JP2007154852A - Lash adjuster in valve gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a lash adjuster for automatically adjusting a valve clearance by the axial movement of an adjust screw from being functionally degraded due to the entry of oil and effectively lubricate the threaded part of a nut member with the adjust screw. <P>SOLUTION: The nut member 13 is fitted onto the lower surface of the end plate 12 of a lifter body 11. The adjust screw 16 threaded with the screw hole 15 of the nut member 13 is biased by an elastic member in the direction that it is separated from the end plate 12. A cap-like slide member 20 covering the lower outer periphery of the nut member 13 is fitted to the lower side of the adjust screw 16. The clearance between the outer diameter surface of the slide member and the inner diameter surface of a lifter body 11 is sealed by mounting a boot 31 therein. Sealed spaces 32a, 32b are formed between the boot 31 and the end plate 12. An FM oil used for an engine is prevented from entering the threaded part of the nut member with the adjust screw 16 by the boot 31 and the slide member 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lash adjuster that automatically adjusts the valve clearance of a valve gear in an internal combustion engine.

  In a valve operating device that opens and closes an intake valve or an exhaust valve (hereinafter simply referred to as a valve) by rotation of a cam, valve clearance is automatically adjusted by incorporating a lash adjuster.

  As the lash adjuster, those described in Patent Documents 1 to 3 are conventionally known. In this lash adjuster, a screw hole having a closed end is formed in the lifter body, and an adjustment screw screw-engaged with the screw hole is pressed in the 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.

  When the end surface of the valve stem is pressed against the end surface of the adjustment screw by the elasticity of a valve spring that is incorporated between, for example, a cam and a valve stem provided on the valve, and presses the valve stem toward the cam. Force is transmitted to the cam through the lifter body so that the valve opens and closes as the cam rotates.

  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 as described above, 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, the adjustment screw is moved to the idle side by the pressing force of the elastic member. 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 adjusting screw is gradually pushed in by the fluctuating axial load applied from the camshaft, and the base circle of the cam comes into contact. Prevents compression leakage due to the valve not closing completely at the end of the valve lift. 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.
US Pat. No. 4,548,168 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 sawtooth screw of the adjustment screw described in Patent Documents 1 to 3, 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 engine in which the lash adjuster is incorporated, when the FM oil is used, the friction coefficient μ between the screw surfaces may be extremely reduced to about 0.04, and the friction coefficient μ If it is less than the free-standing friction coefficient μs of the flank, there is a risk of causing slippage on the pressure side flank. 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.

  An object of the present invention is to provide a stable function even when engine oil such as FM oil that affects the friction coefficient of the screw surface is used in the engine, and to ensure that the nut member and the adjusting screw are It is an object of the present invention to provide a lash adjuster capable of effectively lubricating a screw engaging portion.

  In order to solve the above problems, in the present invention, a lifter body having an end plate on the upper side, a nut member provided on the lower surface side of the end plate of the lifter body, and a screw hole in the screw hole of the nut member The adjusting screw and an elastic member that urges the adjusting screw in a direction away from the end plate of the lifter body, and the adjusting screw is used to adjust the female screw of the screw hole and the thread of the male screw formed on the outer periphery of the adjusting screw. In a lash adjuster in a valve operating device in which the flank angle of the pressure side flank subjected to the axial indentation load applied is larger than the flank angle of the idle side flank, the lower part of the nut member is below the adjustment screw. The cap-shaped slide member that covers the outer diameter surface is locked against the nut member, and It is provided so as to be movable in the axial direction of the just screw, a sealing means is provided between the outer diameter surface of the slide member and the inner diameter surface of the lifter body, and the lubricant is enclosed in a sealed space formed between the sealing means and the end plate of the lifter body. And the structure which provided the oil supply path which connects the inside and the exterior of the nut member in the upper part of the said nut member was employ | adopted.

  Here, as a sealing means, 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 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 surface of the slide member. What consists of composition can be adopted.

  In addition, the oil supply passage may be formed by a radially extending groove formed on an upper surface that abuts the lower surface of the end plate of the nut member, or a radius penetrating from the outer diameter surface of the nut member to the inner diameter surface. It may consist of directional holes.

  As described above, the cap-shaped slide member that covers the lower outer diameter surface of the nut member is provided on the lower side of the adjustment screw, and the sealing means is provided between the outer diameter surface of the slide member and the inner diameter surface of the lifter body. Even when engine oil such as FM oil that affects the friction coefficient of the screw surface is used, the engine oil can be prevented from entering between the screw engaging portion of the adjusting screw and the nut member, It is possible to suppress a decrease in the function of the lash adjuster and maintain a stable function.

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

  Furthermore, by providing the oil supply passage above the nut member, oil as a lubricant can be easily supplied from the oil supply passage to the screw engaging portion of the nut member and the adjustment screw during the assembly of the lash adjuster. .

  In addition, when the lash adjuster is incorporated in the valve operating device, the oil that accumulates inside the slide member flows into the screw engaging portion of the nut member and the adjustment screw from the oil supply passage when the lash adjuster moves up and down. Further, it is possible to prevent wear and seizure of the screw engaging portion, and to suppress a decrease in the function and durability of the lash adjuster.

  In addition, by providing a slide member on the lower side of the adjustment screw, even if the valve stem rotates relative to the lifter body, it is possible to prevent the rotation from being transmitted to the adjustment screw, and a stable valve lift. The quantity can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a state in which a lash adjuster A according to the present invention is assembled between a cam 1 and a valve stem 2 of a direct type valve gear.

  The valve stem 2 has a spring retainer 3 at the upper end, and the valve stem 2 is urged in the direction in which the lower end valve 5 is in close contact with the valve seat 6 by the pressing force of the valve spring 4 loaded on the spring steer 3. Yes.

  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 8 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 contact with the lower surface of the end plate 12 of the lifter body 11 by a retaining ring 14 made of a disc spring attached to the inner periphery of the lifter body 11.

  An adjusting screw 16 is screwed into the screw hole 15 formed in the nut member 13, and the adjusting screw 16 is urged in a direction away from the end plate 12 by an elastic member 17 incorporated on the upper side thereof.

  The female screw 15 a of the screw hole 15 and the male screw 16 a formed on the outer periphery of the adjusting screw 16 have a sawtooth shape in which the flank angle of the pressure side flank 18 that receives the pushing force applied to the adjusting screw 16 is larger than the flank angle of the play side flank 19. The saw-toothed 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.

  A slide member 20 is provided below the adjustment screw 16. The slide member 20 has a cap shape in which a cylindrical portion 22 that covers the outer periphery of the nut member 13 is provided on the outer periphery of the bottom plate 21 that supports the lower surface of the adjusting screw 16. The projecting pieces 23 are formed outward, and the projecting pieces 23 are slidably fitted into notches 24 formed in the flange 13a of the nut member 13. The projecting piece 23 is prevented from falling downward from the cutout portion 24 by the retaining ring 14, and the slide member 20 is prevented from rotating with respect to the nut member 13 by the fitting of the projecting piece 23 and the cutout portion 24, and the shaft It can be moved in any direction.

  A sealing means 30 is provided between the outer diameter surface of the cylindrical portion 22 and the inner diameter surface of the lifter body 11 in the slide member 20.

  The sealing means 30 seals between the outer diameter surface of the slide member 20 and the inner diameter surface of the lifter body 11 by a boot 31 made of an elastic body that can expand and contract in the axial direction.

  Here, the boot 31 has a large diameter cylindrical portion 31a at one end, and a cylindrical cored bar 31b is molded in the large diameter cylindrical portion 31a. Further, a small diameter cylindrical portion 31 c is provided at the other end of the boot 31. A metal ring 31d is fixed to the inner diameter surface of the small-diameter cylindrical portion 31c. The large diameter cylindrical portion 31 a is fixed to the inner diameter surface of the lifter body 11 by press fitting, while the ring 31 d of the small diameter cylindrical portion 31 c is press fitted to the outer diameter surface of the cylindrical portion 22 of the slide member 20.

  By attaching the boot 31, an internal sealed space 32 a is formed inside the nut member 13 and an external sealed space 32 b is formed outside the nut member 13 between the boot 31 and the end plate 12 of the lifter body 11. The oil which lubricates the screw engaging part of the nut member 13 and the adjustment screw 16 is enclosed in 32a, 32b.

  An oil supply path 33 that communicates the inner sealed space 32 a inside the nut member 13 and the outer sealed space 32 b outside the nut member 13 is provided above the nut member 13. In FIG. 2, the oil supply passage 33 is composed of a groove extending in the radial direction on the upper surface of the nut member 13 that abuts the lower surface of the end plate 12. However, as shown in FIG. It may consist of a hole penetrating from the diameter surface to the inner diameter surface.

  When the lash adjuster A having the above structure is incorporated in the valve operating apparatus, if the valve clearance is generated between the valve stem 2 and the adjusting screw 16 due to the thermal expansion of the cylinder head B, the adjusting screw 16 is freed by the pressing of the elastic member 17. While rotating along the side flank 19, it moves in the axial direction and absorbs the valve clearance.

  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 15 a of the nut member 13 and the male screw 16 a of the adjusting screw 16 is tightened. When it moves toward the end plate 12 and further a pressing force is applied, the pressing force is received by the pressure-side flank 18 that presses against each other, and the adjustment screw 16 is prevented 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 adjusting 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 is formed between the screw engaging portions of the female screw 15a of the screw hole 15 and the male screw 16a of the adjusting screw 16. The axial displacement is repeated within the range of the screw thread gap.

  Like the lash adjuster A shown in the embodiment, the boot 31 is used to seal the gap between the inner diameter surface of the lifter body 11 and the outer diameter surface of the slide member 20, so that the friction coefficient of the thread surface such as FM oil is affected on the engine. Even if a new engine oil is used, the engine oil does not enter between the screw engaging portions of the nut member 13 and the adjusting screw 16, and the friction coefficient of the screw surface does not change, so that the stable The function can be maintained.

  Further, the slide member 20 is provided below the adjustment screw 16, the slide member 20 is prevented from rotating with respect to the nut member 13, and is movable in the axial direction, so that the lash adjuster A is incorporated into the valve gear. As a result, the bottom plate 21 of the slide member 20 comes into contact with the upper end surface of the valve stem 2.

  For this reason, 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, and the adjusting screw 16 does not displace in the axial direction while rotating. It can always be kept constant.

  Further, by providing the oil supply passage 33 at the upper part of the nut member 13, as a lubricant from the oil supply passage 33 to the screw engaging portion of the nut member 13 and the adjustment screw 16 during the assembly of the lash adjuster before the boot 31 is assembled. Can be easily supplied with oil.

  Further, in a state in which the lash adjuster is incorporated in the valve operating device, oil accumulated in the slide member 20 due to vibration caused by the vertical movement of the lash adjuster is supplied from the oil supply passage 33 to the screw engaging portion of the nut member 13 and the adjusting screw 16. Therefore, it is possible to prevent wear and seizure of the screw engaging portion and to suppress the function and durability of the lash adjuster.

A longitudinal front view of a valve gear incorporating a lash adjuster according to the present invention Longitudinal front view of the lash adjuster shown in FIG. Sectional view along line III-III in FIG. Longitudinal front view showing another example of a lash adjuster according to the present invention

Explanation of symbols

11 Lifter body 12 End plate 13 Nut member 15 Screw hole 15a Female screw 16 Adjust screw 16a Male screw 17 Elastic member 18 Pressure side flank 19 Play side flank 20 Slide member 22 Cylindrical portion 30 Sealing means 31 Boot 31a Large diameter cylindrical portion 31c Small diameter cylindrical portion 32a Internal sealed space 32b External sealed space 33 Oil supply passage

Claims (4)

A lifter body having an end plate on the upper side, a nut member provided on the lower surface of the end plate of the lifter body, an adjustment screw threadedly engaged with a screw hole of the nut member, and the adjustment screw being separated from the end plate of the lifter body A pressure-side flank that receives an axial indentation load applied to the adjustment screw by using the female screw of the screw hole and the male screw thread formed on the outer periphery of the adjustment screw. In the lash adjuster in the valve operating device in which the flank angle is a serrated screw larger than the flank angle of the play side flank,
A cap-shaped slide member that covers the lower outer diameter surface of the nut member is provided on the lower side of the adjustment screw so as not to rotate with respect to the nut member and is movable in the axial direction of the adjustment screw. Sealing means is provided between the inner diameter surfaces of the lifter body, a lubricant is sealed in a sealed space formed between the sealing means and the end plate of the lifter body, and the inside and outside of the nut member are disposed above the nut member. A lash adjuster in a valve operating apparatus, characterized in that an oil supply passage is provided.   The sealing means has a configuration in which 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 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 surface of the slide member. A lash adjuster in a valve operating apparatus according to claim 1.   The lash adjuster in a valve operating apparatus according to claim 1 or 2, wherein the oil supply passage is formed of a radially extending groove formed on an upper surface that abuts on the lower surface of the end plate of the nut member.   The lash adjuster in the valve operating apparatus according to claim 1 or 2, wherein the oil supply passage is formed of a radial hole penetrating from an outer diameter surface of the nut member to an inner diameter surface.

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