JP2010127075A - Variable valve gear of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent partial abrasion and seizure by falling deformation of a rocker arm 6 of rocking around a control eccentric cam 5. <P>SOLUTION: A variable valve gear includes a driving shaft 2 having a driving eccentric cam 3, a control shaft 4 having the control eccentric cam 5, a link arm 15 rotatably fitted to the outer periphery of the driving eccentric cam 3, the rocker arm 6 rotatably installed on the control eccentric cam 5 and rocked by the link arm 15, and a rocking cam 8 rotatably supported by the driving shaft 2, connected to the rocker arm 6 via a link rod 16 and rocking in response to the rocker arm 6. Since the link rod 16 is connected to one cam part 18 of the rocking cam 8, the link rod inclines in lifting, and the rocker arm 6 also tries to incline in response to this, but a cylindrical part 11 of the rocker arm 6 is extended long, and falling of the rocker arm 6 is restrained thereby. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a variable motion of an internal combustion engine capable of continuously expanding and reducing the operating angle of an intake valve or an exhaust valve of the internal combustion engine (collectively referred to as intake and exhaust valves) by a mechanical mechanism. The present invention relates to a valve device.

  Various variable valve gears that can continuously expand and contract the valve lift characteristics of an intake valve and an exhaust valve of an internal combustion engine, particularly the operating angle thereof, have been proposed by the present applicants. For example, as shown in Patent Document 1, a swing cam that swings around a drive shaft to push the intake and exhaust valves is provided, and the initial posture of the swing cam is controlled by a control eccentric cam. By changing the shaft according to the rotational position of the shaft, the lift and operating angle of the intake / exhaust valve are both enlarged and reduced at the same time. Here, since the rocking cam is provided for each cylinder, in Patent Document 1, for example, the rocking cam includes two cam portions integrally corresponding to a pair of intake valves, and the control eccentricity is described above. It is configured to be connected to one rocker arm that swings around the cam via one link rod.

In Patent Document 1, the swing cam directly presses the tappet of the intake / exhaust valve. However, Patent Document 2 discloses another swing type between the swing cam and the valve stem of the intake / exhaust valve. A configuration in which a rocker arm is interposed is disclosed.
JP 2004-293406 A JP 2004-204822 A

  In the conventional configuration as shown in Patent Document 1, two arm portions in which the axial dimension of the control eccentric cam and the bearing portion of the rocker arm fitted to the control eccentric cam are shifted in the axial direction of the rocker arm are arranged. Because it is the minimum necessary size that can be integrated, the rocker arm tilts following the tilting of the swing cam (displacement in a direction tilting with respect to the axis perpendicular to the axis of the drive shaft). And the eccentric surface of the control eccentric cam come into contact with each other, and uneven wear or the like is likely to occur. In other words, as in Patent Document 1, when the link rod is connected to one side away from the axial center of the swing cam, the swing cam supports the swing cam when the link rod pushes down the swing cam. The rocking cam falls down and deforms within the range of the fitting gap between the drive shaft and the link rod tilts, so that the rocker arm also falls in the same direction. This tends to cause uneven wear and seizure.

  A variable valve operating apparatus for an internal combustion engine according to the present invention is rotatably supported by an internal combustion engine body and rotates in synchronization with the rotation of the internal combustion engine, and includes a drive shaft provided with a drive eccentric cam, and the drive eccentric cam. A link arm having an annular portion rotatably fitted on the outer periphery, a control shaft rotatably supported by the internal combustion engine body and controlled by an actuator, and having a control eccentric cam, and the above control A rocker arm that is rotatably attached to the eccentric cam, is connected to the link arm, and is swingably supported by the link arm, and is rotatably supported by the drive shaft, and is connected to the rocker arm via a link rod. A swing cam that drives the intake and exhaust valves by swinging with the rocker arm, and the rotational position of the control eccentric cam of the control shaft Therefore lift of the intake and exhaust valves increases or decreases varies with the operating angle.

  Here, the swing cam is integrally formed with a plurality of cam portions respectively corresponding to the plurality of intake / exhaust valves, and the link rod is connected at a position offset to one side from the axial center. ing. The drive eccentric cam is located at a position different from the swing cam in the axial direction. In the present invention, one end of the bearing portion of the rocker arm fitted to the control eccentric cam is adjacent to the link arm, and the other end extends in the axial direction beyond the axial position of the link rod. .

  In the above configuration, even if the link rod is tilted as the swing cam is tilted, the rocker arm is prevented from tilting, and local load concentration on the contact surface with the control eccentric cam is alleviated, for example, uneven wear or seizure. Can be suppressed.

  1 and 2 show an embodiment of a variable valve operating apparatus for an internal combustion engine according to the present invention. The variable principle and basic configuration of the variable valve operating device are the same as those of the known devices described in Patent Document 1 and the like described above.

  The figure shows a part of one cylinder, a pair of intake valves 1 slidably provided on a cylinder head (not shown), a drive shaft 2 rotatably supported on the cylinder head, A circular drive eccentric cam 3 fixed to the drive shaft 2 by press-fitting or the like, and a control shaft 4 rotatably supported by the cylinder head at a position above the drive shaft 2 and arranged parallel to the drive shaft 2 A circular control eccentric cam 5 fixed to or integrally formed with the control shaft 4 by press-fitting or the like, a rocker arm 6 rotatably supported on the outer peripheral surface of the control eccentric cam 5, and a valve of each intake valve 1 And a swing cam 8 that drives the stem 1a via a swing type rocker arm 7 for a valve. The valve rocker arm 7 is supported by a known hydraulic lash adjuster 9 at a base end serving as a swing fulcrum. The drive shaft 2 and the control shaft 4 are common to a plurality of cylinders and extend along the longitudinal direction of the engine. The drive shaft 2 is driven by the crankshaft of the engine via a timing chain or a timing belt, and rotates in synchronization with the rotation of the engine in the same manner as a normal camshaft.

  Instead of providing the valve rocker arm 7, the swing cam 8 can directly press the tappet of the intake valve 1 as described in Patent Document 1 described above.

  As shown in FIG. 3, the rocker arm 6 extends from the cylindrical portion 11 to the opposite side, that is, in a direction different by about 180 °, from the cylindrical portion 11 serving as a bearing portion fitted to the outer periphery of the control eccentric cam 5. A first arm portion 12 and a second arm portion 13.

  An annular portion 15a of the link arm 15 is rotatably fitted to the outer periphery of the drive eccentric cam 3 of the drive shaft 2, and the tip of the arm portion 15b extending from the annular portion 15a and the first of the rocker arm 6 are connected. The distal end of the arm portion 12 is slidably connected via a connecting pin 14 (see FIG. 3). Further, the upper end of the link rod 16 is connected to the tip of the second arm portion 13 of the rocker arm 6 via a connecting pin 20 so as to be swingable. The lower end of the link rod 16 is linked to the swing cam 8.

  Specifically, the swing cam 8 has a cylindrical portion 17 that is rotatably fitted on the outer periphery of the drive shaft 2 and a pair of cam portions 18 that protrude from the outer peripheral surface of the cylindrical portion 17. The drive eccentric cam 3 is adjacent to the spacer 19 with the spacer 19 interposed therebetween. The link rod 16 is connected to one cam portion 18 on the side relatively close to the drive eccentric cam 3 via a connecting pin 21. As shown in the drawing, the link rod 16 is configured to be a rod shape by bending a metal plate into a U-shaped cross section, and the inner width of the U-shape (that is, the dimension in the axial direction) is the second arm portion 13 and the cam portion. 18 substantially matches the axial thickness, and the second arm portion 13 and the cam portion 18 are sandwiched from both sides through a minute gap.

  A cam bracket 23 serving as a bearing member for supporting the cylindrical rocking cam 8 and thus the drive shaft 2 on the cylinder head is disposed between the pair of cam portions 18. The cam bracket 23 is fixed to a cylinder head (not shown) by a pair of bolts 24.

  The cam portion 18 has a base circle surface in which the lift amount is substantially zero and a cam surface extending along a predetermined curve so that the lift amount gradually increases from the base circle surface. These surfaces are formed so as to come into contact with the upper surface of the valve rocker arm 7 in accordance with the swing position of the swing cam 8.

  The control shaft 4 is configured to rotate within a predetermined angle range by a lift / working angle control actuator (not shown) provided at one end. The rotation angle of the control shaft 4 is detected by an appropriate sensor (not shown), and the actuator is closed-loop controlled based on the detected actual control state.

  The operation of the lift / operating angle variable mechanism will be described. When the drive shaft 2 rotates, the link arm 15 moves up and down by the cam action of the drive eccentric cam 3, and the rocker arm 6 swings accordingly. The swing of the rocker arm 6 is transmitted to the swing cam 8 through the link rod 16, and the swing cam 8 swings. The cam action of the swing cam 8 presses the intake valve 1 through the valve rocker arm 7 and lifts the intake valve 1 against a valve spring (not shown).

  Here, when the angle of the control shaft 4 changes via the lift / operating angle control actuator, the initial position of the rocker arm 6 changes, and consequently, the initial swing posture of the swing cam 8 changes.

  For example, if the control eccentric cam 5 is positioned upward in the figure, the rocker arm 6 is positioned upward as a whole, and the tip of the cam portion 18 of the swing cam 8 linked via the link rod 16 is relatively upward. It will be in a raised state. That is, the initial position of the cam portion 18 is inclined in a direction in which the cam surface is separated from the upper surface of the valve rocker arm 7. Therefore, when the swing cam 8 swings as the drive shaft 2 rotates, the base circle surface is long and continues to contact the upper surface of the valve rocker arm 7 and the period during which the cam surface contacts the upper surface of the valve rocker arm 7 is short. . Therefore, the lift amount is reduced as a whole, and the angle range from the opening timing to the closing timing, that is, the operating angle is also reduced.

  Conversely, if the control eccentric cam 5 is positioned downward in the figure, the rocker arm 6 is positioned downward as a whole, and the tip of the cam portion 18 of the swing cam 8 is relatively pushed downward. . That is, the initial position of the cam portion 18 is inclined in a direction in which the cam surface approaches the upper surface of the valve rocker arm 7. Therefore, when the swing cam 8 swings as the drive shaft 2 rotates, the portion that contacts the upper surface of the valve rocker arm 7 immediately shifts from the base circle surface to the cam surface. Therefore, the lift amount is increased as a whole, and the operating angle is increased.

  Since the initial position of the control eccentric cam 5 can be continuously changed, the valve lift characteristic continuously changes accordingly. That is, the lift and the operating angle can be continuously expanded and contracted simultaneously.

  Next, the rocker arm 6, which is the main part of the present invention, will be described. The rocker arm 6 includes the cylindrical portion 11, the first arm portion 12, and the second arm portion 13 as described above. Is located at one end portion of the cylindrical portion 11 in the axial direction, specifically, one end portion on the link arm 15 side, and the end surface of the cylindrical portion 11 including the first arm portion 12 is in sliding contact with the end surface of the link arm 15. Further, the second arm portion 13 is located at an intermediate portion in the axial direction of the cylindrical portion 11 and, as shown in FIG. 2, one cam portion 18 (the cam portion on the side to which the link rod 16 is connected) located below. 18) is aligned with the axial position. In other words, the second arm portion 13 and the one cam portion 18 are in positions corresponding to each other so that the link rod 16 is in an upright posture along the axis orthogonal plane of the drive shaft 2.

  The other end of the cylindrical portion 11 extends in the axial direction beyond the axial position of the link rod 16, and the axial position of the other cam portion 18 (more specifically, a plane passing through the central axis of the intake valve 1). Has reached. As shown in FIG. 2, the cylindrical portion 11 has an overall length L in the axial direction, and the distance from the reference point to one end on the link arm 15 side is defined as a with respect to the axial position of the link rod 16 as a reference point. If the distance from the point to the other end on the opposite side is b, the distance b is larger than the distance a. The total length L is shorter than the total length c of the cylindrical portion 17 of the swing cam 8.

  Note that the control eccentric cam 5 into which the cylindrical portion 11 of the rocker arm 6 is fitted has an axial length substantially equal to the entire length L of the cylindrical portion 11, and both of them extend over the entire length L of the cylindrical portion 11. It touches.

  In the configuration as described above, when the link rod 16 pushes down the cam portion 18 so as to push the pair of intake valves 1 open, the link rod 16 is moved away from the axial center of the cylindrical portion 17 of the swing cam 8. Since the cam is connected to a position offset from one side (that is, one cam portion 18), the swing cam 8 as a whole is tilted (so-called collapse) within the range of the fitting gap, but accompanying this, Thus, the link rod 16 sandwiching the cam portion 18 from both sides tends to tilt with respect to the axis orthogonal plane. The force accompanying this tilt is transmitted to the second arm portion 13 of the rocker arm 6 and similarly tries to tilt the rocker arm 6, but the cylindrical portion 11 extends further from the position of the second arm portion 13 as described above. Therefore, the rocker arm 6 is prevented from falling. Accordingly, local load concentration on the contact surface with the control eccentric cam 5 is alleviated, and for example, uneven wear and seizure can be suppressed.

  FIGS. 4 and 5 show a circumferential direction so that a sliding contact surface with the cylindrical portion 11 is divided into a plurality of portions in the axial direction on the outer peripheral surface of the control eccentric cam 5 with which the cylindrical portion 11 of the rocker arm 6 is fitted. An embodiment in which a concave groove 31 is provided is shown. For example, one groove 31 is provided in the central portion in the axial direction so as to be divided into a pair of sliding contact surfaces. In this example, the depth of the groove 31 is not constant, and the groove 31 is formed so that the relatively eccentric shaft portions similar to the portions of the control shaft 4 on both sides remain. In other words, the control shaft 4 is provided with a pair of control eccentric cams 5.

  According to this embodiment, since the sliding area is reduced by the concave groove 31, the friction can be reduced, and the lubricating oil is retained in the concave groove 31, so that uneven wear and seizure are more reliable. To be prevented.

  Next, in the embodiment shown in FIGS. 6 and 7, conversely, a recess 32 is provided on the inner peripheral surface of the cylindrical portion 11, and a gap is secured between the outer peripheral surface of the control eccentric cam 5. The concave portion 32 is provided in the central portion in the axial direction, leaving at least both end portions in the axial direction. In this embodiment, in particular, the inner diameter d of the portion extended from the second arm portion 13 is made large. A recess 32 is provided. In this embodiment, since the lubricating oil is held in the gap formed by the recess 32, uneven wear and seizure are more reliably prevented. Further, the inertial mass and the inertial moment of the rocker arm 6 that is a movable part become smaller.

  The present invention is not limited to the intake two-valve configuration as described above, and can be applied to a variable valve apparatus having a larger number of intake valves and exhaust valves per cylinder.

The perspective view which shows one Example of the variable valve operating apparatus of the internal combustion engine which concerns on this invention. The side view of the variable valve operating apparatus. The perspective view of a rocker arm. The perspective view which shows the modification of a control eccentric cam. The side view of the control eccentric cam. The perspective view which shows the modification of a rocker arm. The side view of the same rocker arm.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Intake valve 2 ... Drive shaft 3 ... Drive eccentric cam 4 ... Control shaft 5 ... Control eccentric cam 6 ... Rocker arm 8 ... Swing cam 11 ... Cylindrical part 12 ... 1st arm part 13 ... 2nd arm part 15 ... Link arm 16 ... Link rod 17 ... Cylindrical part 18 ... Cam part

Claims (8)

A drive shaft that is rotatably supported by the internal combustion engine body and that rotates in synchronization with the rotation of the internal combustion engine, and that includes a drive eccentric cam;
A link arm having an annular portion rotatably fitted on the outer periphery of the drive eccentric cam;
A control shaft that is rotatably supported by the internal combustion engine body and whose rotation angle is controlled by an actuator, and a control eccentric cam;
A rocker arm that is rotatably attached to the control eccentric cam, is connected to the link arm, and is rocked by the link arm;
A swing cam that is rotatably supported by the drive shaft and is connected to the rocker arm via a link rod, and swings with the rocker arm to drive the intake and exhaust valves;
A variable valve operating apparatus for an internal combustion engine configured such that the lift of the intake / exhaust valve varies with the operating angle according to the rotational position of the control eccentric cam of the control shaft.
The swing cam is formed integrally with a plurality of cam portions respectively corresponding to the plurality of intake and exhaust valves, and the link rod is connected at a position offset from the center in the axial direction to one side,
The drive eccentric cam is located at a position different from the swing cam in the axial direction,
One end of the bearing portion of the rocker arm that is fitted to the control eccentric cam is adjacent to the link arm, and the other end extends in the axial direction beyond the axial position of the link rod. Variable valve gear for engine.   The rocker arm includes a cylindrical portion serving as the bearing portion, a first arm portion to which the link arm is connected, and a second arm portion to which the link rod is connected, and the first arm portion is the cylinder. 2. The variable valve operating apparatus for an internal combustion engine according to claim 1, wherein the second arm portion is located at an intermediate portion in the axial direction of the cylindrical portion while being located at one end portion in the axial direction of the portion.   The distance from the reference point to the other end is longer than the distance from the reference point to the one end of the bearing portion, with the axial position of the link rod as a reference point. A variable valve operating apparatus for an internal combustion engine as described.   The swing rocking cam includes a pair of cam portions, and the link rod is connected to one cam portion on a side relatively close to the drive eccentric cam. A variable valve operating apparatus for an internal combustion engine according to claim 1.   The variable valve operating apparatus for an internal combustion engine according to claim 4, wherein the other end of the bearing portion extends to an axial position of the other cam portion.   The swing cam includes a cylindrical portion that is fitted to the drive shaft, and a plurality of cam portions provided on an outer surface of the cylindrical portion, and is longer than an axial length of the cylindrical portion of the swing cam. The variable valve operating apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the axial length of the bearing portion is short.   The outer circumferential surface of the control eccentric cam with which the bearing portion is fitted is provided with a groove along the circumferential direction so as to divide the sliding contact surface with the bearing portion into a plurality of portions in the axial direction. The variable valve operating apparatus for an internal combustion engine according to any one of claims 1 to 6.   The internal combustion engine according to any one of claims 1 to 7, wherein a concave portion is provided in an axially central portion of the inner peripheral surface of the bearing portion so as to form a gap with the control eccentric cam. Variable valve gear for engine.

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