JP4323539B2 - Variable valve operating device for internal combustion engine - Google Patents

Description

  The present invention relates to an improvement in a variable valve gear that can change the opening / closing timing and valve lift amount of an intake / exhaust valve (intake valve or exhaust valve) according to the operating state of an internal combustion engine.

  In the field of internal combustion engines, the intake / exhaust valve opening and closing timings are used to improve fuel efficiency at low speed and low load, to ensure stable operation, and to ensure sufficient output by improving the charging efficiency of intake air at high speed and high load. Various variable valve gears that change the valve lift according to the operating state of the engine have been proposed.

  As such a variable valve operating apparatus, for example, a drive shaft that rotates in synchronization with the engine and a camshaft that drives the intake / exhaust valve are linked by a link mechanism, and the intake / exhaust valve is connected to the link mechanism. Patent Document 1 describes a configuration in which a variable mechanism that changes lift characteristics is linked.

  Briefly described with reference to FIG. 9, a camshaft 2 divided for each cylinder is rotatably fitted on the outer periphery of the drive shaft 1 that rotates in synchronization with the engine. A pair of cam lobes 3 are provided on the outer periphery of each camshaft 2, and each cam lobe 3 is in contact with a tappet (valve lifter) 4 provided at the upper end of the intake / exhaust valve to open / close the intake / exhaust valve. It comes to drive.

  The link mechanism for transmitting the rotational power of the drive shaft 1 to the camshaft 2 includes a drive plate 5 fixed to the outer periphery of the drive shaft 1, and an annular disk linked via a flange 6 a and a pin 6 of the drive plate 5. 7 and a pin 8 that links the annular disk 7 and the flange portion 2a of the camshaft 2 to each other. The annular disk 7 is loosely fitted to the outer periphery of the drive shaft 1 through the gap S, and is interposed in the axial gap between the flange portion 2 a of the camshaft 2 and the flange portion 5 a of the drive plate 5.

  The variable mechanism for changing the lift characteristics of the intake / exhaust valves has a control disk 9 that supports the outer periphery of the annular disk 7 so as to be relatively rotatable. The control disk 9 is swung by a drive mechanism (not shown). By doing so, the eccentric positions of the control disk 9 and the annular disk 7 with respect to the drive shaft 1 change. As a result, the rotational phase of the camshaft 2 with respect to the drive shaft 1 changes, and the lift characteristics are variably controlled.

Although not shown, a predetermined thrust clearance is set between the drive shaft 1 and the cylinder head that rotatably supports the drive shaft 1. Also, predetermined thrust clearances are set between the camshaft 2, the annular disk 7 and the drive plate 5 which are arranged on the same axis.
JP 7-34820 A

  By the way, the tappet 4 that is slidably inserted into the guide hole of the cylinder head uses its pressing force from the cam lobe 3 so that the sliding surface with the cylinder head does not wear unevenly. It is necessary to rotate around appropriately. In order to rotate the tappet 4 in this way, it is necessary to apply a rotational force to the tappet 4 by applying the pressing force of the cam lobe 3 to an axial position deviating from the center of the tappet 4.

  However, in the variable valve operating apparatus as shown in FIG. 9, as described above, in addition to the thrust clearance being set between the drive shaft 1 and the cylinder head, the camshaft 2, the annular disk 7, and the drive Since a thrust clearance is set between each plate 5 and the plate 5, the cam lobe 3 has a relatively large positional variation in the thrust direction with respect to the tappet 4.

  For this reason, even when the cam lobe 3 is offset with respect to the tappet 4, the pressing force from the cam lobe 3 acts on the center portion of the tappet 4 due to the above-described position variation and the like, and the tappet 4 is excellent. Cannot be rotated and the above-mentioned uneven wear may occur.

  The present invention has been made in view of such a problem, and in a variable valve operating apparatus for an internal combustion engine, the pressing force of the cam lobe is surely applied to an axial position away from the center of the tappet, thereby reliably The purpose is to rotate.

  A variable valve operating apparatus for an internal combustion engine according to the present invention includes a drive shaft that rotates in conjunction with the engine, a camshaft having a cam lobe that drives an intake / exhaust valve on the outer periphery, and the cam lobe and the intake / exhaust valve. A link mechanism that spans the tappet interposed between the drive shaft and one axial end portion of the camshaft and transmits the driving force of the drive shaft to the camshaft, and is linked to the link mechanism. And a variable mechanism that changes the lift characteristics of the exhaust valve.

  With such a configuration, when the driving force of the drive shaft is transmitted to the camshaft via the link mechanism, the cam lobe presses the tappet, and the intake and exhaust valves are driven to open and close. Further, when the variable mechanism is driven and controlled in accordance with the operating state of the engine, the lift characteristics of the intake / exhaust valves are variably controlled via the link mechanism.

  Here, the cam shaft has a shape in which the portion on the link connecting portion side in the axial direction is relatively close to the tappet because the link mechanism is connected to one axial end of the cam shaft. For this reason, the cam lobe strongly contacts the tappet at the axial end on the link connecting portion side. Therefore, the pressing position at which the cam lobe presses the tappet is shifted toward the link connecting portion with respect to the axial center of the cam lobe.

  Then, the axial center of the cam lobe contacting the tappet is offset in the axial direction with respect to the center of the tappet toward the link connecting portion side where the link mechanism and one axial end portion of the camshaft are connected.

  In other words, the cam lobe itself is offset with respect to the tappet in a direction in which the pressing position of the cam lobe itself deviates from the axial center.

  As a result, the cam lobe pressing position shifts in the axial direction toward the link connecting portion with respect to the center of the tappet by the sum of the offset amount of the cam lobe itself and the offset amount.

  For this reason, even if some variation occurs in the axial position of the cam lobe relative to the tappet due to the above-described thrust clearance or the like, the pressing position of the cam lobe can be reliably shifted from the center of the tappet to the lift connecting portion side, The tappet can be rotated reliably.

  The camshaft is fitted on the outer periphery of the drive shaft so as to be relatively rotatable, and the variable mechanism includes a control shaft extending substantially parallel to the drive shaft, and a control cam provided on the outer periphery of the control shaft. The link mechanism includes an eccentric cam provided on the outer periphery of the drive shaft, a ring-shaped link that is fitted on the outer periphery of the eccentric cam so as to be relatively rotatable, and is connected to the ring-shaped link at one end, It has a rocker arm that is fitted on the outer periphery of the control cam so as to be relatively rotatable, and a rod-like link that connects the rocker arm and one axial end of the camshaft.

  As described above, when the camshaft is configured to be fitted around the outer periphery of the drive shaft so as to be relatively rotatable, the parts of the link mechanism can be concentrated around the drive shaft to reduce the size. Moreover, since the connection part of a link mechanism becomes surface contact, it is excellent in abrasion resistance and is easy to lubricate.

  In the configuration in which the cam lobe is provided at two locations on both sides in the axial direction for one camshaft, it is caused by the driving force input from the drive shaft to the camshaft through the link mechanism at the initial stage of the valve lift. The cam lobe on the link connecting portion side relatively approaches the tappet.

  As a result, the pressing force acting on the tappet from the cam lobe on the side far from the link connecting portion becomes relatively small, and the rotational force acting on the tappet may be insufficient. Further, the cam lobe on the link connecting portion side may first press the tappet, and the lift timing of the pair of intake / exhaust valves may be shifted.

  Therefore, the offset amount of the cam lobe on the side far from the link connecting portion is set relative to the offset amount of the cam lobe on the side near the link connecting portion so that a sufficient rotational force acts on the tappet on the side far from the link connecting portion. It is characterized by having been set to a large.

  Alternatively, the valve clearance between the cam lobe and the tappet on the side far from the link connecting portion is set so that both cam lobes lift the tappet (suction / exhaust valve) at the same time. It is characterized in that it is set to be relatively smaller than the valve clearance amount.

  Further, as described above, a reaction force from the tappet to the anti-link connecting portion side acts on the camshaft because the portion of the camshaft on the lift connecting portion side relatively approaches the tappet. For this reason, the thrust surface of the camshaft on the side far from the link connecting portion is relatively easily worn.

  Therefore, in accordance with the reaction force acting on the camshaft on the side opposite to the link coupling portion, the camshaft thrust surface on the side far from the link coupling portion is made relative to the camshaft thrust surface on the side closer to the link coupling portion. It is characterized by a large setting.

  The tappet is an inner shim type or a shimless type. In other words, the cam lobe is in direct contact with the tappet so that the tappet rotates well by the pressing force from the cam lobe.

  Further, the outer periphery of the cam lobe is formed in a tapered shape in which a portion close to the link connecting portion is relatively close to the tappet. In this case, in the axial direction of the cam lobe, the pressing position that strongly presses the tappet is more reliably shifted to the link connecting portion side. That is, the difference in the surface pressure in the axial direction of the cam lobe can be given more greatly.

  As described above, according to the present invention, since the pressing position of the cam lobe is surely shifted to the link connecting portion side with respect to the center of the tappet, the tappet can be reliably rotated, and the tappet is insufficiently rotated. The occurrence of uneven wear can be reliably suppressed.

  1 to 4 show an embodiment in which the variable valve system according to the present invention is applied to an internal combustion engine provided with a pair of intake valves and exhaust valves for each cylinder.

  A drive shaft 12 that is continuous over all the cylinders is provided on the upper portion of the cylinder head 10. The drive shaft 12 has a sprocket attached to one end (not shown), and rotates in conjunction with the crankshaft of the engine via a timing chain. The drive shaft 12 is formed in a hollow shape having an axial oil passage 12a for introducing lubricating oil therein. Further, an appropriate thrust clearance is set between the drive shaft 12 and the cylinder head 10 that supports the drive shaft 12 so that the drive shaft 12 rotates smoothly.

  A hollow camshaft 14 divided for each cylinder is fitted on the outer periphery of the drive shaft 12 so as to be relatively rotatable. On the outer periphery of each camshaft 14, a pair of cam lobes 16 as rocking cams are integrally provided at two locations on both sides in the axial direction, and a journal 17 provided at the intermediate portion in the axial direction of these cam lobes 16 includes a lower bracket. 40 and the cylinder head 10 are rotatably supported.

  Here, the cam lobe 16 on the side close to the link connecting portion where one axial end portion (the left end portion in FIG. 1) of the cam shaft 14 is connected to the rod-shaped link 30 of the link mechanism described later is connected to the cam lobe 16A and the link connecting portion. The cam lobe 16 on the far side is the cam lobe 16B. Similarly, in the intake valve 18 and the tappet 19 described later, the side close to the link connecting portion is the intake valve 18A and the tappet 19A, and the side far from the link connecting portion is the intake valve 18B. This is a tappet 19B.

  A bottomed cylindrical tappet 19 is interposed between each cam lobe 16 and a pair of intake valves (or exhaust valves) 18 of each cylinder. Each tappet 19 is attached so as to cover the upper end of the stem of each intake valve 18 and is inserted into the guide hole 10 a of the cylinder head 10. On the other hand, as shown in FIG. 3, a retainer 46 that receives one end of the valve spring 44 is fixed to the upper end of the stem of each intake valve 18. When each cam lobe 16 presses the tappet 19, the intake valve 18 is driven to open and close against the reaction force of the valve spring 44.

  Further, the tappet 19 has a structure in which a shim is not provided at the top of the tappet 19 so as to appropriately rotate around its own axis by a pressing force from the cam lobe 16, and is directly in contact with the cam lobe 16. More specifically, as shown in FIG. 3A, the tappet 19 is a shimless type in which the stem end surface of the intake valve 18 directly contacts the boss portion 19a, or FIG. As shown in FIG. 2, an shim 48 having an appropriate thickness is interposed between the boss portion 19a and the stem end surface.

  A link mechanism for transmitting the rotational driving force of the drive shaft 12 to the camshaft 14 is spanned between the drive shaft 12 and one axial end portion (left end portion in FIG. 1) of the camshaft 14. A variable mechanism that changes the lift characteristic of the intake valve 18 is mechanically linked to the mechanism.

  This variable mechanism has a control shaft 24 extending substantially parallel to the drive shaft 12 and a control cam 26 provided on the outer periphery of the control shaft 24. The control shaft 24 is rotationally controlled in a predetermined angle range according to the operating state of the engine by an actuator or the like (not shown), and an upper bracket 38 and a lower portion that are fastened and fixed to the cylinder head 10 side by bolts 42. The bracket 40 is rotatably supported. The control cam 26 is integrally fixed to the outer periphery of the control shaft 24 by press fitting or the like, and is eccentric by a predetermined amount with respect to the axis of the control shaft 24.

  The link mechanism includes an eccentric cam 20 provided on the outer periphery of the drive shaft 12, a ring-shaped link 22 fitted on the outer periphery of the eccentric cam 20 so as to be relatively rotatable, and the ring-shaped link 22 connected at one end. In addition, a rocker arm 28 that is fitted on the outer periphery of the control cam 26 so as to be relatively rotatable, and a rod-shaped link 30 that connects the rocker arm 28 and one axial end portion of the camshaft 14 are provided.

  The eccentric cam 20 is fixed to the outer periphery of the drive shaft 12 by press fitting or the like, and is eccentric by a predetermined amount with respect to the axis of the drive shaft 12. Further, in this embodiment, the eccentric cam 20 is formed integrally with a drive plate 21 fixed to the outer periphery of the drive shaft 12, and the axial end surface of the camshaft 14, that is, the thrust surfaces 14 a and 14 b together with the drive plate 21. Is configured to receive. An appropriate thrust clearance is set between the camshaft 14 and the eccentric cam 20 or the drive plate 21 so that the camshaft 14 rotates smoothly.

  One end of the rocker arm 28 and the tip of the ring-shaped link 22 are connected to each other via a first pin 32 that passes through both of them so as to be relatively rotatable. As shown in FIG. 1, a flange portion 15 that faces the cam lobe 16 </ b> A on the link connecting portion side is formed at one axial end portion (left side in FIG. 1) of the camshaft 14. Then, by inserting the second pin 34 with one end of the rod-shaped link 30 interposed between the flange portion 15 and the cam lobe 16A, the camshaft 14 and the rod-shaped link 30 are connected so as to be relatively rotatable. It has become so. Furthermore, the other end of the rod-shaped link 30 and the other end of the rocker arm 28 are coupled to each other via a third pin 36 that passes through both of them.

  With the above configuration, when the drive shaft 12 rotates around the shaft in synchronism with the rotation of the engine, the ring-shaped link 22 moves in translation via the eccentric cam 20, and the rocker arm 28 corresponds to the shaft center of the control cam 26. The camshaft 14 swings around the axis of the drive shaft 12 via the rod-shaped link 30. As a result, the cam lobe swings and presses the tappet 19 to drive the intake valve 18 to open and close.

  Further, when the rotation of the control shaft 24 is controlled in accordance with the operating state of the engine, the axial center position of the control cam 26 serving as the rocking fulcrum of the rocker arm 28 changes, and the lift characteristics of the intake valve 18, that is, the valve lift amount. (Operating angle) and opening / closing timing are variably controlled.

  As described above, since the camshaft 14 is externally fitted on the outer periphery of the drive shaft 12 so as to be relatively rotatable, the parts of the link mechanism can be concentrated around the drive shaft 12 to reduce the size. . Further, since the connecting portion of the link mechanism or the variable mechanism is in surface contact, it has excellent wear resistance and is easy to lubricate.

  In this embodiment, as shown in FIG. 1, the center of the tappet 19A with respect to the center of the cam lobe 16A in contact with the tappet 19A is set to a predetermined offset amount Xa toward the link connecting portion, that is, the left side of FIG. Only offset. Similarly, the axial center of the cam lobe 16B contacting the tappet 19B is offset from the center of the tappet 19B by a predetermined offset amount Xb to the link connecting portion side (left side in FIG. 1).

  Next, the operation of this embodiment will be described.

  In the structure in which the tappet 19 slides in the guide hole 10a of the cylinder head 10 as in the present embodiment, the tappet 19 is pivoted by using the pressing force from the cam lobe 16 in order to prevent uneven wear of the tappet 19. Need to rotate around.

  In particular, in the variable valve system of the type in which the cam lobe 16 swings as in the present embodiment, from the lift start timing of the intake valve 18 shown in FIG. 5A to the maximum lift timing shown in FIG. Since the pressing force acting on the tappet 19 from the cam lobe 16 is always in a fixed direction, the load is concentrated on the portions indicated by reference numerals 50 and 52 in FIG. As a result, uneven wear tends to occur on the outer peripheral surface of the tappet 19 and the tappet 19 needs to be reliably rotated.

  In order to rotate the tappet 19, it is necessary that the pressing force of the cam lobe 16 acts on a position off the center of the tappet 19. According to this embodiment, as shown in FIGS. 1 and 6, the pressing positions Fa and Fb at which the pressing force acts from the cam lobe 16 to the tappet 19 are reliably axially moved from the center of the tappet 19 to the link connecting portion side. Can be shifted.

  More specifically, the camshaft 14 has a bearing portion at one location of the central journal 17 and is connected to the rod-shaped link 30 of the link mechanism at one end in the axial direction. Is inclined with respect to the axis of the drive shaft 12 due to the rotational drive force transmitted from the link mechanism through the link mechanism or the spring reaction force from the tappet 19.

  More specifically, in the initial lift state (the state shown in FIGS. 6 and 7) where the cam lobe 16 begins to push the tappet 19 in the valve opening direction (downward in the figure), the drive shaft 12 mainly passes through the link mechanism. Due to the rotational power transmitted to the camshaft 14, the camshaft 14 is inclined so that the portion on the link connecting portion side approaches the tappet 19 side (the lower side in the figure). 6 and 7 exaggerate the inclination of the camshaft 14 for the purpose of clarity, and the actual inclination is very small.

  For this reason, the cam lobes 16A and 16B both come into strong contact with the tappets 19A and 19B at one end in the axial direction on the link connecting portion side, and the contact surface pressure at this portion is the highest. That is, the substantial pressing positions Fa and Fb at which the cam lobes 16A and 16B strongly press the tappets 19A and 19B are the lengths La and Lb (about half of the axial length of the cam lobes 16A and 16B). Only refer to FIG. 1).

  In the present embodiment, as shown in FIG. 1, the centers of the cam lobes 16A and 16B are offset in the axial direction toward the link connecting portion with respect to the axial centers of the tappets 19A and 19B (Xa and Xb). In other words, the cam lobes 16A and 16B themselves are offset with respect to the tappets 19A and 19B in the direction of displacement of the pressing positions Fa and Fb of the cam lobes 16A and 16B themselves.

  As a result, as shown in FIG. 1, the cam lobes 16A and 16B are offset by the sum of the deviation amounts La and Lb of the cam lobes 16A and 16B and the offset amounts Xa and Xb of the cam lobes 16A and 16B (La + Xa, Lb + Xb). The positions Fa and Fb are shifted in the axial direction toward the link connecting portion with respect to the centers of the tappets 19A and 19B.

  For this reason, even if some variation occurs in the axial position of the cam lobes 16A and 16B with respect to the tappets 19A and 19B due to the above-described thrust clearance or the like, the pressing positions Fa and Fb of the cam lobes 16A and 16B are changed to the tappets 19A and 16B. Eccentricity from the center of 19B to the lift connection part side can be carried out reliably.

  Therefore, when the cam lobes 16A and 16B press the tappets 19A and 19B, a rotational moment acts on the tappets 19A and 19B along the traveling direction of the cam lobes 16A and 16B (see FIG. 4), and the tappets 19A and 19B are surely secured. The shaft can be rotated. As a result, occurrence of uneven wear due to insufficient rotation of the tappets 19A and 19B can be reliably suppressed.

  In the initial stage of the valve lift shown in FIGS. 6 and 7, the cam lobe 16 </ b> A and the tappet 19 </ b> A on the link connecting portion side relatively approach each other due to the inclination of the cam shaft 14. As a result, the pressing force of the cam lobe 16B on the side far from the link connecting portion becomes relatively small, and there is a possibility that the rotational moment acting on the tappet 19 is insufficient. Further, as shown in FIG. 7, the cam lobe 16A on the link connecting portion side first presses the tappet 19A, and there is a possibility that the lift timing of both the intake valves 18A, 18B is shifted.

  Therefore, in order to give a sufficient rotational force to the tappet 19B on the anti-link connecting portion side, the offset amount Xb on the anti-link connecting portion side is preferably set larger than the offset amount Xa on the link connecting portion side (Xa <Xb). .

  In the example shown in FIG. 6, the valve clearance amount between the cam lobe 16B far from the link connecting portion and the tappet 19B is set to the link connecting portion side so that both cam lobes 16A and 16B lift the tappets 19A and 19B simultaneously. The valve clearance amount between the cam lobe 16A and the tappet 19A is set to be relatively smaller by ΔC.

  For example, in the case of the inner shim type shown in FIG. 3B, the valve clearance amount is adjusted by selectively using shims 48 having different thicknesses.

  By the way, due to the inclination of the camshaft 14 and the like, a thrust reaction force is applied to the camshaft 14 from the tappet 19 to the side opposite to the link connecting portion (the right side in FIG. 1). For this reason, especially the thrust surface 14b of the camshaft 14 on the side far from the link connecting portion is easily worn.

  Therefore, in this embodiment, as shown in FIG. 1, the thrust surface 14b far from the link coupling portion is set relatively large with respect to the thrust surface 14a of the camshaft 14 near the link coupling portion. (Da <Db).

  FIG. 8 shows another embodiment of the present invention. Here, the outer periphery of each cam lobe 16A, 16B is formed in a taper shape so that the portion close to the link connecting portion in the axial direction is close to the tappet 19A, 19B. In this case, in the axial direction of the cam lobes 16A and 16B, the pressing positions Fa and Fb that strongly press the tappets 19A and 19B are more reliably shifted to the link connecting portion side. That is, the difference in the surface pressure in the axial direction of the cam lobes 16A and 16B can be given more greatly.

The block diagram which shows the variable valve apparatus of the internal combustion engine which concerns on one Embodiment of this invention. FIG. 3 is a cross-sectional view of the variable valve operating device in FIG. 1. (A) is a shimless type, (b) is a sectional view showing a tappet on the inner shim side. The plane corresponding view which looked at the variable valve apparatus of Drawing 1 from the lower side. (A) is a lift start time, (b) is a cross-sectional view corresponding to the main part at the maximum lift time. Explanatory drawing for demonstrating the effect | action of this embodiment. Explanatory drawing for demonstrating the effect | action of this embodiment. The block diagram which shows other embodiment of this invention. Sectional drawing which shows the variable valve apparatus of the internal combustion engine which concerns on a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 ... Drive shaft 14 ... Cam shaft 16A, 16B ... Cam lobe 18A, 18B ... Intake valve 19A, 19B ... Tappet 20 ... Eccentric cam (link mechanism)
22 ... Ring-shaped link (link mechanism)
24 ... Control shaft (variable mechanism)
26 ... Control cam (variable mechanism)
28 ... Rocker arm (link mechanism)
30 ... Rod-shaped link (link mechanism)

Claims (3)

A drive shaft that rotates in conjunction with the engine;
A camshaft externally fitted to the outer periphery of the drive shaft so as to be relatively rotatable, and supported by the drive shaft so as to be swingable;
A pair of cam lobes integrally provided on both axial sides of the outer periphery of the camshaft, each driving a pair of intake valves or exhaust valves;
A pair of cylindrical tappets interposed between the cam lobe and the intake valve or the exhaust valve,
A valve spring that biases the intake valve or the exhaust valve in the closing direction;
A link mechanism that spans between the drive shaft and the cam lobe on one end side in the axial direction of the cam shaft, and transmits the driving force of the drive shaft to the cam lobe;
Linked to this link mechanism, a variable mechanism that changes the lift characteristics of the intake and exhaust valves,
With
The variable mechanism has a control shaft extending substantially parallel to the drive shaft, and a control cam provided on the outer periphery of the control shaft,
The link mechanism includes an eccentric cam provided on the outer periphery of the drive shaft, a ring-shaped link that is fitted on the outer periphery of the eccentric cam so as to be relatively rotatable, and is connected to the ring-shaped link at one end, and the control cam A rocker arm that fits on the outer periphery of the rocker, and a rod-shaped link that connects the rocker arm and one end of the camshaft in the axial direction.
And, with respect to the center of the tappet, the axial center of each of the cam lobe, the variable valve device for an internal combustion engine, characterized in that is axially offset to the side in which the link mechanism is connected. A drive shaft that rotates in conjunction with the engine;
A camshaft externally fitted to the outer periphery of the drive shaft so as to be relatively rotatable, and supported by the drive shaft so as to be swingable;
A pair of cam lobes integrally provided on both axial sides of the outer periphery of the camshaft, each driving a pair of intake valves or exhaust valves ;
A valve spring that biases the intake valve or the exhaust valve in the closing direction;
A link mechanism for tilting the camshaft in a state where the camshaft is swung by the rotation of the drive shaft and the camlob starts to push the intake valve or the exhaust valve in the valve opening direction;
Linked to this link mechanism, has a variable mechanism that changes the lift characteristics of the intake and exhaust valves,
The variable mechanism has a control shaft extending substantially parallel to the drive shaft, and a control cam provided on the outer periphery of the control shaft,
The link mechanism includes an eccentric cam provided on the outer periphery of the drive shaft, a ring-shaped link that is fitted on the outer periphery of the eccentric cam so as to be relatively rotatable, and is connected to the ring-shaped link at one end, and the control cam A rocker arm that fits on the outer periphery of the rocker, and a rod-shaped link that connects the rocker arm and one end of the camshaft in the axial direction.
In addition, the cam lobe is interposed between the intake valve or the exhaust valve so as to be rotatable around an axis, and when the cam shaft is inclined, the portion where the contact surface pressure with the cam lobe is highest is the center in the axial direction. A variable valve operating apparatus for an internal combustion engine, comprising a pair of tappets arranged so as to be displaced with respect to each other. Of the valve clearance amount between the cam lobe and the tappet, the valve clearance amount of the cam lobe farther from the one axial end where the link mechanism is connected is the cam lobe closer to the one axial end where the link mechanism is connected. The variable valve operating apparatus for an internal combustion engine according to claim 1 or 2, wherein the variable valve clearance is set to be smaller than the valve clearance amount .

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