JP2005264830A - Arm type valve gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an arm type valve gear capable of suppressing the wear of a contact part between a lash adjuster and a valve stem by reducing the size and weight of the lash adjuster. <P>SOLUTION: The lash adjuster 20 pushing down the valve stem 8 is assembled in the fitting hole 14 of a swing arm 1 swung by the rotation of a cam 7. The lash adjuster 20 is formed of a nut member 21 slidable in the fitting hole 14, a pusher 22 having a rear end part fixed to the nut member 21, a screw rod 23 threaded to the nut member 21, and an elastic member 24 pressing the pusher 22 against the valve stem 8 to reduce the size and weight of the lash adjuster 20. A cylindrical face 33 is formed at the tip of the pusher 22, and brought into line contact with the top end face of the valve stem 8 to lower a surface pressure at the contact part so as to suppress the wear of the cylindrical face at the contact part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an arm type valve gear in an internal combustion engine.

  In an arm type valve gear that opens and closes an intake valve or an exhaust valve (hereinafter simply referred to as a valve) by rotation of a cam, a camshaft is disposed above an arm that is swingably supported. A swing arm type valve operating device that opens the valve by pushing down the arm with the cam provided on the camshaft, and a camshaft is placed below the arm, and one end of the arm is pushed up by the cam provided on the camshaft There is a rocker arm type valve operating apparatus in which the valve is opened at the other end of the arm.

  In these arm type valve gears, valve clearance is automatically adjusted by incorporating a lash adjuster.

Conventionally, a hydraulic lash adjuster described in Patent Document 1 and a mechanical lash adjuster described in Patent Document 2 are known as lash adjusters incorporated in an arm type valve gear.
Japanese Patent Laid-Open No. 10-231711 Japanese Utility Model Publication No. 5-21602.

By the way, in the hydraulic lash adjuster described in Patent Document 1, since engine oil is used as hydraulic oil, there are the following disadvantages.
(1) Since the engine oil is agitated by the crankshaft, air bubbles are often mixed in the oil. When the mixed oil is supplied to the pressure chamber of the lash adjuster, the lash adjuster is bubbled when the valve is opened. , The lift amount of the valve changes.
(2) The amount of dissolved air in the engine oil increases due to changes in temperature and pressure during engine operation, and the air is separated from the oil and stored in the pressure chamber due to cooling after the engine is stopped. The amount changes.
(3) Since a reservoir chamber is required to maintain the function of the lash adjuster until the hydraulic pressure is secured when the engine is restarted, the lash adjuster becomes large and heavy.
(4) Since the hydraulic oil is guided to the lash adjuster, it is necessary to process a small-diameter oil supply passage in the arm, which is extremely difficult to process.

  On the other hand, the mechanical lash adjuster is extremely advantageous because it does not have the above-described disadvantages of the hydraulic lash adjuster. However, when tapping the internal thread that engages the plunger with the inner periphery of the bottomed cylindrical lifter body, it is necessary to provide a relief for the tool at the closed end of the lifter body. There is a disadvantage that the adjuster becomes larger.

  Further, in order to push down the valve stem by swinging the arm, it is necessary to make the surface at the closed end of the lifter body spherical and make point contact with the upper end surface of the valve stem. For this reason, there is a disadvantage that the contact pressure between the lifter body and the valve stem is high, and wear easily occurs at the contact portion.

  Further, since the contact point moves due to the swinging of the arm due to the point contact, there is a possibility that the lash adjuster cannot be reliably operated due to the rotational force acting on the lash adjuster from the valve stem.

  An object of the present invention is to reduce the axial length of the lash adjuster in the arm type valve operating apparatus in which a mechanical lash adjuster is incorporated between the arm and the valve stem, and to reduce the weight in the axial direction. It is to suppress the wear of the parts and to ensure that the lash adjuster can be operated.

  In order to solve the above-described problems, in the present invention, a fitting hole is provided in the swing side end of the arm that is swung by the rotation of the cam, and the lash adjuster incorporated in the fitting hole is used. In the arm type valve gear configured to push down the valve stem, the lash adjuster includes a nut member slidably fitted in the fitting hole, and a rear end portion fixed to the nut member. A pusher having a cylindrical surface formed at a tip opposed to the upper end, an adjustment screw in which an outer peripheral male screw is screw-engaged with an inner female screw of the nut member, and the pusher provided between the adjustment screw and the pusher. And an elastic member that urges the valve stem toward the valve stem. The female screw of the nut member and the male screw of the adjustment screw are respectively connected to the valve stem from the valve stem. Than is pressure flank for receiving the axial pressing load to be loaded has adopted a configuration in which a larger serrated than the flank angle of clearance flanks to Sutosukuryu.

  Since the present invention is configured as described above, the following effects can be obtained.

  (I) By making the tip surface of the pusher a cylindrical surface, when a pressing force acts between the pusher and the valve stem, the cylindrical surface of the pusher tip slides while maintaining a line contact with the upper end surface of the valve stem. . Further, the pushing force is applied to the nut member in an oblique direction, but the force is supported by the fitting hole of the arm, and a force component in the vertical direction acts on the adjusting screw.

  For this reason, only an axial load is applied between the adjusting screw and the nut member, and the lash adjuster can be operated reliably.

  (II) By making line contact between the tip end surface of the pusher and the upper end surface of the valve stem, the surface pressure of the contact portion is smaller than in the case of point contact, and wear of the contact portion can be suppressed.

  (III) Since the pusher makes contact with the upper end surface of the valve stem in a line, the lash adjuster does not act on the lash adjuster, and the lash adjuster can be operated reliably.

  (IV) Since the lash adjuster has a configuration in which an adjustment screw is screw-engaged with a bottomless nut member fitted in the fitting hole, a female screw is formed on the inner periphery of the bottomed cylindrical lifter body, and the male screw member is screwed. Compared with the case of engaging, the axial length can be reduced in size and weight in processing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a swing arm type valve operating apparatus in which two valves are opened and closed simultaneously. The swing arm 1 is swingably supported around an arm support shaft 2 shown in FIG. A notch 3 is formed at the swinging side end of the swing arm 1, and a roller 5 is rotatably supported around a roller pin 4 whose both ends are supported by both side walls of the notch 3.

  As shown in FIGS. 1 and 2, the camshaft 6 is disposed above the swing side end of the swing arm 1, and when the roller 5 is pushed down by the rotation of the cam 7 provided on the camshaft 6, The swing arm 1 swings downward, and at the time of swinging, the two valve stems 8 are simultaneously pushed down to open the valve 9.

  Here, each of the two valve stems 8 is slidably inserted into a guide cylinder 11 provided in the cylinder head 10. The valve stem 8 has a spring retainer 12 at its upper end, and the valve stem 8 is biased in the direction in which the valve 9 is closed by the elasticity of the valve spring 13 applied to the spring retainer 12.

  As shown in FIGS. 2 and 3, the swing arm 1 is provided with a fitting hole 14 at a position corresponding to the upper end of each valve stem 8. A lash adjuster 20 is incorporated in the fitting hole 14.

  The lash adjuster 20 includes a nut member 21 slidably fitted in the fitting hole 14, a pusher 22 having a rear end fixed to the nut member 21, and an adjuster screw-engaged with the nut member 21. The screw 23 and the adjusting screw 23 are pressed against the upper end surface of the fitting hole 14, and the elastic member 24 presses the pusher 22 against the upper end surface of the valve stem 8.

  Here, the nut member 21 has a key groove 25 extending in the axial direction on the outer periphery, and a key groove 26 extending in the axial direction on the inner periphery of the fitting hole 14. The nut member 21 is prevented from rotating by the key 27 incorporated therebetween. Further, the nut member 21 is prevented from coming off by a retaining ring 28 attached to the inner periphery of the opening end of the fitting hole 14.

  The nut member 21 is formed by plastic working, and a male screw 30 provided on the outer periphery of the adjusting screw 23 is threadedly engaged with a female screw 29 formed on the inner periphery thereof.

  In the female screw 29 of the nut member 21 and the male screw 30 of the adjusting screw 23, the flank angle of the pressure side flank 31 that receives the axial pushing load applied from the valve stem 8 to the adjusting screw 23 is larger than the flank angle of the idle side flank 32. The saw-toothed screw is provided with a lead angle that moves in the axial direction while the adjusting screw 23 is rotated by the pressing of the elastic member 24.

  The pusher 22 has a cylindrical surface 33 at the tip, and the cylindrical surface 33 is in line contact with the upper end surface of the valve stem 8.

  The arm type valve gear shown in the embodiment has the above-described structure. When the camshaft 6 rotates and the roller 5 is pushed down by the protruding portion 7a of the cam 7, the swing arm 1 swings downward, and the lash The two valve stems 8 are simultaneously pushed down through the adjuster 20, and the valve 9 is opened.

  When the cam 7 rotates and the base circle 7b comes into contact with the roller 5, the valve stem 8 is raised by the elastic force of the valve spring 13, and the valve 9 is closed.

  When the valve 9 is opened and closed as described above, a push force in an oblique direction is applied to the pusher 33 shown in FIG. At this time, the nut member 21 is guided into the arm fitting hole 14. The pusher 22 moves in the radial direction of the valve stem 8 with the cylindrical surface 33 at the tip thereof being guided by the upper end surface of the valve stem 8.

  Therefore, when the valve 9 is opened, only the axial load acts on the valve stem 8, the valve stem 8 moves smoothly in the axial direction, and when the valve 9 is opened, the axial load is applied to the adjusting screw 23. The axial load acts and is supported by the pressure side flank 31 that abuts each other.

  If the valve clearance is about to occur between the upper end surface of the valve stem 8 and the cylindrical surface 33 at the tip end of the pusher 22 due to thermal expansion of the cylinder head 10 and the like accompanying the temperature rise of the internal combustion engine, the adjustment screw 23 is pressed by the pressing of the elastic member 24. The valve clearance is absorbed by moving along the idle side flank 32 while moving in the axial direction.

  On the other hand, when the distance between the upper end surface of the valve stem 8 and the camshaft 6 is shortened due to wear of the valve seat with which the valve 9 contacts, the adjusting screw 23 gradually increases due to the fluctuating axial load applied from the valve stem 8. When the valve is closed and the base circle 7b of the cam 7 comes into contact with the roller 5 by the pressing, the valve 9 is brought into close contact with the valve seat to prevent the occurrence of compression leakage.

  Here, when a pushing force is applied from the valve stem 8 to the adjusting screw 23 via the pusher 22 and the nut member 21, the pusher 22 moves in the radial direction in a state of line contact with the upper end surface of the valve stem 8. A rotational force does not act on the nut member 21 and only an axial load acts. Therefore, the adjusting screw 23 rotates smoothly and moves in the axial direction, and operates reliably.

  As described above, since the tip of the pusher 22 is the cylindrical surface 33, only the axial load can be applied to the valve stem 8 and the adjusting screw 23, and the valve stem is opened and closed when the valve 9 is opened and closed by the swing of the arm 1. 8 can be moved smoothly in the axial direction, and the adjust screw 23 can be moved in the axial direction while smoothly rotating, so that the lash adjuster can be operated reliably.

  Further, since the contact between the pusher 22 and the valve stem 8 is a line contact, the surface pressure of the contact portion is small, and wear of the contact portion can be suppressed.

  Further, since the lash adjuster 20 has a simple configuration in which the nut member 21 is fitted in the fitting hole 14 and the adjustment screw 23 is screw-engaged with the nut member 21, the lash adjuster 20 has a simple configuration with a small number of parts. The length can be reduced and the cost can be reduced.

  In the embodiment, the swing arm type valve operating apparatus has been described as an example, but the arm type valve operating apparatus is not limited to this. For example, a rocker arm type valve gear may be used. In the case of a rocker arm type valve gear, a fitting hole is provided at the end of the rocker arm on the stem pressing side, and a lash adjuster is incorporated in the fitting hole.

A longitudinal front view showing an embodiment of an arm type valve gear according to the present invention FIG. 1 is a partially cutaway front view showing the enlarged portion of the lash adjuster shown in FIG. Sectional drawing which expands and shows the installation part of the lash adjuster of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Swing arm 7 Cam 8 Valve stem 14 Fitting hole 20 Rush adjuster 21 Nut member 22 Pusher 23 Adjust screw 24 Elastic member 29 Female screw 30 Male screw 31 Pressure side flank 32 Play side flank 33 Cylindrical surface

Claims (1)

  In the arm type valve operating apparatus in which a fitting hole is provided in the swing side end of the arm that is swung by the rotation of the cam, and the valve stem is pushed down via a lash adjuster incorporated in the fitting hole. The lash adjuster includes a nut member slidably fitted in the fitting hole, a pusher having a rear end portion fixed to the nut member, and a cylindrical surface formed at a tip opposite to the upper end of the valve stem. An adjusting screw in which an outer peripheral male screw is screw-engaged with an inner female screw of the nut member, and an elastic member provided between the adjusting screw and the pusher, and biasing the pusher toward the valve stem, The axial pushing load applied from the valve stem to the adjusting screw is applied to each of the female screw of the nut member and the male screw of the adjusting screw. Arm type valve gear flank angle of the kick pressure flanks is characterized in that a larger serrated than the flank angle of clearance flanks.

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