JP4745286B2 - Variable valve mechanism for internal combustion engine - Google Patents

Description

  The present invention supports the sub cam and the rocker arm on the control arm, and swings the control arm around the support shaft when transmitting the driving force of the valve cam to the engine valve via the sub cam and the rocker arm. The present invention relates to a variable valve mechanism for an internal combustion engine in which at least a valve lift of the engine valve is variable.

  Such a variable valve mechanism for an internal combustion engine has already been proposed by the present applicant in Japanese Patent Application No. 2005-132599.

  The control arm 19 of the variable valve mechanism of the internal combustion engine includes a pair of webs (side walls) 19a and 19a arranged in parallel to each other, and a connecting portion 19c (end wall portion) for connecting between one ends of the webs 19a and 19a. And a pair of shafts 19b, 19b projecting outward from the ends of the webs 19a, 19a opposite to the connecting portion 19c are swingable to the engine body. A sub cam and a pair of rocker arms are pivotally supported between the webs 19a and 19a.

  By the way, the drive means of the control arm of the conventional variable valve mechanism of the internal combustion engine is composed of a sector gear provided integrally with the control arm, a drive gear meshing with the sector gear, and an electric motor for driving the drive gear. However, it is conceivable to use a control cam rotated by an actuator and a cam follower provided on the control arm as a driving means for a control arm of a different type. In this case, if the cam follower does not reliably contact the control cam, there is a concern that the behavior of the control arm becomes unstable and the control accuracy of the valve lift of the engine valve decreases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to stabilize the behavior of a control arm of a variable valve mechanism of an internal combustion engine and increase the control accuracy of the valve lift of the engine valve.

  In order to achieve the above object, according to the first aspect of the present invention, the support arm is swingably supported by the control body supported by the engine body, and the swing support provided on the control arm. A control member that is movably supported and is in contact with the engine valve, and a control member that is swingably supported by the control arm and is driven by a valve cam to drive the rocker arm and is operated by an actuator. The variable valve mechanism of the internal combustion engine is capable of changing at least the valve lift of the engine valve by swinging the control arm around the support shaft portion, and attaches the control arm in a direction to contact the control member. Biasing means for biasing, and the biasing means biases a portion of the control arm provided with the swing support portion. Internal combustion engine of the variable valve mechanism is proposed that.

According to the second aspect of the present invention, in addition to the configuration of the first aspect, the swing support portion is a hydraulic tappet, and the urging means is on the combustion chamber side of the hydraulic tappet in the cylinder axial direction. A variable valve mechanism for an internal combustion engine is proposed.

  According to the invention described in claim 3, in addition to the configuration of claim 1 or claim 2, the control arm connects between the end portions of the pair of side wall portions each provided with the support shaft portion. There is proposed a variable valve mechanism for an internal combustion engine, comprising an end wall portion, wherein the urging means urges a pair of the swing support portions provided on the end wall portion.

  According to the invention described in claim 4, in addition to the configuration of any one of claims 1 to 3, the control member is a control cam that presses the control arm, and the control cam and A variable valve mechanism for an internal combustion engine is proposed in which the urging means is arranged in the same plane perpendicular to the cylinder row line direction.

  According to the invention described in claim 5, in addition to the structure of any one of claims 1 to 4, the guide cylinder of the urging means and the spark plug housing cylinder are integrally formed. A variable valve mechanism for an internal combustion engine is proposed.

  According to the invention described in claim 6, in addition to the configuration of claim 1 or 2, the control arm includes a pair of side wall portions provided with the support shaft portion, and a pair of the urging forces. A variable valve mechanism for an internal combustion engine is proposed in which the means biases the pair of side wall portions.

  According to the seventh aspect of the invention, in addition to the configuration of the sixth aspect, the guide cylinders of the pair of urging means are integrally connected to both sides in the cylinder row direction of the spark plug housing cylinder. A variable valve mechanism for an internal combustion engine is proposed.

  The cylinder head 11 of the embodiment corresponds to the engine body of the present invention, the intake valve 12 of the embodiment corresponds to the engine valve of the present invention, and the control cam 18 of the embodiment corresponds to the control member of the present invention. Correspondingly, the hydraulic tappet 31 of the embodiment corresponds to the rocking support portion of the rocker arm of the present invention.

  According to the configuration of the first aspect, the urging means urges the control arm in a direction to contact the control member, so that the control arm is prevented from being separated from the control member, and the behavior of the control arm is stabilized. The control accuracy of the valve lift of the valve can be increased. In addition, since the urging means urges a portion of the control arm where the rocker arm swinging support portion is provided with high rigidity, the deflection of the control arm due to the urging force of the urging means can be minimized.

According to the second aspect of the present invention, since the urging means is disposed on the combustion chamber side in the cylinder axis direction of the hydraulic tappet that supports the rocker arm so as to be swingable, the urging means is lubricated with oil discharged from the hydraulic tappet. can do.

  According to the third aspect of the present invention, the end wall portion that supports the pair of swing support portions and connects the end portions of the pair of side wall portions of the control arm has high rigidity. By biasing the pair of swing support portions with the biasing means, the deflection of the control arm can be minimized.

  According to the fourth aspect of the present invention, since the control cam and the urging means for pressing the control arm are arranged in the same plane perpendicular to the cylinder row line direction, the load applied from the control cam and the urging means causes the control arm to fall. It does not act in the direction, and the deflection of the control arm due to the load can be minimized.

  According to the fifth aspect of the present invention, since the guide cylinder of the urging means and the spark plug housing cylinder are integrally formed, the guide cylinder and the spark plug housing cylinder reinforce each other to increase the rigidity.

  According to the configuration of the sixth aspect, since the pair of side walls of the control arm are urged by the urging means, the highly rigid side wall of the control arm can be reliably urged. Moreover, by providing a pair of urging means, it is possible not only to distribute the urging force to prevent concentration of load and inclination of the control arm, but also to urge each individual urging means as compared with the case where one urging means is provided. Can be miniaturized to increase the degree of freedom in layout.

  According to the seventh aspect of the present invention, since the guide cylinders of the pair of urging means are integrally connected to both sides of the spark plug housing cylinder in the cylinder row line direction, the guide cylinder and the spark plug housing cylinder reinforce each other. In addition to improving the rigidity, the variable valve mechanism can be made closer to the cylinder row line in the direction orthogonal to the cylinder row line direction to achieve compactness.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1 to 10 show a first embodiment of the present invention. FIG. 1 is a longitudinal side view of an essential part of an internal combustion engine, FIG. 2 is a view taken along line 2-2 in FIG. 1, and FIG. 2 is a sectional view taken along line 3-3 in FIG. 2 in a valve lift state, FIG. 4 is a sectional view taken along line 4-4 in FIG. 2 in a high valve lift state, and FIG. 5 is a sectional view corresponding to FIG. 6 is a perspective view of the variable valve mechanism as seen from one direction, FIG. 7 is a perspective view of the variable valve mechanism as seen from the other direction, FIG. 8 is a perspective view of the control arm as seen from one direction, and FIG. FIG. 10 is a perspective view of the control arm as viewed from the other direction, and FIG. 10 is a view in the direction of arrows 10 in FIGS.

  As shown in FIGS. 1 and 2, a pair of intake valves 12, 12 is provided in the cylinder head 11 of the internal combustion engine so as to be opened and closed for each cylinder, and the intake valves 12, 12 are driven to open and close. The variable valve mechanism 13 includes a camshaft 15 provided with a valve cam 14 and shaft holes 11b and 11b of a pair of support walls 11a and 11a provided in the cylinder head 11 via support shafts 16 and 16, respectively. The control arm 17 is supported in a swingable manner, the control shaft 19 is provided with a control cam 18 for swinging the control arm 17, and is supported by the control arm 17 so as to be swingable through a movable support shaft 20. The sub-cam 21 that swings following the valve-operating cam 14 and the intake valves 12 and 12 are individually interlocked and connected to each other, and the sub-cam 21 is connected to the sub-cam 21. And a pair of rocker arms 22 and 22, it is possible to change the operating characteristics including the valve lift of the intake valves 12, 12 by displacing the movable support shaft 20.

  The stems 12a and 12a of the intake valves 12 and 12 are slidably fitted into guide cylinders 23 and 23 disposed in the cylinder head 11, and retainers 24 and 24 provided at the upper ends of the stems 12a and 12a, The intake valves 12 and 12 are urged in the valve closing direction by the valve springs 26 and 26 interposed between the retainers 25 and 25 in contact with the cylinder head 11.

  Next, the shape of the control arm 17 will be described with reference to FIGS.

  The control arm 17 is composed of a single member and includes a pair of plate-like side wall portions 27 and 27 provided with the pair of support shaft portions 16 and 16, respectively. These side wall portions 27 and 27 are arranged in parallel at a predetermined interval, and both side wall portions 27 and 27 are mutually connected by end wall portions 28 extending between the one end portions in parallel with the support shaft portions 16 and 16. The other end portions are connected to each other by a connecting wall portion 29 extending in parallel with the support shaft portions 16 and 16. That is, when viewed in the direction of FIG. 10, the control arm 17 is formed in a square frame shape by a pair of side wall portions 27, 27, an end wall portion 28, and a connecting wall portion 29. The rigidity of the control arm 17 is increased by the reinforcing effect of 29. In particular, the position where the connecting wall 29 is provided is in the vicinity of the support shafts 16, 16 where the largest load is applied to the control arm 17 so that the connecting wall 29 effectively contributes to improving the rigidity of the control arm 17. Is done.

  The side walls 27 and 27 of the control arm 17 are formed with shaft holes 27a and 27a into which the movable support shaft 20 is press-fitted, in addition to the support shafts 16 and 16 projecting integrally. The end wall portion 28 and the connecting wall portion 29 of the control arm 17 are integrally connected by a partition wall portion 30, and the rigidity of the control arm 17 is further enhanced by the reinforcing effect of the connecting wall portion 29.

  The pair of side wall portions 27 and 27 and the partition wall portion 30 extend in parallel with each other, and two rocker arm accommodation holes 17a and 17a are formed between them. A pair of roller support portions 30a and 30a rises upward at a position near the end wall portion 28 of the partition wall portion 30, and a shaft hole into which a roller shaft 47 described later is press-fitted into these roller support portions 30a and 30a. 30b and 30b are formed. A roller accommodating recess 30c is formed between the pair of roller support portions 30a, 30a, and a part of the bottom wall of the roller accommodating recess 30c is constituted by the end wall portion 28.

  A pair of hydraulic tappet attachment holes 28a and 28a to which hydraulic tappets 31 and 31 described later are attached are formed in the end wall portion 28 so as to face the rocker arm accommodation holes 17a and 17a. The end wall portion 28 is formed with oil discharge holes 28b and 28b communicating with the hydraulic tappet mounting holes 28a and 28a, and the oil discharged from the hydraulic tappets 31 and 31 is downward through the oil discharge holes 28b and 28b. Fall. The connecting wall portion 29 is formed with a biasing means mounting hole 29a to which a biasing means 42 described later is mounted.

  As apparent from FIGS. 2 to 7, the rocker arms 22 and 22 are of a type having no rocker shaft, and a recess 22a formed at one end thereof is mounted in the hydraulic tappet mounting hole 28a of the end wall 28. The hydraulic tappet 31 is swingably supported by the spherical bearing 31a at the tip, and the intake valve 12 is driven at the other end. That is, a contact member 32 that contacts the upper end of the stem 12a of the intake valve 12 is slidably supported at the other end of the rocker arm 22, and the position of the contact member 32 is adjusted with an adjustment screw 33 and a lock nut 34. The seating state of the intake valve 12 can be adjusted by adjusting at. A roller 37 is rotatably supported via a ball bearing 36 on a roller shaft 35 that bridges a roller accommodation hole 22b formed in an intermediate portion of the rocker arm 22.

  The rocker arms 22 and 22 are accommodated so as to be fitted into rocker arm accommodation holes 17 a and 17 a sandwiched between the pair of side wall portions 27 and 27 and the partition wall portion 30 of the control arm 17. The rocker arm 22 having no rocker shaft has one end abutting against the hydraulic tappet 31, the other end abutting against the stem 12 a of the intake valve 12, and the central roller 37 only abutting against the sub cam 21 and being supported. There is a concern that the assembly work becomes difficult because the posture is unstable and easy to fall. However, in the present embodiment, the rocker arms 22 and 22 are sandwiched on both sides by the side wall portions 27 and 27 and the partition wall portion 30 to prevent the rocker arms from falling down, thereby facilitating the assembling work.

  A support shaft 38 is press-fitted into shaft holes 27a, 27a formed in the pair of side wall portions 27, 27 of the control arm 17, and the sub cam 21 is supported by the support shaft 38 so as to be swingable. A roller 41 is supported via a roller shaft 39 and a ball bearing 40 on a first arm 21 a that protrudes from the central portion in the axial direction of the sub cam 21, and this roller 41 comes into contact with the valve cam 14 provided on the cam shaft 15. . Cam surfaces 21c and 21c are formed on a pair of second arms 21b and 21b protruding from both axial ends of the sub cam 21, and the rollers 37 and 37 of the rocker arms 22 and 22 are formed on these cam surfaces 21c and 21c. Abut.

  A biasing means 42 that generates a biasing force that causes the roller 41 of the sub cam 21 to contact the valve cam 14 is mounted in a biasing means mounting hole 29 a formed in the connecting wall portion 29 of the control arm 17. The urging means 42 is provided at the upper end of the pressing member 44, a guide cylinder 43 that is press-fitted into the urging means attachment hole 29 a of the connecting wall portion 29, a pressing member 44 that is slidably fitted into the guide cylinder 43. The contact portion 45 that contacts the lower surface of the first arm 21a of the sub cam 21 and the coil spring 46 that is contracted between the guide tube 43 and the contact portion 45 and biases the pressing member 44 in the protruding direction. The

Of the control arm 17, the portion where the connecting wall portion 29 and the partition wall portion 30 are connected is a highly rigid portion, and since the biasing means 42 is supported on this portion, the biasing means 42 attaches the sub cam 21. The bending deformation of the control arm 17 due to the reaction force of the energizing force can be minimized. Further, the urging means 42, the roller 41 of the sub cam 21 and the valve cam 14 are arranged in the same plane (in the plane of FIG. 4) orthogonal to the cylinder row line. With this arrangement, the load from the valve cam 14 and the load from the urging means 42 do not act in the direction in which the control arm 17 is tilted (inclined with respect to the paper surface of FIG. 4). Roller receiving recess 30c formed in the center of the partition wall 30 of the control arm 17 can improve the control accuracy of the valve lift of the intake valves 12, 12 while minimizing the bending deformation. The roller support portions 30a, 30a A roller 49 rotatably supported via a ball bearing 48 is accommodated in a roller shaft 47 press-fitted into the shaft holes 30b, 30b. A control shaft 19 having a cam surface formed of an involute curve on the control shaft 19 reciprocally rotated by an actuator 50 constituted by an electric motor so as to press the roller 49 and swing the control arm 17 around the support shaft portions 16 and 16. A cam 18 is provided. 3 to 5, when the control shaft 19 rotates clockwise, the control arm 17 swings counterclockwise around the support shafts 16 and 16, and when the control shaft 19 rotates counterclockwise, the control arm 19 17 swings around the support shafts 16 and 16 in the clockwise direction.

  A biasing means 51 is provided on the cylinder head 1 so as to bias the control arm 17 clockwise and bring the roller 49 into contact with the control cam 18. The urging means 51 slidably fits the pressing member 53 into the guide cylinder 52 press-fitted into the cylinder head 11, and the pressing member 53 protrudes from the guide cylinder 52 by the elastic force of the coil spring 54. The spherical portion 53 a at the upper end of the pressing member 53 comes into contact with the lower center surface of the end wall portion 28 of the control arm 17.

  As described above, since the roller 49 is supported using the partition wall portion 30 of the control arm 17, a special member for supporting the roller 49 is not required, and the number of parts can be reduced and the structure can be simplified. Become. In particular, since the roller 49 is housed in the roller housing recess 30c formed in the partition wall 30 of the control arm 17, the roller housing recess 30c is secured while securing the mounting space for the roller 49 using the space of the roller housing recess 30c. The reduction in rigidity of the control arm 17 due to the provision can be minimized by the reinforcing effect of the end wall portion 28 constituting the bottom wall of the roller accommodating recess 30c.

  Further, since the control arm 17 is urged by the urging means 51 and the roller 49 is brought into contact with the control cam 18, the roller 49 is prevented from being lifted from the control cam 18 to stabilize the behavior of the control arm 17, and the intake valve The control accuracy of the 12 and 12 valve lifts can be increased.

  The position where the end wall portion 28 and the partition wall portion 30 of the control arm 17 are connected, more specifically, the position between the pair of hydraulic tappets 31, 31 supported by the end wall portion 28, that is, the position of the control arm 17. Since the portion having high rigidity is pressed by the biasing means 51, the control arm 17 can be prevented from being bent by the pressing force of the biasing means 51, and the control accuracy of the valve lift of the intake valves 12, 12 can be further increased. .

  In particular, the control cam 18, the roller 49 of the control arm 17 with which it abuts, and the urging means 51 for urging the control arm 17 in the direction in which the roller 49 abuts against the control cam 18 are orthogonal to the cylinder row line. Since they are arranged in the same plane (within the paper surface of FIG. 4), the load from the control cam 18 and the load from the urging means 51 in the direction of tilting the control arm 17 (the direction inclined with respect to the paper surface of FIG. 4). This prevents the deformation of the control arm 17 to a minimum, thereby improving the control accuracy of the valve lifts of the intake valves 12 and 12).

Further, since the urging means 51 is disposed below the hydraulic tappets 31 and 31 in the cylinder axis direction (that is, on the combustion chamber side) , the oil discharged from the hydraulic tappets 31 and 31 is discharged from the oil discharge holes 28b and 28b of the end wall portion 28. The urging means 51 can be effectively lubricated by dropping downward.

  As is apparent from FIG. 1, a spark plug housing cylinder 56 for guiding the attachment / detachment of the spark plug 55 is press-fitted into the cylinder head 11, and the guide cylinder 52 formed integrally with the spark plug housing cylinder 56 is also a cylinder head. 11 is press-fitted. Thus, by forming the guide cylinder 52 integrally with the spark plug housing cylinder 56, the rigidity of the biasing means 51 can be increased and the behavior of the control arm 17 can be further stabilized.

  Therefore, when the control arm 17 is disposed at the position shown in FIGS. 3 and 4 by the control cam 18, that is, when the highest lift portion of the control cam 18 abuts on the roller 49, the control cam 17 swings around the axis of the movable support shaft 20. The leading end side (the side far from the movable support shaft 20) of the cam surfaces 21c, 21c of the moving sub cam 21 comes into contact with the rollers 37, 37 of the rocker arms 22, 22, and the rocking angle of the rocker arms 22, 22 increases. Thus, the valve lift of the intake valves 12, 12 is maximized.

  When the control arm 17 is in the position shown in FIG. 5 by the control cam 18, that is, when the lowest lift portion of the control cam 18 abuts on the roller 49, the cam surface of the sub cam 21 that swings around the axis of the movable support shaft 20. The base end side of 21c, 21c (the side close to the movable support shaft 20) abuts on the rollers 37, 37 of the rocker arms 22, 22, and the rocking angle of the rocker arms 22, 22 is reduced. Twelve valve lifts are minimized (zero).

  In this way, the valve lift of the intake valves 12, 12 is changed by swinging the control arm 17 around the support shaft portions 16, 16. The valve cams 14, 14 are driven by the rollers 41 by driving the control arm 17. , 41 also changes the timing at which the intake valves 12, 12 are opened and closed.

  11 and 12 show a second embodiment of the present invention. FIG. 11 is a longitudinal side view of the main part of the internal combustion engine, and FIG. 12 is a view taken along the line 12-12 in FIG.

  The first embodiment includes a single urging means 51, and the urging means 51 controls a pressing member 53 that is urged in a direction protruding from the guide cylinder 52 by the elastic force of the coil spring 54. By abutting against the central lower surface of the end wall portion 28 of the arm 17, the control arm 17 is urged clockwise to abut the roller 49 against the control cam 18.

  On the other hand, in the second embodiment, a pair of urging means 51, 51 are provided, and these urging means 51, 51 are configured so that the pair of side wall portions 27, 27 of the control arm 17 are orthogonal to the cylinder row line. The ends of the extended portions 27b and 27b extending in the direction are urged upward.

  Similar to the urging means 51 of the first embodiment, the urging means 51 of the second embodiment also includes a guide cylinder 52, a coil spring 54, and a pressing member 53. The guide cylinders 52, 52 of the pair of urging means 51, 51 are integrally connected to both sides of the spark plug housing cylinder 56 in the cylinder row line direction. That is, one guide cylinder 52, the spark plug housing cylinder 56, and the other guide cylinder 52 are integrally formed so as to be continuous along the cylinder row line direction.

  Thus, by dividing the urging means 51, 51 into two, not only can the dimensions of the individual urging means 51, 51 be reduced to increase the degree of freedom in layout, but the urging means 51, 51 Since the pair of side walls 27 and 27 having the highest rigidity among the control arms 17 are respectively urged, the deflection of the control arms 17 can be prevented by dispersing the urging force to avoid concentration of the load. In addition, since the guide cylinders 52, 52 of the pair of urging means 51, 51 are integrally connected to both sides of the ignition plug housing cylinder 56 in the cylinder row direction, the guide cylinders 52, 52 and the spark plug housing cylinder 56 are reinforced mutually. Not only can the rigidity be increased, the variable valve mechanism 13 can be brought closer to the cylinder row line in a direction perpendicular to the cylinder row line direction to achieve compactness.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

  For example, in the embodiment, the intake valves 12 and 12 are exemplified as the engine valve, but the engine valve of the present invention may be an exhaust valve.

  In the embodiment, the cam follower of the control arm 17 with which the control cam 18 abuts is constituted by the roller 49, but it may be constituted by a slipper.

1 is a longitudinal sectional side view of an essential part of an internal combustion engine according to a first embodiment. 2-2 line view of FIG. Sectional view along line 3-3 in FIG. 2 in a high valve lift state Sectional view taken along line 4-4 of FIG. 2 in a high valve lift state Sectional view corresponding to FIG. 4 in the low valve lift state Perspective view of variable valve mechanism from one direction Perspective view of variable valve mechanism as seen from other direction A perspective view of the control arm from one direction A perspective view of the control arm as seen from the other direction 10 and 10 arrow views of FIGS. 8 and 9 Longitudinal longitudinal sectional side view of an internal combustion engine according to the second embodiment 12-12 arrow view of FIG.

Explanation of symbols

11 Cylinder head (engine body)
12 Intake valve (engine valve)
14 Valve cam 16 Support shaft 17 Control arm 18 Control cam (control member)
21 Sub cam 22 Rocker arm 27 Side wall portion 28 End wall portion 31 Hydraulic tappet (rocker arm swinging support portion)
50 Actuator 51 Biasing means 52 Guide cylinder 56 Spark plug housing cylinder

Claims (7)

A control arm (17) in which the support shaft (16) is swingably supported by the engine body (11);
A rocker arm (22) that is swingably supported by a swing support portion (31) provided in the control arm (17) and abuts against the engine valve (12);
A sub cam (21) supported by the control arm (17) in a swingable manner and driven by a valve cam (14) to drive the rocker arm (22);
An internal combustion engine in which at least the valve lift of the engine valve (12) can be changed by swinging the control arm (17) around the support shaft (16) by a control member (18) operated by an actuator (50). A variable valve mechanism,
The urging means (51) for urging the control arm (17) in a direction to contact the control member (18) is provided, and the urging means (51) is the swing support portion of the control arm (17). A variable valve mechanism for an internal combustion engine, wherein the portion provided with (31) is energized. The pivot support portion is a hydraulic tappet (31), said biasing means (51), characterized in that it is arranged on the combustion chamber side of the hydraulic tappet (31) in the cylinder axis direction, claim 1 A variable valve mechanism for an internal combustion engine according to claim 1.
  The control arm (17) includes end wall portions (28) that connect between the end portions of a pair of side wall portions (27) provided with the support shaft portions (16), respectively, and the biasing means (51) includes The variable valve mechanism for an internal combustion engine according to claim 1 or 2, characterized in that a bias is applied between the pair of swing support portions (31) provided on the end wall portion (28).   The control member is a control cam (18) that presses the control arm (17), and the control cam (18) and the biasing means (51) are arranged in the same plane perpendicular to the cylinder row direction. The variable valve mechanism for an internal combustion engine according to any one of claims 1 to 3, wherein:   The internal combustion engine according to any one of claims 1 to 4, wherein the guide cylinder (52) and the spark plug housing cylinder (56) of the biasing means (51) are integrally formed. Variable valve mechanism.   The control arm (17) includes a pair of side wall portions (27) provided with the support shaft portion (16), and the pair of biasing means (51) biases the pair of side wall portions (27), respectively. The variable valve mechanism for an internal combustion engine according to claim 1 or 2, characterized in that:   The internal combustion engine according to claim 6, wherein the guide cylinders (52) of the pair of urging means (51) are integrally connected to both sides of the spark plug housing cylinder (56) in the cylinder row direction. Variable valve mechanism.

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