JP3880197B2 - Valve operating device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a valve operating apparatus for an internal combustion engine, and more particularly to a valve operating apparatus for an internal combustion engine that opens and closes an engine valve by a swing cam that swings within a predetermined angle range from a drive cam via a transmission mechanism such as a link arm or a rocker arm. .
[0002]
[Prior art]
The intake / exhaust valve opening / closing timing and valve lift amount are set to improve fuel efficiency at low engine speed and low load, to ensure stable operation, and to ensure sufficient output by improving intake charging efficiency at high speed and high load. Various types of valve gears that are variably controlled according to engine operating conditions have been conventionally provided. For example, those described in the specification and drawings of Japanese Patent Application No. 9-212831 filed earlier by the present applicant. is there.
[0003]
The outline will be described with reference to FIG. 13. The cylinder head 51 is rotatably supported by a pair of intake valves 52 slidably provided via a valve guide (not shown) and a bearing 53 above the cylinder head 51. A drive shaft 54 to which the rotational force is transmitted from the crankshaft of the engine, two drive cams 55 fixed to the center of the drive shaft 54 by a predetermined amount, and the drive shaft 54 A swing cam that is swingably supported and that slides on the upper surface of a valve lifter 56 provided at the upper end of each intake valve 52 to open and close each intake valve 52 with a relative pressure to the spring force of the valve spring 57. 58, a transmission mechanism 59 that is interposed between the swing cam 58 and the drive cam 55 and transmits the eccentric rotation of the drive cam 55 to the swing cam 58, and the transmission mechanism 59. Valve lifter of swing cam 58 By changing the rocking position relative to the surface and a variable mechanism 60 to the valve lift characteristic variable.
[0004]
The transmission mechanism 59 includes a link arm 61 in which a fitting hole 61c of a substantially annular base end portion 61a is rotatably fitted to the outer peripheral surface of the drive cam 55, and a control shaft 67 on the upper end portion of the bearing 53. And a rocker arm 62 whose one end 62 a is connected to the protruding end 61 b of the link arm 61 by a connecting pin 63 so as to be relatively rotatable, and both ends 64 a and 64 b are connected to the other end 62 b of the rocker arm 62. It is comprised from the link rod 64 connected with the cam nose part 58a of the rocking cam 58 via the pins 65 and 66 so that relative rotation was possible.
[0005]
The variable mechanism 60 is fixed to the control shaft 67 whose rotational position is controlled by an actuator (not shown) and the center P1 on the outer periphery of the control shaft 67 in a state where it is decentered by a predetermined amount α from the axis P2 of the control shaft 67. The rocker arm 62 includes an eccentric control cam 68 that is slidably provided in a cam hole 62d that is formed substantially in the center of the rocker arm 62.
[0006]
When the drive shaft 54 and the drive cam 55 start to rotate with the start of the engine, the link arm 61 moves up and down due to the eccentric rotation of the drive cam 55, and the rocker arm 62 swings with the control cam 68 as a fulcrum. Power is transmitted to the link rod 64 and the swing cam 58 is swung in the vertical direction in the figure so that the valve lifter 56 is pressed or released from the cam surface 58b to open and close the intake valve 52. It has become.
[0007]
Further, as the engine operating state changes, the control shaft 67 rotates by a predetermined amount to eccentrically rotate the control cam 68, thereby changing the rocking fulcrum P1 of the rocker arm 62. As a result, the swing cam 58 changes the swing fulcrum position on the upper surface of the valve lifter 56 to the left or right in the figure via the link rod 64, whereby the valve lift characteristic of the intake valve 52 can be varied in size. It is supposed to be.
[0008]
[Problems to be solved by the invention]
By the way, in the structure in which the swing cam 58 is swung by the link mechanism (transmission mechanism 64) such as the link arm 61 and the rocker arm 62 from the drive cam 55 like the valve gear according to the previous application, Due to the relatively large diameter of the drive cam 55 and the large load received by the drive cam 55 from the link arm 61 when the valve is lifted up (upward), the starting torque at the start of the engine increases and the engine starts. There is a problem that the sex gets worse.
[0009]
That is, according to a close examination by the inventors of the present applicant, when considering the load F received by the drive cam 55 from the link arm 61, for example, at the time of valve lift up and down when the rocking fulcrum of the rocker arm 64 does not change. In the same lift, the spring reaction force from the valve spring 57 against the swing cam 58 is the same. However, in the load F, the lift up (up) section and the down (down) section depend on the rocker ratio. The magnitude of the load F is different, and the load F is large in the lift-up section.
[0010]
Next, when the engine is started, there is almost no relative rotation between the drive cam 55 and the link arm 61 until the engine rotation rises stably. A frictional resistance having a large static friction coefficient μ acts between the surfaces. In addition, in the ascending section of the valve lift, the above-described large static frictional resistance acts, and in addition to the increase in the load F and the large drive cam diameter, the start for rotating the drive shaft 54 is started. Torque will increase. Therefore, the engine startability may be deteriorated as a whole.
[0011]
[Means for Solving the Problems]
  The present invention was devised in view of the actual situation of the valve gear according to the prior application, and the invention according to claim 1 includes a drive shaft that is rotationally driven by a crankshaft of an engine, and an outer periphery of the drive shaft. A drive cam that is fixed and whose center is deviated from the axis of the drive shaft by a predetermined amount, a link arm that is rotatably linked to the outer periphery of the drive cam, and a pivot that is swingably supported by the support shaft. A rocker arm that is rotatably linked to the other end of the link arm via a connecting pin, and a follower portion that is pivotally linked to the other end of the rocker arm and has a cam surface at the upper end of the engine valve. A swing cam that opens and closes the engine valve while sliding on theA valve spring that urges the link arm toward the drive cam at one end of the rocker arm via the swing cam while urging the engine valve in a closing direction;In the valve operating apparatus for an internal combustion engine, a perpendicular extending from a rocking fulcrum of the rocker arm with respect to a straight line connecting an axis of the connecting pin that connects the link arm and the rocker arm and a center point of the drive cam. The length ofWhen the lift of the engine valve by the swing cam is an intermediate lift position of each of the descending section and the ascending section,The perpendicular length in the up section is set to be longer than the perpendicular length in the down section of the lift.
[0012]
According to this invention, the perpendicular length L toward the lift up section₁The vertical length L of the lift down section₂Is set longer than the₁= M / L₁Down load is F₂= M / L₂(M: moment when the valve spring turns the rocker arm), F₁<F₂Therefore, the starting torque of the drive shaft in the ascending section can be reduced.
[0013]
According to the second aspect of the present invention, the swing cam is swingably supported on the outer periphery of the drive shaft, and the rotation direction of the drive shaft and the swing direction of the swing cam on the cam lift side are set to be the same. It is characterized by.
[0014]
According to the present invention, the friction torque between the outer diameter of the drive shaft and the inner diameter of the swing cam acts on the swing cam in the lift-up direction rather than the lift-down direction, so that the starting torque can be reduced.
[0015]
The invention described in claim 3 is characterized in that the rotational direction of the drive shaft is set to be the same as the rotational direction of the crankshaft.
[0016]
Therefore, the drive shaft can be easily rotated because it can be driven directly by a crankshaft via a timing chain or timing belt without using a rotation direction reversing pulley or the like in the same way as a normal camshaft drive. It can be driven.
[0017]
According to a fourth aspect of the present invention, there is provided a variable mechanism that varies the relative position of the rocking cam with respect to the follower portion by changing the rocking fulcrum of the rocker arm to vary the valve lift characteristics. .
[0018]
Therefore, the valve lift characteristics can be made variable simply by changing the rocking fulcrum position of the rocker arm by a relatively small eccentric rotation of the control cam, for example, the control cam, and a particularly small valve lift characteristic can be obtained, further reducing the starting torque. Can be made.
[0019]
The invention according to claim 5 is characterized in that the valve lift characteristic is controlled to be a small valve lift by the variable mechanism when the engine is started.
[0020]
Accordingly, since the small valve lift characteristic is always provided when the engine is started, the spring reaction force of the valve spring is reduced, and the starting torque at the time of starting can always be reduced.
[0021]
The invention described in claim 6 is characterized in that the rocker arm and the swing cam are linked by a link rod.
[0022]
Therefore, the presence of the link rod between the rocker arm and the swing cam improves the degree of freedom of variable valve lift characteristics. As a result, a smaller valve lift characteristic can be obtained, further improving startability. Can be increased.
[0023]
The invention according to claim 7 is characterized in that a bearing is interposed between the drive cam and one end of the link arm.
[0024]
Accordingly, since the coefficient of static friction can be reduced between the drive cam and the link arm when the engine is started, the starting torque of the drive shaft can be greatly reduced.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the valve gear of the present invention will be described in detail with reference to FIGS. The valve operating apparatus of this embodiment is similar to that of the prior application, and includes a variable mechanism that includes two intake valves per cylinder and that makes the valve lift of the intake valves variable according to the engine operating state. Yes.
[0026]
That is, this valve operating device is rotatably supported by a pair of intake valves 12 and 12 slidably provided on a cylinder head 11 via a valve guide (not shown) and a bearing 14 above the cylinder head 11. A hollow drive shaft 13, two drive cams 15 and 15 that are eccentric rotary cams fixed to the drive shaft 13 by press-fitting or the like, and a swingable support on the drive shaft 13, each intake valve 12 , 12 and swing cams 17, 17 for opening the intake valves 12, 12 in sliding contact with the flat upper surfaces 16 a, 16 a of the valve lifters 16, 16, which are followers disposed at the upper ends of the drive valves 15, 12. And the swing cams 17 and 17, and a transmission mechanism 18 that transmits the rotational force of the drive cam 15 as the swing force of the swing cams 17 and 17, and the operating position of the transmission mechanism 18 is variable. With variable mechanism 19 That.
[0027]
The drive shaft 13 is arranged along the longitudinal direction of the engine and is rotated from the crankshaft of the engine via a driven sprocket (not shown) provided at one end, a timing chain wound around the driven sprocket, and the like. Force is transmitted, and the direction of rotation is set in the clockwise direction (arrow direction) in FIG.
[0028]
As shown in FIG. 2, the bearing 14 is provided at the upper end portion of the cylinder head 11 and supports the upper portion of the drive shaft 13, and the control shaft is provided at the upper end portion of the main bracket 14a and will be described later. The brackets 14a and 14b are fixed together from above by a pair of bolts 14c and 14c.
[0029]
The drive cams 15 are substantially ring-shaped as shown in FIGS. 1 to 3, and are composed of a small-diameter cam main body 15a and a flange portion 15b integrally provided on the outer end surface of the cam main body 15a. A drive shaft insertion hole 15c is formed so as to penetrate in the axial direction, and the axis X of the cam body 15a is offset from the axis Y of the drive shaft 13 by a predetermined amount in the radial direction. Each drive cam 15 is press-fitted and fixed to both sides of the drive shaft 13 through the drive shaft insertion hole 15c so as not to interfere with the valve lifters 16 and 16, and both the cam main bodies 15a and 15a are fixed. The outer peripheral surfaces 15d and 15d are formed in the same cam profile.
[0030]
The swing cam 17 has a substantially horizontal raindrop shape as shown in FIGS. 1 and 4 to 6, and is supported by the drive shaft 13 being inserted into a substantially annular base end 20 so as to be rotatably supported. A hole 20a is formed through, and a pin hole 21a is formed through the cam nose 21 at one end. Further, a cam surface 22 is formed on the lower surface of the swing cam 17, and a base circle surface 22a on the base end portion 20 side, a ramp surface 22b extending from the base circle surface 22a to the cam nose portion 21 side in an arc shape, and the lamp The top surface 22c of the maximum lift that is provided at the tip side of the surface 22b is formed, and the base circle surface 22a, the ramp surface 22b, and the top surface 22c are arranged in accordance with the swing position of the swing cam 17 according to each valve lifter. The upper surface 16a of 16 is in contact with a predetermined position. The swing cam 17 has a swing direction on the cam lift side that slides from the base surface 22 a to the top surface 22 c in the same direction as the rotation direction of the drive shaft 13.
[0031]
As shown in FIG. 1, the transmission mechanism 18 includes a rocker arm 23 disposed above the drive shaft 13, a link arm 24 that links one end 23 a of the rocker arm 23 and the drive cam 15, and the other end of the rocker arm 23. A link rod 25 that links the portion 23b and the swing cam 17 is provided.
[0032]
As shown in FIG. 3, each of the rocker arms 23 is bent in a substantially crank shape as viewed from above, and a cylindrical base portion 23c at the center is rotatably supported by a control cam 33 described later. In addition, a pin hole 23d into which a pin 26 that is rotatably connected to the link arm 24 is press-fitted is formed in the one end 23a protruding from each outer end of each base 23c. A pin hole 23e is formed in the other end portion 23b projecting from each inner end portion of the base portion 23c. The pin hole 23e is press-fitted with a pin 27 that is rotatably connected to the one end portion 25a of each link rod 25. .
[0033]
The link arm 24 includes an annular base 24a having a relatively large diameter and a projecting end 24b projecting at a predetermined position on the outer peripheral surface of the base 24a. A fitting hole 24c is formed in the outer peripheral surface of the cam main body 15a of the cam 15 so as to be rotatably fitted. On the protruding end 24b, a pin hole 24d through which the pin 26 is rotatably inserted is formed. Yes.
[0034]
Further, as shown in FIG. 1, the link rod 25 has a flat plate shape with a predetermined length, and its center is bent into a square shape. The circular end portions 25 a and 25 b have the rocker arm 23 in addition to the rocker arm 23. Pin insertion holes 25c and 25d through which end portions of the pins 27 and 28 press-fitted into the pin holes 23e and 21a of the end portion 23b and the end portion 21 of the swing cam 17 are rotatably inserted are formed.
[0035]
In addition, snap rings 29, 30, 31 for restricting the axial movement of the link arm 24 and the link rod 25 are provided at one end of each pin 26, 27, 28.
[0036]
The variable mechanism 19 includes a control shaft 32 that is rotatably supported by the same bearing 14 above the drive shaft 13, and a control cam 33 that is fixed to the outer periphery of the control shaft 32 and serves as a swing fulcrum of the rocker arm 23. It has.
[0037]
Each of the control cams 33 has a cylindrical shape, and the position of the axis P1 is deviated from the axis P2 of the control shaft 32 by α as shown in FIG.
[0038]
The control shaft 32 extends in parallel with the drive shaft 13 and is controlled to rotate within a predetermined rotation angle range by an electromagnetic actuator (not shown) provided at one end, and the electromagnetic actuator is an engine It is driven by a control signal from a controller (not shown) that detects the operating state of the motor. The controller detects the current engine operating state based on detection signals from various sensors such as a crank angle sensor, an air flow meter, and a water temperature sensor, and outputs a control signal to the electromagnetic actuator.
[0039]
  As shown in FIGS. 4 and 6, the drive cam 15Extending from the center P1 of the rocking fulcrum of the rocker arm 23, that is, the center P1 of the control cam 33, with respect to a straight line S connecting the shaft center X and the axis Z of the pin 26 connecting the link arm 24 and the rocker arm 23. Length L of perpendicular Q₁, L₂Is set so as to be changed at each intermediate valve lift position in the upward (lift-up) section (FIG. 4 state) and the downward (lift-down) section (FIG. 6 state) of the valve lift by the swing cam 17. That is, the length L of the vertical line Q at the intermediate lift position at the time of climbing₁, The length L of the perpendicular Q at the intermediate lift position when descending₂It was set to be longer. At this point, the valve lift amount is the same for both.
[0040]
Hereinafter, the operation of the present embodiment will be described. First, at the time of engine start and at the time of low rotation and low load, the electromagnetic actuator is rotationally driven in one direction by a control signal from a controller that detects engine operation, and the control shaft 32 is driven. The control cam 33 is rotated to the position shown in FIGS. 1 and 4 to 6 to rotate the thick portion 33a in the lower left direction. For this reason, the rocker arm 23 has its swing fulcrum center P1 moved to the left as shown in the figure, and the other end 23b slightly lifts the cam nose 21 of the swing cam 17 upward via the link rod 25. The entire swing cam 17 is rotated by a predetermined amount to the illustrated counterclockwise position.
[0041]
In this state, the swinging action of the swinging cam 17, that is, the cam lifting action of the swinging cam 17 by the drive cam 15 and the transmission mechanism 18 will be described with reference to FIGS. 1 and 4 to 6. First, as shown in FIG. When the base circle surface 22a of the swing cam 17 is located on the upper surface 16a of the valve lifter 16, the intake valve 12 is in the closed operation state in the base circle region.
[0042]
From this state, as shown in FIG. 4, the link arm 24 moves in the upper left direction as the drive cam 15 rotates and pushes up the one end 23 a of the rocker arm 23. Accordingly, the rocker arm 23 swings in the clockwise direction as shown in the drawing, and the link rod 25 is pressed downward at the other end 23b. As a result, the swing cam 17 swings in the clockwise direction, and the cam lift is started. It becomes the lift up section. From this point, when the drive cam 15 further rotates, the swing cam 17 swings clockwise to the position shown in FIG. 5 and reaches the maximum lift when the top surface 22c contacts the upper surface 16a of the valve lifter 16. . When the drive cam 15 further rotates, the swing cam 17 reverses as shown in FIG. 6 to become a lift down section, and further, the base circle region (valve closed region) shown in FIG. )become.
[0043]
Therefore, since the valve lift characteristic of the intake valve 12 is a small lift characteristic as shown by the broken line in FIG. 11, the gas flow of the intake air is enhanced and the fuel consumption is improved.
[0044]
And, at the intermediate lift position (the position shown in FIGS. 4 and 6) of the up and down sections, the vertical line Q of the up section is set longer than the normal line Q of the down section as described above. The starting torque for driving 13 can be reduced. That is, with reference to FIGS. 4 and 6, the line S is formed between the straight line S at the intermediate lift position in the upward section shown in FIG. 4, the connection S <b> 2 of the pin 26 axis Z and the center P <b> 1 of the control cam 33. Angle (opening angle between link arm 24 and rocker arm 23) θ₁Is the corresponding angle θ shown in FIG.₂Larger than both θ₁, Θ₂Since both are 90 ° or less, L₁> L₂It has become.
[0045]
In addition, since the valve lift amount is the same at the intermediate lift position shown in FIGS. 4 and 6, the spring reaction force from the valve spring 34 is the same. Therefore, the moment M by which the valve spring 34 rotates the rocker arm 23 counterclockwise via the swing cam 17 and the link rod 25 is also the same. Then, the load acting on the center X of the drive cam 15 from the rocker arm 23 via the link arm 24 is F (the upward side is F).₁, F on the down₂), Since F = M / L, the upward load F₁Is F₁= M / L₁And the downward load F₂F₂= M / L₂It becomes. Therefore, F₁<F₂And the upward load F₁Is the downward load F₂Smaller than.
[0046]
On the other hand, considering the starting torque for the drive cam 15 (drive shaft 13), in the lift up section, the spring force of the valve spring 34 is opposite to the rotation direction of the drive shaft 13 via the transmission mechanism 18, as shown in FIG. The calculated value is T_S1= F₁× l₁(L) Then this F₁Is L as described above.₁Due to the lengthening of F₂Therefore, the torque in the direction opposite to the rotation direction of the drive shaft 13 is reduced. Where l₁(L) is the length of a perpendicular extending from the center X of the drive cam 15 with respect to the straight line S.
[0047]
Further, at the time of starting the engine, the drive cam 15 and the link arm 24 have almost no relative rotation until the rotation rises stably, and therefore a relatively large static friction coefficient between the inner and outer peripheral surfaces of the both 15 and 24. μ acts and its friction torque μF₁× D / 2 is also added, but F₁Since it is small, it becomes a relatively small value. This friction torque reduction effect and the T_S1Due to the reduction effect, the starting torque TK can be reduced. Where TK = F_S1+ ΜF₁× D / 2 where D is the diameter of the drive cam.
[0048]
In the lift down section, the spring force of the valve spring 34 acts in the same direction as the rotation direction of the drive shaft 13 via the transmission mechanism 18 as shown in FIG. Assist. That is, the calculated value is T_S2= F₂× l₂(L), F₂The effect of T, that is, the large torque (spring force) assists the rotational force of the drive shaft 13.
[0049]
(In the lift up section,₁And l in the lift down section₂Is l for the same valve lift₁= L₂It has become. )
As described above, the starting torque TK decreases in the lift up section, and a relatively large rotational assist force in the same direction as the drive shaft 13 acts in the lift down section. And the rise of the rotation immediately after starting becomes good. As a result, the engine startability can be improved and the starter such as a cell motor can be reduced in size and simplified.
[0050]
In addition, in this embodiment, the variable valve lift characteristic of the intake valve 12 by the variable mechanism 19 is set so as to be the minimum lift when the engine is started, so that the spring reaction force of the valve spring 34 is small in this small valve lift state. Therefore, the starting torque T_K Can be further reduced, and such an effect is always obtained at the time of starting, and the starting performance is further improved. Further, since the rotation direction of the drive shaft 13 and the swing direction (arrow direction) when the swing cam 17 is lifted up are set to be the same, the outer peripheral surface of the drive shaft 13 and the support hole 20a of the swing cam 17 are set. A friction moment with the inner peripheral surface acts on the swing cam in the lift upward direction. Therefore, the starting torque of the drive shaft 13 can be reduced.
[0051]
Further, the variable width of the valve lift characteristic can be freely changed by changing the length of the link rod 25 due to the presence of the link rod 25. Therefore, the starting torque of the drive shaft 13 can be reduced by setting the small valve lift characteristic. Can do.
[0052]
7 to 10 show a second embodiment of the present invention, in which the intermediate lift position L in the up section when the valve lift is controlled to the maximum lift by the variable mechanism 19 is shown.₁L of the intermediate lift position in the descending section₂Is set longer. That is, the electromagnetic actuator is rotationally driven in the other direction by a control signal from the controller, and the control shaft 32 rotates the control cam 33 to the position shown in FIGS. 7 to 10 to rotate the thick portion 33a to the lower right. . For this reason, the rocker arm 23 has its swing fulcrum center P1 position moved to the right as shown in the figure, and the other end 23b slightly pushed the cam nose 21 of the swing cam 17 downward, so that the entire swing cam 17 is moved. Is rotated to a clockwise position shown in the figure by a predetermined amount.
[0053]
Accordingly, in the state in which the position of the swing cam 17 is controlled by the variable mechanism 19, the valve lift accompanying the rotation of the drive shaft 13 and the drive cam 15 passes through the lift up section shown in FIG. 8 from the base circle area shown in FIG. 9, the position where the valve lifter 16 is pressed is on the edge side of the top surface 22c of the cam nose portion 21, so that the valve lift amount is the maximum lift as shown by the solid line in FIG. Thereafter, the swing cam 17 reverses and passes through the intermediate lift area of the lift down section as shown in FIG. 10 and shifts to the original base circle area.
[0054]
Even in this valve lift characteristic state, that is, in the state controlled to the maximum lift, the L of the perpendicular line S₁The length of L₂Is set to be longer than F, so that F₁<F₂Therefore, it is possible to reduce the starting torque at the start of the engine of the drive shaft 13 in the ascending section, and therefore it is possible to improve the startability even when the engine output is emphasized and controlled to a large lift.
[0055]
FIG. 12 shows a third embodiment of the present invention based on the first embodiment. A rolling bearing is used between the outer peripheral surface of the drive cam 15 and the inner peripheral surface of the fitting hole 24c of the link arm 24. A needle bearing 40 is interposed.
[0056]
Accordingly, the sliding friction resistance between the drive cam 15 and the link arm 24 is greatly reduced, and particularly the static friction coefficient μ can be sufficiently reduced. Therefore, the starting torque of the drive shaft 13 at the time of starting as described above is greatly increased. Therefore, the startability can be further improved.
[0057]
【The invention's effect】
As is apparent from the above description, according to the first aspect of the invention, the starting torque of the drive shaft at the time of starting the engine can be reduced, so that the startability can be improved and the starting cell motor or the like can be started. The device can be miniaturized and simplified.
[0058]
According to the second aspect of the present invention, the wear moment generated on the outer peripheral surface of the drive shaft and the inner peripheral surface of the drive shaft insertion hole of the swing cam acts on the lift up side rather than the lift down side of the swing cam. Further, the starting torque of the drive shaft at the time of starting can be further reduced.
[0059]
According to the third aspect of the invention, since the drive shaft is rotated in the same direction as the rotation direction of the crankshaft, the drive shaft can be easily rotated, so that the rotational driveability of the drive shaft is improved.
[0060]
According to the fourth aspect of the invention, the valve lift can be greatly changed by slightly changing the rocking fulcrum of the rocker arm by the rotation of the control cam, so that the engine performance can be sufficiently exerted. In other words, the starting torque of the drive shaft can be further reduced by controlling the small valve lift.
[0061]
According to the fifth aspect of the present invention, since the valve lift is always controlled to be a small valve lift when the engine is started, the starting torque of the drive shaft can be reduced, so that a good startability can always be obtained.
[0062]
According to the invention described in claim 6, by providing the link rod, the degree of freedom of the variable range of the valve lift characteristic by the swing cam is improved by changing the length and the like, and a smaller valve lift is set. As a result, the starting torque can be greatly reduced, and the startability can be further improved.
[0063]
According to the seventh aspect of the present invention, the sliding friction resistance between the drive cam and the link arm can be greatly reduced by the needle bearing, and particularly the static friction coefficient can be sufficiently reduced. The starting torque can be greatly reduced, and the startability can be further improved.
[Brief description of the drawings]
1 is a cross-sectional view taken along line AA of FIG. 2 showing an embodiment of the present invention.
FIG. 2 is a side view of the embodiment.
FIG. 3 is a plan view of the embodiment.
FIG. 4 is a cross-sectional view showing an intermediate lift state in an up section during small valve lift control in the present embodiment.
FIG. 5 is a cross-sectional view showing a maximum lift state during small valve lift control in the present embodiment.
FIG. 6 is a cross-sectional view showing an intermediate lift state in a descending section during small valve lift control in the present embodiment.
FIG. 7 is a cross-sectional view showing a lift state during a base circle during large valve lift control in the second embodiment.
FIG. 8 is a cross-sectional view showing an intermediate lift state in an ascending section during large valve lift control in the second embodiment.
FIG. 9 is a cross-sectional view showing a maximum lift state during large valve lift control in the second embodiment.
FIG. 10 is a cross-sectional view showing an intermediate lift state in a descending section during large valve lift control in the second embodiment.
FIG. 11 is a valve lift characteristic diagram of the first and second embodiments.
FIG. 12 is a sectional view showing a third embodiment.
FIG. 13 is a cross-sectional view showing a valve gear according to a previous application.
[Explanation of symbols]
  11 ... Cylinder head
  12 ... Intake valve
  13 ... Drive shaft
  15 ... Driving cam
  16 ... Valve lifter
  17 ... Oscillating cam
  18 ... Transmission mechanism
  19 ... Variable mechanism
  21 ... Cam nose
  22 ... Cam surface
  23 ... Rocker arm
  23a, 23b ... end
  24 ... Link arm
  24a ... proximal end
  24b ... protruding end
  25 ... Link rod
  25a, 25b ... both ends
  34 ... Valve spring

Claims (7)

A drive shaft that is rotationally driven by the crankshaft of the engine;
A drive cam fixed to the outer periphery of the drive shaft and having a center deviated by a predetermined amount from the axis of the drive shaft;
A link arm whose one end is rotatably linked to the outer periphery of the drive cam;
A rocker arm supported by a support shaft in a swingable manner, and having one end portion rotatably linked to the other end portion of the link arm via a connecting pin;
A swing cam linked to the other end portion of the rocker arm so as to be swingable so as to open and close the engine valve while the cam surface is in sliding contact with the follower portion of the upper end portion of the engine valve;
A valve spring that urges the link arm toward the drive cam at one end of the rocker arm via the swing cam while urging the engine valve in a closing direction;
In the internal combustion engine valve gear comprising:
The length of the perpendicular extending from the rocking fulcrum of the rocker arm with respect to the straight line connecting the shaft center of the connecting pin that connects the link arm and the rocker arm and the center point of the drive cam is the engine by the rocking cam. When the lift of the valve is an intermediate lift position in each of the descending section and the ascending section, the perpendicular length in the ascending section is set to be longer than the perpendicular length in the descending section of the lift. A valve operating apparatus for an internal combustion engine.   The swing cam is supported on the outer periphery of the drive shaft in a freely swingable manner, and the rotation direction of the drive shaft and the swing direction of the swing cam on the cam lift side are set to be the same. Valve gear for internal combustion engine.   3. The valve operating apparatus for an internal combustion engine according to claim 1, wherein the rotation direction of the drive shaft is set to be the same as the rotation direction of the crankshaft.   4. A variable mechanism for changing valve lift characteristics by changing a relative position of the rocking cam with respect to a follower by changing a rocking fulcrum of the rocker arm. The valve operating apparatus for an internal combustion engine according to 1.   5. The valve operating apparatus for an internal combustion engine according to claim 4, wherein the valve lift characteristic is controlled to be a small valve lift by the variable mechanism when the engine is started.   6. The valve operating apparatus for an internal combustion engine according to claim 4, wherein the rocker arm and the swing cam are linked by a link rod.   7. The valve operating apparatus for an internal combustion engine according to claim 1, wherein a bearing is interposed between the drive cam and one end of the link arm.

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