JP4696215B2 - Variable valve operating device for internal combustion engine - Google Patents

Description

  The present invention relates to a variable valve operating apparatus for an internal combustion engine that continuously controls valve drive output for driving intake valves and exhaust valves.

In reciprocating engines (internal combustion engines) installed in automobiles, a variable valve that continuously controls at least the valve characteristics of the intake valve at the cylinder head to prevent engine exhaust and improve pumping loss. The device is mounted.
Many of these variable valve operating devices use a variable valve operating mechanism that continuously changes at least the valve lift amount in order to adjust the intake air amount. In many cases, the structure that outputs the valve drive output in response to the cam displacement of the intake cam formed on the camshaft and the obtained valve drive output (valve lift amount, opening / closing timing, valve opening period, etc.) Is used in combination with a structure that is continuously variable according to the rotational displacement input from (see, for example, Patent Document 1).

In particular, in the variable valve mechanism, the control rotation output from the drive source such as an electric motor is transmitted to the rotational displacement of the control shaft so that the valve drive output can be varied with a drive force that exceeds the valve reaction force, for example, A control shaft is driven with a high torque output by using a speed reduction mechanism using gear engagement such as a worm gear mechanism (see Patent Document 2).
By the way, the backlash for smoothly meshing the gear teeth is set for the meshing of the gear. This backlash is appropriately set to suppress the hitting sound between the gears. However, in the case of a variable valve mechanism, a valve reaction force acts on the transmission mechanism from the intake valve side through the variable valve mechanism. The valve reaction force not only fluctuates with the opening and closing of the valve, but also increases as the valve lift increases. In addition, the high engine speed range where high valve lift is frequently used is affected by valve springs that repeatedly expand and contract at high speeds and valve vibrations caused by high speed rotations. It's easy to do.

For this reason, unlike the other mechanisms, the variable valve mechanism is likely to generate a significantly large gear hitting sound.
In such a transmission structure using a general gear, in order to suppress the occurrence of such a hitting sound, a structure for closing backlash is provided.
Therefore, even in the variable valve operating apparatus, for example, as disclosed in Patent Document 2, a coil spring is used to constantly bias one gear to the other gear meshing with the gear so that the gap between the gear teeth. The technology that packs backlash is used.
JP 2005-299536 A Japanese Patent Laid-Open No. 2007-2686

  By the way, the responsiveness of the control of the variable valve operating device is practically high or low load when the lift is controlled by a small lift rather than during high speed operation of the engine where the valve lift is controlled by a large lift. Responsiveness during mid / low speed operation is required. Responsiveness of control is particularly important in the small valve lift area, and it is necessary to respond quickly to driver requests and control unit commands, and to suppress instability in engine rotation that accompanies changes in the driving environment. It is done.

  However, as shown in Patent Document 2, when an urging force that closes backlash is applied across the entire variable range, the high valve lift region can suppress the occurrence of sound hitting between gears by the urging force, but in the small valve lift region. The biasing force affects the variable control. Specifically, the urging force that closes backlash makes the control shaft that requires fine variable control responsiveness difficult to move. As a result, the control responsiveness in the small valve lift region is reduced.

Usually, as a countermeasure, in order to improve the control responsiveness in the small valve lift region, a measure is taken to change the electric motor (drive source) that outputs the control rotation to a motor with a large output.
However, this increases the control responsiveness in the small valve lift region, but requires the use of a large electric motor, which imposes a considerable cost burden. In addition, the adoption of the electric motor increases the weight and size of the variable valve operating apparatus, which causes NVH and mounting problems.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a variable valve operating apparatus for an internal combustion engine that can effectively suppress the occurrence of hitting sound between gears of a transmission mechanism while ensuring control responsiveness in a small valve lift region. .

In order to achieve the above object, the invention according to claim 1 swings on a camshaft having a valve drive cam, a swing cam having a cam surface for driving the valve, and a control shaft capable of rotational displacement. A transmission arm that is freely supported and is interposed between the swing cam and the valve drive cam and transmits the displacement of the valve drive cam to the swing cam, and according to the rotational displacement input from the control shaft, From the drive source, a variable valve mechanism that variably controls the valve lift amount within a predetermined low valve lift to high valve lift range while changing the position of the transmission arm that contacts the valve drive cam and controlling the valve characteristics of the valve A transmission mechanism for transmitting a control rotation for setting a required valve lift amount to the control shaft by meshing the gears, and a transmission mechanism provided in the transmission mechanism; Only in the high valve lift region of the lift range, and a backlash filling means for applying a biasing force to backlash in the gear of the transmission mechanism, and the variable valve mechanism, low valve lift to high valve lift In an area other than the high valve lift area in the range, the maximum load received from the transmission arm during the valve lift is set to be a load for rotating the control shaft in one direction.
Due to this configuration, the high valve lift range, which is likely to generate a large hitting noise in the low valve lift to high valve lift range, gives a biasing force to pack backlash in the gear of the transmission mechanism, and the other regions give a biasing force. I didn't have to.

According to the second aspect of the present invention, the transmission mechanism meshes with the worm wheel gear provided on the control shaft and the worm wheel gear so that the backlash filling means can be completed with a simple configuration, and transmits the control rotation to the worm wheel gear. When the backlash stuffing means is set in the high valve lift range, the worm wheel gear gear teeth are increased while the urging force is increased. A pressing mechanism part that presses against is adopted.

In the invention according to claim 3 , the press mechanism portion is wound around the rotation fulcrum portion of the worm wheel gear so as to have a simpler structure. A configuration having a toggle spring member that elastically displaces in the direction of contraction following the rotational displacement and presses the gear teeth of the worm wheel gear against the gear teeth of the worm shaft gear is adopted.

According to the first aspect of the present invention, the high balf lift region in which a large hitting sound is likely to occur is caused by the action of the urging force that packs backlash, and the other regions are geared to each other without applying the urging force that packs backlash. The occurrence of the hitting sound can be suppressed.
Therefore, it is possible to effectively suppress the occurrence of hitting sound between the gears of the transmission mechanism while ensuring control responsiveness in the small valve lift region .

According to the invention of claim 2, the backlash filling means can be simply configured by adopting a structure in which the pressing mechanism is assembled to the worm speed reduction mechanism which is advantageous for driving the control shaft and requires a small number of parts. .
According to the invention of claim 3, the backlash packing means may be configured to wind the toggle spring member around the rotation fulcrum portion of the worm wheel gear, and the structure can be further simplified.

Hereinafter, the present invention will be described based on the first embodiment shown in FIGS. 1 to 10 and FIG. 13.
1 is a perspective view of a main body of an internal combustion engine, for example, an in-line four-cylinder reciprocating gasoline engine, FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIG. 3 is a rocker cover and timing chain cover in FIG. 4 is an exploded perspective view with the valve system in FIG. 3 removed, FIG. 5 is a cross-sectional view of the variable valve system along the line BB in FIG. 3, and FIG. Sectional drawing of the variable valve operating apparatus along CC line in FIG. 3, FIGS. 7-10 has each shown the structure of each part which stuffs backlash.

In FIG. 1, 1 is a cylinder block constituting the engine body, 2 is a cylinder head mounted on the cylinder block 1, 3 is a rocker cover that also covers the cylinder head 2, and 4 is a lower portion of the cylinder block 1. 1 is a timing chain cover provided at the front of the cylinder block 1.
As shown in FIG. 5, the cylinder block 1 is formed with four cylinders 6 (only a part of which is shown) along the longitudinal direction of the engine. In these cylinders 6, pistons 7 are housed so as to be reciprocally movable. These pistons 7 are connected to a crankshaft 9 disposed in the front-rear direction of the cylinder block 1 via connecting rods 8 and crankpins 9a, and the reciprocating motion transmitted from the pistons 7 is converted into rotational motions to the crankshaft 9. It is trying to output.

  As shown in FIG. 5, combustion chambers 11 are formed on the lower surface of the cylinder head 2 following the four cylinders 6. A pair of intake ports 12 and a pair of exhaust ports 13 (both only one side is shown) are formed on both sides of the combustion chamber 11. The upper center of the cylinder head 2 is recessed in the front-rear direction. And the both sides of the recessed part 2a have protruded to the side, respectively. On both sides of the combustion chamber 11, an intake valve 14 that opens and closes the intake port 12 and an exhaust valve 15 that opens and closes the exhaust port 13 are provided for each cylinder 6. The intake valve 14 and the exhaust valve 15 are both normally closed types that are urged in a closing direction by a valve spring 16 (shown only in FIG. 5).

  As shown in FIGS. 2 to 6, a variable valve operating device 20 composed of a SOHC valve operating mechanism is mounted in the recess 2 a formed in the upper part of the cylinder head 2. The variable valve gear 20 is housed in the rocker cover 3. The variable valve operating device 20 includes a camshaft 26, a variable valve mechanism 21 that continuously changes the valve characteristics of the intake valve 14, and a rocker arm mechanism 22 that opens and closes the exhaust valve 15 uniquely. A structure that is integrated into a unit is used.

  1 to 6, reference numeral 25 denotes a holding member, 26 denotes a camshaft, 27 denotes an exhaust rocker shaft, 28 denotes a control shaft that also serves as an intake rocker shaft, and 29 denotes a support shaft. is there. Each of the shafts 26 to 29 is formed of a shaft member that extends in the front-rear direction of the engine. Among these, the camshaft 26 includes a cam group, for example, an intake cam 26a (corresponding to the valve drive cam of the present application) and a pair of valves disposed on both sides of each cam as shown in a part of FIG. Three cams such as an exhaust cam 26b (only part of which is shown in FIG. 5) are formed.

  The holding member 25 is disposed at each point on the upper part of the cylinder head 2, for example, at the frontmost part, between the cylinders, and at the rearmost part of the cylinder row. As shown in FIG. 6, the holding member 25 includes a combination of a holder portion 32 and a cap portion 33 that is assembled to the lower end portion of the holder portion 32. The camshaft 26 is sandwiched between a journal surface formed on the lower end surface of each holder portion 32 and a journal surface formed on the upper surface of the cap portion 33 and is rotatably supported. The control shaft 28 is rotatably supported on the intake side (one side in the width direction) of the middle stage of each holder portion 32. The exhaust rocker shaft 27 is fixed on the exhaust side (the other side in the width direction) opposite to the middle control shaft 28 of each holder portion 32. Further, the support shaft 29 is fixed at the upper part of each holder portion 32. As shown in FIG. 6, a pair of fixed seats 34 are formed on both sides of each holder portion 32 at positions near the exhaust rocker shaft 27 and the control shaft 28. With such a structure, a frame that can be mounted on the cylinder head 2 is formed.

In the same frame, a variable valve mechanism 21 and a rocker arm mechanism 22 are assembled for each cylinder. For example, as shown in FIG. 5, the variable valve mechanism 21 has a structure in which a rocker arm 40, a swing cam 50 (swing cam), and a center rocker arm 60 (transmission arm) are combined.
That is, as shown in FIG. 3 and FIG. 4, the rocker arm 40 is an arm member divided into two parts. As shown in FIG. 5, the central portion of the arm member is rotatably supported by the control shaft 28, and an adjustment screw portion 41 provided at the distal end portion of the arm member is projected to the side of the frame, A needle roller 42 provided at the base end is disposed on the support shaft 29 side.

As shown in FIGS. 3 to 5, the swing cam 50 is formed of a swing cam member having one end rotatably supported by the support shaft 29 and the other end protruding toward the needle roller 42 of the rocker arm 40. The The cam surface 51 formed on the other end surface is in rolling contact with the needle roller 42. A sliding roller 52 is rotatably incorporated in the lower portion of the swing cam member.
As shown in FIG. 5, the center rocker arm 60 is disposed at a point surrounded by the intake cam 26 a, the control shaft 28, and the sliding roller 52. The center rocker arm 60 is formed in an L shape by an arm portion 61 that extends toward the upper sliding roller 52 and an arm portion 62 that extends directly below the control shaft 28 in the lateral direction. A slope 61 a (for example, a surface having a low control shaft side and a high support shaft side) formed on the tip surface of the arm portion 61 is in contact with the sliding roller 52 of the swing cam 50. The sliding roller 63 supported by the intersecting portion of the arm portions 61 and 62 is brought into rolling contact with the cam surface of the intake cam 26a, and the cam displacement of the intake cam 26a, which becomes a valve drive output, passes through the arm portion 61 and swing cam. Output to 50. The pin part 64 supported at the end of the arm part 62 so as to be freely bent is inserted into a through hole 65 formed in the control shaft 28 so as to be freely rotatable. By this insertion, the center rocker arm 60 is swingably supported with the bending point as a fulcrum. When the control shaft 28 is rotationally displaced by the built-in structure of the center rocker arm 60, the center rocker arm 35 changes the direction of contact with the intake cam 26a and the direction intersecting the cam shaft 16 (advance direction or delay). (Angular direction).

  Due to this displacement, the valve drive output output from the center rocker arm 60, for example, the valve lift amount and the opening / closing timing of the intake valve 14 are continuously varied simultaneously. That is, the cam surface 51 has a base circle section corresponding to the base circle of the intake cam 26a on the upper side and a lift section (corresponding to the cam shape of the lift area of the intake cam 26a) on the lower side. . Thereby, when the sliding roller 63 of the center rocker arm 60 is displaced in the advance angle direction or the retard angle direction of the intake cam 26a, the posture of the swing cam 50 changes, and the region of the cam surface 51 on which the needle roller 42 swings is changed. Change. In other words, the ratio between the base section where the needle roller 42 swings and the lift section changes. The valve lift amount of the intake valve 14 is reduced by the cam shape at the top of the intake cam 26a by using the change in the ratio of the base section and the lift section with the phase change in the advance direction and the phase change in the retard direction. It is continuously variable from the valve lift to the high valve lift provided by the cam shape from the top to the base end of the intake cam 26a. At the same time, the opening / closing timing of the intake valve 14 is made variable so that the closing timing is larger than the opening timing.

In other words, the variable valve mechanism 21 allows the valve lift amount and the opening / closing timing to be continuously variable with the lift variable range from the low valve lift to the high valve lift. A screw member 66 for adjusting the protruding amount of the pin portion 64 is screwed into the through hole 65 so as to be able to advance and retract (for adjusting the valve opening / closing timing and valve lift amount for each cylinder).
The rocker arm mechanism 22 (exhaust side) has a pair of rocker arms 67 as shown in FIG. 5 (only one side is shown). The pair of rocker arms 67 are positioned on both sides of the center rocker arm 35 and are rotatably supported by the exhaust rocker shaft 27. A roller member (not shown) at one end is brought into rolling contact with the cam surface of the exhaust cam 26b, and an adjusting screw portion 67a at the other end is projected to the side of the frame.

  With these structures, the camshaft 26, the variable valve mechanism 21, and the rocker arm mechanism 22 are integrated into one. Each fixed seat 34 of the unitized variable valve apparatus 20 is installed on the boss portion 17 protruding from the bottom surface of the recess 2a (cylinder head 2) as shown in FIGS. Each fixed seat 34 is fixed together with the cylinder head 2 by a cylinder head bolt 18 screwed into the cylinder block 1 through the fixed seat 34 and the cylinder head 2 as shown in FIGS. Tighten together). The foremost and rearmost holding members 25 are fixed to the cylinder head 2 with other fixing bolts 18a.

  As shown in FIG. 5, the adjustment valve portion 41 of each rocker arm 40 (for intake air) is disposed at the stem end of the intake valve 14 assembled to the cylinder head 2 as shown in FIG. The adjusting screw portion 41 of the rocker arm 67 is disposed at the stem end of the exhaust valve 15 assembled to the cylinder head 2. A pusher 68 is assembled to the swing cam 50. The pusher 68 is a component that presses the center rocker arm 60 against the intake cam 26 a via the swing cam 50.

  Further, one end portion of the camshaft 26 protrudes forward through a penetrating portion 1b provided on an end wall surrounding the concave portion 2a of the cylinder head 1 as shown in FIG. As shown in FIGS. 1 to 3, a cam sprocket 70 that is a timing component is provided at the protruding end portion of the camshaft 26. An endless timing chain 72 is stretched between the cam sprocket 70 and a crank sprocket 71 provided at one end of the crankshaft 9 so that the camshaft 26 is rotated by crank output.

  As shown in FIG. 3, a drive device 80 that drives the control shaft 28 is provided at the foremost portion of the cylinder head 1. This driving device 80 is a device that constitutes the variable valve operating device 20 together with the variable valve operating mechanism 21. For example, an electric motor 81 as a drive source and a transmission mechanism separate from the electric motor 81, for example, a worm gear reduction mechanism 82 are provided. A combined structure is used. For the worm gear reduction mechanism 82, for example, a combination of a fan-shaped worm wheel gear 83 and a worm shaft gear 84 meshing therewith is used. Of these, the portion including the worm shaft gear 84 is unitized as a worm shaft gear unit 85 separate from the worm wheel gear 83.

  That is, the fan-shaped worm wheel gear 83 has a large number of gear teeth 87 on the outer peripheral edge portion of the fan-shaped plate-shaped main body 86 as shown in FIGS. A plate-shaped part is used. This fan-shaped component mounting seat 88 is fixed to the shaft end of the control shaft 28 protruding forward from the foremost holder portion 32 (holding member 25) by a fixing bolt 89, and the gear teeth 87 are placed above the cylinder head 2. It is arranged.

  The worm shaft gear unit 85 has a frame 90 as shown in FIGS. The frame 90 includes a base portion 90a extending in the width direction of the cylinder head 2 and a pair of arm portions 90b extending in the front-rear direction of the cylinder head 2 from both end portions of the base portion 90a. A bearing surface 90c (shown in FIG. 2) is formed at the tip of the arm portion 90b. The worm shaft gear 84 uses a shaft portion 84b having a worm gear tooth 84a in the middle. Both end portions of the shaft portion 84b are rotatably supported by the bearing surface 90c, and the worm gear portion 84b is disposed between the bearing surfaces 90c. And one of the male part 91a and the female part 91b which comprise the Oldham coupling 91, for example, the male part 91a, is connected to one of the shaft parts 84b protruding from the arm part 90b. In addition, installation seats 92 for mounting on the cylinder head 2 are formed at both ends of the base portion 90a.

  These installation seats 92 are formed on the upper part of the foremost holder part 32 (holding member 25), specifically on the part directly above the control shaft 28, using fixing bolts 93 as shown in FIG. The worm shaft gear unit 85 is attached to the cylinder head 2 sideways. During this attachment, the worm shaft gear 84 meshes with the worm wheel gear 83 as shown in FIG. In particular, the worm shaft gear unit 85 is assembled in an inclined posture lowered to the cylinder head 2 side so that the Oldham coupling 91 side is lower than the point of the meshing portion 95 where the worm shaft gear 84 and the worm wheel gear 83 are engaged. is there. Thereby, the control rotation (rotation that determines the valve lift amount and the required valve characteristics of the opening / closing timing) input from the male portion 91a of the Oldham coupling 91 is transmitted to the control shaft 28 through the meshing portion 95 of both the gears 83 and 84. To be. Thus, for example, when the worm wheel gear 83 is rotationally displaced in the direction toward the exhaust rocker shaft 27 as shown by the arrow in FIG. 2, the controlled rotation controlled to the high valve lift side is directed to the control shaft 28. On the contrary, when the rotational displacement is made in the direction toward the Oldham coupling 91, the control rotation to be controlled to the low valve lift side is transmitted to the control shaft 28.

  Here, the control shaft 28 is assembled so that each part of the variable valve mechanism 21 is assembled so that the valve reaction force (spring reaction force) transmitted from the variable valve mechanism 21 acts only in one rotation direction, for example, in the low valve lift direction. Is set. Thus, the worm shaft gear 84 has a structure in which the valve reaction force acts only in one axial direction. In order to receive this valve reaction force, a thrust receiving portion 96 is provided on the shaft portion on the Oldham coupling 91 side. Specifically, the thrust receiving portion 96 is formed in a flange shape and is disposed at a point adjacent to the arm portion 90b on the Oldham coupling 91 side. The thrust receiving portion 96 is slidably received by a thrust surface 97 (shown in FIG. 2) formed on the arm portion 90b. Thus, the thrust force caused by the valve reaction force is prevented from being transmitted to the Oldham coupling 91 side.

  Further, the direction of the gear teeth 84a and 87 with which the worm wheel gear 83 and the worm shaft gear 84 are engaged is an oblique direction that causes the worm wheel gear 83 itself to generate a force toward the holding member 25 by the valve reaction force. Is set. Thereby, the control shaft 28 has a structure in which a thrust force acts only in one axial direction. Further, although not shown, the thrust force (one direction) acting on the control shaft 28 includes a thrust surface formed at one end portion of the control shaft 28, for example, an end portion on the worm wheel gear 83 side, and a frontmost holder portion 32 (holding). It is received by a receiving structure formed by a thrust receiving portion formed on the front surface of the member 25).

  As shown in FIGS. 2 and 3, the electric motor 81 uses a motor main body 81a in which a normal rotor and a stator (not shown) are combined. That is, the electric motor 81 includes an electric motor portion 81a having a cylindrical insertion portion 81d at the tip and a mounting bracket 81b attached to the body. And the motor shaft 81c of the electric motor part 81a has penetrated the center of the insertion part 81d, and is extended ahead. The remaining part of the Oldham coupling 91, that is, the female portion 91b is attached to the front end portion of the motor shaft 81c extending forward.

  The mounting bracket 81b is formed of an L-shaped bracket member that can be attached to a motor mounting surface 2b (shown in FIG. 2) formed on the side of the cylinder head 2. Moreover, the insertion part 81d has comprised the shape which can be inserted in the cylindrical insertion port part 3a formed in the side wall of the rocker cover 3, as FIG.1 and FIG.2 shows. An annular oil seal member 98 is attached to the outer peripheral surface of the insertion portion 81d so as to protrude outward from the outer peripheral surface.

  Using these structures, the electric motor 81 is assembled to the worm shaft gear unit 85. That is, in the electric motor 81, as shown in FIGS. 2 and 3, the insertion part 81d is inserted into the insertion part 3a, and the female part 91b at the tip is used as the male part of the worm shaft gear unit 85 with the insertion part 3a as a guide. Then, the mounting bracket 81b is bolted to the motor mounting surface 2b of the cylinder head 2 so as to be detachably assembled to the worm shaft gear unit 85. As shown in FIG. 2, when the insertion portion 81d is inserted into the insertion port portion 3a, only the oil seal member 98 elastically contacts the inner surface of the insertion port portion 3a, and the outer peripheral surface of the other insertion portion 81d is the insertion port portion. 3a away from the inner surface.

  On the other hand, the worm gear speed reduction mechanism 82 (transmission mechanism) incorporates a backlash stuffing mechanism 100 (corresponding to the backlash stuffing means and the pressing mechanism portion of the present application) that packs backlash generated in the meshing portion 95. The backlash stuffing mechanism 100 uses a structure that applies a biasing force to stuff backlash into only a part of the variable range of lift from the low valve lift to the high valve lift. Specifically, a structure that applies an urging force only to the high valve lift region is used. The structure of the backlash stuffing mechanism 100 is shown in FIGS.

  As shown in FIGS. 7 to 9, the structure is advantageous in driving the control shaft 28 (high torque) and has a function of reducing the number of parts, and a compact toggle spring member. A structure in which 101 is assembled is used. That is, as shown in FIG. 8, the toggle spring member 101 is a spring component in which, for example, a plurality of strands are wound in a ring shape and both end portions 101a of the strands are projected in parallel in the diametrical direction. When an external force is applied to one end 101a from a state in which no external force is applied to 101a), the wound coil portion 101b is elastically displaced in the torsional direction, and a spring force corresponding to the elastic displacement is generated. As shown in FIG. 7, the coil portion 101b of the toggle spring member 101 has an annular boss portion 88a (control) formed on the rotating fulcrum portion of the worm wheel gear 83, for example, the back surface of the mounting seat 88 of the worm wheel gear 83. Assemble it so that it is wound around the shaft end). One of both end portions 101a arranged in parallel with the rotation direction of the worm wheel gear 83, for example, the end portion 101a on the electric motor 81 side is fixed to the back surface of the main body 86 of the worm wheel gear 83. It is fixed by being inserted into a fixing hole 86a formed on the back surface. The remaining end portion 101a is locked by an arc-shaped wall portion 88b formed so as to surround a part (lower side) of the coil portion 101b on the back surface of the mounting seat 88, and the toggle spring member 101 is almost entirely It is kept free. This remaining end portion 101b becomes an external force input portion 103 that receives an external force.

  Corresponding to the external force input portion 103, as shown in FIGS. 2 and 7, the holding member 25 has a surface facing the worm wheel gear 83. A contact portion 104 that can be contacted is provided. The contact portion 104 is formed from a protrusion protruding from the front surface of the holder portion 32, for example. The contact portion 104 is, for example, a low valve lift region with a small valve reaction force in a worm wheel gear 83 that rotates and displaces within a predetermined point, specifically, a lift variable range from a low valve lift to a high valve lift. In the middle valve lift area, it does not come into contact with the external force input portion 103 (end portion 101b), but comes into contact with the external force input portion 103 when reaching the high valve lift region where the valve reaction force is large as shown in FIG. Is arranged. Due to the contact portion 104, the toggle spring member 101 starts to be elastically displaced in the direction of contraction when the high valve lift amount is reached, and thereafter, the elastic displacement proceeds to the end of the high valve lift.

In other words, the toggle spring member 101 has the gear teeth of the worm wheel gear 83 only when it is set, for example, in the region of the high valve lift amount section in the lift variable region in which the valve lift amount of the intake valve 14 is continuously variable. 87 is incorporated so that a force (urging force) is applied to the tooth surface of the worm shaft gear 84 against the tooth surface of the worm gear tooth 84a.
Next, the operation of the variable valve operating apparatus 20 configured as described above will be described.

Now, it is assumed that the camshaft 26 is driven (rotated) by the shaft output of the crankshaft 9 transmitted from the timing chain 72 as shown in the direction of the arrow in FIGS.
At this time, as shown in FIG. 5, the sliding roller 63 of the center rocker arm 60 receives the cam displacement of the intake cam 26a. As a result, a valve drive output is output from the center rocker arm 60. That is, the center rocker arm 60 swings in the vertical direction with the pin portion 64 as a fulcrum according to the cam displacement.

  The sliding roller 52 of the swing cam 50 receives the swinging displacement of the center rocker arm 60 through an inclined surface 61 a that is in rolling contact with the sliding roller 52. For this reason, the swing cam 50 repeats the swinging motion that is pushed up or lowered by the slope 61a while rolling on the slope 61a. As the swing cam 50 swings, the cam surface 51 of the swing cam 50 reciprocates in the vertical direction.

At this time, since the cam surface 51 is in rolling contact with the needle roller 42 of the rocker arm 40, the cam surface 51 periodically presses the needle roller 42. In response to this pressing, the rocker arm 40 is swung with the control shaft 28 as a fulcrum to open and close the pair of intake valves 14.
On the other hand, each exhaust rocker arm 67 receives the exhaust cam 26b and is driven in accordance with the cam shape of the cam 26b. Thus, each exhaust rocker arm 67 swings in the vertical direction with the exhaust rocker shaft 27 as a fulcrum, thereby opening and closing the exhaust valve 15, respectively.

  At this time, it is assumed that the electric motor 81 is actuated to increase the valve lift amount according to a command from a control unit (not shown). Then, the rotation of the electric motor 81 is transmitted to the worm shaft gear 84 through the Oldham coupling 91, and the fan-shaped worm wheel gear 83 engaged with the worm shaft gear 84 is rotationally displaced (in the high lift direction in FIG. 2). . Thereby, the rotation of the electric motor 81 is transmitted to the control shaft 28 while being decelerated, and the control shaft 28 is rotated to the point of the required valve characteristic. Due to this rotational displacement, the position of the center rocker arm 60 is displaced. As a result, the sliding roller 63 of the center rocker arm 60 is displaced along the rotation direction on the intake cam 26a, and the cam surface 51 of the swing cam 50 is positioned so as to have an angle close to vertical as shown in FIG. Decide.

Due to the posture of the cam surface 51, the region (ratio) of the cam surface 51 where the needle roller 42 crosses is set to a region that provides a high valve lift amount. For example, the ratio is set to the shortest base circle section and the longest lift section. Thereby, for example, the intake valve 14 is driven so as to ensure the maximum valve lift amount.
Here, since the worm wheel gear 83 does not reach the contact portion 104 as shown in FIG. 9 until the worm wheel gear 83 reaches the low valve lift and middle valve lift sections, the toggle spring member 101 remains free. Be drunk. During this time, the worm gear speed reduction mechanism 82 is not given an urging force to close the backlash, but when the worm wheel gear 83 enters the high valve lift section, from that point on, as shown in FIG. 2 and FIG. The external force input portion 103 of the toggle spring member 101 abuts against the contact portion 104 on the cylinder head 2 side.

  From that time, as shown in FIGS. 10A and 10B, the toggle spring member 101 starts to be elastically displaced (in the direction of contraction). The elastic displacement increases as the valve lift amount increases (as the rotational displacement of the worm wheel gear 83 advances). The elastic force of the toggle spring member 101 obtained by this elastic displacement is input to the worm wheel gear 83 displaced to the high valve lift region. Due to this elastic force, the worm wheel gear 83 is biased in a direction in close contact with the worm shaft gear 84, and the tooth surfaces of the gear teeth 87 of the worm wheel gear 83 are pressed against the tooth surfaces of the worm gear teeth 84 a of the worm shaft gear 84. . Thus, the backlash (gap) between the gear teeth 87 and the worm gear teeth 84a in the meshing portion 95 is filled.

As a result, a large stroke is generated in a variable region where a large hitting sound is likely to occur, particularly in a high valve lift region where a high valve reaction force transmitted to the variable valve mechanism 21, a valve spring 16 that repeatedly expands and contracts at high speed, and valve vibrations act. The generation of sound is suppressed.
On the other hand, it is assumed that the valve lift amount is low. At this time, the electric motor 81 is operated in the opposite direction to that of the high valve lift. Then, the rotation of the electric motor 81 is transmitted to the worm shaft gear 84 through the Oldham coupling 91, and the fan-shaped worm wheel gear 83 is rotationally displaced in the opposite direction (low lift direction in FIG. 2). Thereby, the rotation of the electric motor 81 is transmitted to the control shaft 28 while being decelerated, and the control shaft 28 is rotated to a required valve characteristic, for example, a point of low valve lift.

  With this rotational displacement, the fulcrum position (pin portion 64) of the center rocker arm 60 is rotationally displaced in the direction approaching the intake cam 26a. Then, the sliding roller 63 of the center rocker arm 60 is displaced forward in the rotational direction on the intake cam 26a. As a result, the rolling contact position between the center rocker arm 60 and the intake cam 26a is shifted in the direction of advance on the intake cam 26a. By changing the rolling position, the TOP position of the valve lift curve moves in the advance direction. The slope 63 is also displaced in the advance direction in response to the movement of the center rocker arm 60. By the movement of the center rocker arm 60, the swing cam 50 changes to a posture in which the cam surface 51 is inclined downward. As the inclination increases, the area of the cam surface 51 where the needle rollers 42 come and go changes to a ratio in which the base circle section is gradually longer and the lift section is gradually shorter. Due to this change in the ratio, the intake valve 14 changes from being driven using the entire lift section of the intake cam 26a to being driven in a limited manner at a portion where it gradually shifts to the top of the lift section.

As a result, the opening / closing timing and valve lift amount of the intake valve 14 serving as the valve drive output are kept at the same valve opening timing as the maximum valve lift according to the rotational displacement input from the control shaft 28. On the other hand, it is continuously variably controlled while greatly changing the valve closing timing.
At this time, the external force input portion 103 of the toggle spring member 101 remains arranged at a point away from the contact portion 104 as shown in FIGS. 9 (a) and 9 (b). The state continues between the low valve lift region and the middle valve lift region (does not hit until the high valve lift is reached). For this reason, while the required valve characteristic is required in the variable region, the urging force that closes backlash does not act on the worm wheel gear 83.

That is, the small variable region (because the valve reaction force is small) and the middle variable region where the hitting sound between the gears is small are released from the biasing force that closes backlash. As a result, good control responsiveness is ensured in a small variable region, particularly in a variable region such as a small valve lift or an intermediate valve lift that requires fine control.
Therefore, the variable valve operating apparatus 20 can suppress the generation of a large hitting sound while ensuring the control response of the small variable region. In addition, since the electric motor 81 (drive source) that drives the control shaft 28 does not need to be changed to a large-capacity large motor, the variable valve operating apparatus 20 also has an advantage that the weight reduction and the compactness can be maintained. In particular, when an urging force that closes backlash is applied with emphasis only on the high valve lift range, it is possible to effectively prevent the occurrence of sound hitting between gears and improve control responsiveness in a small variable range. Can do.

  In addition, when the transmission mechanism employs a worm gear speed reduction mechanism 82 that is advantageous for driving the control shaft 28 and requires a small number of parts, and a structure in which the backlash stuffing mechanism 100 is assembled to the speed reduction mechanism 82, a simple structure is achieved. That's okay. In particular, when a structure in which the toggle spring member 101 is assembled to the rotation fulcrum portion of the worm wheel gear 83 is used as the backlash stuffing mechanism 100, a simple structure using the structure of the worm gear speed reducer 82 is sufficient.

Since the lubricating oil adhering to the timing chain 72 is scattered and supplied not only to the speed reduction mechanism but also to the backlash packing mechanism 100 by centrifugal force, wear of the assembly portion of the toggle spring member 101 is suppressed, and the contact portion of the spring Since the coefficient of friction is also stable, a stable spring force is exhibited and the effect is maintained.
As shown in FIG. 13, the load W1 acting on the swing fulcrum S1 when the swing cam 50 swings in the valve opening direction and the swing fulcrum S1 when the swing cam 50 swings in the valve closing direction. The direction of the load acting on the control shaft 28 is set to the same direction as indicated by the loci of the loads W1 and W2 in FIG. Thereby, when the swing cam 50 swings in the valve opening direction or when the swing cam 50 swings in the valve closing direction, the rotation direction of the load generated at the swing fulcrum S1 with respect to the control shaft 28 is changed to the control shaft 28. On the other hand, it becomes one direction clockwise, and it can suppress that the control shaft 28 rotates in the reverse direction. For this reason, the control shaft 28 is urged in one direction by the valve lift, and it is not necessary to operate the backlash packing mechanism 100. Further, the loads W1 and W2 may not be set to rotate the control shaft 28 in the same direction, but the maximum load W3 may be set to rotate the control shaft in one direction.

11 and 12 show a second embodiment of the present invention.
This embodiment employs a structure using, for example, a piston-type pusher mechanism 110 instead of the toggle spring member 101 as in the first embodiment as the backlash packing mechanism 100.
In the pusher mechanism 110, for example, as shown in FIGS. 11 and 12, a piston pusher portion 111 is assembled to a frame 90 of a worm shaft gear unit 85, and an abutting portion 112 is projected from the front surface of the worm wheel gear 83. The structure is used.

  Specifically, for example, as shown in FIG. 12, the piston pusher portion 111 has a cylindrical main body portion 115 formed on one side of the arm portion 90 b, and can be moved back and forth in series in the main body portion 115. A structure in which a piston 116, a coil spring member 118 that presses the piston 116 in the protruding direction, and a screw-type adjuster 119 for adjusting the elastic force of the coil spring member 118 is used. The piston pusher portion 111 is disposed laterally (in a direction parallel to the worm wheel gear 83) so that the tip portion of the piston 116 protruding from the main body portion 115 faces the contact portion 112 of the worm wheel gear 83. Yes.

  Further, the tip end portion of the piston 116 protruding from the main body 115 and the contact portion 112 of the worm wheel gear 83 are rotationally displaced within a lift variable range from a low valve lift to a high valve lift, as in the first embodiment. Of the worm wheel gear 83 to be operated, for example, in the low valve lift region and the middle valve lift region where the valve reaction force is small, as shown by the solid line in FIG. When it reaches, it is set to abut as shown by a two-dot chain line in FIG. As a result, when the piston pusher portion 111 reaches the section of the high valve lift amount, the elastic displacement in the direction in which the coil spring member 118 contracts starts, and thereafter, until the end of the high valve lift, the coil spring member 118 in the contracting direction. The piston 116 retreats with elastic displacement. As a result, the piston pusher 111 is set to the gear of the worm wheel gear 83 only when, for example, the region of the high valve lift amount section is set in the lift variable region in which the valve lift amount of the intake valve 14 is continuously variable. The tooth surface of the tooth 87 is configured to apply a force (urging force) to press against the tooth surface of the worm gear tooth 84 a of the worm shaft gear 84. In FIG. 12, reference numeral 120 denotes a clip member for restricting the piston 116 protruding forward from the main body 115.

In this way, the same effects as those of the first embodiment are obtained. However, in FIG. 11 and FIG. 12, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
In addition, this invention is not limited to any embodiment mentioned above, You may implement variously within the range which does not deviate from the main point of this invention. For example, in the above-described embodiment, the present invention is applied to a variable valve apparatus that continuously varies the valve characteristics of the intake valve. However, the present invention is not limited to this, and a variable valve apparatus that continuously varies the valve characteristics of the exhaust valve. The present invention may be applied to. In the above-described embodiment, the lift amount and the opening / closing timing can be changed at the same time. However, for example, a variable valve operating apparatus that changes only one of them, for example, a variable valve apparatus that changes the opening / closing timing using a constant velocity joint. Can also be applied.

1 is a perspective view showing an overview of an internal combustion engine according to a first embodiment of the present invention. Sectional drawing which follows the AA line in FIG. The perspective view of the internal combustion engine which removed the rocker cover and the timing chain cover, and exposed the variable valve apparatus. The perspective view which removed the variable valve apparatus from the cylinder head. Sectional drawing of the variable valve apparatus which follows the BB line in FIG. Sectional drawing of the variable valve apparatus which follows the CC line in FIG. The perspective view for demonstrating a backlash packing mechanism. The disassembled perspective view which decomposed | disassembled the principal part of the mechanism. The figure for demonstrating the behavior of the backlash packing mechanism when set to a low valve lift. The figure for demonstrating the behavior of the backlash packing mechanism when set to a high valve lift. The disassembled perspective view which shows the different backlash packing mechanism used as the principal part of the 2nd Embodiment of this invention. The partially sectional side view for demonstrating the behavior of the backlash packing mechanism. Sectional drawing of the variable valve apparatus which follows the BB line in FIG. 3 when it sets to a low valve lift.

Explanation of symbols

2 Cylinder Head 14 Intake Valve 20 Variable Valve Operating Device 21 Variable Valve Mechanism 26 Cam Shaft 26a Intake Cam (Valve Drive Cam)
28 Control shaft 81 Electric motor (drive source)
82 Worm gear reduction mechanism (transmission mechanism)
83 Worm wheel gear 84 Worm shaft gear 100 Backlash filling mechanism (backlash filling means, pressing mechanism)
101 toggle spring member 104 contact portion.

Claims (3)

A camshaft having a valve drive cam;
A swing cam having a cam surface for driving the valve, and a swingable support shaft rotatably supported by the swing drive cam and the valve drive cam. A transmission arm that transmits the displacement to the swing cam, and changes the valve characteristic of the valve by changing the position of the transmission arm that contacts the valve drive cam according to the rotational displacement input from the control shaft. A variable valve mechanism that variably controls the valve lift amount in a predetermined low valve lift to high valve lift range while controlling,
A transmission mechanism that outputs a control rotation that is output from the drive source and sets a required valve lift amount to the control shaft by meshing the gear;
Backlash stuffing means that is provided in the transmission mechanism and provides a biasing force to stuff backlash into the gear of the transmission mechanism only in the high valve lift region of the low valve lift to high valve lift range,
In the variable valve mechanism, the maximum load received from the transmission arm during valve lift rotates the control shaft in one direction in a region other than the high valve lift region in the low valve lift to high valve lift range. A variable valve operating apparatus for an internal combustion engine, characterized by being set to be a load. The transmission mechanism comprises a worm gear reduction mechanism having a worm wheel gear provided on the control shaft, a worm shaft gear that meshes with the worm wheel gear and transmits the control rotation to the worm wheel gear,
When the backlash stuffing means is assembled to the worm gear reducer and is set in the high valve lift range, the pressing force presses the gear teeth of the worm wheel gear against the gear teeth of the worm shaft gear while increasing the urging force. The variable valve operating apparatus for an internal combustion engine according to claim 1 , further comprising a mechanism portion. When the pressing mechanism portion is wound around the rotation fulcrum portion of the worm wheel gear and is set in a high valve lift region, the pressing mechanism portion is elastically displaced in a contraction direction following the rotation displacement of the worm wheel gear, The variable valve operating apparatus for an internal combustion engine according to claim 2 , further comprising a toggle spring member that presses the gear teeth of the worm wheel gear against the gear teeth of the worm shaft gear.

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