reduce friction, but there are few ideas that can deal with all aspects, and trial and error are often performed for each case. In the case of a valve lifter, there may be a range that can be dealt with by forming a dent as in Patent Document 1, but the cam width, the diameter of the valve lifter, and further, the engine displacement, the high rotation type or the low rotation type, The friction state also changes depending on the engine characteristics to be applied to the engine.

  Further, reducing the friction on the top surface of the valve lifter is very effective in reducing the mechanical loss of the entire engine. Therefore, finer control is desired to reduce the friction on the top surface of the valve lifter.

  In particular, since a metal contact always exists between the valve lifter and the cam, the top surface of the valve lifter must also have a concave portion in order to support the load. In the technique disclosed in Patent Document 1, once the total area of the recess is determined, it is necessary to deal with various frictional states only by the shape of the recess. Therefore, if the total area of the dent is small, there is a problem that fine control of friction reduction is difficult.

  The present invention has been conceived in view of the above problems, and aims to finely control the friction state between the cam and the valve lifter even if the total area of the recess is a small proportion of the total area of the top surface of the valve lifter. To do.

Specifically, the present invention provides:
A valve lifter disposed between an intake valve or an exhaust valve of a vehicle internal combustion engine and a valve drive cam,
Provided is a valve lifter characterized in that fan-shaped depressions having micro grooves formed on the bottom surface are arranged in a concentric checkered pattern on the top surface of the valve lifter.

In the valve lifter of the present invention,
The minute groove formed in the fan-shaped depression is formed concentrically with respect to the center of the valve lifter.

In the valve lifter of the present invention,
The minute grooves formed in the fan-shaped depression are formed radially with respect to the center of the valve lifter.

In the valve lifter of the present invention,
On the top surface,
A fan-shaped depression having a minute groove formed concentrically with respect to the center of the valve lifter;
A fan-shaped depression having minute grooves formed radially with respect to the center of the valve lifter is mixed.

  In the valve lifter according to the present invention, the rectangular recesses having micro grooves formed on the top surface are arranged in a staggered pattern, so that the friction reducing effect by the dynamic pressure that can be obtained in the direction in which the lubricating oil flows in the micro grooves, and lubrication The friction reduction effect obtained by the Rayleigh step effect (or oil sump effect) obtained in the direction in which the oil crosses the minute groove can be used alone or in combination, so fine friction control is possible depending on the engine design become.

It is a figure which shows the outline of a valve operating part. It is a figure which illustrates the top face of the valve lifter of the present invention. It is the figure which expanded the hollow formed in the top surface of a valve lifter. It is the figure which showed the hollow of the other form. 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 by a hollow. It is a figure explaining a mode that friction is reduced by the minute groove in a hollow. It is a figure which shows the variation of the hollow formed in the top surface of a valve lifter. It is a figure which shows the other form of a hollow.

  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. 2 shows the top surface 4 of the valve lifter of the present invention. A recess 6 is formed on the top surface 4 of the valve lifter 1 of the present invention. In FIG. 2, the indentation is represented by a black area. The indentation is formed in a concentric section 8 with respect to the center of the valve lifter 1. Here, the concentric section 8 refers to a ring shape having a predetermined width 10. For the sake of explanation, numbers assigned in order from the center of the valve lifter toward the periphery are referred to as section numbers. Further, a portion that is not recessed in the same section is referred to as a flat portion 12. In FIG. 2, it is a white part. The flat portion 12 is the surface of the top surface 4 of the valve lifter 1.

  The recesses 6 are formed at equal intervals in the concentric compartments 8. That is, the recess 6 has a fan shape precisely. However, since it is a small area, it may be said to be rectangular. Furthermore, the depressions formed in the sections before and after the section number are not formed continuously along the radius from the center of the valve lifter. That is, when viewed from the entire top surface 4 of the valve lifter, the recesses 6 are arranged in a concentric checkered pattern. Or it can be said that it is arranged in the shape of a dart.

  The concentric section 8 is formed between the center of the top surface 4 and a predetermined radius. In other words, there is a portion where no dent is formed in the peripheral portion. This is because this region is a portion where the cam does not contact, and it is not necessary to reduce the friction. Further, in the central portion of the top surface 4, the recess 6 becomes too small and the processing is not easy, so the recess 6 does not need to be formed.

  The width 10 of each section 8 may not be the same. That is, the width of the partition may be changed between the central portion and the peripheral portion. This is because it can be adjusted so that the effect of reducing friction is optimized by adjusting the size of the recess formed in the compartment.

  FIG. 3A shows an enlarged perspective view of one of the recesses 6. In the figure, symbol C represents the center direction of the valve lifter top surface 4, and symbol E represents the peripheral direction of the valve lifter top surface 4. A minute groove 14 is formed at the bottom of the recess 6. FIG. 3B shows a cross section taken along the line AA of FIG. A plurality of minute grooves 14 are formed at the bottom of the recess 6, and a flange 16 is formed between each minute groove 14. The apex 18 of the flange portion 16 is formed at least below the flat portion 12. When the depth from the flat portion 12 to the apex 18 of the flange portion 16 is changed, friction control described later can be performed. The depth from the flat portion 12 to the apex 18 of the flange portion 16 is referred to as a recess depth 20, and the depth from the apex 18 of the flange portion 16 to the bottom of the groove is defined as a groove depth 22.

  The size of the minute groove is not particularly limited, but the width is about 1 μm or less, and the size of the recess is preferably about 1 to 2 mm. In addition, such a groove with a minute groove may be formed at the bottom of the depression after the depression is formed first, or the groove is formed continuously as a result of forming the minute groove continuously. Also good. These minute grooves and depressions can be formed by wet etching using photolithography, dry etching using sputtering, or laser processing.

  In FIG. 3A, the minute groove 14 is formed in the circumferential direction with respect to the center of the valve lifter 1. However, the minute grooves 14 can also be formed radially with respect to the center of the valve lifter 1. FIG. 4 exemplifies the recess 7 having the minute grooves 15 formed in a radial pattern.

  Next, the effect of the valve lifter 1 of the present invention will be described. FIG. 5 is a diagram outlining the contact between the cam 2 and the valve lifter 1. FIG. 5E shows a sliding locus on the top surface. Referring to FIG. 5A, at the base position of cam 2, cam 2 and valve lifter 1 are not in contact. Referring to FIG. 5B, 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. 5E). Thereafter, as 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. 5 (e)).

  Then, referring to FIG. 5C, after the tip of the cam crest comes into contact, the contact portion goes to the center of the valve lifter (reference numeral 26 in FIG. 5E). After the center of the top surface of FIG. 5 (d) has passed and the tip of the cam crest has moved away from the top surface, the contact portion moves toward the center of the top surface (reference numeral 27 in FIG. 5 (e)) and again. The cam leaves.

  FIG. 6 shows the sliding surface 30 with the above cam superimposed on the top surface of the valve lifter of the present invention. Here, a case is shown in which the minute groove formed at the bottom of the recess is formed concentrically with respect to the center of the top surface. In order to show that the indentation 6 has the minute grooves 14 in the circumferential direction, the indentation 6 is shown with a white line 32 in the circumferential direction.

  In the case of FIG. 6, the minute groove 14 is parallel to the sliding direction of the cam 2 in the portion 34 close to the center of the top surface where the sliding speed of the cam is fast. That is, referring to FIG. 6B, the lubricating oil 38 tends to flow in the direction of the minute groove 14 in the recess 6. Since the lubricating oil that has flowed in the direction of the minute groove 14 hits the edge 40 of the recess 6, dynamic pressure is generated here. The shape indicated by reference numeral 41 schematically shows the pressure received by the cam passing above the recess 6. That is, an oil film is secured by the dynamic pressure at the center of the top surface, and a reduction in friction can be expected.

  On the other hand, in the peripheral portion of the top surface 4 where the sliding speed of the cam 2 is slow, the minute groove 14 is perpendicular to the sliding direction of the cam 2. FIG. 7A shows a radial cross section of the recess 6. Reference numeral 42 indicates the sliding direction of the cam 2. FIG. 7B is an enlarged view of the portion 44 in FIG. As the cam 2 slides, the lubricating oil in the recess 6 must get over the flange 16.

  The pressure rises and falls before and after getting over the flange 16, but when the lubricating oil is an incompressible solution such as oil, the pressure does not become lower than the vapor pressure of the liquid, and the saturated atmospheric pressure of the gas dissolved in the liquid Not lower. For this reason, when the pressure is reduced at the part over the flange part 16, 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. Reference numeral 47 is a schematic view showing a pressure change before and after the flange portion 16.

  That is, in the peripheral portion of the top surface 4, a pressure that supports the load from the cam 2 is generated by the Rayleigh step effect generated by the minute groove 14 formed at the bottom of the recess 6, which contributes to a reduction in friction.

  As described above, the obtained effect differs depending on whether the minute groove 14 formed at the bottom of the recess 6 arranged in a concentric checkered pattern is parallel or perpendicular to the sliding direction of the cam 2. Therefore, the direction in which the microgrooves 14 are formed can be selected as appropriate depending on whether the dynamic pressure is obtained and the friction is reduced or the Rayleigh step effect can reduce the friction.

  FIG. 8 shows a case where the minute grooves 15 formed at the bottom of the depression 7 are formed radially with respect to the center of the top surface 4. In FIG. 8A, a radial white line is written in the depression 7 to represent this. In this case, in the central portion of the top surface 4, the minute groove 15 is perpendicular to the sliding direction of the cam, and in the peripheral portion of the top surface 4, the minute groove 15 is parallel to the sliding direction of the cam. . That is, when the minute grooves are formed radially, a Rayleigh step effect can be expected at the central portion of the top surface of the valve lifter, and an effect due to dynamic pressure can be expected at the peripheral portion.

  In addition, the degree of the dynamic pressure and the Rayleigh step effect can be adjusted by adjusting the depth of the micro-grooves formed at the bottom of the recess and the depth from the top surface to the heel. Or it can set suitably according to the rotation area which wants to reduce mechanical loss by the specification of an engine.

  FIG. 8 (b) shows an example of a case where a concentric circular groove portion and a radially formed portion are mixed. In the region close to the central part, the micro grooves 14 are concentric, and in the part close to the peripheral part, the micro grooves 15 are radial. That is, the recess 6 is formed at the central portion, and the recess 7 is formed at the peripheral portion. In this way, it is possible to expect a friction reduction effect due to dynamic pressure in both the central portion and the peripheral portion. Further, if the direction of the minute groove is reversed between the central portion and the peripheral portion, the friction reduction effect due to the Rayleigh step effect can be expected in the central portion and the peripheral portion.

  In the present invention, the concentric checkered pattern does not exclude the case where the lengths of the recess 6 and the flat portion 12 are not equal in the circumferential direction of the section. For example, referring to FIG. 9A, the case where the length 5 of the recess 6 is longer than the length 11 of the flat portion 12 in the same section 8 is shown. If it does in this way, the part 48 in which the hollow 6 will overlap before and behind a division arises. In this case, contribution to the Rayleigh step effect can be expected. On the other hand, FIG. 9B shows a case where the length 5 of the recess 6 is shorter than the length 11 of the flat portion 12. Before and after the section, the portion 50 that is not the recess 6 is formed radially from the center of the top surface 4, and the metal contact increases, but the load is supported more strongly.

  Further, the case where the radial width 52 is not the same as the section width 10 in the section is not excluded. For example, FIG. 9C shows a case where the indentation width 52 is shorter than the section width 10.

  As described above, the valve lifter according to the present invention has a concentric checkered dent formed on the top surface that slides with the cam, and a minute groove formed on the bottom of the dent. Fine friction control becomes possible by adjusting the step effect.

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

1 Valve lifter 2 Cam 4 Top surface of valve lifter 6 Indentation (circumferential groove)
7 Indentation (radial minute groove)
8 compartments 10 compartment widths 12 flat parts 14 micro grooves (circumferential direction)
15 Micro groove (radial direction)
16 ridge portion 18 apex of ridge portion 20 depth of depression 22 groove depth 24 to 27 sliding locus 30 sliding locus 32 white line 34 central portion 36 peripheral portion 38 flow of lubricating oil 40 wall of depression 40 pressure 42 flow of lubricating oil 46 Bubble 47 Pressure

Claims (4)

A valve lifter disposed between an intake valve or an exhaust valve of a vehicle internal combustion engine and a valve drive cam,
A valve lifter, wherein a fan-shaped depression having a minute groove formed on the bottom surface is arranged in a concentric checkered pattern on the top surface of the valve lifter.   The valve lifter according to claim 1, wherein the minute groove formed in the fan-shaped depression is formed concentrically with respect to the center of the valve lifter.   2. The valve lifter according to claim 1, wherein the minute groove formed in the fan-shaped depression is formed radially with respect to a center of the valve lifter. On the top surface,
A fan-shaped depression having a minute groove formed concentrically with respect to the center of the valve lifter;
2. The valve lifter according to claim 1, wherein fan-shaped depressions having minute grooves formed radially are mixed with respect to a center of the valve lifter.