JP2008255873A - Variable valve gear for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable valve gear equipped with a variable valve characteristic mechanism which enhances the workability of adjustment work of a clearance in a transmission path of valve driving force reaching an engine valve from a valve cam through the variable valve characteristic mechanism and cam follower. <P>SOLUTION: A variable valve characteristic mechanism C of a variable valve gear 20 is equipped with an adjustment mechanism A for preventing or suppressing the occurrence of a clearance in a transmission path of valve driving force of an intake cam 21a reaching an intake valve 7 from an intake cam 21a through a sub-cam 40 and rocker arm 24. The adjustment mechanism A for adjusting a position of a rocking center line Ls of the sub-cam 40 in a holder 30 includes a support shaft 50 which rockably supports the sub-cam 40 and which is provided to the holder 30 so as to be positionally adjustable, and an adjustment screw 60 provided to the holder 30. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention includes a valve characteristic variable mechanism that includes a holder driven by a control member and a sub cam that is swingably supported by the holder and driven by a valve cam. The present invention relates to a variable valve operating apparatus for an internal combustion engine in which a maximum lift amount of an engine valve is changed by a mechanism.

A variable valve operating device for an internal combustion engine is driven by a valve operating cam that is driven in synchronization with the engine rotational speed, a holder that is driven by a control member, and a swingable support that is supported by the holder. A variable valve characteristic mechanism including a swinging sub cam and a cam follower (for example, a rocker arm) that is driven by the sub cam to open and close the engine valve, and when the holder is driven by the control member, the sub cam and the cam follower It is known that the maximum lift amount of the engine valve is changed by changing the contact position of the engine valve. (For example, see Patent Document 1)
JP 2005-315182 A

In a variable valve operating apparatus having a variable valve characteristic mechanism, a valve operating cam opens and closes an engine valve via a variable valve characteristic mechanism and a cam follower (for example, a rocker arm), so that the valve operating apparatus opens and closes the engine valve only through the cam follower. Compared to a valve operating device that drives (hereinafter referred to as “invariable valve operating device”), many members are present in the transmission path of the valve driving force from the valve operating cam to the engine valve.
For this reason, in order to ensure the control accuracy of the changing maximum lift amount, a clearance (hereinafter referred to as “clearance”) is formed in the transmission path from the valve cam to the engine valve via the valve characteristic variable mechanism and the cam follower. ) Is important.
By the way, when the adjustment mechanism for adjusting the position of the member constituting the transmission path is provided in the rocker arm so that the clearance does not occur in the variable valve operating apparatus, it corresponds to the fact that the rocker arm is arranged in the vicinity of the engine valve. The adjustment mechanism is disposed near the bottom of the valve operating chamber in which the variable valve operating device is accommodated, and the variable valve characteristic mechanism is disposed between the valve operating cam and the rocker arm. However, since the work is performed while avoiding the valve characteristic variable mechanism at the back of the valve operating chamber, the workability is not good. Therefore, if an attempt is made to arrange the adjustment mechanism at a position where adjustment work can be easily performed on the rocker arm, the rocker arm will be enlarged, or the shape and arrangement of components of the variable valve characteristic mechanism will be restricted, and the variable valve characteristic mechanism will be enlarged. There is.
Further, if the adjusting member is provided on a member driven by the valve cam, such as a rocker arm, the valve system equivalent mass driven by the valve cam increases due to the adjusting member. The engine speed at which the engine is generated decreases, the frequency of occurrence of bounce increases, and the frequency of occurrence of noise due to the bounce may increase. In the variable valve operating apparatus, bounce is likely to occur because the valve system equivalent mass is larger than that of the invariable valve operating apparatus by the variable valve characteristic mechanism.

  The present invention has been made in view of such circumstances, and the invention according to claims 1 to 9 is a variable valve operating apparatus having a valve characteristic variable mechanism, wherein the valve characteristic variable mechanism and the cam follower are changed from the valve cam. An object of the present invention is to improve the workability of the clearance adjustment work in the transmission path of the valve driving force through the engine valve. The inventions of claims 2 and 4 further aim to prevent an increase in the valve system equivalent mass due to the adjustment mechanism and to suppress the bounce of the engine valve and the noise caused by the bounce, The inventions of claims 5 and 7 further aim to prevent fluctuations in the position of the swing center line caused by the swing of the sub cam, and claim 8 further facilitates processing of the support member and An object of the present invention is to simplify the structure, and an object of the present invention is to further reduce the size of a variable valve characteristic mechanism including an adjusting mechanism.

According to the first aspect of the present invention, the valve drive cam driven in synchronization with the engine rotational speed, the holder driven by the control member, the swingable support supported by the holder and the drive of the valve drive cam. And a cam follower that is driven by the sub cam to open and close the engine valve, and the holder is driven by the control member, whereby the sub cam and the cam follower are provided. In the variable valve operating apparatus of the internal combustion engine in which the relative lift position of the engine valve is changed and the maximum lift amount of the engine valve is changed, the valve characteristic variable mechanism passes through the valve characteristic variable mechanism and the cam follower from the valve operating cam. An adjustment mechanism that prevents or suppresses the generation of clearance in the transmission path of the valve driving force of the valve drive cam leading to the engine valve; A variable valve device for an internal combustion engine for adjusting the position of the swing center line of the sub-cam of the holder.
According to a second aspect of the present invention, in the variable valve operating apparatus for an internal combustion engine according to the first aspect, the adjustment mechanism has a support member that supports the sub cam so as to be swingable and is provided on the holder so that the position can be adjusted. Is.
According to a third aspect of the present invention, in the variable valve operating apparatus for an internal combustion engine according to the second aspect, the adjustment mechanism adjusts the position of the support member relative to the holder by applying an adjustment force to the support member. It is what has.
According to a fourth aspect of the present invention, in the variable valve operating apparatus for an internal combustion engine according to the third aspect, the adjustment member is provided in the holder.
According to a fifth aspect of the present invention, in the variable valve operating apparatus for an internal combustion engine according to the fourth aspect, the holder has a support wall that supports the support member, and the adjustment member is provided on the support wall. is there.
According to a sixth aspect of the present invention, in the variable valve operating apparatus for an internal combustion engine according to any one of the third to fifth aspects, the adjusting member is configured such that the cam follower is applied to the sub cam with respect to the swing center line. It is arrange | positioned on the opposite side to the cam surface which touches.
A seventh aspect of the present invention is the variable valve operating apparatus for an internal combustion engine according to any one of the third to sixth aspects, wherein the adjustment member is provided with a drive gear, and the support member is provided with the drive gear. A meshing driven gear is provided, and the driving gear and the driven gear constitute a worm gear as a worm and a worm wheel, respectively.
The invention according to claim 8 is the variable valve operating apparatus for an internal combustion engine according to any one of claims 2 to 7, wherein the support member is supported by the holder so as to be rotatable, and It is an eccentric shaft having an eccentric portion that swingably supports the sub cam so that the sub cam has a swing center line parallel to the rotation center line of the supported portion.
According to a ninth aspect of the present invention, in the variable valve operating apparatus for an internal combustion engine according to the eighth aspect, the supported portion is arranged inside the holder, and the adjustment member is adjusted to the supported portion inside the holder. It adds power.

According to the first aspect of the present invention, the adjusting mechanism prevents or suppresses the generation of clearance in the transmission path of the valve driving force of the valve operating cam from the valve operating cam to the engine valve via the valve characteristic variable mechanism and the cam follower. However, since the position of the swing center line of the sub cam is adjusted, the sub cam driven by the valve cam is compared with the cam follower that is driven by the sub cam and opens and closes the engine valve. Because the sub-cam is supported close to the holder and the holder is not easily hindered from adjusting the swing center line, the adjustment mechanism can be easily adjusted. Will improve.
According to the second aspect of the present invention, since the support member constituting the adjustment mechanism supports the sub cam in a swingable manner and is provided on the holder, the valve system equivalent mass may be increased by the support member of the adjustment mechanism. Therefore, the engine rotational speed at which the engine valve bounces can be shifted to a higher speed side, so that the occurrence of bounces and the noise caused by the bounces are suppressed. Further, since the support member that supports the sub cam constitutes the adjustment mechanism, the number of parts is reduced.
According to the third aspect of the present invention, since the position of the support member that supports the sub cam so as to be able to swing is adjusted by the adjustment member, the adjustment work of the swing center line is facilitated.
According to the fourth aspect of the present invention, since the adjusting member constituting the adjusting mechanism is provided in the holder, the valve operating system equivalent mass is not increased by the adjusting member. Since the speed can be shifted to a higher speed side, occurrence of bounce and generation of noise due to the bounce are suppressed.
According to the fifth aspect of the present invention, since the adjustment member is provided on the support wall which is a highly rigid portion in the holder in order to support the sub cam via the support member, the adjustment member can be provided firmly. Therefore, the torque generated by the swing of the sub cam is prevented from changing the position of the adjustment member through the support member, the change of the position of the adjusted swing center line is prevented, and the control accuracy of the maximum lift amount is improved. Contributes to improvement.
According to the sixth aspect of the present invention, since the adjustment member and the cam follower are arranged with the swing center line interposed therebetween, the adjustment work by the adjustment member is not hindered by the cam follower, and the workability is improved.
According to the seventh aspect, since the drive gear as the worm and the driven gear as the worm wheel constitute the worm gear, it is possible to prevent the torque generated by the swing of the sub cam from rotating the adjustment member through the support member. Therefore, the adjusted position of the swing center line is reliably maintained without fluctuation, contributing to improvement in control accuracy of the maximum lift amount.
According to the eighth aspect, since the support member is an eccentric shaft, the processing of the support member is easy, the structure is simplified, and the cost is reduced.
According to the ninth aspect of the present invention, an adjustment force is applied to the supported portion by utilizing the fact that the supported portion is a portion having high rigidity in the eccentric shaft in order to support the sub cam on the holder. Therefore, the eccentric shaft can be reduced in size. In addition, since the supported portion is disposed inside the holder and the adjusting member applies adjusting force to the supported portion inside the holder, the valve characteristic variable mechanism including the adjusting mechanism can be reduced in size.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
Referring to FIG. 1, the variable valve operating apparatus to which the present invention is applied is provided in an overhead camshaft type valve operating apparatus, and the valve operating apparatus is provided in an internal combustion engine E mounted on a vehicle. The multi-cylinder four-stroke internal combustion engine E includes a cylinder block 1 in which a plurality of cylinders 1 a are integrally formed, a cylinder head 2 coupled to the upper end portion of the cylinder block 1, and a head cover 3 coupled to the upper end portion of the cylinder head 2. The engine body is composed of

  In this embodiment, the vertical direction coincides with the direction of the cylinder axis Ly of the cylinder 1a, and the center line direction is a direction parallel to a swing center line Ls of a sub cam 40 described later (that is, a swing center line direction). Alternatively, it means a direction parallel to the rotation center line Lc of the cam 21a, which will be described later, the side view means viewing from the center line direction, and the plan view means viewing from the up and down direction.

A piston 4 connected to the crankshaft via a connecting rod is fitted to each cylinder 1a so as to be able to reciprocate. In the cylinder head 2, for each cylinder 1 a, an intake port 6 and a pair having a combustion chamber 5 facing the piston 4 in the cylinder axial direction (or vertical direction) and a pair of intake ports opening to the combustion chamber 5, respectively. An exhaust port having an exhaust port, an intake valve 7 (see also FIGS. 3 and 4) as a pair of engine valves for opening and closing the intake port, and an exhaust as a pair of engine valves for opening and closing the exhaust port A valve and a spark plug 9 disposed in the housing cylinder 8 and facing the combustion chamber 5 are provided.
The intake valve 7 and the exhaust valve for each combustion chamber 5 are driven to open and close by the valve operating device housed in the valve operating chamber 10 formed by the cylinder head 2 and the head cover 3.

  Then, the intake air passing through the intake passage formed by the intake device (not shown) of the internal combustion engine E is mixed with the fuel supplied from the air-fuel mixture forming device constituted by the fuel injection valve to form an air-fuel mixture. In the intake stroke, the intake valve 7 is sucked into the combustion chamber 5 through the intake port 6 when the valve is opened. The air-fuel mixture is compressed during the compression stroke in which the piston 4 rises, is ignited and burned by the spark plug 9 at the end of the compression stroke, and the piston 4 driven by the pressure of the combustion gas in the expansion stroke in which the piston 4 descends The crankshaft is driven to rotate. The combustion gas is discharged from the combustion chamber 5 as exhaust gas when the exhaust valve is opened in the exhaust stroke in which the piston 4 is lifted, passes through the exhaust port, and then passes through an exhaust passage formed by an exhaust device (not shown). And discharged outside the internal combustion engine E.

The valve operating device provided in the cylinder head 2 includes an intake side valve operating device that includes an intake cam shaft 21 provided with an intake cam 21a as a valve operating cam and opens and closes the intake valve 7, and an exhaust as a valve operating cam. An exhaust side valve device (not shown) that includes an exhaust cam shaft provided with a cam and drives the exhaust valve to open and close is configured. And in this embodiment, the said intake side valve operating apparatus is comprised from the variable valve operating apparatus 20 which can change the valve operating characteristic containing the maximum lift amount of the intake valve 7 according to the engine operating state of the internal combustion engine E. FIG. .
The exhaust side valve operating device is configured by a valve operating device whose valve operating characteristics are constant with respect to the engine operating state, but may be configured by a variable valve operating device having basically the same structure as the variable valve operating device 20. Good.

The intake camshaft 21 and the exhaust camshaft that are disposed across a central plane 11 that includes the cylinder axis Ly and that is parallel to the rotation centerline Lc of the intake camshaft 21 rotate in parallel to the rotation centerline of the crankshaft. Provided integrally with the cylinder head 2 so as to have a center line (respectively the rotation center line of the intake cam 21a and the exhaust cam, and the intake cam 21a is the rotation center line Lc as shown in FIG. 1). The cylinder head 2 is rotatably supported by a cam shaft holder 12 (see FIG. 2).
The intake camshaft 21 and the exhaust camshaft are rotationally driven at a rotational speed 1/2 that of the crankshaft by the power of the crankshaft transmitted through a valve train transmission mechanism having a timing chain.

Hereinafter, the variable valve gear 20 will be mainly described.
Referring to FIGS. 1 to 6, the variable valve gear 20 takes in the valve driving force of the cam 21 a in addition to the cam shaft 21 having the cam 21 a that is driven to rotate in synchronization with the engine rotation speed of the internal combustion engine E. A variable valve characteristic mechanism C that can transmit to the valve 7 and change the maximum lift amount of the intake valve 7; a control member 22 that drives the holder 30 of the variable valve characteristic mechanism C to change the maximum lift amount; A cam follower that opens and closes the intake valve 7 by being driven by a sub-cam 40 of a valve characteristic variable mechanism C and a biasing member 23 for a holder that is provided in the head 2 and generates a biasing force that presses the holder 30 against the control cam 22c of the control member 22. As a rocker arm 24. The control member 22 drives the holder 30 according to the engine operating state of the internal combustion engine E, and the relative position or the contact position between the sub cam 40 and the rocker arm 24 according to the position of the holder 30 that is displaced with respect to the cylinder head 2. Is changed, and the maximum lift amount and the opening / closing timing, which are the valve operating characteristics of the intake valve 7, are changed.

The variable valve characteristic mechanism C is displaceable to the cylinder head 2 around a holder center line Lh parallel to the rotation center line Lc. Here, the valve characteristic variable mechanism C is swingably supported and driven by the control force of the control member 22 to swing. Holder 30, a sub cam 40 that is supported by the holder 30 so as to be swingable about a swing center line Ls, and is driven by the cam 21 a to swing, and the holder 30 is provided to press the sub cam 40 against the cam 21 a. The cam biasing member 48 and the sub cam in the holder 30 for preventing or suppressing the occurrence of clearance in the transmission path of the valve driving force of the cam 21a from the cam 21a through the sub cam 40 and the rocker arm 24 to the intake valve 7 And an adjustment mechanism A for adjusting the position of the 40 swing center lines Ls.
Here, the holder center line Lh and the swing center line Ls are parallel to the rotation center line Lc of the cam 21a.

  The control member 22 is provided on an electric motor 22a as an actuator attached to the cylinder head 2 and a drive shaft 22b that is rotationally driven by the electric motor 22a via a speed reduction mechanism, and has a driving force for swinging or stopping the holder 30. And a control cam 22c as a drive unit that acts on the holder 30. The electric motor 22a is controlled by an electronic control unit to which a detection signal from an operation state detection means for detecting the engine operation state of the internal combustion engine E such as the engine rotation speed and the engine load is input, so that the holder 30 is in the engine operation state. The holder 30 is driven so as to occupy the swing position set according to the above.

  A holder 30 that is swingably supported by a camshaft holder 12 (see FIG. 2) adjacent in the center line direction and arranged for each cylinder 1a is disposed between the cam 21a and the intake valve 7 in the vertical direction, and It arrange | positions under the cam 21a. The holder 30 has a pair of support walls 31 and 32 that are separated in the direction of the center line, and each support wall 31 and 32 in a direction (hereinafter referred to as “orthogonal direction”) orthogonal to the center plane 11 (see FIG. 1). A pair of connecting walls 33, 34 for connecting the both ends of each of them, a pair of columnar holder fulcrum portions 35 provided on the support walls 31, 32 and pivotally supported by the camshaft holder 12, and control It has a roller 36 as an action portion that abuts on the cam 22c and acts on the cam 22c. The pair of support walls 31 and 32 and the pair of connecting walls 33 and 34 form an accommodation space 39 in which the sub cam 40, the rocker arm 24, and the roller 36 are accommodated.

  The sub cam 40 disposed above the rocker arm 24 abuts on the intake cam 21a and a cylindrical fulcrum portion 41 that is swingably supported by the eccentric shaft portion 53 of the support shaft 50 that defines the swing center line Ls. It has a roller 42 as a cam contact portion, a pair of drive cam portions 44 that respectively contact the pair of rocker arms 24, and an action portion 46 on which the urging force of the urging member 23 acts. The roller 42 is rotatably supported by a pair of holding portions 43 projecting radially outward from the fulcrum portion 41. Since the action portion 46 connects the pair of holding portions 43, the rigidity of the pair of holding portions 43 that receive the valve driving force from the cam 21a is increased.

  The urging member 48 held by the connecting wall 33 includes a pressing member 48a that abuts on the acting portion 46 so as to apply an urging force, and a spring 48b disposed between the pressing member 48a and the connecting wall 33. The The pressing member 48a is slidably fitted into a cylindrical guide tube 49 that is press-fitted into the connecting wall 33 and fixed. The guide tube 49 disposed inside the spring 48b functions as a spring guide that prevents the spring 48b from falling down.

  Each drive cam portion 44 disposed inside the pair of support walls 31 and 32 in the center line direction has a cam surface 45 with which the roller 24c of the rocker arm 24 abuts, and the valve of the cam 21a input from the roller 42 The driving force is output to the intake valve 7 via the rocker arm 24. The cam surface 45 swings the rocker arm 24 regardless of the swing of the sub cam 40, and the drive surface 45a that swings the rocker arm 24 when the sub cam 40 swings to open the intake valve 7. And a non-driving surface 45b that keeps the intake valve 7 closed. The non-driving surface 45b is composed of a cylindrical surface centered on the swing center line Ls.

  Each rocker arm 24 includes a fulcrum portion 24a that is pivotably supported by a pivot 25 serving as a swing support portion that also serves as a hydraulic lash adjuster, and a roller as a driven contact portion that contacts the cam surface 45 of the drive cam portion 44. 24c and a valve pressing portion 24b that presses the valve stem of the intake valve 7. The pair of pivots 25 are attached to support portions 37 that are provided in the connecting wall 34 so as to be separated from each other in the center line direction. Therefore, the rocker arm 24 is swingably supported by the holder 30 via the pivot 25.

  The urging member 23 is accommodated in a pressing member 23a that abuts against an action portion 38 provided between the support portions 37 in the connecting wall 34, and in the accommodating portion 14a that is integrally formed with the accommodating cylinder 8, and the accommodating portion 14a. It is comprised by the spring 23b arrange | positioned between the press members 23a and urging | biasing the press member 23a.

  Referring mainly to FIGS. 7 and 8, the adjustment mechanism A provided in the holder 30 supports the sub cam 40 so as to be swingable and supports a support shaft 50 as a support member provided so that the position of the holder 30 can be adjusted. As an adjusting member that adjusts the positions of the support shaft 50 and the swing center line Ls with respect to the holder 30 by applying an adjusting force that moves the support shaft 50 in contact with a driven gear 54 as a driven-side contact portion of the shaft 50. The adjusting screw 60 has a washer 68 and a lock nut 69. The washer 68 and the lock nut 69 constitute a fixing member that prevents a change in the position of the adjusting screw 60 due to the torque that the sub cam 40 applies to the support shaft 50.

  A support shaft 50 that can be moved relative to the holder 30 and is pivotally supported in this embodiment is inserted into the support holes 31a and 32a provided in the support walls 31 and 32. , 32 slidably and rotatably supported by a pair of columnar supported parts 51, 52 and the supported parts 51, 52, and the sub cam 40 is connected to the supported part 51. , 52 and a cylindrical eccentric shaft portion 53 as an eccentric portion that supports the sub cam 40 so as to be swingable so as to have a swing center line Ls that is parallel to the rotation center line La and decentered by a predetermined eccentricity e. An eccentric shaft integrated so as to rotate integrally.

In this embodiment, the support shaft 50 is divided in which a first member 50a in which the supported portion 51 and the eccentric shaft portion 53 are integrally formed and a second member 50b forming the supported portion 52 are integrated by a screw portion. It is a member having a structure. Further, the movement of the support shaft 50 in the center line direction is restricted by a retaining ring 58 that is mounted across the support wall 32 and the supported portion 52.
The supported portion 52 and the eccentric shaft portion 53 are provided with an oil passage 59c through which oil is guided from the oil passage 59a provided in the camshaft holder 12 through the holder fulcrum portion 35 and the oil passage 59b of the support wall 32. The oil in the passage 59c is supplied to the sliding portion between the eccentric shaft portion 53 and the fulcrum portion 41 of the sub cam 40.

  The driven gear 54 provided in the supported portion 51 is formed over the entire circumference in a part of the outer peripheral surface of the supported portion 51 in the center line direction, but the adjustment range of the position of the swinging center line Ls. Corresponding to the above, it may be formed in a part in the circumferential direction.

The adjustment screw 60 attached to the support wall 31 is inserted into an insertion hole 31 b provided in the support wall 31 and is provided so as to be movable relative to the holder 30. The adjustment screw 60 includes a screw portion 61 that engages with the screw portion 31c in the insertion hole 31b, a drive gear 62 that meshes with the driven gear 54, and an operation portion that engages with a tool that operates and rotates the adjustment screw 60. 63.
The drive gear 62 is a drive side contact portion that contacts the driven gear 54 and applies adjustment force to the driven gear 54. The drive gear 62 and the driven gear 54 constitute a worm gear as a worm and a worm wheel, respectively.
The entire driven gear 54 and the entire drive gear 62 that is a part of the adjustment screw 60 are disposed inside the support wall 31.

Referring to FIG. 1, the supported portion 51, the adjustment screw 60, the washer 68, and the lock nut 69 are disposed above the head cover 3 and the mating surface 2a of the cylinder head 2, and in the vertical direction, the swing center line Ls or The support shaft 50 is disposed on the opposite side of the cam surface 45 and the rocker arm 24 of the sub cam 40 and above the swing center line Ls or the support shaft 50. Therefore, the adjustment screw 60 is disposed above the rocker arm 24, the drive cam portion 44, and the urging member 48, close to the cam 21a in the vertical direction, and is disposed at a position overlapping the roller 42 in a side view. The adjusting screw 60 and its operating portion 63 are arranged on the opposite side of the center plane 11 with respect to the swing center line Ls in the orthogonal direction.
Therefore, when the adjustment screw is provided in the rocker arm 24 which is disposed in the bottom portion of the valve operating chamber 10 near the intake valve 7 and which is disposed in the accommodation space 39 formed by the holder 30 and below the sub cam 40. In comparison, since the adjustment screw 60 is near the uppermost portion of the holder 30, the adjustment operation of the position of the swing center line Ls is facilitated.

Referring to FIGS. 7 and 8, in order to adjust the position of the swing center line Ls, the adjustment screw 60 is rotated by a tool and is in the direction on the axis Ln of the adjustment screw 60 as one straight line. Advancing and retreating moves into or out of the support wall 31 along the adjustment direction Ds. As a result, the adjusting screw 60 applies adjusting force to the supported portion 51 through the driven gear 54 with which the drive gear 62 meshes, and the two supported portions 51 and 52 integral with the eccentric shaft portion 53, and thus the support shaft 50, Around the rotation center line La, it is rotated in one direction in the rotation direction or the other in the opposite direction. Here, the support shaft 50 is rotated by a combined motion of the advance / retreat movement of the adjustment screw 60 and the rotation of the drive gear 62 in the adjustment direction Ds.
Then, by the rotation of the support shaft 50, the swing center line Ls moves on a circle with the eccentric amount e as a radius around the rotation center line La, and the swing center line Ls with respect to the holder 30 and the sub cam. 40 positions are adjusted. Thereafter, the adjustment screw 60 is fixed by the lock nut 69 screwed to the washer 68 and the screw portion 61, and the position adjustment of the swing center line Ls by the adjustment mechanism A is completed.

Next, the operation of the variable valve gear 20 will be described.
Referring to FIG. 9, when the internal combustion engine E is operated in a high load region, for example, the holder 30 occupies an upper limit position where the maximum lift amount of the intake valve 7 becomes the maximum value. At this time, the control cam 22c comes into contact with the roller 36 at a position where the height of the cam crest is maximum in the rotation range. The sub cam 40 driven by the cam 21a drives the rocker arm 24 by the drive surface 45a of the drive cam portion 44, and the intake valve 7 opens at the maximum value. FIG. 9 shows the cam 21a, the sub cam 40, the rocker arm 24, and the intake valve 7 at this time by a two-dot chain line, the roller 42 contacts the base circle of the cam 21a, and the roller 24c contacts the non-driving surface 45b. The intake cam 21a, the sub cam 40, and the rocker arm 24 when they are in contact and the intake valve 7 is in a closed state are indicated by solid lines.

  When the internal combustion engine E shifts to a smaller load region, the holder 30 has the roller 36 at the height of the cam crest of the control cam 22c as the control cam 22c is driven by the electric motor 22a and rotates counterclockwise. By contacting the lower part, the holder rotates about the holder center line Lh in the clockwise direction. By this rotation of the holder 30, the swing center line Ls moves in the clockwise direction, and the roller 24c comes into contact with the drive cam portion 44 at a position moved from the drive surface 45a side to the non-drive surface 45b side. For this reason, when the rocker arm 24 is driven by the drive surface 45a, the maximum lift amount of the intake valve 7 is continuously reduced.

  As shown in FIG. 5, when the roller 36 comes into contact with the position where the cam crest height of the control cam 22c is minimized, the holder 30 is the lower limit position where the maximum lift amount of the intake valve 7 becomes the minimum value. Occupy. At this time, although the sub cam 40 is driven by the cam 21a and rotates in the clockwise direction, the roller 24c contacts only the non-drive surface 45b of the drive cam portion 44, so that the rocker arm 24 does not swing and the intake valve 7 maintains the valve closed state. In FIG. 5, the intake cam 21a and the sub cam 40 at this time are indicated by a two-dot chain line, and the intake cam 21a when the roller 42 is in contact with the base circle of the intake cam 21a and the intake valve 7 is in the closed state. The sub cam 40 and the rocker arm 24 are indicated by solid lines. When the minimum value is set to zero, for example, the intake valve 7 is in a resting state.

Next, operations and effects of the embodiment configured as described above will be described.
The variable valve characteristic mechanism C of the variable valve apparatus 20 prevents or suppresses the generation of clearance in the transmission path of the valve driving force of the cam 21a from the cam 21a to the intake valve 7 via the sub cam 40 and the rocker arm 24. The adjustment mechanism A adjusts the position of the swing center line Ls of the sub cam 40 in the holder 30 so that the cam 21a is compared with the case where the adjustment mechanism is provided in the rocker arm 24 that is driven by the sub cam 40 to open and close the engine valve. Because the sub cam 40 driven by the cam 21a is arranged near the cam 21a and the sub cam 40 is supported by the holder 30, the arrangement of the holder 30 is unlikely to hinder the adjustment operation of the swing center line Ls. Adjustment work by the adjustment mechanism A is facilitated, and the workability is improved.

  The adjustment mechanism A includes a support shaft 50 that supports the sub cam 40 so that the sub cam 40 can swing and a position that can be adjusted on the holder 30, and an adjustment screw 60 that is provided on the holder 30. Therefore, the engine rotation speed at which the bounce of the intake valve 7 occurs can be shifted to a higher speed side, so that the bounce is generated and the noise caused by the bounce is generated. Is suppressed. Further, since the support shaft 50 that supports the sub cam 40 constitutes the adjusting mechanism A, the number of parts is reduced.

  The adjustment mechanism A has an adjustment screw 60 that adjusts the position of the support shaft 50 with respect to the holder 30 by applying an adjustment force to the support shaft 50, so that the adjustment shaft 60 supports the sub cam 40 in a swingable manner. Since the position of 50 may be adjusted, the adjustment work of the swing center line Ls is facilitated.

  The holder 30 includes support walls 31 and 32 that support the support shaft 50, and the adjustment screw 60 is provided on the support wall 31, so that the adjustment screw 60 is a holder for supporting the sub cam 40 via the support shaft 50. Since the adjustment screw 60 can be firmly provided because it is provided on the support wall 31 which is a highly rigid portion at 30, the torque generated by the swing of the sub cam 40 fluctuates the position of the adjustment screw 60 through the support shaft 50. This prevents the fluctuation of the position of the adjusted swing center line Ls and contributes to the improvement of the control accuracy of the maximum lift amount.

  The adjusting screw 60 is disposed on the opposite side of the swing cam center line Ls from the cam surface 45 with which the rocker arm 24 abuts, so that the adjusting screw 60 and the rocker arm 24 sandwich the swing center line Ls. Therefore, the adjustment work by the adjustment screw 60 is not hindered by the rocker arm 24 and is not hindered by the drive cam portion 44 of the sub cam 40, and the workability is improved.

  The adjustment screw 60 is provided with a drive gear 62, and the support shaft 50 is provided with a driven gear 54 that meshes with the drive gear 62. The drive gear 62 and the driven gear 54 constitute a worm gear as a worm and a worm wheel, respectively. Thus, torque generated by the swing of the sub cam 40 is prevented from rotating the adjusting screw 60 through the support shaft 50, so that the position of the adjusted swing center line Ls is reliably maintained without fluctuation. This contributes to the improvement of the control accuracy of the maximum lift amount.

  The support shaft 50 has supported portions 51 and 52 that are rotatably supported by the holder 30, and the sub cam 40 has a swing center line Ls that is parallel to the rotation center line La of the supported portions 51 and 52. Since the support shaft 50 is an eccentric shaft by having an eccentric shaft that supports the sub cam 40 in a swingable manner, the processing of the support shaft 50 is easy, the structure is simplified, and the cost is reduced. Reduced.

  The supported portion 51 is disposed inside the support wall 31 of the holder 30, and the adjusting screw 60 applies an adjustment force to the supported portion 51 inside the support wall 31 of the holder 30, so that the supported portion 51 is brought into contact with the sub cam 40. Since the adjusting force is applied to the supported portion 51 by utilizing the fact that the support shaft 50 is a portion having high rigidity to support the holder 30 with the holder 30, the support shaft 50 can be reduced in size. In addition, since the supported portion 51 is disposed inside the holder 30 and the adjusting screw 60 applies adjusting force to the supported portion 51 inside the holder 30, the variable valve characteristic mechanism C including the adjusting mechanism A can be reduced in size. .

Hereinafter, an embodiment in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
The support shaft 50 may be a member formed as a whole so long as the sub-cam 40 can be assembled.
The support member may not be provided with the eccentric shaft portion 53 that swings and supports the sub cam 40, but may be swingably supported by a support member, for example, a supported portion, at a position where the sub cam 40 itself is eccentric.
The cam follower driven by the sub cam 40 may be a cylindrical valve lifter that is slidably supported by the cylinder head.
The support member may move relative to the holder 30 in a form other than rotation, such as linear movement.
The drive gear 62 and the driven gear 54 may be outside the support wall 31.
The internal combustion engine may be a single cylinder internal combustion engine. Moreover, although the internal combustion engine is used for a vehicle in the embodiment, it may be used for a ship propulsion apparatus such as an outboard motor having a crankshaft oriented in the vertical direction.

It is principal part sectional drawing in the plane orthogonal to the rotation centerline of a crankshaft of an internal combustion engine provided with the variable valve apparatus to which this invention was applied. It is a figure of the principal part by the 2 arrow view of FIG. It is a perspective view of the variable valve apparatus of FIG. It is a perspective view from the direction different from FIG. 3 of the variable valve apparatus of FIG. It is sectional drawing of the variable valve apparatus of FIG. 1 corresponded to the 5-5 line arrow of FIG. It is sectional drawing of the variable valve apparatus of FIG. 1 corresponded to the 6-6 line arrow of FIG. FIG. 7 is an essential part cross-sectional view taken along line 7-7 in FIG. 1. FIG. 8 is an enlarged cross-sectional view of a main part taken along line 8-8 in FIG. 7. It is a figure corresponding to FIG. 5 when the holder of a variable valve apparatus occupies the position different from FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Cylinder head, 7 ... Intake valve, 20 ... Variable valve apparatus, 21a ... Cam, 22 ... Control member, 24 ... Rocker arm, 30 ... Holder, 31, 32 ... Support wall, 33, 34 ... Connection wall, 40 ... Sub cam, 45 ... cam surface, 50 ... support shaft, 51,52 ... supported portion, 53 ... eccentric shaft portion, 54 ... driven gear, 60 ... adjusting screw, 62 ... drive gear,
E: internal combustion engine, C: variable valve characteristic mechanism, Ls: swing center line, La: rotation center line, A: adjustment mechanism, Ds: adjustment direction.

Claims (9)

A valve cam that is driven in synchronism with the engine speed;
A variable valve characteristic mechanism comprising a holder driven by a control member, and a sub cam that is swingably supported by the holder and driven by the valve cam;
A cam follower driven by the sub cam to open and close the engine valve;
In the variable valve operating apparatus for an internal combustion engine in which the relative position between the sub cam and the cam follower is changed by changing the maximum lift amount of the engine valve by driving the holder from the control member.
The valve characteristic variable mechanism prevents or suppresses generation of a clearance in a transmission path of the valve driving force of the valve cam from the valve cam to the engine valve via the valve characteristic variable mechanism and the cam follower. A variable valve operating apparatus for an internal combustion engine, comprising an adjustment mechanism, wherein the adjustment mechanism adjusts a position of a swing center line of the sub cam in the holder.   The variable valve operating apparatus for an internal combustion engine according to claim 1, wherein the adjustment mechanism includes a support member that supports the sub cam in a swingable manner and is provided on the holder so that the position of the sub cam can be adjusted.   The variable valve operating apparatus for an internal combustion engine according to claim 2, wherein the adjustment mechanism includes an adjustment member that adjusts a position of the support member with respect to the holder by applying an adjustment force to the support member.   The variable valve operating apparatus for an internal combustion engine according to claim 3, wherein the adjustment member is provided in the holder.   5. The variable valve operating apparatus for an internal combustion engine according to claim 4, wherein the holder has a support wall that supports the support member, and the adjustment member is provided on the support wall.   6. The internal combustion engine according to claim 3, wherein the adjustment member is disposed on a side opposite to a cam surface with which the cam follower comes into contact with the sub cam with respect to the swing center line. Variable valve gear for engine.   The adjustment member is provided with a drive gear, the support member is provided with a driven gear that meshes with the drive gear, and the drive gear and the driven gear constitute a worm gear as a worm and a worm wheel, respectively. The variable valve operating apparatus for an internal combustion engine according to claim 3, wherein the variable valve operating apparatus is an internal combustion engine.   The support member is capable of swinging the sub cam such that the supported portion is supported rotatably on the holder, and the sub cam has a swing center line parallel to the rotation center line of the supported portion. The variable valve operating apparatus for an internal combustion engine according to any one of claims 2 to 7, wherein the variable valve operating apparatus is an eccentric shaft having an eccentric portion to be supported.   9. The variable valve operating apparatus for an internal combustion engine according to claim 8, wherein the supported portion is disposed inside the holder, and the adjusting member applies an adjusting force to the supported portion inside the holder.

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