VARIABLE VALVE DRIVING APPARATUS OF INTERNAL COMBUSTION ENGINE

Abstract

A variable valve driving apparatus of an internal combustion engine, including a drive shaft rotatably supported by a cam bracket, a drive cam disposed about an outer periphery of the drive shaft, a link arm having a first end connected to the drive cam, an oscillating cam extending from the drive cam configured to press and release a drive valve of the engine to open and close the drive valve, a link rod having a first end rotatably connected to the oscillating cam, and a control shaft rotatably supported by the cam bracket. The control shaft includes a main shaft rotatably supported by the cam bracket, an eccentric shaft spaced apart from the main shaft, and a plurality of webs connecting the main shaft and the eccentric shaft. The eccentric shaft is connected to an oscillating arm configured to transfer a drive force of the drive cam. The oscillating arm has a first portion rotatably connected to a second end of the link arm and a second portion rotatably connected to a second end of the link rod, the first and second portions being spaced apart axially with respect to the eccentric shaft. A first flow path for supplying lubricant to a first sliding contact area between the oscillating arm and the eccentric shaft is formed through the control shaft. The first flow path extends from the main shaft to the eccentric shaft through a web located beside the second portion of the oscillating arm.

Description

This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2007-214529, filed on Aug. 21, 2007, which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a variable valve driving apparatus of an internal combustion engine for variably controlling an operating state such as a valve lift amount or operating angle of a suction or exhaust valve of an internal combustion engine depending on an operating state of the engine. In particular, the present invention relates to a variable valve driving apparatus of an internal combustion engine suitable for improving a lubricating performance of the variable valve driving apparatus by forcibly supplying a lubricant to pivotally moving portions.

BACKGROUND OF THE INVENTION

To improve the lubricating performance of a variable valve driving apparatus, Japanese Laid-Open Patent Publication No. 2005-113720 discloses a variable valve driving apparatus for forcibly supplying a lubricant to each pivotally supporting portion such as a rocker arm and a link rod.

Such a variable valve driving apparatus is configured to open each suction valve by transferring a rotation force of a drive cam via a link arm and a link rod to an oscillating cam and also to variably control a valve lift amount of the suction valve by a rotation of a control shaft and a control cam. Further, a cam nose portion is arranged at a control shaft side compared to a straight line S, which connects a shaft center Q of a pin (a first pivotally supporting portion) and a shaft center X of a drive shaft. The lubricant, which flows between the control cam and the rocker arm which is eventually dropped on an upper surface of the oscillating cam, spreads along the upper surface of the oscillating cam in the axial direction of the pin, thereby forcibly lubricating the oscillating cam.

However, in the conventional variable valve driving apparatus, as a means for oscillateably supporting the rocker arm and changing an oscillating angle and oscillating area thereof, the control cam is integrally fixed on an outer peripheral surface of the control shaft functioning as a rocker arm. Thus, the range of the control cam is limited to avoid interference with other components within a rocker cover. Thus, the operation control range may be restricted, thereby restricting a lift property or a valve opening timing of the suction valve.

In order to resolve such a problem, an eccentric shaft, in which a shaft center is offset, is integrally formed in the control shaft in a crank shaft shape, which significantly spaces apart a shaft center of the control shaft and a shaft center of the eccentric shaft. As a result, the distance between the centers of the control shaft and eccentric shaft can be increased. However, since an overlap between the control shaft and the eccentric shaft becomes smaller when adopting the control shaft in the crank shape, it is not possible to form a straight communicating lubricant path in an inner portion. Further, if a complicated oil hole arrangement is adopted for the control shaft formed of a relatively thin shaft, which is generally adopted in a crank shaft having a relatively large diameter, then an oil hole forming process becomes complicated and a stress is concentrated around the oil hole. Thus, it becomes difficult to introduce the lubricant to a sliding contact area around the eccentric shaft.

Given the above problem, it is an object of the present invention to provide a variable valve driving apparatus of an internal combustion engine including a lubricant supplying structure suitable for using a control shaft in a crank shape.

SUMMARY OF THE INVENTION

In an embodiment, the invention provides a variable valve driving apparatus of an internal combustion engine, including a drive shaft rotatably supported by a cam bracket, a drive cam disposed about an outer periphery of the drive shaft, a link arm having a first end connected to the drive cam, an oscillating cam extending from the drive cam configured to press and release a drive valve of the engine to open and close the drive valve, a link rod having a first end rotatably connected to the oscillating cam, and a control shaft rotatably supported by the cam bracket. The control shaft includes a main shaft rotatably supported by the cam bracket, an eccentric shaft spaced apart from the main shaft, and a plurality of webs connecting the main shaft and the eccentric shaft. The eccentric shaft is connected to an oscillating arm configured to transfer a drive force of the drive cam. The oscillating arm has a first portion rotatably connected to a second end of the link arm and a second portion rotatably connected to a second end of the link rod, the first and second portions being spaced apart axially with respect to the eccentric shaft. A first flow path for supplying lubricant to a first sliding contact area between the oscillating arm and the eccentric shaft is formed through the control shaft. The first flow path extends from the main shaft to the eccentric shaft through a web located beside the second portion of the oscillating arm.

In another embodiment, the invention provides a method of driving a valve with a variable valve driving apparatus of an internal combustion engine, including rotatably supporting a drive shaft by a cam bracket, disposing a drive cam about an outer periphery of the drive shaft, connecting a first end of a link arm to the drive cam, extending an oscillating cam from the drive cam to press and release a drive valve of the engine to open and close the drive valve, rotatably connecting a first end of a link rod to the oscillating cam, and rotatably supporting a control shaft by the cam bracket. The control shaft includes a main shaft rotatably supported by the cam bracket, an eccentric shaft spaced apart from the main shaft, and a plurality of webs connecting the main shaft and the eccentric shaft. The method also includes connecting the eccentric shaft to an oscillating arm to transfer a drive force of the drive cam. The oscillating arm has a first portion rotatably connected to a second end of the link arm and a second portion rotatably connected to a second end of the link rod, the first and second portions being spaced apart axially with respect to the eccentric shaft. The method further includes supplying lubricant through a first flow path formed through the control shaft to a first sliding contact area between the oscillating arm and the eccentric shaft. The first flow path extends from the main shaft to the eccentric shaft through a web located beside the second portion of the oscillating arm.

In the present invention, since the part of the control shaft having the angled flow path spans the length of the cam shaft which includes the oscillating cam, the relatively long span along the axial direction can be used to form the flow path. Thus, the degree of freedom for arranging the diameter and angle of the angled oil hole can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain features of the invention.

FIG. 1 is a perspective view of a variable valve driving apparatus in accordance with a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the variable valve driving apparatus.

FIG. 3 is a cross-sectional view of a lubricant path configuration of the variable valve driving apparatus.

FIG. 4 is a cross-sectional view of a lubricant path configuration of a bearing portion.

FIG. 5 shows an oil groove of a bearing surface of a main shaft of a cam bracket.

FIG. 6 shows a force exerted in a middle operating angle of the variable valve driving apparatus.

FIG. 7 is a cross-sectional view of a lubricant path configuration of a variable valve driving apparatus in accordance with a second embodiment of the present invention.

FIG. 8 is a perspective view of an oil groove configuration provided in a bearing bracket in accordance with a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A variable valve driving apparatus of an internal combustion engine, which is constructed in accordance with embodiments of the present invention, will be explained below.

First Embodiment

FIGS. 1 to 5 show a variable valve driving apparatus of an internal combustion engine in accordance with a first embodiment of the present invention. FIG. 1 is a perspective view of the variable valve driving apparatus. FIG. 2 is a cross-sectional view of the variable valve driving apparatus. FIG. 3 is a cross-sectional view of a lubricant path configuration of the variable valve driving apparatus. FIG. 4 is a cross-sectional view of a lubricant path configuration of a bearing portion. FIG. 5 shows an oil groove of a bearing surface of a main shaft of a cam bracket. FIG. 6 shows a force exerted in a middle operating angle of the variable valve driving apparatus. The variable valve driving apparatus of the present embodiment includes two suction valves in one cylinder and is applied to an internal combustion engine for variably controlling a valve lift in each suction valve depending on an operating state of the engine.

In FIGS. 1 to 3, the variable valve driving apparatus of the internal combustion engine includes the following: a drive shaft 1 rotatably supported on a cam bracket 3 in an upper portion of a cylinder head (not shown); a drive cam 2 coupled to the drive shaft 1, by a pin for example; a control shaft 4 including a main shaft 5 arranged in parallel to the drive shaft 1, spaced vertically from the drive shaft 1, and being rotatably supported by the cam bracket 3; the control shaft 4 further including an eccentric shaft 6, the axis of which is offset from the axis of the main shaft 5 via a web 7 at both sides of the main shaft 5; an oscillating arm 8 rotatably supported by the eccentric shaft 6 of the control shaft 4; and an oscillating cam 9 arranged on the drive shaft 1 in order to contact a rocker arm 31, wherein a roller 32 of each suction valve 30 is installed.

The drive cam 2 is connected to the oscillating arm 8 by the link arm 10. Further, the oscillating arm 8 is connected to the oscillating cam 9 by the link rod 11. The drive shaft 1 is driven by a crankshaft of the engine via a timing chain or timing belt (not shown). The drive cam 2 has a circular outer peripheral surface the axis of which is offset by a predetermined amount from the axis the drive shaft 1, wherein a ring-shaped portion of the link arm 10 is rotatably fitted around the outer peripheral surface of the drive cam 2.

A base of the oscillating arm 8 is divided into two portions, a bearing bracket 15 and an arm portion 16. Further, the oscillating arm is rotatably coupled to the link arm 10 and the link rod 11. The bearing bracket 15 and arm portion 16 of the oscillating arm 8 are coupled by a fastener such as coupling bolt 17 and form a bearing hole 18 through which the eccentric shaft 6 passes, so that the oscillating arm 8 can be rotatably supported by the eccentric shaft 6. A flange 57 extending from one side of the arm portion 16 is rotatably coupled to an upper end of the link rod 11 via a connecting pin 19. The one side of the arm portion 16 is also rotatably coupled to an upper end of the link arm 10 via a connecting pin 20, which is formed on the arm portion 16 at a position spaced apart from the flange in the axial direction of the control shaft 4.

The control shaft 4 includes the main shaft 5 which is rotatably supported at the cam bracket 3 and the eccentric shaft 6 spaced apart from the main shaft 5 via the web 7. The position of the eccentric shaft 6 is changed by changing the angular position of the control shaft 4. Accordingly, the axis of rotation of the oscillating arm 8 is thereby moved corresponding to the change in position of the eccentric shaft 6. The length of the eccentric shaft 6 is preferably at least as long as the width (W) of the oscillating arm 8 plus the length (L) of the connecting pin 20 so that the webs 7 arranged at both ends of the eccentric shaft 6 do not interfere with the link arm 10 and the link rod 11.

Two oscillating cams 9 corresponding to the rocker arm 31 of each suction valve 30 are integrally formed with a cam shaft 25, which is rotatably supported by an outer periphery of the drive shaft 1. A radial protrusion 58 forming a cam surface 59 extends from a portion of the outer periphery of the oscillating cam 9 and is connected to a lower end of the link rod 11 via a connecting pin 21. Although the cam shaft 25 is rotatably supported at the outer periphery of the drive shaft 1, an end of the cam shaft 25 is also rotatably supported by the cam bracket 3 and a middle portion of the cam shaft 25 is rotatably supported by a middle bracket 3A installed at the cylinder head. At a portion of the outer periphery opposite the radial protrusion 58, of each oscillating cam 9, a basic circular surface 60 forming a circular arc corresponding to the shape of the drive shaft 1 and a cam surface 59 defined by a predetermined curved line from the basic circular surface are continuously formed. The basic circular surface 60 and the cam surface 59 are configured to contact an upper surface of the roller 32 of the rocker arm 31 of each suction valve 30 according to an oscillating position of the oscillating cam 9.

That is, the basic circular surface 60 is a base circle section configured to contact the roller 32 of the rocker arm 31 without applying pressure so that the suction valve 30 is not lifted. The oscillating cam 9 oscillates such that the cam surface contacts the roller 32 of the rocker arm 31, so that the suction valve 30 is gradually lifted. Further, a slight lap stage is provided between the base circle section and the lift section. The suction valve 30 of the present embodiment is configured to be opened and closed by the rocker arm 31 pivoting around the roller 32 as shown in FIG. 2. A base of the rocker arm 31 is provided with a hydraulic lash adjuster (HLA) 33, which receives a supply of lubricant.

The control shaft 4 is configured to rotate within a predetermined angle range by an actuator 23 installed at one end. The actuator 23 for controlling includes, for example, an electric actuator and is controlled by a control signal from an engine controller (not shown), and a rotation angle of the control shaft 4 is detected by a sensor (not shown).

In the variable valve driving apparatus configured as above, when the drive shaft 1 rotates, the link arm 10 moves upwardly and downwardly by a cam operation of the drive cam 2 while causing the oscillating arm 8 to oscillate as a result. The oscillations of the oscillating arm 8 are transferred via the link rod 11 to the oscillating cam 9 to thereby oscillate the oscillating cam 9. The rocker arm 31 is pressed by a cam operation of the oscillating cam 9, thereby being operated to lift the suction valve 30.

When the angle position of the control shaft 4 is changed by the actuator 23, the initial position of the oscillating arm 8 is changed, which thereby changes the initial oscillating position of the oscillating cam 9. For example, at a low speed and low load operating state of the internal combustion engine, the eccentric shaft 6 is positioned closer to the drive shaft 1 by rotating along the axis of the main shaft 5 in a clockwise direction (in FIG. 2). This causes the base of the oscillating arm 8 to also be positioned closer to the drive shaft 1, which then causes the radial protrusion 58 of the oscillating cam 9 to be lifted. That is, the initial position of the oscillating cam 9 is inclined so that the cam surface 59 of the oscillating cam 9 is disposed away from the roller 32 of the rocker arm 31. Thus, when the oscillating cam 9 oscillates along with rotation of the drive shaft 1, the oscillating cam 9 is positioned so that the basic circular surface 60 maintains contact with the roller 32 of the rocker arm 31 for the majority of the oscillation so that the period when the cam surface contacts the roller 32 of the rocker arm 31, thereby lifting the suction valve 30, is relatively short. Accordingly, the lift amount becomes generally smaller and an angle range from an opening timing to a closing timing (i.e., operating angle) is reduced.

On the contrary, at a high speed and high load operating state of the internal combustion engine, since the eccentric shaft 6 is positioned farther from the drive shaft 1 by rotating along the axis of main shaft 5 in a counterclockwise direction (in FIG. 2), the base of the oscillating arm 8 is also positioned closer to the drive shaft 1, causing the radial protrusion 58 of the oscillating cam 9 to be lowered. That is, the initial position of the oscillating cam 9 is inclined so that the cam surface 59 of the oscillating cam 9 is positioned closer to the roller 32 of the rocker arm 31. Thus, when the oscillating cam 9 oscillates along with rotation of the drive shaft 1, the oscillating cam 9 is positioned so that the basic circular surface 60 only briefly contacts the roller 32 of the rocker arm 31 so that the period when the cam surface 59 contacts the roller 32 of the rocker arm 31, thereby lifting the suction valve 30, is relatively long. Accordingly, the lift amount becomes generally greater and the operating angle is increased. FIG. 2 shows a state of a middle operating angle wherein a maximum input load is exerted.

Since the initial position of the eccentric shaft 6 can be continuously changed, a valve lift property is continuously changed as a result. That is, both the lift amount and the operating angle can be continuously increased or reduced at the same time. Such a change is based on layouts of each part, for example, the opening timing and closing timing of the suction valve 30 are changed as a result of the magnitude of change of each of the lift amount and the operating angle.

Although it is not shown in the drawings, an actuator for controlling rotation of the drive shaft 1 within a predetermined angle range is arranged between the drive shaft 1 and the sprocket driven by the timing chain or timing belt in the crankshaft. The drive shaft 1 is rotated relative to the sprocket by controlling the actuator using a control signal from the engine controller. This is so that a lift center angle in the valve lift may be advanced or delayed. That is, without changing a curve of the lift property itself, an overall angle may be advanced or delayed.

Referring to FIG. 3, a lubricant path 41 for introducing the lubricant supplied from a main oil gallery 40 of the internal combustion engine is formed in the drive shaft 1 by passing axially through an inner portion of the drive shaft 1. The lubricant introduced to the lubricant path 41 is supplied to a first lubricant supplying channel (corresponding to an oil hole 42) for lubricating a sliding contact area (SCA) between the link arm 10 and the drive cam 2, and a sliding contact area between the link arm 10 and the connecting pin 20; a second lubricant supplying channel (corresponding to an oil hole 44) for lubricating each sliding contact area between the drive shaft 1 and the cam shaft 25, and the sliding contact area between the oscillating cam 9 and the rocker arm 31 of the suction valve 30; and a third lubricant supplying channel (corresponding to an oil hole 46) for lubricating each sliding contact area between the cam shaft 25 and the cam bracket 3, each sliding contact area between the cam bracket 3 and the main shaft 5, and the sliding contact area between the oscillating arm 8 and the eccentric shaft 6. Further, the lubricant is additionally supplied from the main gallery 40 to the hydraulic lash adjuster (HAL) 33.

The first lubricant supplying channel is in fluid communication with a first sliding contact area between an outer peripheral surface of the drive cam 2 and a first inner peripheral surface of the link arm 10 via an oil hole 42 formed radially through a relatively thin portion of the wall of the drive cam 2 and the corresponding wall of the drive shaft 1. Further, the first sliding contact area is in fluid communication with a second sliding contact area between a second inner peripheral surface of the link arm 10 and an outer peripheral surface of the connecting pin 20 by an oil passage hole 43, which is formed through link arm 10 and having a first opening through the first inner peripheral surface of the link arm 10 at the first sliding contact area and a second opening through the second inner peripheral surface of the link arm 10 at the second sliding contact area. Thus, the first sliding contact area between the first inner peripheral surface of the link arm 10 and the outer peripheral surface of the drive cam 2 and the second sliding contact area between the second inner peripheral surface of the link arm 10 and the outer peripheral surface of the connecting pin 20 are lubricated.

The second lubricant supplying channel is in fluid communication with a third sliding contact area between an inner peripheral surface of the cam shaft 25 and an outer peripheral surface of the drive shaft 1 via an oil hole 44 formed radially through the wall of the drive shaft 1 in a position corresponding to each of the oscillating cams 9. Further, the third sliding contact area is in fluid communication with a fourth sliding contact area between an outer surface of the oscillating cam 9 and an outer surface of the rocker arm 31 by a thin oil hole (not shown). As such, the third sliding contact area between the outer peripheral surface of the drive shaft 1 and the inner peripheral surface of the cam shaft 25 and the fourth sliding contact area between the outer peripheral surface of the oscillating cam 9 and the outer peripheral surface of the rocker arm 31 are lubricated. The third sliding contact area between the outer peripheral surface of the drive shaft 1 and the inner peripheral surface of the cam shaft 25 is also in fluid communication with a fifth sliding contact area between an outer peripheral surface of the cam shaft 25 and an inner peripheral surface of the middle bracket 3A via the oil hole 45 formed radially through the wall of the cam shaft 25 and having a first opening through the inner peripheral surface of the cam shaft 25 at the third sliding contact area and a second opening through the outer peripheral surface of the cam shaft 25 in a position corresponding to the middle bracket 3A at the fifth sliding contact area. Thus, the fifth sliding contact area between the middle bracket 3A and the outer peripheral surface of the cam shaft 25 is configured to be lubricated as well.

The third lubricant supplying channel is in fluid communication first with a sixth sliding contact area between the inner peripheral surface of the cam shaft 25 and the outer peripheral surface of the drive shaft 1 by an oil hole 46. The oil hole 46 is formed radially through the wall of drive shaft 1 in a position corresponding to the cam bracket 3. The sixth sliding contact area is then in fluid communication with a seventh sliding contact area between a first inner peripheral surface of the cam bracket 3 and the outer peripheral surface of the cam shaft 25 via an oil hole 47 formed through the wall of the cam shaft 25 and having a first opening through the inner peripheral surface of the cam shaft 25 at the sixth sliding contact area and a second opening through the outer peripheral surface of cam shaft 25 at the seventh sliding contact area in a position corresponding to the cam bracket 3. The seventh sliding contact area is then in fluid communication with an eighth sliding contact area between a second inner peripheral surface of the cam bracket 3 and an outer peripheral surface of the main shaft 5 via an oil hole 48 formed through the cam bracket 3 and having a first opening through the first inner peripheral surface of the cam bracket 3 at the seventh sliding contact area, and a second opening through the second inner peripheral surface of the cam bracket 3 at a first point in the eight sliding contact area. Thus the sixth sliding contact area between the inner peripheral surface of the cam shaft 25 and the outer peripheral surface of the drive shaft 1, the seventh sliding contact area between the first inner peripheral surface of the cam bracket 3 and the outer peripheral surface of the cam shaft 25, and the eighth sliding contact area between the second inner peripheral surface of the cam bracket 3 and an outer peripheral surface of the main shaft 5 are all lubricated.

Further, a through hole 53 is formed through the main shaft 5 along the radial direction of main shaft 5 and having a first opening through the outer peripheral surface of main shaft 5 at the first point of the eighth sliding contact area and a second opening through the outer peripheral surface of main shaft 5 at a second point in the eighth sliding contact area. This is so that sliding contact between the main shaft 5 and cam bracket 3 during rotational operation of the main shaft 5 becomes smooth.

Additionally, the eight sliding contact area between the second inner peripheral surface of the cam bracket 3 and an outer peripheral surface of the main shaft 5 is in fluid communication with a ninth sliding contact area between an outer peripheral surface of the eccentric shaft 6 and an inner peripheral surface of the oscillating arm 8 via an angled oil hole 50 formed through the control shaft 4 and having a first opening through the outer peripheral surface of the main shaft 5 at the eighth sliding contact area and a second opening through the outer peripheral surface of the eccentric shaft 6 at a first point in the ninth sliding contact area. The angled oil hole 50 forms a straight line extending directly from the eighth sliding contact area to the ninth sliding contact area, so that the angled oil hole 50 passes through the main shaft 5, web 7, and eccentric shaft 6 at an acute angle relative to the axes of the main shaft 5 and eccentric shaft 6. The second opening of angled oil hole 50 through the outer peripheral surface of the eccentric shaft 6 is configured to be located proximate to a side of the oscillating arm 8 where the oscillating arm 8 is connected to link arm 10. Further, at a point along angled oil hole 50 between the first and second openings of the angled oil hole 50, an oil hole 51 is formed extending radially through eccentric shaft 6 in fluid communication with angled oil hole 50 and having a first opening at the angled oil hole 50 and a second opening through the outer peripheral surface of the eccentric shaft 6 at a second point in the ninth sliding contact area. The second opening of oil hole 51 through the outer peripheral surface of the eccentric shaft 6 is configured to be located proximate to a side of the oscillating arm 8 where the oscillating arm 8 is connected to the link rod 11.

Since an area around the web 7 for connecting the corresponding main shaft 5 and eccentric shaft 6 is relatively large in size, it is fairly easy to employ a web 7 with an increased thickness along the axial direction of control shaft 4. Thus, by increasing the thickness of the web 7 along the axial direction of the control shaft 4, it is possible to increase the degree of freedom for forming and arranging the angled oil hole 50, including dimensions such as diameter or angle of the angled oil hole 50.

Thus, the third lubricant supplying channel lubricates each sliding contact area between the cam shaft 25 and the cam bracket 3, each sliding contact area between the cam bracket 3 and the main shaft 5, and each sliding contact area between the oscillating arm 8 and the eccentric shaft 6. Further, since the lubricant is supplied from the angled oil hole 50 and the oil hole 51 to two points in the ninth sliding contact area between the outer peripheral surface of the eccentric shaft 6 and the oscillating arm 8, both load points can be sufficiently lubricated with a small amount of the lubricant. Moreover, the lubricant can be thoroughly supplied to the side of the oscillating arm 8 where the load of the ninth sliding contact area is greater.

As shown in FIG. 4, on the inner peripheral surface of the cam bracket 3 for rotatably supporting the main shaft 5 at the eighth sliding contact area, an oil groove 54 is formed along the upper and lower peripheral surfaces of cam bracket 3. As shown in FIGS. 4 and 5, the width of the oil groove 54 is maximized at the intersection with the oil hole 48, and the width of the oil groove 54 becomes narrower when moving away circumferentially from the intersection. The first opening of the angled oil hole 50 moves along the oil groove 54 according to changes of a rotation position of the control shaft 4, allowing the flow amount of the lubricant supplied via the oil groove 54 to be controlled according to the width of the oil groove 54.

Specifically, in a small operating angle (Point A in FIG. 5) where the eccentric shaft 6 is rotated to position angled oil hole 50 to Point A, the width of the oil groove 54 is formed smaller. Further, an amount of lubricant supplied to the sliding contact areas of the oscillating arm 8 is relatively small. This is so that at the time of initiating or low rotating the internal combustion engine, when the amount of lubricant supplied to the hydraulic lash adjuster 33 tends to be diminished, the lubricant can be first supplied to the hydraulic lash adjuster (HLA) 33 by decreasing the amount of lubricant supplied to the third lubricant supplying channel. In other words, a priority supply of lubricant may be provided to the hydraulic lash adjuster 33.

Further, in a middle operating angle (Point B in FIG. 5) where the eccentric shaft 6 is rotated to be positioned on an extension of a line for connecting a center of the main shaft 5 and a center of the drive shaft 1 (shown in FIG. 6), attitudes of the link arm 10 and the link rod 11 are steepest and the input load becomes greatest. However, since the width of the oil groove 54 is largest at Point B, where the oil groove 54 intersects the oil hole 48, so that the amount of lubricant supplied to the sliding contact area of the oscillating arm 8 is at a maximum value.

Also, in a large operating angle (Point C in the FIG. 5) where the eccentric shaft 6 is rotated to be positioned over an extension of the line for connecting a center of the main shaft 5 and a center of the drive shaft 1, the width of the oil groove 54 at Point C becomes slightly narrower than the maximum value, but a sufficient amount of lubricant is still supplied to the sliding contact area of the oscillating arm 8.

FIGS. 7 and 8 show a variable valve driving apparatus of an internal combustion engine in accordance with a second embodiment of the present invention. In this embodiment of a variable valve driving apparatus, only the second opening of angled oil hole 50 at the ninth sliding contact surface between the inner peripheral surface of the oscillating arm 8 and the outer peripheral surface of the eccentric shaft 6 differs from the first embodiment.

In the variable valve driving apparatus of the second embodiment, the second opening of the angled oil hole 50 passes through the outer peripheral surface of the eccentric shaft 6 at a third point in the ninth sliding contact area which is configured to be proximate to a side of the oscillating arm 8 where the oscillating arm 8 is connected to the link rod 11. Further, an oil groove 55 is formed on an inner peripheral surface of the bearing bracket 15 of the oscillating arm 8 along an axial direction of the eccentric shaft 6, and oil grooves 56 extend from both ends of oil groove 55 along the circumferential direction of the eccentric shaft 6 as shown in FIG. 8.

As such, the lubricant introduced via the angled oil hole 50 is supplied along an axial direction to the ninth sliding contact area to a side of oscillating arm 8, which is proximate to where the oscillating arm 8 is connected to the link rod 11, via the oil groove 56 along the circumferential direction of eccentric shaft 6. However, the lubricant is additionally supplied to another side, which is proximate to where the oscillating arm 8 is connected to the link arm 10, of the ninth sliding contact area via the oil groove 55 along the axial direction of the eccentric shaft 6 and via the oil groove 56 along the circumferential direction of the eccentric shaft 6. Thus, by supplying the lubricant to two places along the ninth sliding contact area via two oil grooves 56 along the circumferential direction connected by the oil groove 55 along the axial direction installed at the bearing bracket 15, it is possible to supply the lubricant thoroughly to an end where the one-side contact load of the slide-moving portion of the oscillating arm 8 is greatest.

Further, since the oil groove 55 extended along the axial direction and the oil grooves 56 extended along each circumferential direction at both ends of the oil groove 55 are formed in the inner peripheral surface of the bearing bracket 15 of the oscillating arm 8, the angled oil hole 50 provided in the control shaft 4 can be shorter. Also, the degree of freedom of the diameter and the angle of the angled oil hole 50 can be increased. Moreover, to form the oil groove 55 extended along the axial direction and the oil grooves 56 extended along each circumferential direction at both ends of the oil groove 55, it is inexpensive and easy to manufacture since it only requires forming a projection for the oil groove 55 and oil grooves 56 previously in a cast when forming the bearing bracket 15 by casting.

In the present embodiment, the following advantages can be achieved.

(a) Since the part of the control shaft 4 having the angled oil hole 50 spans the length of the cam shaft 25 which includes the oscillating cam 9, the relatively long span along the axial direction can be used to form the angled oil hole 50. Thus, the degree of freedom for arranging the diameter and angle of the angled oil hole 50 can be increased.

(b) Since the angled oil hole 50, which is formed through the control shaft 4, is in fluid communication with the lubricant path 41, which is formed though the drive shaft 1, via the oil hole 48 installed at the cam bracket 3, a higher priority region closer to the drive shaft 1 which requires lubrication because of a high input load and sliding contact speed can be lubricated prior to a lower priority region closer to the control shaft 4.

(c) Since the angled oil hole 50 formed through the control shaft 4 forms a straight line from the outer peripheral surface of the main shaft 5 to the outer peripheral surface of the eccentric shaft 6 in a sliding contact area between the oscillating arm 8 and the eccentric shaft 6, the flow path is a direct oil hole. Thus, it is easy to manufacture the oil hole 50.

(d) Since the web 7 at the link rod 11 side of the oscillating arm 8 connected to the eccentric shaft 6 and main shaft 5 of the control shaft 4 is formed larger than the web 7 at the link arm 10 side of the oscillating arm 8 in terms of width in the axial direction, the degree of freedom for forming the diameter and angle of the angled oil hole 50 can be further increased.

(e) Since the angled oil hole 50 formed through the control shaft 4 has an opening at the sliding contact area between the outer peripheral surface of the eccentric shaft 6 and the inner peripheral surface of the oscillating arm 8 on the link rod 11 side of the oscillating arm 8, and since the oil hole 50 is also in fluid communication with a radially directed oil hole 51 which has an opening at the sliding contact area between the outer peripheral surface of the eccentric shaft 6 and the inner peripheral surface of the oscillating arm 8 on the link arm 10 side of the oscillating arm 8, the lubricant is supplied to two points along the sliding contact area between the outer peripheral surface of the eccentric shaft 6 and the inner peripheral surface of the oscillating arm 8. Thus, the load point can be sufficiently lubricated by a small amount of the lubricant. Further, the lubricant can be thoroughly supplied to an end of the sliding contact area between the outer peripheral surface of the eccentric shaft 6 and the inner peripheral surface of the oscillating arm 8 where the one-side contact load becomes greater.

(f) Along the inner peripheral surface of the oscillating arm 8, the oil groove 55 is formed along the axial direction of the eccentric shaft 6 and the oil grooves 56 fluidly communicating with both ends of the oil groove 55 are formed along the circumferential direction of eccentric shaft 6. Also, the angled oil hole 50 formed through the control shaft 4 has an opening through the outer peripheral surface of the eccentric shaft 6 so that the angled oil hole 50 fluidly communicates with one of the oil grooves 55 and 56. This is so that the angled oil hole 50 can be shortened and the degree of freedom of forming the diameter and the angle thereof can be increased while facilitating the manufacture of the angled oil hole 50. Also, the oil groove 55 and 56 are inexpensive and easy to manufacture because it is preferred to form the oil grooves 55 and 56 by forming projections for the oil grooves 55 and 56 in the cast when forming the bearing bracket 15 of oscillating arm 8 during casting.

(g) Along the inner peripheral surface of the cam bracket 3 at the sliding contact surface between the inner peripheral surface of cam bracket 3 and the outer peripheral surface of the main shaft 5, the oil groove 54 is formed along the circumferential direction of the main shaft 5, and the oil groove 54 fluidly communicates with the opening of the angled oil hole 50 through the outer peripheral surface of the main shaft 5. Further, the width of the oil groove 54 varies depending on a position along its length in the circumferential direction of main shaft 5. This is so the lubricant supplied from oil hole 48 through oil groove 54 can be adjusted according to the angle position of the main shaft 5 of control shaft 4.

(h) The width of the oil groove 54 along its length in the circumferential direction is large at a part of the rotation position of the main shaft 5 of control shaft 4 where the suction valve 30 is operated at the large operating angle. The width of the oil groove 54 along its length in the circumferential direction is small at a part of the rotation position of the main shaft 5 of control shaft 4 where the suction valve 30 is operated at the small operating angle. This is so that the amount of the lubricant supplied may be decreased in the small operating angle of the suction valve 30 and increased in the large operating angle of the suction valve 30.

(i) The width of the oil groove 54 along its length in the circumferential direction is large at an intersection of a straight line connecting the center axis of the oscillating cam 9, the axis of the main shaft 5, and the axis of the eccentric shaft 6. It becomes smaller when the axis of the eccentric shaft 6 moves away from the line. This is so that the amount of the lubricant supplied can be maximized in the middle operating angle of the suction valve 30 where the axis of the eccentric shaft 6 is aligned with a line connecting of the center axis of the oscillating cam 9 and the axis of the main shaft 5. The angled oil hole 50 can provide sufficient lubrication with respect to the maximum input load in the middle operating angle.

(j) The opening of the angled oil hole 50 is coincident with the opening of the oil hole 48 through oil groove 54 when the axis of the eccentric shaft 6 is positioned on the line connecting the center axis of the oscillating cam 9 and the axis of the main shaft 5. This is so that the lubricant can be directly supplied from oil hole 48 and the amount of the lubricant supplied can be maximized. This ensures sufficient lubrication with regard to the maximum input load in the middle operating angle since the openings of the oil hole 48 and angled oil hole 50 become coincident with each other through oil groove 54 at the time of operating in the middle operating angle of the suction valve 30 when the axis of the eccentric shaft 6 is positioned on the extension of the center axis of the oscillating cam 9 and the axis of the main shaft 5.

(k) The drive valve of the suction valve 30 includes the rocker arm 31, which opens and closes the suction valve 30 in response to pressure applied and released by the oscillating cam, and the hydraulic lash adjuster 33 for supporting the rocker arm 31. The lubricant is supplied to the hydraulic lash adjuster 33 directly from main gallery by being diverted from lubricant path 41 formed through the drive shaft 1. Thus, the lubricant can be first supplied to the hydraulic lash adjuster (HLA) 33 at times when the supply flow rate to the hydraulic lash adjuster 33 tends to be lacking.

While the invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the invention, as defined in the appended claims and their equivalents thereof. Accordingly, it is intended that the invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims.

Claims

1. A variable valve driving apparatus of an internal combustion engine, comprising:

a drive shaft rotatably supported by a cam bracket;

a drive cam disposed about an outer periphery of the drive shaft;

a link arm having a first end connected to the drive cam;

an oscillating cam extending from the drive cam configured to press and release a drive valve of the engine to open and close the drive valve;

a link rod having a first end rotatably connected to the oscillating cam; and

a control shaft rotatably supported by the cam bracket;

wherein the control shaft includes a main shaft rotatably supported by the cam bracket, an eccentric shaft spaced apart from the main shaft, and a plurality of webs connecting the main shaft and the eccentric shaft;

wherein the eccentric shaft is connected to an oscillating arm configured to transfer a drive force of the drive cam;

wherein the oscillating arm has a first portion rotatably connected to a second end of the link arm and a second portion rotatably connected to a second end of the link rod, the first and second portions being spaced apart axially with respect to the eccentric shaft; and

wherein a first flow path for supplying lubricant to a first sliding contact area between the oscillating arm and the eccentric shaft is formed through the control shaft, the first flow path extending from the main shaft to the eccentric shaft through a web located beside the second portion of the oscillating arm.

2. The variable valve driving apparatus of claim 1, wherein the first flow path is in fluid communication with a lubricant path passing through the drive shaft.

3. The variable valve driving apparatus of claim 1, further comprising a second flow path, wherein the second flow path supplies lubricant to a second slide contacting area between the cam bracket and the main shaft, and wherein the second flow path is in fluid communication with the first flow path to supply lubricant to the first sliding contact area between the oscillating arm and the eccentric shaft.

4. The variable valve driving apparatus of claim 1, wherein the first flow path forms a straight line from a surface of the main shaft at the second sliding contact area to a surface of the eccentric shaft at the first sliding contact area.

5. The variable valve driving apparatus of claim 1, wherein the plurality of webs includes a first web coupled to the eccentric shaft beside the first portion of the oscillating arm and having a first width, and a second web coupled to the eccentric shaft beside the second portion of the oscillating arm and having a second width; and wherein the second width is larger than the first width.

6. The variable valve driving apparatus of claim 1, wherein the first flow path includes a first opening opened to the first sliding contact area at a location proximate to the second portion of the oscillating arm, and a third flow path in fluid communication with the first flow path includes a second opening opened to the first sliding contact area at a location proximate the first portion of the oscillating arm.

7. The variable valve driving apparatus of claim 1, wherein the oscillating arm includes a first oil groove formed along the axial direction of the eccentric shaft, and wherein the first flow path is in fluid communication with the first oil groove.

8. The variable valve driving apparatus of claim 7, wherein the oscillating arm includes a second oil groove formed along a circumferential direction of the eccentric shaft, and wherein the second oil groove is in fluid communication with the first oil groove at a first end of the first oil groove.

9. The variable valve driving apparatus of claim 8, wherein the oscillating arm includes a third oil groove formed along a circumferential direction of the eccentric shaft, the third oil groove is in fluid communication with the first oil groove at a second end of the first oil groove, the second oil groove provides lubricant to the first sliding contact area at a location proximate to the first portion of the oscillating arm, and the third oil groove provides lubricant to the first sliding contact area at a location proximate to the second portion of the oscillating arm.

10. The variable valve driving apparatus of claim 1, wherein the main shaft includes a tapered oil groove along a circumferential direction of the main shaft, wherein the tapered oil groove is in fluid communication with a second opening of the first flow path, and wherein a width of the tapered oil groove varies along the circumferential direction of the main shaft.

11. The variable valve driving apparatus of claim 10, wherein the width of the tapered oil groove along the circumferential direction of the main shaft is wide at a location where the second opening of the first flow path faces the tapered oil groove when operating a drive valve in a large operating angle, and wherein a width of the tapered oil groove is narrow at a location where the second opening of the first flow path faces the tapered oil groove when operating the drive valve in a small operating angle.

12. The variable valve driving apparatus of claim 10, wherein a width of the tapered oil groove is maximized at a location along the circumferential direction of the main shaft corresponding to the intersection of a straight line connecting a center axis of the oscillating cam, an axis of the main shaft, and an axis of the eccentric shaft; and wherein the width of the tapered oil groove becomes narrower as the oil groove proceeds away from the intersection.

13. The variable valve driving apparatus of claim 12, wherein the second opening of the first flow path and an opening of the second flow path are aligned at the intersection.

14. The variable valve driving apparatus of claim 1, wherein the drive valve includes a rocker arm configured to open and close a suction valve and a hydraulic lash adjuster for supporting a base of the rocker arm, wherein a third flow path supplies lubricant to the hydraulic lash adjuster from a main gallery which supplies lubricant to the first flow path, wherein the third flow path supplies lubricant from the main gallery to the hydraulic lash adjuster independently from the first flow path.

15. A method of driving a valve with a variable valve driving apparatus of an internal combustion engine, comprising:

rotatably supporting a drive shaft by a cam bracket;

disposing a drive cam about an outer periphery of the drive shaft;

connecting a first end of a link arm to the drive cam;

extending an oscillating cam from the drive cam to press and release a drive valve of the engine to open and close the drive valve;

rotatably connecting a first end of a link rod to the oscillating cam;

rotatably supporting a control shaft by the cam bracket, the control shaft including a main shaft rotatably supported by the cam bracket, an eccentric shaft spaced apart from the main shaft, and a plurality of webs connecting the main shaft and the eccentric shaft;

connecting the eccentric shaft to an oscillating arm to transfer a drive force of the drive cam, the oscillating arm having a first portion rotatably connected to a second end of the link arm and a second portion rotatably connected to a second end of the link rod, the first and second portions being spaced apart axially with respect to the eccentric shaft; and

supplying lubricant through a first flow path formed through the control shaft to a first sliding contact area between the oscillating arm and the eccentric shaft, the first flow path extending from the main shaft to the eccentric shaft through a web located beside the second portion of the oscillating arm.

16. The method of claim 15, further comprising supplying lubricant from a lubricant path passing through the drive shaft to the first flow path.

17. The method of claim 15, further comprising supplying lubricant through a second flow path to a second slide contacting area between the cam bracket and the main shaft, the second flow path being in fluid communication with the first flow path to supply the lubricant to the first sliding contact area between the oscillating arm and the eccentric shaft.

18. The method of claim 15, further comprising forming the first flow path in a straight line from a surface of the main shaft at the second sliding contact area to a surface of the eccentric shaft at the first sliding contact area.

19. The method of claim 15, further comprising coupling a first web to the eccentric shaft beside the first portion of the oscillating arm, the first web and having a first width, and coupling a second web to the eccentric shaft beside the second portion of the oscillating arm, the second web having a second width that is larger than the first width.

20. The method of claim 15, further comprising:

supplying lubricant through a first opening of the first flow path opened to the first sliding contact area at a location proximate to the second portion of the oscillating arm; and

supplying lubricant through a second opening of a third flow path in fluid communication with the first flow path opened to the first sliding contact area at a location proximate the first portion of the oscillating arm.

21. The method of claim 15, further comprising supplying lubricant from the first flow path to a first oil groove formed in the oscillating arm along the axial direction of the eccentric shaft.

22. The method of claim 21, further comprising supplying lubricant from the first oil groove to a second oil groove formed in the oscillating arm along a circumferential direction of the eccentric shaft at a first end of the first oil groove.

23. The method of claim 22, further comprising supplying lubricant from the first oil groove to a third oil groove formed in the oscillating arm along a circumferential direction of the eccentric shaft at a second end of the first oil groove, the second oil groove providing lubricant to the first sliding contact area at a location proximate to the first portion of the oscillating arm, and the third oil groove providing lubricant to the first sliding contact area at a location proximate to the second portion of the oscillating arm.

24. The method of claim 15, further comprising supplying lubricant to a tapered oil groove formed in the main shaft along a circumferential direction of the main shaft, the tapered oil groove being in fluid communication with a second opening of the first flow path, a width of the tapered oil groove varying along the circumferential direction of the main shaft.

25. A variable valve driving apparatus of an internal combustion engine, comprising:

a drive shaft rotatably supported by a cam bracket;

a drive cam disposed about an outer periphery of the drive shaft;

a link arm having a first end connected to the drive cam;

an oscillating cam extending from the drive cam configured to press and release a drive valve of the engine to open and close the drive valve;

a link rod having a first end rotatably connected to the oscillating cam; and

a control shaft rotatably supported by the cam bracket;

the control shaft including a main shaft rotatably supported by the cam bracket, an eccentric shaft spaced apart from the main shaft, and a plurality of webs connecting the main shaft and the eccentric shaft;

the eccentric shaft being connected to an oscillating arm configured to transfer a drive force of the drive cam;

the oscillating arm having a first portion rotatably connected to a second end of the link arm and a second portion rotatably connected to a second end of the link rod, the first and second portions being spaced apart axially with respect to the eccentric shaft; and

means for supplying lubricant to a first sliding contact area between the oscillating arm and the eccentric shaft formed through the control shaft from the main shaft to the eccentric shaft.