JP2009270505A - Lash adjuster - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lash adjuster without concentrating a load in an axial end of a male screw and a female screw, when the falling moment acts on an adjusting screw. <P>SOLUTION: This lash adjuster of a valve gear includes a nut member 14, the adjusting screw 17 having on the outer periphery a male screw 16 engaging by a screw with a female screw 15 of its nut member 14, and a return spring 19 for energizing its adjusting screw 17 in the direction for projecting from the nut member 14, and is provided so that the male screw 16 and the female screw 15 are formed in a sawtooth shape larger than a flank angle of a play side flank 26 in a flank angle of a pressure side flank 25. The male screw 16 is formed as a tapered screw for contacting with the female screw 15 in a state of making the falling moment act on the adjusting screw 17. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lash adjuster incorporated in an engine valve gear.

  As a valve operating device that operates a valve provided at the intake port or exhaust port of an engine, the central part of the arm supported so as to be swingable with one end as a fulcrum is pushed down by a cam, and the valve stem is moved at the other end of the arm. One end of the arm that is pushed down (swing arm type valve operating device) or the arm supported so as to be able to swing with the center as a fulcrum is pushed up with a cam, and the valve stem is pushed down at the other end of the arm There are known devices (a rocker arm type valve operating device), and a device in which a lifter body supported so as to be slidable up and down is pushed down by a cam and a valve stem is pushed down by the lifter body (direct type valve operating device).

  In these valve operating apparatuses, during engine operation, gaps between the constituent members of the valve operating apparatus change due to thermal expansion differences that occur between the constituent members of the valve operating apparatus, and abnormal noise and compression leakage occur due to changes in the gaps. There is a fear. Further, even if the sliding portion of the valve operating device is worn, the gap between the constituent members of the valve operating device changes, and there is a possibility that abnormal noise is generated due to the change in the clearance.

  In order to prevent this abnormal noise and compression leakage, a lash adjuster is incorporated in the valve operating device, and the lash adjuster often absorbs a change in a gap between the components of the valve operating device.

  As such a lash adjuster, in the above swing arm type valve gear, the nut member inserted into the accommodation hole opened on the upper surface of the cylinder head and the female screw formed on the inner periphery of the nut member are screw-engaged. An adjusting screw having a male screw on the outer periphery, and a return spring that urges the adjusting screw in a direction protruding upward from the nut member. The protruding end of the adjusting screw from the nut member holds the arm of the valve gear. There is known one that can swingably (Patent Document 1).

  Further, in the rocker arm type valve gear, the screw member is engaged with a nut member inserted into a receiving hole opened in the lower surface of the arm that swings according to the rotation of the cam, and a female screw formed on the inner periphery of the nut member. An adjusting screw having a male screw on the outer periphery thereof, and a return spring for biasing the adjusting screw in a direction protruding downward from the nut member, and a protruding end of the adjusting screw from the nut member What presses a valve stem is known (patent document 2).

  In the direct valve operating apparatus, a lifter body that is slidably inserted into a guide hole formed in the cylinder head, a nut member that moves up and down integrally with the lifter body, and an inner periphery of the nut member An adjustment screw having a male screw on its outer periphery that engages with the formed female screw, and a return spring that urges the adjustment screw in a direction that protrudes downward from the nut member, from the nut member of the adjustment screw A device that presses a valve stem of a valve operating device at a protruding end is known (Patent Document 3).

  In these lash adjusters, the male screw of the adjusting screw and the female screw of the nut member are the pressure side flank that receives pressure when a load in the direction in which the adjusting screw is pushed into the nut member (hereinafter referred to as the “pushing direction”) is applied. The flank angle is formed in a sawtooth shape larger than the flank angle of the play side flank, and when a static load in the push-in direction is applied to the adjustment screw, it is adjusted by the frictional resistance between the pressure side flank of the male screw and the female screw. When the screw is prevented from rotating and, on the other hand, when a static load in the protruding direction is applied to the adjusting screw, the adjusting screw is allowed to rotate by sliding between the play side flank of the male screw and the female screw.

  Therefore, when a load in the pushing direction is applied to the adjustment screw due to the rotation of the cam, the pressure side flank of the male screw is received by the pressure side flank of the female screw, and the axial position of the adjustment screw is fixed. Strictly speaking, a slight slip occurs between the pressure flank of the male screw and the female screw at this time, and the adjustment screw moves in the pushing direction due to the sliding, but when the cam further rotates and the load in the pushing direction is released. In addition, the adjustment screw moves in the protruding direction due to the load in the protruding direction applied from the return spring, and returns to the original position.

  In addition, when the gap between the components of the valve operating device becomes large due to thermal expansion of the valve operating device, the cam is further pushed than the adjustment screw is pushed in when the load in the pushing direction is applied by the cam. The amount of protrusion of the adjusting screw when the load in the pushing direction is released by rotation is increased. As a result, each time the cam rotates, the adjustment screw gradually moves in the protruding direction to absorb the change in the gap between the constituent members of the valve gear.

On the other hand, when the gap between the components of the valve operating device becomes small, the cam rotates further than the amount of pushing of the adjusting screw when the load in the pushing direction is applied by the cam. The protruding amount of the adjusting screw when released is reduced. As a result, each time the cam rotates, the adjustment screw gradually moves in the push-in direction to absorb the change in the gap between the constituent members of the valve gear.
JP 2005-273510 A JP 2006-132426 A Japanese Patent No. 3641355

  By the way, the lash adjuster of the swing arm type valve device or the rocker arm type valve device falls over the adjustment screw due to a deviation between the moving direction of the arm and the moving direction of the valve stem when the valve stem is pushed down by the arm. A moment may act. In addition, the lash adjuster of the direct type valve operating device may also be subject to a tilting moment on the adjusting screw due to dimensional errors of the components of the valve operating device and play between the components of the valve operating device.

  However, in each lash adjuster, the male screw and the female screw are both parallel screws. Load tends to concentrate on the edge.

  For this reason, each of the lash adjusters is likely to wear at the axial ends of the male screw and the female screw, and the friction coefficient between the pressure side flank of the male screw and the female screw may be reduced. In this case, every time the cam rotates, abnormal noise due to slippage between the pressure side flank of the male screw and female screw may occur, or the adjusting screw moves in the pushing direction each time the cam rotates, resulting in a decrease in valve lift. This may reduce fuel consumption. Further, if the axial clearance between the male screw and the female screw becomes excessive due to wear, an abnormal noise may occur due to a collision between the pressure side flank of the male screw and the female screw every time the cam rotates.

  The problem to be solved by the present invention is to provide a lash adjuster in which the load is less likely to concentrate on the axial ends of the male screw and the female screw when a falling moment acts on the adjusting screw.

  In order to solve the above-described problem, at least one of the male screw and the female screw is a taper screw that contacts the other screw in a state where a tilting moment is applied to the adjusting screw.

  In this way, when a falling moment is applied to the adjusting screw, the part of the male screw and female screw that is the tapered thread contacts the other screw, and the load is distributed to the contact part. Compared with the lash adjuster in which both the female screw and the female screw are parallel screws, the load is less likely to concentrate on the axial ends of the male screw and the female screw.

The above configuration can be applied to the following lash adjuster, for example.
1) The nut member is inserted into a receiving hole opened in the upper surface of the cylinder head, and the adjusting screw swingably supports the arm of the valve operating device at a protruding end from the nut member. Rush adjuster for equipment.
2) The nut member is fixed to a lifter body that is slidably inserted into a guide hole formed in a cylinder head, and the adjustment screw presses a valve stem of a valve operating device at a protruding end from the nut member. Rush adjuster for direct valve operating.
3) The nut member is inserted into a receiving hole opened on the lower surface of the arm that swings in accordance with the rotation of the cam, and the adjustment screw presses the valve stem of the valve gear at the protruding end from the nut member. Rush adjuster for rocker arm type valve gear.

  Of the male screw and the female screw, the female screw may be a parallel screw, and a part or all of the male screw may be a tapered screw whose effective diameter gradually decreases toward the insertion end of the adjusting screw into the nut member. If it does in this way, a taper screw can be processed easily and it is low-cost.

  Furthermore, it is preferable that at least one of the pressure side flank of the male screw and the pressure side flank of the female screw is a matte surface having a surface roughness of Ra 0.4 or more. In this way, even when the pressure side flank of the male screw and the pressure side flank of the female screw are worn due to long-term use, the unevenness of the matte surface of the pressure side flank is large compared to the amount of wear, and the pressure side flank The surface of the flank is difficult to be smooth. Therefore, it is possible to more effectively prevent a reduction in the friction coefficient between the pressure side flank of the male screw and the female screw.

  Here, the satin finish may be formed by electric discharge machining or laser machining, but if it is formed by shot peening, the pressure side flank can be cured to increase durability.

  When the axial clearance between the male screw and the female screw is set in a range of 0.2 to 0.4 mm, the engine stops at a high temperature, and then the engine cools and contracts between the components of the valve gear. When the difference occurs, the contraction difference can be absorbed by the axial gap between the male screw and the female screw. Therefore, when the engine is restarted, there is no compression leakage due to the contraction difference between the constituent members of the valve gear.

  In the lash adjuster of the present invention, when a falling moment is applied to the adjusting screw, the load is less likely to concentrate on the axial ends of the male screw and the female screw. Therefore, local wear of the male screw and the female screw is unlikely to occur, and stable performance can be exhibited over a long period of time.

  FIG. 1 shows a valve gear incorporating a lash adjuster 1 according to a first embodiment of the present invention. This valve operating apparatus has a valve 4 provided in an intake port 3 of an engine cylinder head 2, a valve stem 5 connected to the valve 4, and an arm 7 that swings in response to rotation of a cam 6. .

  The valve stem 5 extends upward from the valve 4 and slidably penetrates the cylinder head 2. An annular spring retainer 8 is fixed to the upper outer periphery of the valve stem 5, and a valve spring 9 is incorporated between the lower surface of the spring retainer 8 and the upper surface of the cylinder head 2. The valve spring 9 urges the valve stem 5 upward via the spring retainer 8, and the valve 4 is seated on the valve seat 10 by the urging force.

  One end of the arm 7 is supported by the lash adjuster 1, and the other end is in contact with the upper end of the valve stem 5. A roller 11 is attached to the central portion of the arm 7, and the roller 11 is in contact with a cam 6 provided above the arm 7. The cam 6 is integrally formed with a camshaft 12 that rotates in synchronization with the crankshaft (not shown) of the engine. When the camshaft 12 rotates, a cam crest 6b that is raised with respect to the base circle 6a is formed. The arm 7 is pushed down via the roller 11.

  As shown in FIG. 2, the lash adjuster 1 is screwed into a cylindrical nut member 14 inserted into a receiving hole 13 opened in the upper surface of the cylinder head 2 and a female screw 15 formed on the inner periphery of the nut member 14. The adjusting screw 17 has a male screw 16 to be fitted on the outer periphery of the lower portion, a bottom member 18 fixed to the lower end of the nut member 14, and a return spring 19 incorporated between the adjusting screw 17 and the bottom member 18.

  The return spring 19 has a lower end supported by the bottom member 18 and an upper end pressing the adjustment screw 17 via the spring seat 20, and the adjustment screw 17 is protruded upward from the nut member 14 by the pressing. It is fast.

  As shown in FIG. 1, the adjustment screw 17 has a protruding end 21 from the nut member 14 formed in a hemispherical shape, and the protruding end 21 fits into a recess 22 formed on the lower surface of the end of the arm 7. is doing. Here, the protruding end 21 is slidably in contact with the inner surface of the recess 22 and supports the arm 7 so as to be swingable by the sliding.

  As shown in FIG. 2, the bottom member 18 has a through hole 23 penetrating vertically, and an oil drain hole 24 communicating with the through hole 23 is formed on the inner bottom surface of the accommodation hole 13. . Therefore, the engine oil that has flowed into the nut member 14 from the upper end surface of the nut member 14 through the gap between the male screw 16 and the female screw 15 passes through the through hole 23 and the oil drain hole 24 in order, and is discharged from the nut member 14. .

  The male screw 16 and the female screw 15 have a sawtooth shape in which the flank angle of the pressure side flank 25 that receives pressure when a load in the direction of pushing the adjusting screw 17 into the nut member 14 is applied is larger than the flank angle of the play side flank 26. When the static load in the pushing direction is applied to the adjustment screw 17, the rotation of the adjustment screw 17 is prevented by the frictional resistance between the pressure side flanks 25, 25 of the male screw 16 and the female screw 15, When a static load in the protruding direction is applied to the adjustment screw 17, the adjustment screw 17 is allowed to rotate by sliding between the play side flanks 26, 26 of the male screw 16 and the female screw 15. As the male screw 16 and the female screw 15, for example, those having a flank angle of the pressure side flank 25 of 75 ° and a flank angle of the play side flank 26 of 15 ° can be employed.

  As shown in FIG. 3, the male screw 16 includes a parallel screw portion 16A having a constant effective diameter, and a taper screw whose effective diameter gradually decreases from the parallel screw portion 16A toward the insertion end of the adjusting screw 17 into the nut member 14. Part 16B. On the other hand, as shown in FIG. 2, the female screw 15 is a parallel screw having a constant effective diameter. As a result, a radial play that gradually increases toward the insertion end of the adjusting screw 17 into the nut member 14 is formed between the male screw 16 and the female screw 15.

  The pressure-side flank 25 of the male screw 16 is a matte surface having a surface roughness Ra of 0.4 or more by performing shot peening. This satin can be formed by shot peening using sharp-angled media, and when the adjustment screw 17 is subjected to heat treatment (for example, carburizing or nitriding), shot peening is performed before the heat treatment. Can be formed. The surface roughness Ra is based on JIS0601 (product geometric characteristic specification (GPS) -surface property: contour curve method-terminology, definition and surface property parameter).

  In addition, an axial gap is provided between the male screw 16 and the female screw 15, and the axial gap is set in a range of 0.2 to 0.4 mm.

  Next, an operation example of the lash adjuster 1 will be described.

  When the cam 6 is rotated by the operation of the engine and the cam crest 6b of the cam 6 pushes down the arm 7, the valve 4 is separated from the valve seat 10 and the intake port 3 is opened. At this time, a load in the pushing direction is applied to the adjustment screw 17, but the pressure side flank 25 of the male screw 16 is received by the pressure side flank 25 of the female screw 15, and the axial position of the adjustment screw 17 is fixed.

  When the cam 6 further rotates and the cam crest 6b passes the position of the roller 11, the valve stem 5 is raised by the urging force of the valve spring 9, the valve 4 is seated on the valve seat 10, and the intake port 3 is close.

  Strictly speaking, when the cam crest 6b of the cam 6 pushes down the arm 7, a slight slip occurs between the pressure-side flanks 25, 25 of the male screw 16 and the female screw 15, and the adjustment screw 17 moves in the pushing direction by the slip. However, when the cam crest 6b passes the position of the roller 11 and the load in the pushing direction is released, the adjusting screw 17 moves in the protruding direction by the load in the protruding direction loaded from the return spring 19, Return to the original position.

  During engine operation, when a difference in thermal expansion occurs between the components of the valve operating device such as the cylinder head 2, the valve stem 5, and the arm 7, and the distance between the cam 6 and the arm 7 increases, The amount of protrusion of the adjusting screw 17 when the cam 6 rotates and the load in the pushing direction is released is larger than the amount of pushing of the adjusting screw 17 when the cam crest 6b pushes down the arm 7. As a result, each time the cam 6 rotates, the adjusting screw 17 gradually moves in the protruding direction, so that no gap is generated between the base circle 6 a of the cam 6 and the roller 11.

  On the contrary, when the contact surface of the valve 4 and the valve seat 10 is worn, the biasing force of the valve spring 9 acts on the adjustment screw 17 even when the base circle 6a of the cam 6 is at the position of the roller 11. The amount of protrusion of the adjusting screw 17 when the cam 6 rotates and the load in the pushing direction is released is smaller than the amount of pushing of the adjusting screw 17 when the cam crest 6b of the cam 6 pushes down the arm 7. As a result, each time the cam 6 rotates, the adjustment screw 17 gradually moves in the pushing direction and the valve stem 5 rises, so that no gap is generated between the contact surfaces of the valve 4 and the valve seat 10.

  When the lash adjuster 1 pushes down the valve stem 5 with the arm 7, a tilting moment may act on the adjusting screw 17 due to a shift between the moving direction of the arm 7 and the moving direction of the valve stem 5. In this case, since the taper screw portion 16B of the male screw 16 contacts the female screw 15 and the load is distributed to the contact portion, the male screw 16 and the female screw are compared with the lash adjuster in which the male screw 16 and the female screw 15 are both parallel screws. The load is less likely to concentrate on the 15 axial ends. Therefore, local wear of the male screw 16 and the female screw 15 is unlikely to occur, and stable performance can be exhibited over a long period of time.

  Further, the lash adjuster 1 has a large uneven height of the matte surface of the pressure side flank 25 even when the pressure side flank 25 of the male screw 16 is worn due to long-term use. The surface of the pressure side flank 25 is difficult to be smooth. Therefore, the lash adjuster 1 can effectively prevent the friction coefficient between the pressure side flank 25, 25 of the male screw 16 and the female screw 15 from being lowered.

  Further, in this lash adjuster 1, since the axial clearance between the male screw 16 and the female screw 15 is 0.2 mm or more, the engine stops at a high temperature, and then the engine cools and contracts between the components of the valve gear. When a difference occurs, the contraction difference can be absorbed by the axial gap between the male screw 16 and the female screw 15. Therefore, when the engine is restarted, a gap due to a contraction difference between the constituent members of the valve operating device does not occur between the valve 4 and the valve seat 10, and compression leakage does not occur.

  As shown in the above embodiment, when the male screw 16 and the female screw 15 are parallel screws and the male screw 16 is composed of the parallel screw portion 16A and the taper screw portion 16B, the taper screw can be easily processed. Although low in cost, as shown in FIG. 4, the male screw 16 is a parallel screw, the female screw 15 is a parallel screw portion 15A, and the taper whose effective diameter gradually increases from the parallel screw portion 15A toward the back of the nut member 14. You may comprise with the thread part 15B.

  In this embodiment, a part of the male screw 16 is a taper screw, but the whole male screw 16 may be a taper screw whose effective diameter gradually decreases toward the insertion end of the adjustment screw 17 into the nut member 14. . Similarly, in the nut member 14 shown in FIG. 4, the entire female screw 15 can be a taper screw whose effective diameter gradually increases toward the back of the nut member 14.

  In this embodiment, of the pressure side flank 25 of the male screw 16 and the female screw 15, the pressure side flank 25 of the male screw 16 is a matte finish. However, the pressure side flank of the female screw 15 is replaced with the pressure side flank 25 of the male screw 16. 25 may be satin having a surface roughness Ra of 0.4 or more. Even in this case, the unevenness height of the satin finish is large as compared with the wear amount of the pressure side flank 25 due to long-term use, so that a reduction in the friction coefficient between the pressure side flank 25 and 25 is effectively prevented. It becomes possible. Further, the pressure side flank 25 of the male screw 16 and the female screw 15 may be satin having a surface roughness of Ra 0.4 or more.

  FIG. 5 shows a valve gear incorporating a lash adjuster 31 according to the second embodiment of the present invention. Similar to the first embodiment, this valve operating apparatus has a valve 34 provided in the intake port 33 of the cylinder head 32 and a valve stem 35 connected to the valve 34. The valve stem 35 extends upward from the valve 34, and a spring retainer 36 is fixed to the upper portion of the valve stem 35. The spring retainer 36 is biased upward by a valve spring 37, and the valve 34 is seated on the valve seat 38 by the biasing force.

  As shown in FIGS. 5 and 6, the lash adjuster 31 includes a lifter body 40 that is slidably inserted into a guide hole 39 formed in the cylinder head 32, and a nut member 41 that moves up and down integrally with the lifter body 40. The nut member 41 includes an adjustment screw 44 having a male screw 43 that engages with a female screw 42 formed on the inner periphery thereof, and a return spring 45 that biases the adjustment screw 44.

  As shown in FIG. 6, the lifter body 40 includes a cylindrical portion 46 and an end plate 47 provided at the upper end of the cylindrical portion 46. A cam 48 is provided above the lifter body 40. The cam 48 is integrally formed with a camshaft 49 that rotates in synchronization with the crankshaft (not shown) of the engine. When the camshaft 49 rotates, a cam crest 48b that is raised with respect to the base circle 48a is formed. The lifter body 40 is pushed down by pressing the upper surface of the end plate 47 (see FIG. 5).

  The nut member 41 is fixed to the lower surface of the end plate 47 with a retaining ring 50. The return spring 45 is incorporated between the adjustment screw 44 and the end plate 47 and urges the adjustment screw 44 in a direction protruding downward from the nut member 41.

  The adjustment screw 44 has a protruding end from the nut member 41 in contact with the spacer 51 and presses the upper end of the valve stem 35 via the spacer 51. The spacer 51 is prevented from rotating with respect to the nut member 41 by a retainer 52 and can move up and down within a range of a notch 53 formed in the retainer 52.

  The end plate 47 is formed with an oil passage hole 54 penetrating vertically, so that the engine oil splashed on the upper surface of the end plate 47 is introduced into the nut member 41 through the oil passage hole 54. It has become. The engine oil introduced into the nut member 41 lubricates the male screw 43 and the female screw 42.

  The male screw 43 and the female screw 42 have a sawtooth shape in which the flank angle of the pressure flank 55 that receives pressure when a load in the direction of pushing the adjusting screw 44 into the nut member 41 is applied is larger than the flank angle of the play flank 56. When the static load in the pushing direction is applied to the adjustment screw 44, the adjustment screw 44 is prevented from rotating by the frictional resistance between the pressure side flank 55, 55 of the male screw 43 and the female screw 42, When a static load in the protruding direction is applied to the adjustment screw 44, the adjustment screw 44 is allowed to rotate by sliding between the play side flanks 56, 56 of the male screw 43 and the female screw 42.

  As shown in FIG. 7, the male screw 43 is a taper screw whose effective diameter gradually decreases toward the insertion end of the adjusting screw 44 into the nut member 41. On the other hand, as shown in FIG. 6, the female screw 42 is a parallel screw having a constant effective diameter. As a result, a radial play that gradually increases toward the insertion end of the adjusting screw 44 into the nut member 41 is formed between the male screw 43 and the female screw 42.

  The pressure-side flank 55 of the male screw 43 is a matte surface having a surface roughness Ra of 0.4 or more by performing shot peening.

  An axial gap is provided between the male screw 43 and the female screw 42, and the axial gap is set in a range of 0.2 to 0.4 mm.

  In the lash adjuster 31, when the cam crest 48b of the cam 48 pushes down the lifter body 40 and a load in the pushing direction is applied to the adjustment screw 44, the pressure side flank 55 of the male screw 43 42, the axial position of the adjusting screw 44 relative to the nut member 41 is fixed. At this time, strictly speaking, slight slip occurs between the pressure side flanks 55 and 55 of the male screw 43 and the female screw 42, and the adjustment screw 44 moves in the pushing direction due to the sliding, but the cam 48 further rotates to push in the pushing direction. When the load is released, the adjustment screw 44 moves in the protruding direction due to the load in the protruding direction applied from the return spring 45, and returns to the original position.

  When the lash adjuster 31 pushes down the valve stem 35 with the adjusting screw 44, a tilting moment is applied to the adjusting screw 44 due to a dimensional error of a component of the valve operating device or play between the components of the valve operating device. However, in this case, the male screw 43, which is a tapered screw, contacts the female screw 42, and the load is distributed to the contact portion. Therefore, compared to the lash adjuster in which the male screw 43 and the female screw 42 are both parallel screws, The load is less likely to concentrate on the axial ends of the male screw 43 and the female screw 42. Therefore, local wear of the male screw 43 and the female screw 42 hardly occurs, and stable performance can be exhibited over a long period of time.

  In addition, the lash adjuster 31 has a large uneven height of the matte surface of the pressure side flank 55 even when the pressure side flank 55 of the male screw 43 is worn due to long-term use. The surface of the pressure side flank 55 is difficult to be smooth. Therefore, the lash adjuster 31 can effectively prevent a decrease in the friction coefficient between the pressure side flank 55, 55 of the male screw 43 and the female screw 42.

  Further, the lash adjuster 31 has an axial clearance between the male screw 43 and the female screw 42 of 0.2 mm or more, so that the engine stops at a high temperature, and then the engine cools and contracts between the components of the valve gear. When the difference occurs, the contraction difference can be absorbed by the axial gap between the male screw 43 and the female screw 42. Therefore, when the engine is restarted, a gap due to a contraction difference between the constituent members of the valve operating device does not occur between the valve 34 and the valve seat 38, and compression leakage does not occur.

  As shown in the above embodiment, when the male screw 43 and the female screw 42 are parallel screws and the male screw 43 is a taper screw, the taper screw can be easily processed and the cost is low. Parallel screws may be used, and the female screw 42 may be a taper screw whose effective diameter gradually increases toward the back of the nut member 41. The female screw 42 is a parallel screw, and the male screw 43 is composed of a parallel screw portion and a taper screw portion whose effective diameter gradually decreases from the parallel screw portion toward the insertion end of the adjusting screw 44 to the nut member 41. May be.

  In this embodiment, of the pressure side flank 55 of the male screw 43 and the female screw 42, the pressure side flank 55 of the male screw 43 is a matte finish. However, the pressure side flank 55 of the female screw 42 is replaced with the pressure side flank 55 of the male screw 43. 55 may be a satin having a surface roughness Ra of 0.4 or more. Further, the pressure side flank 55 of the male screw 43 and the female screw 42 may be a satin surface having a surface roughness Ra of 0.4 or more.

  FIG. 8 shows a valve gear incorporating a lash adjuster 61 according to a third embodiment of the present invention. This valve operating apparatus has a valve 64 provided in an intake port 63 of a cylinder head 62 of the engine, a valve stem 65 connected to the valve 64, and an arm 67 that swings according to the rotation of a cam 66. .

  The valve stem 65 extends upward from the valve 64, and a spring retainer 68 is fixed to the upper portion of the valve stem 65. The spring retainer 68 is biased upward by a valve spring 69, and the valve 64 is seated on the valve seat 70 by the biasing force.

  The arm 67 is supported at the center by a fulcrum shaft 71 so as to be swingable. A roller 72 that contacts the cam 66 is attached to one end of the arm 67, and a lash adjuster 61 is incorporated into the other end of the arm 67. A cam 66 provided below the arm 67 is integrally formed with a camshaft 73 that rotates in synchronization with an engine crankshaft (not shown). When the camshaft 73 rotates, the cam 66 rotates relative to the base circle 66a. The raised cam crest 66b presses the roller to swing the arm.

  As shown in FIG. 9, the lash adjuster 61 includes a nut member 74, an adjustment screw 75, and a return spring 76. The nut member 74 is inserted into a receiving hole 77 that penetrates the arm 67 vertically, and a female screw 78 formed on the inner periphery of the nut member 74 is engaged with a male screw 79 formed on the outer periphery of the adjusting screw 75. is doing.

  The upper end of the nut member 74 protrudes from the upper surface of the arm 67, and a bottomed cylindrical cap 80 is fitted and fixed to the protruding portion. The cap 80 is engaged with the upper edge of the receiving hole 77 to prevent the nut member 74 from dropping downward from the receiving hole 77. On the other hand, a flange 81 that contacts the lower surface of the arm 67 is formed at the lower end of the nut member 74, and the upward force acting on the nut member 74 is received by the flange 81.

  The return spring 76 has an upper end supported by the cap 80 and a lower end that presses the adjustment screw 75, and urges the adjustment screw 75 to protrude downward from the nut member 74 by the pressing. The protruding end of the adjusting screw 75 from the nut member 74 presses the upper end of the valve stem 65 (see FIG. 8).

  An oil passage hole 82 penetrating vertically is formed in the cap 80, and the engine oil splashed by the arm 67 is introduced into the nut member 74 through the oil passage hole 82. . The lubricating oil introduced into the nut member 74 lubricates the male screw 79 and the female screw 78.

  The male screw 79 and the female screw 78 have a sawtooth shape in which the flank angle of the pressure side flank 83 that receives pressure when a load in the direction of pushing the adjusting screw 75 into the nut member 74 is applied is larger than the flank angle of the play side flank 84. When the static load in the pushing direction is applied to the adjustment screw 75, the rotation of the adjustment screw 75 is prevented by the frictional resistance between the pressure side flanks 83, 83 of the male screw 79 and the female screw 78, When a static load in the protruding direction is applied to the adjustment screw 75, the adjustment screw 75 is allowed to rotate by sliding between the play side flank 84, 84 of the male screw 79 and the female screw 78.

  The male screw 79 includes a parallel screw portion 79A having a constant effective diameter, and a tapered screw portion 79B having an effective diameter gradually decreasing from the parallel screw portion 79A toward the insertion end of the adjusting screw 75 into the nut member 74. On the other hand, the female screw 78 is a parallel screw having a constant effective diameter. As a result, a radial play that gradually increases toward the insertion end of the adjusting screw 75 into the nut member 74 is formed between the male screw 79 and the female screw 78.

  The pressure-side flank 83 of the male screw 79 is a matte surface having a surface roughness Ra of 0.4 or more by performing shot peening.

  An axial gap is provided between the male screw 79 and the female screw 78, and the axial gap is set in a range of 0.2 to 0.4 mm.

  In the lash adjuster 61, when the cam crest 66b of the cam 66 pushes up the end of the arm 67 and a load in the pushing direction is applied to the adjusting screw 75, as in the first embodiment, the pressure side flank of the male screw 79 is applied. 83 is received by the pressure side flank 83 of the female screw 78, and the axial position of the adjusting screw 75 with respect to the nut member 74 is fixed. At this time, strictly speaking, a slight slip occurs between the pressure side flanks 83 and 83 of the male screw 79 and the female screw 78, and the adjustment screw 75 moves in the pushing direction due to the sliding, but the cam 66 further rotates to push in the pushing direction. When the load is released, the adjustment screw 75 is moved in the protruding direction by the load in the protruding direction loaded from the return spring 76 and returns to the original position.

  When the lash adjuster 61 pushes down the valve stem 65 with the arm 67, a tilting moment may act on the adjusting screw 75 due to a shift between the moving direction of the arm 67 and the moving direction of the valve stem 65. In this case, since the taper screw portion 79B of the male screw 79 contacts the female screw 78 and the load is distributed to the contact portion, the male screw 79 and the female screw are compared with the lash adjuster in which the male screw 79 and the female screw 78 are both parallel screws. The load is less likely to concentrate on the axial end of 78. Therefore, local wear of the male screw 79 and the female screw 78 is unlikely to occur, and stable performance can be exhibited over a long period of time.

  In addition, the lash adjuster 61 has a large uneven height of the matte surface of the pressure side flank 83 even when the pressure side flank 83 of the male screw 79 is worn due to long-term use. The pressure side flank 83 is difficult to be smooth. Therefore, the lash adjuster 61 can effectively prevent the friction coefficient between the pressure side flanks 83 of the male screw 79 and the female screw 78 from decreasing.

  Further, the lash adjuster 61 has an axial clearance between the male screw 79 and the female screw 78 of 0.2 mm or more, so that the engine stops at a high temperature, and then the engine cools and contracts between the components of the valve gear. When the difference occurs, the contraction difference can be absorbed by the axial gap between the male screw 79 and the female screw 78. Therefore, when the engine is restarted, a gap due to a contraction difference between the constituent members of the valve operating device does not occur between the valve 64 and the valve seat 70, and compression leakage does not occur.

  As shown in the above embodiment, when the male screw 79 and the female screw 78 are parallel screws and the male screw 79 is composed of a parallel screw portion 79A and a taper screw portion 79B, the taper screw can be easily processed. Although the cost is low, the male screw 79 may be a parallel screw, and the female screw 78 may be constituted by a parallel screw portion and a taper screw portion whose effective diameter gradually increases from the parallel screw portion toward the back of the nut member 74. . In this embodiment, a part of the male screw 79 is a taper screw, but the whole male screw 79 may be a taper screw whose effective diameter gradually decreases toward the insertion end of the adjusting screw 75 into the nut member 74. .

  In this embodiment, of the pressure side flank 83 of the male screw 79 and the female screw 78, the pressure side flank 83 of the male screw 79 is a matte surface, but the pressure side flank of the female screw 78 is replaced with the pressure side flank 83 of the male screw 79. 83 may be a satin having a surface roughness Ra of 0.4 or more. Further, the pressure side flank 83 of the male screw 79 and the female screw 78 may both be satin having a surface roughness of Ra 0.4 or more.

The front view which shows the valve operating apparatus incorporating the lash adjuster of 1st Embodiment of this invention 1 is an enlarged cross-sectional view near the lash adjuster in FIG. Enlarged sectional view of the male screw shown in FIG. The expanded sectional view of the internal thread which shows the modification of the lash adjuster shown in FIG. The front view which shows the valve operating apparatus incorporating the lash adjuster of 2nd Embodiment of this invention. Fig. 5 is an enlarged cross-sectional view near the lash adjuster. Enlarged sectional view of the male screw shown in FIG. Front view showing a valve gear incorporating a lash adjuster according to a third embodiment of the present invention. FIG. 8 is an enlarged sectional view near the lash adjuster.

Explanation of symbols

1 Rush Adjuster 2 Cylinder Head 7 Arm 13 Receiving Hole 14 Nut Member 15 Female Thread 16 Male Thread 17 Adjusting Screw 19 Return Spring 21 Projecting End 25 Pressure Side Flank 26 Play Side Flank 31 Rush Adjuster 32 Cylinder Head 35 Valve Stem 39 Guide Hole 40 Lifter Body 41 Nut member 42 Female screw 43 Male screw 44 Adjust screw 45 Return spring 55 Pressure side flank 56 Play side flank 61 Rush adjuster 65 Valve stem 66 Cam 67 Arm 74 Nut member 75 Adjust screw 76 Return spring 77 Housing hole 78 Female screw 79 Male screw 83 Pressure side flank 84 Playing Frank

Claims (8)

A nut member (14) having an internal thread (15) on the inner periphery, an adjustment screw (17) having an external thread (16) threadedly engaged with the female thread (15) of the nut member (14), and the adjustment screw And a return spring (19) for urging the nut (17) in a direction protruding from the nut member (14). The male screw (16) and the female screw (15) are arranged so that the adjusting screw (17) A lash adjuster for a valve operating device in which the flank angle of the pressure side flank (25) that receives pressure when a load in the direction of pushing in is applied is larger than the flank angle of the idle side flank (26) In
A part or all of at least one of the male screw (16) and the female screw (15) is brought into contact with the other screw (15) in a state where a tilting moment is applied to the adjusting screw (17). Rush adjuster characterized by taper screw.   The nut member (14) is inserted into a receiving hole (13) opened on the upper surface of the cylinder head (2), and the adjustment screw (17) is moved by a protruding end (21) from the nut member (14). The lash adjuster according to claim 1, wherein the arm (7) of the valve device is swingably supported.   The nut member (41) is fixed to a lifter body (40) that is slidably inserted in a guide hole (39) formed in a cylinder head (32), and the adjustment screw (44) The lash adjuster according to claim 1, wherein the valve stem (35) of the valve gear is pressed by a protruding end from (41).   The nut member (74) is inserted into a receiving hole (77) opened in the lower surface of the arm (67) that swings according to the rotation of the cam (66), and the adjustment screw (75) 74. The lash adjuster according to claim 1, wherein the valve stem (65) of the valve gear is pressed by a protruding end from (74).   The female screw (15) is a parallel screw, and a part or all of the male screw (16) is a taper screw whose effective diameter gradually decreases toward an insertion end of the adjusting screw into the nut member. The lash adjuster according to any one of the above.   Of the pressure-side flank (25) of the male screw (16) and the pressure-side flank (25) of the female screw (15), at least one pressure-side flank (25) is a matte surface having a surface roughness Ra of 0.4 or more. The lash adjuster according to any one of claims 1 to 5.   The lash adjuster according to claim 6, wherein the satin is formed by shot peening.   The lash adjuster according to any one of claims 1 to 7, wherein an axial clearance between the male screw (16) and the female screw (15) is set in a range of 0.2 to 0.4 mm.

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