JP2009257145A - Valve opening characteristic variable type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit shift of a relative position between a driving section of an actuator and a driven section of a valve opening characteristic control member when an engine cover is fastened to a plurality of cam holders. <P>SOLUTION: In a valve opening characteristic variable engine, the five cam holders 11 for rotatably holding a camshaft 4 are provided on an upper surface of a cylinder head 1 of an in-line four-cylinder engine slidably holding valves 2, the engine cover 13 is arranged on upper surfaces of the cam holders 11 and fastened with bolts B1, an electric motor 14 is attached on the engine cover 13, a drive gear 14a fitted to an output shaft of the motor is engaged with a driven gear 20 of a valve opening characteristic variable mechanism 18, and valve opening characteristics of the valves 2 are varied by drive of the electric motor 14. Knock pins 41 for positioning the engine cover 13 to the cam holders 11 are arranged on the center cam holder 11c adjacent to the driven gear 20 in a cylinder bank. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a variable valve opening characteristic internal combustion engine, and more particularly, to a technique for effectively suppressing valve jump and valve bounce without employing a lost motion spring having a large spring force.

  Many 4-cycle gasoline engines (hereinafter simply referred to as engines) are equipped with various valve opening characteristic variable mechanisms in order to improve output and fuel consumption, reduce harmful exhaust gas components, and the like. As a valve opening characteristic variable mechanism, there is a mechanism that switches between a low-speed cam and a high-speed cam according to the operating situation. However, in recent years, in order to realize further improvement of transient characteristics and reduction of throttle, etc. One that variably controls the phase and valve lift individually has become the mainstream.

  The variable valve lift device used for variable control of the valve lift includes a variable valve lift mechanism that changes the valve opening characteristics of the valve body in accordance with the rotational position of the control shaft. The worm wheel that is installed at the center of the control shaft and transmits the driving force of the electric actuator, and the spur gear that meshes with the spur gear provided on the control shaft are in the same plane near the axial center of the control shaft. A variable valve lift device has been proposed (see Patent Document 1).

  Further, in a variable valve opening characteristic internal combustion engine in which the valve opening characteristic of the valve is changed by swinging and driving the control shaft supported by the support member by the actuator, the actuator is disposed in parallel with the axis of the control shaft, The applicant of the present invention has proposed that the actuator drive unit is arranged at each center divided into two in the axial direction of the control shaft (see Patent Document 2).

These actuators that drive the control shaft are usually installed on a plurality of cam holders that support the camshaft and an engine cover that is fastened so as to cover the upper part of the engine by connecting them. On the other hand, in order to facilitate the attachment of the engine cover to the engine member, the positioning portion and the reference fixing portion are provided in the engine cover, and the reference fixing portion is temporarily attached to the corresponding fixed portion of the engine member. There has been proposed an engine cover mounting structure in which the engine cover is rotated by rotating the engine cover until the positioning portion comes into contact with the engine member around the reference fixing portion (see Patent Document 3).
JP 2005-248874 A JP 2006-262905 A JP-A-2005-290996

  In a conventional variable valve opening characteristic internal combustion engine, when the engine cover is fastened to the cam holder, two positioning means are provided at positions opposite to the cam holders located at both ends of the plurality of cam holders, The engine cover is fastened after restricting relative movement to the cam holder. However, when such a fastening method is adopted, due to manufacturing errors and assembly errors of the respective members, an actuator driving unit attached to the engine cover and a driven portion of the valve opening modification characteristic control member driven by the actuator There is a possibility that an error occurs in the relative position and the assembly becomes difficult.

  The present invention has been made in view of such a background, and when the engine cover is fastened to a plurality of cam holders, there is a shift in the relative position between the actuator drive portion and the driven portion of the valve opening modification control member. The purpose is to suppress the occurrence.

  In order to solve the above-described problems, the present invention provides a cylinder head that is fastened to a cylinder block in which a plurality of cylinders are arranged in series, and that holds a valve in a slidable manner. A plurality of cam holders rotatably holding a camshaft having a cam for use, a valve opening characteristic control member disposed between the valve and the cam and having a driven portion, and the cylinder head of the cam holder being separated from the cylinder head An engine cover arranged on the side to be mounted, positioning means for positioning the engine cover with respect to the cam holder, fastening means for fastening the engine cover to the cam holder, attached to the engine cover, and connected to the driven portion. And an actuator having a driving unit to be coupled, and by driving the actuator, the bar In the valve opening characteristics variable type internal combustion engine for varying the valve opening characteristics of the probe, the positioning means is adapted to be disposed adjacent to the driven portion of the valve opening characteristic control member in the cylinder row direction.

  In the variable valve opening characteristic internal combustion engine configured as described above, the driven portion of the valve opening characteristic control member is disposed near the center in the cylinder row direction, and the positioning means is disposed on the cam holder adjacent to the driven portion. It may be configured to be formed.

  According to the present invention, even when the engine cover is fastened to the plurality of cam holders, the positioning means is disposed at a position adjacent to the driven portion of the valve opening characteristic control member in the cylinder row direction, so that each member is manufactured. It is possible to reduce the relative positional deviation between the actuator driving portion and the valve opening characteristic control member driven portion due to errors or assembly errors. Therefore, the actuator can be easily attached to the engine cover with the drive unit engaged with the valve opening modification characteristic control member driven unit. Further, it is possible to prevent the assembled drive unit from dropping from the driven unit during operation.

  Further, the driven portion of the valve opening characteristic control member is disposed near the center in the cylinder row direction, and the positioning means is formed on the cam holder adjacent to the driven portion, so that the driving force transmission shaft of the valve opening characteristic control member is Bending and twisting are suppressed, and the difference in valve lift between the cylinders according to the displacement of the driving force transmission shaft can be reduced.

  Hereinafter, embodiments of the present invention and some modifications thereof will be described in detail with reference to the drawings.

<< Configuration of Embodiment >>
FIG. 1 is a perspective view showing an upper portion of an engine according to the present invention, FIG. 2 is a perspective view showing a main part of a valve opening characteristic variable mechanism 18 of the engine according to the present invention, and FIGS. 3 and 4 are engines according to the present invention. It is a longitudinal cross-sectional view which shows the valve opening characteristic variable operation | movement state of.

  This engine (variable valve opening type internal combustion engine) is an in-line four-cylinder engine mounted on an automobile, and two exhaust valves 2 for each cylinder are slidably held in the cylinder head 1. As a valve operating mechanism for driving the valve 2, the camshaft 4 provided with the cam 3, the rocker arm 6 interposed between the valve 2 and the cam 3, and the valve 2 are always urged in the closing direction. A valve spring 7 is provided.

  Although not shown, two intake valves are provided for each cylinder on the intake side, and a camshaft, a rocker arm, and a valve spring are provided as valve operating mechanisms for driving the valves.

  The camshaft 4 is rotatably supported by a cam holder 11 that is integrally fastened by a bolt B2. The cam holder 11 is provided so as to partition a valve operating chamber for each cylinder, and is fastened and fixed to the upper surface of the cylinder head 1 by a bolt B2.

  This engine is equipped with a variable valve opening characteristic mechanism 18 that variably controls the lift amount of the valve 2. In this variable valve opening characteristic mechanism 18, an electric motor (actuator) 14 installed on the upper surface of the engine cover 13 is used to connect a link mechanism 15 provided for each cylinder via a reduction gear mechanism 19 (see FIG. 3). A gear shaft 16 serving as a driving force transmission shaft provided with a gear 17 to be interlocked is rotated. The gear shaft 16 is also rotatably supported by the cam holder 11. Both the electric motor 14 and the gear shaft 16 are arranged so that the axis thereof is parallel to the axis of the camshaft 4. The engine cover 13 is fastened and fixed to the upper surfaces of the plurality of cam holders 11 by bolts B1 (fastening means) so as to cover the upper part of the engine.

  As shown in FIG. 2, the link mechanism 15 constituting the variable valve opening characteristic mechanism 18 includes a gear link 21 rotatably supported by the cam holder 11, and is held swingably by the gear link 21. The free end side has a roller link 22 interposed between the cam 3 and the rocker arm 6, and the lift amount of the valve 2 according to the displacement of the swing fulcrum of the roller link 22 as the gear link 21 rotates. Is to change.

  The gear link 21 extends in the circumferential direction from an arm portion 24 that rotates around a support shaft 23 provided in the cam holder 11, and the gear 17 of the gear shaft 16 (see FIG. 1). And a gear portion 25 that meshes with each other, and rotates by the driving force of the electric motor 14. Further, a bearing portion 26 that holds the roller link 22 in a swingable manner is formed on the side surface on the free end side of the arm portion 24 so as to protrude in the axial direction. The gear portion 25 of the gear link 21 and the cam holder 11 are in slidable contact with each other in the axially opposed surface.

  The roller link 22 is fitted to the bearing portion 26 of the gear link 21 and has a base portion 28 provided at both ends with support shaft portions 27 serving as swing fulcrums, and a pair of arm portions 29 extending from the base portion 28. And have. At the tip of the arm portion 29, there are a roller 31 that is in rolling contact with the cam 3 of the camshaft 4 and a roller shaft 32 that is in contact with the slipper surface 33 of the rocker arm 6.

  The rocker arm 6 includes a base portion 35 rotatably supported by a rocker shaft 34 held by the cam holder 11, and a pair of arm portions 36 extending from the base portion 35, and the pair of arms As shown in FIG. 3, each part 36 is provided with an adjusting screw 39 for adjusting the position of a tip part 38 that presses the stem end 37 of the valve 2.

  In the valve opening characteristic variable mechanism 18 configured as described above, the gear link 21 rotates about the support shaft 23 (see FIG. 2) as the gear shaft 16 rotates, and accordingly. The bearing 26 serving as a swing fulcrum of the roller link 22 is displaced, and the lift amount of the valve 2 can be adjusted steplessly according to the rotation angle position (link angle) of the gear link 21.

  In order to reduce the valve lift during idling or the like, the gear link 21 is set to the minimum lift position shown in FIG. 3 (for example, the link angle = 0 degree), and in this case, the bearing portion 26 serving as the swing fulcrum of the roller link 22 is used. However, even when the roller 31 is pushed down by the cam 3 even if the roller 31 is pushed down by the cam 3, the roller 31 rolls along the slipper surface 33 as shown by the arrow, and the rocker arm 6 swings (that is, The lift amount of the valve 2 is reduced.

  On the other hand, when increasing the valve lift during high load operation or the like, the gear link 21 is set to the maximum lift position (for example, link angle = 60 degrees) shown in FIG. When the bearing portion 26 is positioned on the side of the camshaft 4 and the roller 31 is pushed down by the cam 3, almost no rolling occurs along the slipper surface 33, so that the rocker arm 6 swings, and the valve The lift amount of 2 is also increased.

  As shown in FIG. 3, the reduction gear mechanism 19 includes a driven gear 20 (driven portion) meshed with a drive gear 14 a (driving portion) fitted to the output shaft of the electric motor 14, and a gear portion of the gear link 21. And a gear 17 that meshes with the gear 25, and is configured by meshing a plurality of gears between the driven gear 20 and the gear 17. With this configuration, the rotation of the electric motor 14 is transmitted to the gear link 21 with a relatively large reduction ratio, and a small electric motor 14 with a small generated torque can be employed. Further, since the electric motor 14 can be installed at a relatively low position on the engine cover 13, the center of gravity and the overall height of the engine are lowered, and the mountability of the engine is improved.

  FIG. 5 is a plan view of the engine according to the present invention with the engine cover 13 removed. As shown in the figure, among the five cam holders 11 arranged in series, on the side surface of the center cam holder 11c arranged at the center, the driven gear 20 of the reduction gear mechanism 19 and the electric motor 14 meshing with the driven gear 20 are provided. The drive gear 14a is closely disposed.

  A plurality of bolt holes N1 are formed on the upper surface of the cam holder 11, and the engine cover 13 is fastened to the cam holder 11 by screwing the bolts B1 into the bolt holes N1. A cylindrical knock pin hole N1 '(positioning means) is formed in the vicinity of both ends for positioning on the upper surface of the center cam holder 11c. That is, the knock pin 41 is disposed at a position adjacent to the driven gear 20 that is the driven portion of the valve opening characteristic variable mechanism 18 in the cylinder row direction.

  When attaching the engine cover 13 to the cam holder 11, as shown in FIG. 3, knock pins 41 (positioning means) are respectively inserted into the two knock pin holes N 1 ′ formed in the center cam holder 11 c, and the lower surface of the engine cover 13 After the knock pin 41 is inserted into the knock pin hole N1 ′ formed in the above, the relative position of the engine cover 13 with respect to the cam holder 11 is determined, and then the bolt B1 is fastened to the cam holder 11. When the electric motor 14 is attached to the engine cover 13, similarly, the knock pin 42 is inserted into the knock pin hole N 2 ′ formed on the upper surface of the engine cover 13, and the knock pin hole N 2 formed on the lower surface of the electric motor 14. By inserting the knock pin 42 into ', the relative position of the electric motor 14 with respect to the engine cover 13 is determined.

<< Effects of Embodiment >>
In the engine configured as described above, when the engine cover 13 is fastened to the cam holder 11, the knock pin 41 is disposed at a position adjacent to the driven gear 20 of the valve opening characteristic variable mechanism 18 in the cylinder row direction. Deviations in the relative position between the drive gear 14a of the electric motor 14 and the driven gear 20 of the valve opening characteristic variable mechanism 18 due to manufacturing errors and assembly errors of the respective members can be reduced. Therefore, the electric motor 14 can be easily assembled to the engine cover 13 with the drive gear 14 a engaged with the driven gear 20. Further, since the assembled drive gear 14a has a small positional deviation with respect to the driven gear 20, it is also possible to prevent the gears from being disengaged during operation.

  Further, the driven gear 20 of the variable valve opening characteristic mechanism 18 is disposed close to the center cam holder 11c disposed in the center in the cylinder row direction, and the knock pin 41 is formed on the center cam holder 11c. And torsion are suppressed, and the difference in valve lift between the cylinders corresponding to the displacement of the gear shaft 16 is reduced.

  Although the description of the specific embodiment is finished as above, the present invention is not limited to the above embodiment and can be widely modified. For example, in the above embodiment, the present invention is applied to an in-line four-cylinder DOHC gasoline engine that variably controls only the lift amount on the exhaust valve side, but the lift amount on the intake valve side is also variably controlled. Of course, the present invention can also be applied to SOHC engines and diesel engines. In the above embodiment, the drive gear of the electric motor drives the gear shaft via the speed reduction mechanism. However, the drive gear may be directly engaged with the gear shaft. Further, the valve opening characteristic variable mechanism is not limited to the one having the above configuration, and can be applied to mechanisms having various configurations. Other modifications can be made as appropriate without departing from the spirit of the present invention.

It is a perspective view which shows the upper part of the engine by this invention. It is a perspective view which shows the principal part of a valve opening characteristic variable mechanism. It is a longitudinal cross-sectional view which shows a valve opening characteristic variable operation condition. It is a longitudinal cross-sectional view which shows a valve opening characteristic variable operation condition. It is a top view which shows the upper part of the engine by this invention.

Explanation of symbols

1 Cylinder head 2 Valve 3 Cam 4 Cam shaft 11 Cam holder 11c Center cam holder 13 Engine cover 14 Electric motor (actuator)
14a Drive gear (drive unit)
16 gear shaft 18 variable valve opening characteristic mechanism 19 reduction gear mechanism 20 driven gear (driven part)
41 dowel pin (positioning means)
B1 bolt (fastening means)
N1 'knock pin hole (positioning means)

Claims (2)

A cylinder head that is fastened to a cylinder block in which a plurality of cylinders are arranged in series, and that holds a valve slidably;
A plurality of cam holders provided on the cylinder head and rotatably holding a camshaft having a valve driving cam;
A valve opening characteristic control member disposed between the valve and the cam and having a driven portion;
An engine cover disposed on the cam holder on the side away from the cylinder head;
Positioning means for positioning the engine cover with respect to the cam holder;
Fastening means for fastening the engine cover to the cam holder;
An actuator attached to the engine cover and having a drive unit engaged with the driven unit;
A variable valve opening characteristic internal combustion engine that changes the valve opening characteristic of the valve by driving the actuator,
The variable valve opening characteristic internal combustion engine, wherein the positioning means is disposed at a position adjacent to a driven portion of the valve opening characteristic control member in the cylinder row direction. The driven portion of the valve opening characteristic control member is disposed near the center in the cylinder row direction,
The variable valve opening characteristic internal combustion engine according to claim 1, wherein the positioning means is formed in a cam holder adjacent to the driven portion.

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