JP2006307785A - Variable valve gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a decline in gear transmission efficiency and ensure the excellent control responsiveness of valve opening characteristics in regard to a variable valve gear. <P>SOLUTION: A control shaft 12 having a helical gear 12a concentric with a shaft center is provided. A motor 22 driving the control shaft 12 is provided. A worm gear mechanism 20 converting a drive force from the motor 22 into a rotational force of the control shaft 12 is provided. The orientation of each helix angle of the helical gear 12a and a helical gear 14a of a worm wheel 14 is set such that the direction of a thrust force applied to the control shaft 12 via the helical gear 12a is the same as the direction of a thrust force applied to the control shaft 12 via the worm gear mechanism 20 during the rotation of the control shaft 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a variable valve operating apparatus, and more particularly to a variable valve operating apparatus for an internal combustion engine that can mechanically change the valve opening characteristics of the valve.

  Conventionally, for example, Patent Document 1 discloses a variable valve operating apparatus for an internal combustion engine that can mechanically change a valve opening characteristic. In this variable valve operating apparatus, a variable mechanism for changing the valve opening characteristic of the valve is interposed between the rotary cam and the valve. The variable mechanism includes a swing arm that pushes the rocker arm by swinging in synchronization with the rotating cam, and a control arm that changes the swing range of the swing arm. The swing arm and the control arm are coupled via an input arm and a transmission arm having an input roller in contact with the rotating cam. The control arm is meshed with the control shaft via a helical gear. According to such a configuration, the rotation angle of the control arm is changed by driving the control shaft in the axial direction or the rotation direction, and as a result, the swing range of the swing arm is changed. For this reason, according to the conventional variable valve apparatus, the valve opening characteristics of the valve can be continuously changed according to the drive amount of the control shaft.

JP 2004-1000055 A JP 2003-239712 A Japanese Patent No. 3245492

  By the way, as a configuration for driving the control shaft of the variable valve device as described above, a worm gear mechanism including a worm wheel fixed to the control shaft and a worm gear meshing with the worm wheel is provided, and an actuator such as a motor is used. A device that rotationally drives a control shaft through the worm gear mechanism is known.

  When the worm gear mechanism as described above or the helical gear in the conventional variable valve operating apparatus is incorporated in the drive unit of the control shaft, a thrust force is generated on the control shaft when the control shaft is driven to rotate. In such a case, if a large thrust force acts on the tooth surfaces of the worm gear mechanism or the helical gear, the frictional force between the tooth surfaces of these gears increases, and the transmission efficiency of the gears decreases. As a result, the control response at the time of changing the valve opening characteristic of the valve is lowered.

  The present invention has been made to solve the above-described problems, and provides a variable valve operating apparatus that can suppress a reduction in transmission efficiency of a gear and ensure good control response of a valve opening characteristic. The purpose is to do.

In order to achieve the above object, a first invention is a variable valve operating device that mechanically changes a valve opening characteristic with respect to rotation of a camshaft,
A control shaft provided with a helical gear concentric with the shaft center;
A worm gear mechanism for converting a force from a drive source into a rotational force of the control shaft;
A member that meshes with the helical gear, and a variable mechanism that changes a valve opening characteristic according to a rotational position of the control shaft,
The directions of the torsion angles of the helical gear and the worm gear mechanism are as follows:
The thrust force acting on the control shaft via the helical gear and the thrust force acting on the control shaft via the worm gear mechanism are set to be in the same direction when the control shaft is rotationally driven. Features.

Further, a second invention is the first invention according to the first invention, a support portion for supporting the control shaft so that an axial position of the control shaft is regulated;
Friction force alleviating means for alleviating a friction force generated based on the thrust force in the same direction acting on the support portion is provided.

  When the control shaft is driven to rotate, the reaction force of the valve spring acts on the helical gear of the control shaft. As a result, a thrust force acts on the control shaft in the axial direction of the control shaft via the helical gear. When the control shaft is driven to rotate, a thrust force acts on the control shaft in the axial direction of the control shaft via the worm gear mechanism. According to the first aspect, since the thrust force is in the same direction, it is possible to avoid the thrust force from acting on the tooth surface of the helical gear of the control shaft or the gear of the worm gear mechanism. For this reason, according to the present invention, it is possible to suppress a reduction in transmission efficiency of the gear accompanying an increase in the frictional force between the tooth surfaces of these gears, and thereby good control of the valve opening characteristics. Responsiveness can be ensured.

  According to the second invention, while avoiding the thrust force from acting on the tooth surface of the gear, it is avoided that the drive force of the control shaft increases with the increase of the friction force in the support portion receiving the thrust force. can do.

Embodiment 1 FIG.
[Configuration of variable valve gear]
FIG. 1 is a diagram for explaining a configuration of a drive unit in the variable valve operating apparatus 1 of the present embodiment. More specifically, FIG. 1 (A) is a view of the variable valve operating apparatus 1 as viewed from the axial direction of the worm gear 18, and FIG. 1 (B) is an illustration of the variable valve operating apparatus 1 in FIG. 1 (A). It is the figure seen from the A arrow direction shown in FIG. Here, the variable valve operating apparatus 1 according to this embodiment is combined with an in-line four-cylinder internal combustion engine, and has four variable valve mechanisms 10 provided corresponding to individual cylinders. Moreover, the variable valve operating apparatus 1 of this embodiment is provided with the control shaft 12 arrange | positioned so that all the variable valve mechanisms 10 may be cut through four cylinders. The control shaft 12 is held on the cylinder head of the internal combustion engine by a bearing (not shown).

  A helical gear 12 a having a predetermined twist angle and concentric with the control shaft 12 is formed on the outer peripheral surface of the control shaft 12. The helical gear 12a is formed corresponding to each cylinder so as to mesh with a helical gear 42a (see FIG. 2) provided on a control arm 42 (described later) disposed in each cylinder. The helical gear 12 a is formed in a left-handed spiral with respect to the axial direction of the control shaft 12.

  A worm wheel 14 is fixed to one end of the control shaft 12. Further, a flange 16 formed in a disk shape so as to protrude in the radial direction of the control shaft 12 is fixed to the other end side of the control shaft 12. The flange 16 is disposed with a predetermined clearance between the flange 16 and a support member such as a cylinder head. The flange 16 is configured to restrict the axial position of the control shaft 12. According to such a configuration, the thrust force acting on the control shaft 12 can be received by the flange 16.

  A helical gear 14 a having a predetermined twist angle is formed on the outer peripheral surface of the worm wheel 14. The helical gear 14 a is formed in a right-handed spiral with respect to the axial direction of the control shaft 12. The helical gear 14 a of the worm wheel 14 is meshed with a worm gear 18 whose longitudinal direction is a direction orthogonal to the axial direction of the control shaft 12. According to the worm gear mechanism 20 including the worm gear 18 and the worm wheel 14, the rotation of the worm gear 18 can be converted into the rotation of the control shaft 12 with a large reduction ratio.

  A motor 22 is connected to the worm gear 18 as an actuator for driving the control shaft 12. The motor 22 can receive a drive signal supplied from the outside and rotate its rotating shaft. For this reason, according to the variable valve operating apparatus 1 of this embodiment, the control shaft 12 can be rotationally driven by controlling the rotation of the motor 22. In the configuration shown in FIG. 1, the worm wheel 14 is fixed to one end of the control shaft 12, but the position of the worm wheel 14 on the control shaft 12 is not limited to this. It can be arbitrarily set between the variable valve mechanism 10 of the cylinder.

  FIG. 2 is a cross-sectional view for explaining the configuration of the variable valve mechanism 10 shown in FIG. More specifically, FIG. 2 is the figure which looked at the variable valve mechanism 10 from the II arrow direction shown in FIG. The variable valve mechanism 10 is a mechanism for driving the valve 30 of the internal combustion engine that functions as an intake valve or an exhaust valve. As shown in FIG. 2, the variable valve mechanism 10 is a rocker arm type mechanical valve mechanism. The rotational movement of the cam shaft 32 in the variable valve mechanism 10 is converted into the rocking movement of the rocker arm 36 by the main cam 34 provided on the cam shaft 32, and is converted into the lift movement of the valve 30 supported by the rocker arm 36. The In the variable valve mechanism 10, the rocker arm 36 is not directly driven by the main cam 34, but the control mechanism 38 and the swing cam arm 40 are interposed between the main cam 34 and the rocker arm 36.

  The control mechanism 38 is a mechanism that can continuously change the interlocking state between the rotational motion of the main cam 34 and the rocking motion of the rocker arm 36 by changing the rocking range of the rocking cam arm 40. For this reason, according to the variable valve mechanism 10 of the present embodiment, the swing amount and swing timing of the rocker arm 36 are changed by variably controlling the control mechanism 38, and the lift amount and valve timing of the valve 30 are changed. It can be changed continuously.

  As described below, the control mechanism 38 includes the control shaft 12, the control arm 42, and the intermediate arm 44 as main constituent members. The control shaft 12 described above is arranged in parallel with the cam shaft 32. The control arm 42 is rotatably attached to the cam shaft 32. The control arm 42 is formed with a helical gear 42 a that is paired with the helical gear 12 a of the control shaft 12. The helical gear 42 a of the control arm 42 is formed in a fan shape along the rotation center of the control arm 42, that is, an arc concentric with the cam shaft 32. Therefore, the torque of the control shaft 12 is input to the control arm 42 via the helical gear 12a and the helical gear 42a.

  The intermediate arm 44 is rotatably attached to the swing fulcrum 46 of the control arm 42. A cam roller 48 that comes into contact with the main cam 34 and a slide roller 50 arranged coaxially with the cam roller 48 are incorporated in the intermediate arm 44. The slide roller 50 is configured to come into contact with a slide surface 52 provided on the swing cam arm 40.

  The swing cam arm 40 is rotatably held by the control shaft 12. The slide surface 52 is formed on the swing cam arm 40 so as to face the main cam 34. The slide surface 52 is a surface for the swing cam arm 40 to come into contact with the slide roller 50, and the main cam 34 increases as the slide roller 50 moves from the distal end side of the swing cam arm 40 toward the axial center of the control shaft 12. Is formed with a curved surface that gradually narrows. On the opposite side of the slide surface 52, a rocking cam surface 56 is formed as a surface in contact with the rocker roller 54 of the rocker arm 36. The oscillating cam surface 56 is formed such that the distance from the oscillating center of the oscillating cam arm 40 is constant, and the position away from the non-operating surface 56a is closer to the axis of the control shaft 12. It is comprised with the action surface 56b formed so that distance may become far.

  The swing cam arm 40 is provided with a spring seat 60 for applying a lost motion spring 58. The lost motion spring 58 is a compression spring, and the other end is fixed to the cylinder head. The urging force of the lost motion spring 58 acts as a force that the slide surface 52 urges the slide roller 50 and presses the cam roller 48 against the main cam 34. In other words, this urging force acts as a force for always maintaining the mechanical contact between the main cam 34 and the swing cam arm 40.

  A valve shaft 62 that supports the valve 30 is in contact with one end of the rocker arm 36. The valve shaft 62 is urged by a valve spring (not shown) in the valve closing direction, that is, in the direction of pushing up the rocker arm 36. The pressing force of the main cam 34 is transmitted to the rocker arm 36 through the control mechanism 38 and the swing cam arm 40, and the pressing force of the main cam 34 is transmitted from the rocker arm 36 to the valve shaft 62 against the spring force of the valve spring. Thus, the opening / closing operation of the valve 30 is realized. The other end of the rocker arm 36 is rotatably supported by a hydraulic lash adjuster 64.

[Operation of variable valve gear]
Next, referring to FIG. 3 and FIG. 4, the required drive of the control shaft 12 that changes with the operation of the variable valve mechanism 10 shown in FIG. Explain the power.
3 (A) and 3 (B) show how the variable valve mechanism 10 operates so as to give a small lift to the valve 30, and FIG. 3 (A) shows the closed state. FIG. 3B shows a state where the valve 30 has reached the maximum lift position. In FIG. 3 and FIG. 4 to be described later, the configuration of the control mechanism 38 is shown in a simplified manner except for the necessary portions, but the specific configuration is the same as in FIG.

(1) Lifting Operation of Variable Valve Mechanism First, the lifting operation of the variable valve mechanism 10 will be described with reference to FIGS. 3 (A) and 3 (B).
In the state shown in FIG. 3A, the pressing force of the main cam 34 does not act on the cam roller 48, and the contact point X between the swing cam surface 56 and the rocker roller 54 (hereinafter referred to as "roller contact point X"). ) Shows a state in which the biased force of the lost motion spring 58 is maintained at a predetermined position on the non-action surface 56a.

  In the above state, when the cam nose presses the cam roller 48 as the main cam 34 rotates, the force is transmitted to the slide surface 52 via the slide roller 50, and the swing cam arm 40 is centered on the control shaft 12. A clockwise rotation in FIG. 3B occurs. At this time, while the roller contact point X is on the non-operation surface 56a, the pressing force of the main cam 34 is not transmitted to the rocker arm 36, but the roller contact point X is further rotated by the further rotation of the swing cam arm 40. Reaches the working surface 56b, the rocker arm 36 is pushed down, and the valve 30 is given movement in the valve opening direction.

  The state shown in FIG. 3B shows a state where the top of the cam nose presses the cam roller 48. When the valve 30 starts the lift operation, the reaction force F1 of the valve spring acts on the swing cam arm 40. As a result, a moment around point P (the rotation center of the swing cam arm 40) regarding the reaction force F1 acts on the slide roller 50. The force F2 shown in FIG. 3B is a force acting on the roller contact point Y (the contact point between the slide roller 50 and the slide surface 52) of the slide roller 50 based on the moment.

  As described above, the slide roller 50 is supported by the swing fulcrum 46 (see FIG. 2) provided on the control arm 42. For this reason, the circumferential tangential direction component F2a of the force F2 acts on the control arm 42 with respect to the tangential direction of the circumference around the cam shaft center Q. This force F2a acts as a force for rotating the control arm 42 in the counterclockwise direction in FIG. As a result, the above-described reaction force F1 of the valve spring is transmitted from the control arm 42 side to the helical gear 12a of the control shaft 12. That is, the reaction force F1 of the valve spring acts as a force for rotating the control shaft 12 in the clockwise direction in FIG.

(2) Changing operation of working angle and lift amount of variable valve mechanism FIG. 4 (A) and FIG. 4 (B) operate so that the variable valve mechanism 10 gives a large lift to the valve 30. FIG. 4A shows the closed state, and FIG. 4B shows the state where the valve 30 has reached the maximum lift position.
The large lift state shown in FIG. 4 (A) shows a state where the control shaft 12 is rotated more in the counterclockwise direction in FIG. 4 (A) than the small lift state shown in FIG. 3 (A). Yes. When the control shaft 12 is rotated counterclockwise in FIG. 4A, the control arm 42 transmits the driving force of the control shaft 12 via the helical gear 42a, so that the control arm 12 rotates clockwise in FIG. 4A. Rotate in the direction. As a result, the slide roller 50 supported by the swing fulcrum 46 moves in a direction approaching the control shaft 12 while maintaining contact with the slide surface 52 and the main cam 34.

  Since the swing cam arm 40 is always urged toward the slide roller 50 by the lost motion spring 58, if the roller contact point Y changes, the rotation position of the swing cam arm 40 also changes following the change. In the valve-closed state shown in FIG. 4A, the roller contact point X in the state where the pressing force of the main cam 34 is not applied by moving the slide roller 50 in the direction approaching the control shaft 12 is shown in FIG. Compared with the state shown in A), the rotation is closer to the working surface 56b. If the initial position of the roller contact point X is closer to the working surface 56b, the roller contact point X in the state where the top of the cam nose is in contact with the cam roller 48 is shown in FIG. 4B. It will move more greatly to the tip side of 40.

  As described above, the action surface 56b of the swing cam arm 40 of the present embodiment is formed such that the distance from the center of the control shaft 12 increases as the distance from the non-action surface 56a increases. For this reason, when the valve 30 is lifted, the roller contact point X is further moved to the tip end side of the swing cam arm 40, and as shown in FIG. That is, the lift amount and operating angle of the valve 30 increase. As described above, according to the variable valve mechanism 10 of the present embodiment, the swing range of the swing cam arm 40 is changed by rotationally driving the control shaft 12 and changing the position of the roller contact point Y of the slide roller 50. As a result, the operating angle and lift amount of the valve 30 can be continuously changed.

  Further, when the valve 30 is lifted, the reaction force F1 of the valve spring acts on the helical gear 12a of the control shaft 12 as described above. The direction of action of the reaction force F1 is a direction that prevents the control shaft 12 from rotating in an attempt to increase the lift amount of the valve 30. That is, if the control shaft 12 is driven in the direction in which the lift amount of the valve 30 is increased, a large driving force is required as compared with the opposite case. Further, the reaction force F1 increases as the lift amount of the valve 30 increases. Therefore, in the configuration of the variable valve mechanism 10, the required driving force of the control shaft 12 becomes larger as it is controlled to a larger lift amount.

[Advantages of the variable valve operating apparatus of this embodiment]
If the control shaft 12 is driven while the reaction force F1 is acting on the helical gear 12a, a thrust force is generated in the axial direction of the control shaft 12. Further, when the control shaft 12 on which such reaction force F1 is applied is driven through the worm gear 18 and the worm wheel 14, a thrust force is generated in the axial direction of the control shaft 12. If the thrust force acting on the control shaft 12 acts on the tooth surfaces of the helical gear 12a and the worm gear 18 in this way, the frictional force between the tooth surfaces of these gears increases and the transmission efficiency of the gears decreases. . Therefore, in the variable valve operating apparatus 1 of the present embodiment, the direction of the torsion angle of the helical gear 12a formed on the control shaft 12 and the direction of the torsion angle of the worm wheel 14 are set to the directions shown in FIG. .

Next, with reference to FIG. 5, the effect obtained by setting the twist angle of this embodiment will be described.
FIG. 5A is a diagram for explaining the thrust force acting on the control shaft 12 during the large lift operation, and FIG. 5B is a diagram for explaining the thrust force acting on the control shaft 12 during the small lift operation. FIG.

  As described above, the helical gear 12a of the control shaft 12 is formed in a left-handed spiral with respect to the axial direction of the control shaft 12. For this reason, when the control shaft 12 is rotated to the large lift control side (see “large lift rotation direction” shown in FIG. 5A), when the helical gear 12a of each cylinder receives the reaction force F1 of the valve spring, A thrust force F3a is generated in the right direction in FIG.

  On the other hand, the helical gear 14a formed on the worm wheel 14 is formed in a right-handed spiral with respect to the axial direction of the control shaft 12 as described above. Therefore, when the helical gear 14a receives the driving force of the motor 22 when rotating the control shaft 12 to the large lift control side, the thrust force is applied to the control shaft 12 in the right direction in FIG. F3b is generated. Thus, according to the setting of the torsion angle of the present embodiment, the thrust force F3a generated via the helical gear 12a and the thrust force F3b generated via the helical gear 14a are both in the same direction. The resultant force F3 of the thrust forces F3a and F3b acts on the cylinder head that regulates the axial position of the flange 16.

  Further, according to the configuration of the present embodiment, even in the case of the small lift operation, as shown in FIG. 5B, the thrust force F4a generated through the helical gear 12a and the thrust force F4b generated through the helical gear 14a. Both act in the left direction shown in FIG. 5B and are in the same direction. In the case of a small lift operation, the drive force of the control shaft 12 is assisted by the reaction force F1 of the valve spring. Therefore, the thrust force F4 generated on the control shaft 12 is larger than that during the large lift control. Small value.

  Unlike the configuration shown in FIG. 5, when one of the helical angles of the helical gear 12a and the helical gear 14a is set in the opposite direction to the above configuration, the respective thrust forces acting on the control shaft 12 via these gears. Will come to face each other. Then, the thrust force is received between the tooth surfaces of the helical gear 12a of the control shaft 12 and the helical gear 42a of the control arm 42 and between the tooth surfaces of the helical gear 14a of the worm wheel 14 and the worm gear 18. On the other hand, according to the configuration of the above-described embodiment, since it is possible to prevent the thrust force from being received between the gear tooth surfaces, the friction force between the gear tooth surfaces is increased, and thereby The resulting reduction in gear transmission efficiency can be suppressed. For this reason, according to the variable valve apparatus 1 of the present embodiment, it is possible to ensure good control responsiveness of the operating angle and lift amount of the valve 30.

  The motor 22 is required to generate the largest driving force at the moment of starting to drive the control shaft 12. If the thrust force generated via the helical gear 12a of the control shaft 12 and the thrust force generated via the helical gear 14a of the worm wheel 14 are set to face each other, the driving force from the motor 22 is applied to these gears. When this occurs, a large force is applied to the gear. On the other hand, according to the configuration of the present embodiment, these thrust forces are not opposed to each other, and the thrust force is maintained until the clearance provided between the flange 16 and the cylinder head disappears. Does not act on the flange 16. That is, the thrust force can be released until the flange 16 contacts the cylinder head. For this reason, the mechanical load can be reduced at the start of driving of the control shaft 12 that requires the greatest driving force. Along with this, the following effects are also obtained.

  From the viewpoint of the drivability of the internal combustion engine, there is a demand for changing to a higher operating angle and a larger lift amount side during acceleration or the like. In the variable valve operating apparatus 1, as described above, when changing from the small lift amount side to the large lift amount side, a larger reaction force F1 of the valve spring is generated, and a larger driving force of the control shaft 12 is generated. Necessary. According to the configuration of the present embodiment, since the initial driving force at the start of driving of the control shaft 12 can be reduced, control to the large lift amount side can be performed with higher response, acceleration performance and fuel consumption performance can be improved, and exhaust Improved gas properties can be realized. In addition, the maximum load of the motor 22 can be reduced under all engine use conditions regardless of whether the viscosity of the lubricating oil is excessive as at low temperatures. In addition, the motor 22 can be reduced in size, reduced in power consumption, reduced in weight, and reduced in cost.

  By the way, in the first embodiment described above, the helical gear 12a of the control shaft 12 is formed in a left-handed spiral shape with respect to the axial direction of the control shaft 12, and the helical gear 14a formed on the worm wheel 14 is Although the right-handed spiral is formed with respect to the axial direction of the control shaft 12, the thrust force F3a generated through the helical gear 12a and the thrust force F3b generated through the helical gear 14a are both in the same direction. However, the method for setting the twist angle is not limited to this. That is, the twist angle described with reference to FIG. 6 below may be set.

  6A is a diagram for explaining the thrust force acting on the control shaft 12 during the large lift operation, and FIG. 6B is a diagram for explaining the thrust force acting on the control shaft 12 during the small lift operation. In the configuration shown in FIG. 6, the helical gear 12 b formed on the control shaft 12 is formed in a right-handed spiral with respect to the axial direction of the control shaft 12. The helical gear 14 b formed on the worm wheel 14 is formed in a left-handed spiral with respect to the axial direction of the control shaft 12. According to such setting of the twist angle, when the control shaft 12 is rotated to the large lift control side, the thrust force F3a is applied to the control shaft 12 in the left direction as shown in FIG. 6A via the helical gear 12b. In addition, a thrust force F3b is generated in the left direction shown in FIG. 6A via the helical gear 14b. Thus, the thrust force F3a and the thrust force F3b are in the same direction. The same applies to the small lift control shown in FIG.

  In the first embodiment described above, the control arm 42 is the “member engaged with the helical gear” in the first invention, and the control mechanism 28 and the swing cam arm 40 are the “variable mechanism” in the first invention. Respectively.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.
FIG. 7 is a cross-sectional view for explaining the configuration of the frictional force relaxation means provided in the variable valve apparatus 70 of the second embodiment. The variable valve device 70 of the present embodiment is provided with a friction force relaxation means for reducing the friction force generated between the flange 72 and the cylinder head 74 when the thrust force F3 acts on the flange 72. The setting of the torsion angle of the gear and other configurations are the same as those of the variable valve operating apparatus 1 in the first embodiment described above.

  As shown in FIG. 7, the oil groove 76 is provided in the flange 72 provided in the control shaft 12 in this embodiment. The oil groove 76 is formed in an annular shape on one side surface of the flange 72. More specifically, the oil groove 76 is formed on one side surface of the flange 72 that is a side for receiving the thrust force F3 at the time of large lift control in which a relatively large thrust force is generated. However, the present invention is not limited to this, and the oil groove 76 may also be provided on the other side surface of the flange 72, that is, the side surface that receives the thrust force F4 during the small lift control of the control shaft 12.

  An oil passage 80 for supplying lubricating oil to the clearance portion 78 communicates with the clearance portion 78 between the flange 72 and the cylinder head 74. As shown in FIG. 7, the lubricating oil supplied to the clearance portion 78 is guided to the oil groove 76, and inside the control shaft 12 to lubricate each sliding portion of the variable valve mechanism 10 of each cylinder. be introduced. Further, in the configuration shown in FIG. 7, the lubricating oil is supplied from one side of the flange 72 provided with the oil groove 76.

  According to the setting of the torsion angle according to the first embodiment described above, the helical gear 12a and the worm wheel 14 of the control shaft 12 both when the control shaft 12 is driven to the large lift side or to the small lift side. Since the thrust forces (F3a and F3b, or F4a and F4b) acting on the control shaft 12 via the helical gear 14a are not opposed to each other, these thrust forces are received by the flange 72 and the cylinder head 74. It will be.

  Further, whenever the valve 30 is lifted, the thrust force based on the reaction force F1 of the valve spring acts in the same direction as the thrust forces F3a and F3b when the control shaft 12 is driven to the large lift side. To do. That is, every time the lift operation of the valve 30 is performed, the side surface of the flange 72 and the side surface of the cylinder head 74 collide, and the lubricating oil existing between them is pushed out. At the time of large lift control, as described above, a larger driving force of the control shaft 12 is required than at the time of small lift control. However, if there is the above problem, such a relatively large driving force is required. At the time of large lift control, the frictional resistance of the contact surface between the flange 72 and the cylinder head 74 on the side receiving the thrust force F3 generated on the control shaft 12 increases due to lack of lubricating oil.

  According to the configuration of the present embodiment described above, the oil groove 76 is provided on the contact surface on the side where the thrust force F3 is generated when the control shaft 12 is driven to the large lift side, and lubricating oil is supplied from the contact surface side. By adopting such a configuration, it is possible to suppress the shortage of the lubricating oil accompanying the lift operation of the valve 30, and it is possible to always maintain the contact surface in a state in which good lubrication is ensured. For this reason, according to the configuration of the present embodiment, it is possible to increase the frictional force in the support portion that receives the thrust force while avoiding the thrust force from acting on the gear tooth surface by appropriately setting the torsion angle of the helical gear. Along with this, it is possible to avoid an increase in the driving force of the control shaft 12.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
FIG. 8 is a cross-sectional view for explaining the configuration of the frictional force relaxation means provided in the variable valve apparatus 90 of the third embodiment. The variable valve operating apparatus 90 of the present embodiment is configured in the same manner as in the above-described second embodiment except that the configuration of the frictional force relaxation means provided in the support portion that receives the thrust force F3 is different.

  That is, as shown in FIG. 8, the variable valve operating apparatus 90 of this embodiment includes a ball bearing 96 between a flange 92 provided on the control shaft 12 and a cylinder head 94. More specifically, the ball bearing 96 is formed on one side surface of the flange 92 which is a side for receiving the thrust force F3 at the time of large lift control in which a relatively large thrust force is generated. However, the present invention is not limited to this, and ball bearings 96 may be provided on both side surfaces of the flange 92.

  Even with the configuration of the present embodiment described above, the thrust force is prevented from acting on the tooth surface of the gear by appropriately setting the helical gear torsion angle, and the frictional force in the support portion receiving the thrust force is increased. Thus, an increase in the driving force of the control shaft 12 can be avoided.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIG.
FIG. 9 is a cross-sectional view for explaining the configuration of the frictional force relaxation means provided in the variable valve apparatus 100 of the fourth embodiment. The variable valve operating apparatus 100 of the present embodiment is configured in the same manner as in the second and third embodiments described above except that the configuration of the frictional force relaxation means provided in the support portion that receives the thrust force F3 is different.

  That is, as shown in FIG. 9, the variable valve operating apparatus 100 of this embodiment includes a disc spring 106 between a flange 102 provided on the control shaft 12 and a cylinder head 104. More specifically, the disc spring 106 is formed on one side surface of the flange 102 which is a side for receiving the thrust force F3 at the time of large lift control in which a relatively large thrust force is generated. However, the present invention is not limited thereto, and a disc spring 106 may be provided on both side surfaces of the flange 102.

  According to said structure, the surface contact of the flange 102 as a rotating surface and the cylinder head 104 can be reduced, and the increase in the frictional force by lubricating oil running out can be prevented. For this reason, even with the configuration of the present embodiment described above, the frictional force in the support portion that receives the thrust force is avoided while avoiding the thrust force from acting on the gear tooth surface by appropriately setting the torsion angle of the helical gear. It can be avoided that the driving force of the control shaft 12 increases with the increase.

  Further, according to the configuration of the present embodiment, it is possible to mitigate the impact when the thrust force F3 acts between the flange 102 and the cylinder head 104 during the large lift control of the control shaft 12. For this reason, during the lift operation of the valve 30, it is possible to suppress the generation of a hitting sound caused by the collision between the flange 102 and the cylinder head 104, and the contact surface is roughened or slightly crushed due to such a collision. Deformation and the like can be suppressed.

It is a figure for demonstrating the structure of the drive part in the variable valve apparatus of this embodiment. It is sectional drawing for demonstrating the structure of the variable valve mechanism shown in FIG. It is a figure which shows a mode that the variable valve mechanism shown in FIG. 1 performs operation | movement so that a small lift may be given with respect to a valve | bulb. It is a figure which shows a mode that the variable valve mechanism shown in FIG. 1 performs operation | movement so that a big lift may be given with respect to a valve | bulb. It is a figure for demonstrating the advantage by the structure of Embodiment 1 of this invention. It is a figure for demonstrating the modification of Embodiment 1 of this invention. It is sectional drawing for demonstrating the structure of the frictional force relaxation means with which the variable valve apparatus of Embodiment 2 of this invention is provided. It is sectional drawing for demonstrating the structure of the frictional force relaxation means with which the variable valve apparatus of Embodiment 3 of this invention is provided. It is sectional drawing for demonstrating the structure of the frictional force relaxation means with which the variable valve apparatus of Embodiment 4 of this invention is provided.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 70, 90, 100 Variable valve apparatus 10 Variable valve mechanism 12 Control shaft 12a Helical gear 14 of control shaft 14 Worm wheel 14a Helical gears 16, 72, 92, 102 of worm wheel Flange 18 Worm gear 20 Worm gear mechanism 22 Motor 30 Valve 38 Control mechanism 40 Oscillating cam arm 76 Oil groove 96 Ball bearing 106 Disc spring

Claims (2)

A variable valve operating device that mechanically changes a valve opening characteristic with respect to rotation of a camshaft,
A control shaft provided with a helical gear concentric with the shaft center;
A worm gear mechanism for converting a force from a drive source into a rotational force of the control shaft;
A member that meshes with the helical gear, and a variable mechanism that changes a valve opening characteristic according to a rotational position of the control shaft,
The directions of the torsion angles of the helical gear and the worm gear mechanism are as follows:
The thrust force acting on the control shaft via the helical gear and the thrust force acting on the control shaft via the worm gear mechanism are set to be in the same direction when the control shaft is rotationally driven. A variable valve operating device. A support portion that supports the control shaft such that an axial position of the control shaft is regulated;
2. The variable valve operating apparatus according to claim 1, further comprising frictional force relaxation means for relaxing a frictional force generated based on the thrust force in the same direction acting on the support portion.

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