JP2006336584A - Direct type valve system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the functional degradation of a lash adjuster for automatically adjusting a valve clearance of a direct type valve system, caused by the intrusion of FM (friction modifier) oil used for an engine. <P>SOLUTION: A lower face of an end plate 12 of a lifter body 11 built in between a cam 1 and a valve stem 2 is provided with a nut member 13, and an adjusting screw 16 screw-engaged with a threaded hole 15 of the nut member 13 is energized in a direction to abut on the upper end of the valve stem 2 by an elastic member 17. Sealing between the upper end outer diameter face of the valve stem 2 and the inner diameter face of the lifter body 11 is performed by the built-in of a seal member 21, and the seal member 21 prevents the FM oil used for the engine, from entering a screw-engaged part of the nut member 13 and adjusting screw 16. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a direct valve operating apparatus incorporating a lash adjuster for automatically adjusting a valve clearance.

  In a direct type valve gear that directly opens and closes an intake valve or an exhaust valve (hereinafter simply referred to as a valve) by rotation of a cam, the valve clearance is usually automatically adjusted by incorporating a lash adjuster.

  As the lash adjuster, those described in Patent Documents 1 and 2 are conventionally known. The lash adjuster forms a screw hole having a closed end in the lifter body, and presses an adjusting screw screwed into the screw hole in an axial direction by an elastic member incorporated in the closed end of the screw hole. Each of the female screw of the screw hole and the male screw of the adjusting screw is a serrated screw in which the flank angle of the pressure side flank receiving the pushing load applied to the adjusting screw is larger than the flank angle of the play side flank.

  The lash adjuster is assembled between the cam and the valve stem provided on the valve, and when the end face of the valve stem is pressed against the end face of the adjustment screw by the elasticity of the valve spring that presses the valve stem toward the cam, It is transmitted to the cam through the lifter body, and the valve is opened and closed by the rotation of the cam.

  In general, when an axial compressive load is applied to a screw, the self-supporting friction coefficient μs (μs = tan α cos θ, where the friction coefficient μ between screw surfaces is determined by the screw specifications, regardless of the magnitude of the axial load. However, if it is larger than α: lead angle and θ: flank angle, the screw will stand by itself without causing sliding rotation. On the other hand, if the friction coefficient μ between the screw faces is smaller than the self-supporting friction coefficient μs, the screw causes sliding rotation and is pushed in.

  In the lash adjuster, of the two flank of the serrated screw, the self-supporting friction coefficient μs of the pressure side flank that receives the pushing load applied to the adjusting screw is smaller than the friction coefficient μ between the screw surfaces, and the self-supporting friction of the play side flank The coefficient μs is designed to be larger than the friction coefficient μ between the thread surfaces.

  As a result, in the incorporation of the lash adjuster into the internal combustion engine, if the valve clearance is about to occur between the valve stem and the adjustment screw due to the thermal expansion of the cylinder head or the like, the adjustment screw is moved to the idle side by the pressing force of the elastic body. While rotating along the flank, the valve clearance is absorbed by moving in the axial direction.

  In addition, when the adjusting screw receives a pushing force by the valve stem, the adjusting screw moves backward until the axial screw gap formed in the screw engaging portion of the male screw and the female screw is filled, and when the pushing force is further applied, the pressure that presses against each other It is possible to prevent the adjustment screw from moving backward while receiving the above pushing force by the side flank.

  On the other hand, when the distance between the valve stem end and the camshaft is shortened due to wear of the valve seat, etc., the adjust screw is gradually pushed in by the fluctuating axial load applied from the valve stem and moves to the lifter body side. The valve prevents the valve from being completely closed when the valve is closed when the base circle contacts the lifter body. At this time, the adjustment screw is further pushed in from the position where the minimum value of the fluctuating load in the axial direction becomes 0, and does not move back further.

  In recent years, an engine oil containing organic molybdenum (friction modifier oil, hereinafter referred to as FM oil) has been generally used in automobile engines for the purpose of reducing friction and reducing direct contact between sliding parts. When FM oil is used, a reaction film having a very low friction coefficient is generated at the sliding portion, and the sliding resistance of each portion is reduced.

Typical examples of organic molybdenum mixed in FM oil include MoDTC (molybdenum dithiocarbamate) and MoDTP (molybdenum dithiophosphate), which produce a reaction film containing MoS ₂ (molybdenum disulfide) on the friction surface. It is known to reduce the coefficient of friction.
Japanese Patent Laid-Open No. 11-324617 JP-A-11-324618

By the way, it has been experimentally confirmed that the friction coefficient in the sliding portion under the lubrication of oil not containing organic molybdenum (hereinafter referred to as non-FM oil) is about 0.1 to 0.15. In the serrated screw of the adjustment screw described in Patent Documents 1 and 2, for example, the lead angle α = 11.5 °, the flank angle θ ₁ = 75 ° of the pressure side flank, and the flank angle θ ₂ = 15 of the play side flank By setting the angle to 0 °, the self-supporting friction coefficient μs of the pressure side flank is smaller than 0.1 and the self-supporting friction coefficient μs of the play-side flank is larger than 0.15, so that the function of the lash adjuster under non-FM oil lubrication is achieved. Can be realized.

  However, in the direct type valve gear incorporating the lash adjuster, when the FM oil is used as the engine oil, the friction coefficient μ between the thread surfaces may be extremely reduced to about 0.04. When the friction coefficient μ is lower than the self-supporting friction coefficient μs of the pressure side flank, there is a possibility that the pressure side flank slips. If slippage on the pressure side flank is excessive, the adjust screw is pushed when an axial load is applied to the lash adjuster, causing valve lift loss and impacting the valve, causing abnormal noise. There is a case.

  The object of the present invention is to make the lash adjuster incorporated in the direct valve operating system always function stably even when engine oil such as FM oil that affects the friction coefficient of the thread surface is used in the engine. Is to be able to.

  In order to solve the above-described problems, in the present invention, a lash adjuster is incorporated between a cam and a valve stem, and the lash adjuster has an end plate that contacts the cam on the upper side and is movable in an axial direction. And a nut member provided on the lower surface side of the end plate of the lifter body, an adjustment screw that is screw-engaged with a screw hole of the nut member, and an urging force toward the direction in which the adjustment screw contacts the upper end of the valve stem The flank angle of the pressure-side flank that receives the axial pushing load applied to the adjusting screw is used for the female-side thread of the screw hole and the external thread formed on the outer periphery of the adjusting screw. A serrated screw larger than the flank angle of the valve and the axial movement of the adjusting screw In the direct type valve gear that automatically adjusts the rear lance, a configuration is adopted in which a sealing means is provided between the opposed surfaces of the outer periphery of the upper end of the valve stem and the inner periphery of the lifter body to seal between the opposed surfaces. is there.

  Here, the sealing means is such that the outer cylindrical portion of the elastically deformable ring-shaped seal member having a U-shaped cross section is fixed to the inner diameter surface of the lifter body, and the inner cylindrical portion is brought into elastic contact with the outer diameter surface of the valve stem. Alternatively, the large-diameter cylindrical portion at one end of the boot made of an elastic body that can expand and contract in the axial direction may be fixed to the inner diameter surface of the lifter body, and the small-diameter cylindrical portion at the other end may be fixed to the outer diameter surface of the valve stem. Good.

  In the direct type valve gear according to the present invention, a slide member is incorporated between the opposing surfaces of the valve stem and the adjustment screw, the slide member is prevented from rotating with respect to the nut member, and is supported so as to be movable in the axial direction. Thus, even when the valve stem rotates relative to the lifter body, the rotation can be prevented from being transmitted to the adjusting screw, and a stable valve lift amount can be obtained.

  As described above, the engine oil that affects the friction coefficient of the screw surface such as FM oil is used for the engine by sealing the gap between the opposed surfaces of the upper end of the valve stem and the inner periphery of the lifter body by the sealing means. Even in this case, the engine oil can be prevented from entering between the screw engaging portions of the adjustment screw and the nut member, and the deterioration of the function of the lash adjuster can be suppressed, and the stable function can be maintained. .

  In addition, even when soot is mixed into the engine oil and there is a concern about wear of the valve system including the lash adjuster, the durability of the lash adjuster can be maintained by providing a sealed structure inside the lash adjuster. .

  Furthermore, by providing a sealing means between the opposed surfaces of the outer periphery of the valve stem and the inner periphery of the lifter body, a sealing structure is maintained while maintaining a good adjustment function without causing resistance that affects the rotation of the adjustment screw. Can be taken.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, a lash adjuster A is incorporated in the cam 1 and the valve stem 2.

  A spring retainer 3 is attached to the upper end portion of the valve stem 2, and the valve stem 2 is biased in a direction in which the lower end valve 5 is in close contact with the valve seat 6 by the elastic force of the valve spring 4 applied to the spring retainer 3. ing.

  As shown in FIG. 2, the lash adjuster A has a cylindrical lifter body 11. As shown in FIG. 1, the lifter body 11 is slidable in a guide hole 7 formed in the cylinder head B. The lifter body 11 has an end plate 12 in contact with the cam 1 on the upper side, and a nut member 13 is provided on the lower surface side of the end plate 12. The nut member 13 has a flange 13a on the upper outer periphery. The nut member 13 is held in a state of abutting against the lower surface of the end plate 12 of the lifter body 11 by a retaining ring 14 attached to the inner periphery of the lifter body 11.

  An adjusting screw 16 is screw-engaged with the screw hole 15 formed in the nut member 13, and the adjusting screw 16 is urged in a direction to abut on the upper end of the valve stem 2 by an elastic member 17 incorporated on the upper side thereof. Yes.

  The internal thread of the screw hole 15 and the external thread formed on the outer periphery of the adjusting screw 16 are serrated screws whose flank angle of the pressure side flank 18a that receives the pushing force applied to the adjusting screw 16 is larger than the flank angle of the play side flank 18b. The sawtooth screw is provided with a lead angle that moves in the axial direction while the adjusting screw 16 is rotated by the pressing of the elastic member 17.

  Sealing means 20 is provided between the opposed surfaces of the outer periphery of the upper end portion projecting on the spring retainer 3 of the valve stem 2 and the inner periphery of the lifter body 11 to seal the space between the opposed surfaces.

  The sealing means 20 is configured to incorporate a ring-shaped seal member 21 made of an elastic body between the outer diameter surface of the upper end portion of the valve stem 2 and the inner diameter surface of the lifter body 11. The sealing member 21 has a U-shaped cross section, and has an outer cylinder part 21a and an inner cylinder part 21b, and a cored bar 21c having an L-shaped cross section is molded inside.

  The outer cylinder portion 21 a of the seal member 21 is fixed to the inner diameter surface of the lifter body 11 by press fitting, and the inner cylinder portion 21 b is fitted to the upper end outer diameter surface of the valve stem 2. The inner cylinder portion 21 b is tightened by a garter spring 22 provided on the outer side thereof, and is in elastic contact with the outer diameter surface of the valve stem 2.

  In the direct type valve operating apparatus configured as described above, when a valve clearance is generated between the valve stem 2 and the adjusting screw 16 due to thermal expansion of the cylinder head B, the adjusting screw 16 is moved along the play-side flank 18b by the pressing of the elastic member 17. The valve clearance is absorbed by moving in the axial direction while rotating.

  Further, when the adjusting screw 16 receives a pushing force by the valve stem 2, the adjusting screw 16 is moved until the axial screw gap formed in the screw engaging portion of the female screw of the nut member 13 and the male screw of the adjusting screw 16 is tightened. When it moves toward 12 and further push-in force is applied, it receives the push-in force from the pressure-side flank 18a that presses against each other, and prevents the adjustment screw 16 from moving toward the end plate 12 while rotating.

  On the other hand, when the distance between the upper end of the valve stem 2 and the cam 1 is shortened due to wear of the valve seat 6 or the like, the adjusting screw 16 is gradually pushed in and rotated by the fluctuating axial load applied from the valve stem 2. The valve 5 moves to the end plate 12 side and prevents the valve 5 from being incompletely closed when the valve is closed when the base circle 1a of the cam 1 contacts the end plate 12 of the lifter body 11. At this time, the adjustment screw 16 is further pushed in by the screw gap from the position where the minimum value of the fluctuating load in the axial direction becomes 0, and does not move back further.

  On the other hand, in a steady operating state where adjustment of the valve clearance is not necessary, the adjusting screw 16 hardly rotates, and the screw formed between the screw engaging portion of the female screw of the screw hole 15 and the male screw of the adjusting screw 16. Repeated axial displacement within the gap.

  In the lash adjuster A shown in FIG. 2, a seal member 21 is assembled between the outer diameter surface of the upper end portion of the valve stem 2 and the inner diameter surface of the lifter body 11 so that the outer surfaces of the upper end portion of the valve stem 2 and the inner periphery of the lifter body 11 are opposed to each other. Even if engine oil such as FM oil that affects the coefficient of friction of the screw surface is used for the engine, the engine oil is between the nut member 13 and the screw engaging portion of the adjusting screw 16. Since no intrusion occurs and the friction coefficient of the thread surface does not change, it is possible to maintain a stable function.

  Further, since the sealing member 21 that seals between the outer diameter surface of the upper end portion of the valve stem 2 and the inner diameter surface of the lifter body 11 does not affect the rotation of the adjusting screw 16, the sealing structure is maintained in a state in which the adjusting function is maintained well. Can be taken.

  FIG. 3 shows another example of the lash adjuster A. This example is different from the lash adjuster A shown in FIG. 2 in that a cap-shaped slide member 30 that covers the lower outer periphery of the nut member 13 is provided below the adjust screw 16. For this reason, the same components as those in the lash adjuster A shown in FIG.

  Here, the slide member 30 is provided with a cylindrical portion 32 that covers the outer periphery of the nut member 13 on the outer periphery of the bottom plate 31 that supports the lower surface of the adjusting screw 16, and a pair of projecting pieces at a position facing the upper opening end of the cylindrical portion 32. The protrusions 33 are slidably fitted into notches 34 formed in the flange 13a of the nut member 13. The projecting piece 33 is prevented from coming out of the notch 34 by the retaining ring 14, and the slide member 30 is prevented from rotating with respect to the nut member 13 by the fitting of the projecting piece 33 and the notch 34.

  As shown in FIG. 3, the slide member 30 is provided on the lower side of the adjustment screw 16, the slide member 30 is prevented from rotating with respect to the nut member 13, and is movable in the axial direction. Since the bottom plate 31 comes into contact with the upper end surface of the valve stem 2, even if the valve stem 2 of the valve 5 that repeatedly opens and closes rotates, the rotation is not transmitted to the adjusting screw 16. For this reason, since the adjusting screw 16 does not displace in the axial direction while rotating, the valve lift amount can always be kept constant.

  FIG. 4 shows another example of the sealing means 20. In this example, the boot 23 made of an elastic body that can expand and contract in the axial direction seals between the outer diameter surface of the upper end portion of the valve stem 2 and the inner diameter surface of the lifter body 11.

  Here, the boot 23 has a large-diameter cylindrical portion 23a at one end, a cylindrical cored bar 23b is molded in the large-diameter cylindrical portion 23a, and a small-diameter cylindrical portion 23c is provided at the other end. The large diameter cylindrical portion 23a is fixed to the inner diameter surface of the lifter body 11 by press fitting. On the other hand, the small-diameter cylindrical portion 23c is press-fitted into the outer diameter surface of the upper end portion of the valve stem 2, and is fixed to the valve stem 2 by tightening a garter spring 24 provided on the outer side.

  As described above, the gap between the inner diameter surface of the lifter body 11 and the outer diameter surface of the upper end portion of the valve stem 2 is sealed by the boot 23 so that the engine oil enters between the screw engaging portions of the nut member 13 and the adjusting screw 16. Can be prevented, and deterioration of the function of the lash adjuster can be suppressed.

  Further, since the boot 23 does not affect the rotation of the adjusting screw 16, it is possible to adopt a sealed structure while maintaining the adjusting function well.

Longitudinal front view showing an embodiment of a direct type valve gear according to the present invention Longitudinal front view of the lash adjuster shown in FIG. Longitudinal front view showing another example of lash adjuster Longitudinal front view showing another example of sealing means

Explanation of symbols

11 Lifter body 12 End plate 13 Nut member 15 Screw hole 16 Adjust screw 17 Elastic member 18a Pressure side flank 18b Play side flank 20 Sealing means 21 Seal member 21a Outer cylinder part 21b Inner cylinder part 23 Boot 23a Large diameter cylinder part 23c Small diameter cylinder part 30 Slide member

Claims (4)

  A lash adjuster is incorporated between the cam and the valve stem, and the lash adjuster has an end plate on the upper side and an axially movable lifter body, and a nut provided on the lower surface of the end plate of the lifter body. A member, an adjustment screw engaged with the screw hole of the nut member, and an elastic member that urges the adjustment screw in a direction in which the adjustment screw comes into contact with the upper end of the valve stem. The thread of the male screw formed on the outer periphery of the screw is a serrated screw whose flank angle of the pressure side flank receiving the axial pushing load applied to the adjustment screw is larger than the flank angle of the play side flank. Direct type with automatic adjustment of valve clearance by axial movement In the valve device, between the facing surfaces of the inner circumference of the upper end outer periphery and the lifter body of the valve stem, a direct Shikido valve apparatus characterized in that a sealing means for sealing between the opposing surfaces.   The sealing means has a U-shaped elastically deformable seal member having an outer cylinder part and an inner cylinder part, the outer cylinder part of the seal member is press-fitted into the inner diameter surface of the lifter body, and the inner cylinder part is a valve 2. The direct valve operating apparatus according to claim 1, comprising a configuration in which the outer diameter surface of the stem is elastically contacted.   The sealing means has a boot made of an elastic body that can be expanded and contracted in the axial direction, the large-diameter cylindrical portion at one end of the boot is fixed to the inner diameter surface of the lifter body, and the small-diameter cylindrical portion at the other end is fixed to the outer diameter of the valve stem. The direct valve operating apparatus according to claim 1, comprising a structure fixed to a surface.   4. The slide member according to claim 1, wherein a slide member is assembled between opposing surfaces of the valve stem and the adjustment screw, the slide member is supported with respect to the nut member, and supported so as to be movable in the axial direction. Direct valve gear.

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