JP2008019784A - Supporting structure to cylinder head of variable valve train - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize especially a supporting structure of a control shaft to the cylinder head, with the control shaft positioned higher than a driving shaft on the upper side of the cylinder head, in the supporting structure of a variable valve train to the cylinder head, arranged on the upper side of the cylinder head. <P>SOLUTION: The control shaft 5 of a lift/operating angle varying mechanism 2 being the variable valve train is rotatably supported by a control shaft bearing wall 21 and a bearing cap 15. The control shaft bearing wall 21 has: a control shaft bearing part 22 composing a bearing for the control shaft together with the bearing cap 15; and a partition wall part 23 whose both ends in the width direction of the cylinder head 1 project to further outer side of the control shaft bearing part 22. The end part of a cap fastening bolt 14 fastening the bearing cap 15 to the control shaft bearing part 22 reaches the partition wall part 23. Screw meshing force generated in the end part of the cap fastening bolt 14 is thereby received by the partition wall part 23 wider than the control shaft bearing part 22, and screw meshing stress applied to the control shaft bearing wall 21 is relatively reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a support structure for a cylinder head of a variable valve mechanism.

  Patent Document 1 discloses a configuration in which a cam shaft for an intake valve is rotatably supported by a bearing portion integrally provided on a cylinder head and a cap body fastened to the bearing portion. .

  Further, Patent Document 2 discloses a variable valve mechanism that can simultaneously and continuously enlarge and reduce the lift and operating angle of an intake valve. This variable valve mechanism has a drive shaft along the cylinder row direction driven by a crankshaft, and a control shaft parallel to the drive shaft linked to this drive shaft via a link mechanism, and the control shaft is driven It arrange | positions above a cylinder head so that it may be located above a shaft.

In Patent Document 2, the control shaft and the drive shaft are positioned above the cylinder head. These two shaft members are respectively connected to the cylinder head as in Patent Document 1. It becomes the structure supported rotatably.
JP 2000-73732 A JP 2001-234721 A

  Here, in the variable valve mechanism, the control shaft is positioned above the drive shaft, and the drive shaft is positioned between the control shaft and the upper surface of the cylinder head. For this reason, the bearing structure of the control shaft is set so as not to hinder the operation of the drive shaft and the link mechanism in addition to durability, but it is not necessarily optimized for the support structure of the control shaft. There is a problem that it is not planned.

  In view of this, the present invention aims to optimize the support structure for the cylinder head of the control shaft, which is located above the drive shaft, as the support structure for the cylinder head of the variable valve mechanism disposed above the cylinder head. The purpose is that.

  The support structure for the cylinder head of the variable valve mechanism in the present invention is such that the control shaft of the variable valve mechanism is positioned above the cylinder head with respect to the drive shaft of the variable valve mechanism, and the control shaft and the drive shaft are cylinders. The control shaft is attached to the cylinder head along the column direction, and the control shaft is controlled integrally with the control shaft bearing member which is elongated in the cylinder head width direction and supports the control shaft from the drive shaft side. A bearing cap that constitutes a bearing for the shaft is rotatably supported by the bearing cap, and the control bearing member includes a control bearing that constitutes a bearing for the control shaft together with the bearing cap, and a lower portion of the control bearing. And a partition wall portion having both ends in the cylinder head width direction projecting outward from the control shaft bearing portion, and the bearing cap is connected to the control shaft bearing portion. Tip of the cap fastening bolt for fastening is configured so as to reach the partition wall.

  According to the present invention, since the meshing force of the screw generated at the tip of the cap fastening bolt at the time of fastening can be received by the partition wall portion wider than the control shaft bearing portion, the screw acting on the control shaft bearing member can be received. The meshing stress can be made relatively small, and the durability of the control bearing member can be improved.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an example of a variable valve mechanism provided on a cylinder head 1 (see FIGS. 2 to 4 to be described later), and an intake valve lift amount and an operating angle while opening and closing an intake valve (not shown). 2 shows the structure of the lift / operating angle variable mechanism 2 capable of continuously and variably controlling both. FIG. 1 shows an example applied to a three-cylinder engine. In order to change the valve lift characteristics of the intake valves of the three cylinders, a variable lift / operating angle mechanism 2 is provided for each cylinder.

  The lift / operating angle variable mechanism 2 includes an intake valve (not shown), a hollow drive shaft 3 rotatably supported by a ladder cam bracket 1b (described later) on the cylinder head 1, and a drive shaft 3 An eccentric cam 4 fixed by press fitting or the like, and a hollow control shaft 5 which is rotatably supported by a ladder cam bracket 1b (described later) at a position above the drive shaft 3 and arranged in parallel with the drive shaft 3. And a rocker arm 7 that is swingably supported by the eccentric cam portion 6 of the control shaft 5, and a swing cam 8 that abuts against a tappet (not shown) disposed at the upper end portion of the intake valve. Yes. The eccentric cam 4 and the rocker arm 7 are linked by a link arm 9, and the rocker arm 7 and the swing cam 8 are linked by a link member 10.

  The drive shaft 3 is driven by a crankshaft (not shown) of an engine via a timing chain or a timing belt (not shown).

  The eccentric cam 4 has a circular outer peripheral surface, the center of the outer peripheral surface is offset from the axis of the drive shaft 3 by a predetermined amount, and the annular portion 9a of the link arm 9 is rotatable on the outer peripheral surface. It is mated.

  The rocker arm 7 is supported at its substantially central portion by an eccentric cam portion 6, and an extension portion of the link arm 9 is linked to one end portion thereof, and an upper end portion of the link member 10 is linked to the other end portion thereof. ing. The eccentric cam portion 6 is eccentric from the axis of the control shaft 5, and accordingly, the rocking center of the rocker arm 7 changes according to the angular position of the control shaft 5.

  The swing cam 8 is rotatably supported by being fitted to the outer periphery of the drive shaft 3, and the lower end portion of the link member 10 is linked to an end portion 8 a extending laterally. On the lower surface of the swing cam 8, a base circle surface concentric with the drive shaft 3 and a cam surface extending in a predetermined curve from the base circle surface are continuously formed. These base circle surface and cam surface come into contact with the upper surface of a tappet (not shown) according to the swing position of the swing cam 8.

  The control shaft 5 is configured to rotate within a predetermined angle range by an unillustrated lift / operating angle control actuator provided at one end.

  In FIG. 1, 11 is an adjusting bolt that adjusts the link length of the link member 10 to adjust the valve lift amount, and 12 is a lock bolt that locks (fixes) the adjusting bolt 11.

  According to the lift / operating angle variable mechanism 2 as described above, the lift and the operating angle of the intake valve are continuously expanded and reduced simultaneously in accordance with the rotational angle position of the control shaft 5. With the change in size, the opening timing and closing timing of the intake valve change substantially symmetrically.

  The above-described lift / operating angle variable mechanism 2 is rotatably supported by bearings on the upper part of the cylinder head 1.

  As shown in FIGS. 2 and 3, the cylinder head 1 includes a ladder cam bracket 1b having a so-called ladder frame structure in which a plurality of bearing caps are integrally formed with a frame-like frame on the upper surface of a head lower 1a that functions as a head body. The ladder cam bracket 1b that is detachably mounted and functions as a head upper is fastened and fixed to the head lower 1a by a plurality of mounting bolts 13.

  The ladder cam bracket 1b has a structure in which a control shaft bearing wall 21 described later is bridged and connected to two outer frames along the outer wall of the cylinder head 1 along the cylinder row direction.

  The drive shaft 3 and the control shaft 5 both extend in the cylinder row direction while maintaining a parallel state, and the drive shaft 3 is supported by bearings so as to be sandwiched between the head lower 1a and the ladder cam bracket 1b. The shaft 5 is placed on the upper surface of the ladder cam bracket 1b and supported by a bearing cap 15 that is bolted and fixed to the ladder cam bracket 1b by a cap fastening bolt 14. The bearing cap 15 is disposed so as to straddle the control shaft 5 and is fixed to the ladder cam bracket 1b by two cap fastening bolts 14 and 14 sandwiching the control shaft 5 in a direction perpendicular to the control shaft 5. .

  As described above, the drive shaft 3 and the control shaft 5 extending in the cylinder row direction are shared by a plurality of cylinders constituting the cylinder row, whereas the components of the lift / operating angle variable mechanism 2 are used. The rocking cam 8, the rocker arm 7, the link arm 9, the link member 10 and the like are provided independently for each cylinder constituting the cylinder row.

  FIG. 4 is a cross-sectional view taken along the line AA in FIG. 3 and shows a support structure of the control shaft 5 to the cylinder head 1.

  The ladder cam bracket 1b has a ladder frame structure as described above, and the control shaft 5 is rotatably supported by the control shaft bearing wall 21 and the bearing cap 15 of the ladder cam bracket 1b. The control shaft bearing wall 21 corresponds to a control shaft bearing member that is elongated in the width direction of the cylinder head 1 (vertical direction in FIG. 3, horizontal direction in FIG. 4). It is located between two outer frames along two outer walls along the width direction.

  The control shaft bearing wall 21 includes a control shaft bearing portion 22 which forms a bearing of the control shaft 5 together with the bearing cap 15, and both ends of the control shaft bearing portion 22 whose both ends in the width direction of the cylinder head 1 are in the width direction of the cylinder head 1. And a partition wall portion 23 protruding outward.

  That is, the control shaft bearing wall 21 has a partition wall portion 23 that is elongated along the width direction of the cylinder head 1 and a control shaft bearing portion 22 that is shorter than the partition wall portion 23 along the cylinder head 1 width direction. When viewed from the cylinder row direction (longitudinal direction of the cylinder head 1), it is formed in a substantially T-shaped outer shape. More specifically, the partition wall portion 23 is formed wider than the control shaft bearing portion 22 when viewed from the cylinder row direction (longitudinal direction of the cylinder head 1).

  The partition wall portion 22 is located below the control shaft bearing portion 22, in other words, on the drive shaft 3 side of the control shaft bearing portion 22, in other words, between the drive shaft 3 and the control shaft 5. Further, the partition wall portion 22 has a concave portion 24 having an arcuate cross section that is continuous in the axial direction of the drive shaft 3 (longitudinal direction of the cylinder head 1) so as not to interfere with the rotation of the drive shaft 3 on the side facing the head lower 1a. Is formed.

  When the bearing cap 15 is fastened and fixed to the control shaft bearing portion 22 by the cap fastening bolt 14, the tip end portion of the cap fastening bolt 14 passes through the control shaft bearing portion 22 and reaches the partition wall portion 3. Is set.

  More specifically, the tip position P1 of the complete screw portion 14a of the cap fastening bolt 14 is located in the partition wall 23 beyond the boundary position P2 between the control shaft bearing portion 22 and the partition wall 23, and the wall surface of the recess 24 Among these, it is configured to be positioned closer to the control shaft bearing portion 22 than the position P3 closest to the control shaft bearing portion 22 side. In other words, when the bearing cap 15 is fastened to the control bearing portion 22, the recess 24 is not positioned on the radially outer peripheral side of the tip position P1 of the complete screw portion 14a of the cap fastening bolt 14. Has been.

  In the support structure for the cylinder head of the lift / operating angle variable mechanism 2 configured as described above, the engagement force of the screw generated at the tip position P1 of the complete screw portion 14a of the cap fastening bolt 14 at the time of fastening is controlled by the control shaft bearing. Since it can be received by the partition wall portion 23 wider than the portion 22, the engagement stress of the screw acting on the control shaft bearing wall 21 can be relatively reduced, and the durability of the control shaft bearing wall 21 can be improved. Can do.

  In particular, when the recessed portion 24 is formed in the partition wall portion 23 of the control shaft bearing wall 21, the tip position P1 of the complete screw portion 14 a of the cap fastening bolt 14 is determined between the control shaft bearing portion 22 and the partition wall portion 23. By setting it so as to be positioned in the partition wall 23 beyond the boundary position P2 and positioned closer to the control shaft bearing portion 22 than the position P3 closest to the control shaft bearing portion 22 on the wall surface of the recess 24, It is possible to maximize the cross-sectional area of the control shaft bearing wall 21 on the outer peripheral side of the distal end of the complete thread portion 14a that receives the meshing force of the screw generated at the distal end position P1 of the thread portion 14a. That is, since the tip of the complete screw portion 14a is located at a position where the cross-sectional area of the control shaft bearing wall 21 along the plane orthogonal to the axis of the cap fastening bolt 14 is maximum, the complete screw portion 14a It is possible to minimize the meshing stress of the screw acting on the outer peripheral side of the tip position P1, which is particularly advantageous in improving the durability of the control shaft bearing wall 21.

  The technical idea of the present invention that can be grasped from the above embodiment will be listed together with the effects thereof.

  (1) An eccentric cam that is rotationally driven by a drive shaft, a link arm that is fitted to the outer periphery of the eccentric cam so as to be relatively rotatable, and a rotatable that is provided in parallel with the drive shaft and includes an eccentric cam portion. Control shaft, a rocker arm that is rotatably mounted on an eccentric cam portion of the control shaft and is oscillated by the link arm, and is rotatably supported by the drive shaft, and is connected to the rocker arm via a link. And a swing cam that lifts the intake valve or the exhaust valve by swinging along with the rocker arm, and a support for the cylinder head of the variable valve mechanism that can change the valve lift characteristics of the intake valve or the exhaust valve In the structure, the variable valve mechanism is configured such that the control shaft is positioned above the cylinder head with respect to the drive shaft, and the control shaft and the drive shaft are arranged in the cylinder row direction. The control shaft is attached to the cylinder head in such a manner that the control shaft is a control shaft bearing member that is elongated in the width direction of the cylinder head that supports the control shaft from the drive shaft side, and the control shaft bearing member is integrated with the control shaft bearing member. A bearing cap that constitutes a bearing, and is rotatably supported by the bearing member, and the control bearing member includes a control bearing that constitutes a bearing for the control shaft together with the bearing cap, and a position below the control bearing. And both ends of the cylinder head in the width direction protruded outward from the control shaft bearing portion, and a tip end portion of a cap fastening bolt for fastening the bearing cap to the control shaft bearing portion is It is comprised so that a partition part may be reached. As a result, the engagement force of the screw generated at the tip of the cap fastening bolt at the time of fastening can be received by the partition wall portion wider than the control shaft bearing portion, so that the engagement stress of the screw acting on the control shaft bearing member can be reduced. It can be made relatively small, and the durability of the control shaft bearing member can be improved.

  (2) In the support structure for the cylinder head of the variable valve mechanism according to (1) above, the partition wall is specifically positioned between the control shaft and the drive shaft, and the cylinder head Is provided with a recess so as not to interfere with the rotation of the drive shaft, and the tip of the cap fastening bolt is more controlled than the position of the wall surface of the recess closest to the control shaft bearing portion. It is comprised so that it may be located in the bearing part side.

  (3) In the support structure for the cylinder head of the variable valve mechanism according to (1) or (2), specifically, the control shaft bearing member is formed on an outer wall along the cylinder row direction of the cylinder head. A ladder frame structure is formed by the control shaft bearing member and the outer frame.

  (4) In the support structure for the cylinder head of the variable valve mechanism according to any one of (1) to (3) above, the tip of the cap fastening bolt is specifically the tip position of the complete screw portion. It is.

The perspective view which shows schematic structure of the lift and the working angle variable mechanism as a variable valve mechanism. The perspective view of the cylinder head concerning this invention. The top view of the cylinder head concerning this invention. Sectional drawing along the AA line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cylinder head 3 ... Drive shaft 5 ... Control shaft 14 ... Cap fastening bolt 15 ... Bearing cap 21 ... Control shaft bearing wall 22 ... Control shaft bearing part 23 ... Partition part 24 ... Recessed part

Claims (4)

An eccentric cam that is rotationally driven by a drive shaft, a link arm that is fitted to the outer periphery of the eccentric cam so as to be relatively rotatable, and a rotatable control shaft that is provided in parallel with the drive shaft and includes an eccentric cam portion. A rocker arm that is rotatably attached to the eccentric cam portion of the control shaft and is rocked by the link arm, and is rotatably supported by the drive shaft, and is connected to the rocker arm via a link, In a support structure for a cylinder head of a variable valve mechanism that includes a swing cam that lifts an intake valve or an exhaust valve by swinging along with the rocker arm, and that can change a valve lift characteristic of the intake valve or the exhaust valve.
The variable valve mechanism is attached to the cylinder head such that the control shaft is located above the drive shaft above the drive shaft, and the control shaft and the drive shaft are along the cylinder row direction.
The control shaft is rotated by a control shaft bearing member that is elongated in the width direction of the cylinder head that supports the control shaft from the drive shaft side, and a bearing cap that forms a bearing for the control shaft integrally with the control shaft bearing member. Supported as possible,
The control shaft bearing member is positioned below the control shaft bearing portion, which forms a control shaft bearing together with the bearing cap, and both ends in the cylinder head width direction are from the control shaft bearing portion. And a partition wall portion protruding outward,
A support structure for a cylinder head of a variable valve mechanism, wherein a tip end portion of a cap fastening bolt for fastening the bearing cap to the control shaft bearing portion reaches the partition wall portion. The partition wall is located between the control shaft and the drive shaft, and a recess is provided on the side facing the cylinder head so as not to interfere with the rotation of the drive shaft,
The tip end portion of the cap fastening bolt is configured to be positioned closer to the control shaft bearing portion than the position of the wall surface of the recess closest to the control shaft bearing portion. A support structure for the cylinder head of the variable valve mechanism described above.   The control shaft bearing member is bridged and connected to two outer frames along the outer wall along the cylinder row direction of the cylinder head, and a ladder frame structure is formed by the control shaft bearing member and the outer frame. The support structure for the cylinder head of the variable valve mechanism according to claim 1 or 2, wherein   The support structure for the cylinder head of the variable valve mechanism according to any one of claims 1 to 3, wherein a tip end portion of the cap fastening bolt is a tip position of a complete screw portion.

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