JP3455956B2 - Continuous variable valve lift mechanism - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for continuously changing a lift amount of a valve driven by a rocker arm in a valve train of an internal combustion engine. 2. Description of the Related Art As a conventional continuously variable valve lift mechanism, an example is disclosed in which a rocking pivot of a rocker arm is displaced (Japanese Patent Application Laid-Open No. 60-108511, Japanese Patent Application Laid-Open No. 5-202720).
Japanese Patent Application Laid-Open No. 60-125304 and Japanese Patent Application Laid-Open No. Sho 60-125304, in which the contact angle between the rocker arm and the cam peak is changed.
No. 27411), and an example in which the lever ratio is changed by having a variable fulcrum between the rocker arm and the tappet (Japanese Patent Application Laid-Open No. 60-228717). In an example in which the pivot point of the rocker arm is directly displaced or an example in which the lever ratio is changed with a variable fulcrum between the rocker arm and the tappet, the lift curve is similar due to the displacement of the fulcrum. Since the size changes, if the lift amount is reduced, the buffer curve becomes relatively low, the tappet clearance also changes, and the tappet sound increases. Further, in the case of changing the contact angle of the rocker arm with the cam peak, the tappet clearance changes, and the total opening angle of the valve also changes greatly, so that the intake and exhaust efficiency deteriorates. [0004] The present invention has been made in view of such a point,
The purpose is to provide a continuously variable valve lift mechanism in which the maximum lift can be sufficiently reduced without extremely lowering the buffer curve and the tappet clearance does not change much. [0005] In order to achieve the above object, the present invention provides a valve operating method for an internal combustion engine in which a valve is opened and closed by a rocker arm that swings based on rotation of a cam. In the apparatus, a link member swinging about a movable pivot point is provided, and pivot point moving means for moving a pivot point of the link member, wherein the pivot point moving means is
The link member when the base circle of the cam is acting
Move the pivot point along an arc centered on the rocking
So it can be, the link member swings based on the rotation of the cam about a pivot point which is moved by the pivot point moving means for oscillating the rocker arm on the basis of the swing of the link member The valve lift amount is continuously variable. When the pivot point of the link member is displaced by the pivot point moving means, the swing locus of the link member with respect to the rocker arm can be changed, that is, the swing direction in which the rocker arm swings out of the swing of the link member. Since the components are changed and the valve is opened and closed by swinging the rocker arm, the maximum lift amount can be sufficiently reduced without lowering the buffer curve, and the change in tappet clearance can be suppressed to a small value. . An embodiment of the present invention shown in FIGS. 1 to 8 will be described below. This embodiment is applied to a valve train of a V-type four-cylinder engine, and FIG.
2 is a sectional view taken along line II-II in FIG. 1. The cylinder block 3 on the crankcase 2 is provided with two cylinders 4 arranged in a V-shape on the right and left in parallel at the front and rear, and the upper part of the cylinder 4 is covered with a cylinder head 5. A connecting rod 7 having one end pivotally connected to a piston 6 which reciprocates in the cylinder 4 has the other end pivotally connected to a crankpin of a crankshaft 8 so that the piston 6
Is converted into rotation of the crankshaft 8. A camshaft 9 is rotatably supported in parallel with the crankshaft 8 in a V-shaped valley formed by the left and right cylinders 4. The camshaft 9 is fitted to a sprocket 11 fitted to the main shaft of the crankshaft 8. A chain 13 is bridged between the sprocket 12 and the camshaft 9 so that the camshaft 9 rotates at half the rotation speed of the crankshaft 8. Eight cams 10 are sequentially formed on the camshaft 9. On the other hand, the cylinder head 5 is provided with one intake port 20 and one exhaust port 21 for each cylinder 4, and a valve body 30a can be seated on a valve seat 22 provided at the opening of each port 20, 21 to the combustion chamber. The valve 30 is the valve guide 23
And is slidably supported by The valve 30 has a valve spring retainer 31 fitted to the base end thereof, which presses one end of a valve spring 32 and is urged upward. The base end of the valve 30 is exposed through the center of the valve spring retainer 31,
A rocker arm 33 is swingably supported by a rocker shaft 34 so that one end thereof is in contact with the base end surface. The other end of the rocker arm 33 is fitted with the upper end of a push rod 35, and the push rod 35 itself passes through a hole provided in the cylinder block 3 to form the camshaft 9.
Extending towards. The rocker arm 33 is covered by a head cover 14. An ignition plug 15 is attached to the cylinder head 5 toward the combustion chamber, and an injector 16 is attached to the intake port 20. In accordance with each cam 10 of the camshaft 9, a driven lever 36 is pivotally supported by a fixed support shaft 37 provided on the cylinder block 3 so as to be swingable.
The swing of the driven lever 36 moves the push rod 35 via a link mechanism described below. The link mechanism will be described with reference to FIGS. At the tip of the driven lever 36, opposing side walls extend, and a roller 39 is rotatably supported by a pin 38 provided between both side walls.The cam 10 contacts the roller 39 by contacting the outer peripheral surface of the roller 39 with the roller 39. The driven lever 36 swings through the intervening lever 36. pin
Numeral 38 protrudes outward from both side walls at the tip of the driven lever 36, a pair of connecting arms 40 is pivotally mounted on the protruding portion, and a pin 41 is bridged between the other ends of the same pair of connecting arms 40. 41
The lower end of the push rod 35 is pivotally mounted on the push rod 35, and a pair of link members 42 are pivotally mounted between the connecting arm 40 and the push rod 35. A pin 43 is provided between the ends of the pair of link members 42 with both ends protruding outward, and a pair of revolving levers 44 is pivotally mounted on the protruding portions on both sides, so that the same pair of revolving levers are provided. The lever 44 has a pin having substantially the same shape as the link member 42.
The rotary pins 45 are located outside of the rotary levers 44, and pivot pins 45 are integrally provided on both ends of the rotary levers 44 so as to protrude outward. The rotation pin 45 is rotatably supported at a fixed position on the cylinder block 3. A pin 41 for pivotally connecting the link member 42 to the connecting arm 40 and the push rod 35 is
And can be located on the same axis. The link mechanism for transmitting the rotation of the cam 10 to the valve 30 is structured as described above. When the rotation pin 45 is rotated, the rotation lever 44 is integrally rotated to move the position of the pin 43. Can be. Since the pin 43 contacts the pivot point of the link member 42, the rotation of the rotation pin 45 causes the link member 42 to rotate.
Pivot point (pin 43) can be displaced. That is, when the roller 39 is in contact with the base circumferential surface of the cam 10 as shown in FIG. 3, the pin 41 at the swinging end of the link member 42 is on the same axis as the rotating pin 45, When the turning pin 45 is turned to turn the turning lever 44, the link member 42 turns around the pin 41 (turning pin 45) together with the turning lever 44 via the pin 43 to displace the position of the pin 43. be able to. When the pin 43 is set at an appropriate turning position in this way, the swing trajectory of the pin 41 at the other end of the link member 42 is determined, and the push rod 35 pivotally connected at one end to the pin 41 swings. Reciprocates according to the movement trajectory, and rocker arm 33
The valve 30 is lifted via the valve. If the pivot pin 45 is operated to set the pin 43 to the position shown in FIG. 6 and the pivot point (center of the pin 43) of the link member 42 at this time is point A, the link member 42 swings. The swing trajectory of the center of the end pin 41 is an arc a around the point A.
It becomes. FIG. 6 does not show the turning lever 44 and the turning pin 45. As shown by the solid line in FIG. 6, when the roller 39 at the swing end of the driven lever 36 is in contact with the base circumferential surface of the cam 10, the center of the pin 41 is connected to the arc a through the connecting arm 40.
At point B above, the valve 30 in this state has its valve body
It is seated on 22 and the valve opening is closed. Then, the cam 10 rotates, and the cam peak is
When the roller 39 is pushed up along the arc a via the connecting arm 40, the center of the pin 41 reaches the point C as shown by a two-dot chain line in FIG. Since the pin 41 hits the lower end of the push rod 35, the pivot movement from the point B to the point C of the pin 41 mainly causes the push rod 35 to rotate.
The push rod 35 is pushed up by the axial component of, and the rocker arm 33 swings to lift the valve 30 by the maximum lift amount L to open the exhaust opening. As described above, the pivot point of the link member 42 (the pin 43
Is at point A, the movement of the pin 41 is from point B to point C of the arc a, and the swing trajectory from point B to point C is substantially parallel to the axial direction of the push rod 35. Therefore, the movement amount of the push rod 35 is large, and the lift amount of the valve 30 is also large (high-lift state). Next, when the rotation pin 45 is operated to move the pin 43 to the position of the point A 'shown in FIG. 7, the swing locus of the center of the pin 41 at the swing end of the link member 42 is the point A'. Arc a as center
'. When the roller 39 at the swinging end of the driven lever 36 is in contact with the basic circumferential surface of the cam 10 as shown by the solid line in FIG. 7, the pin 41 is at the same position B in FIG.
The valve body is seated on the valve seat 22 to close the valve opening. When the cam 10 rotates and the cam peak pushes up the roller 39, the pin 41 moves along the arc a 'via the connecting arm 40, and when the roller 39 reaches the top of the cam peak, two points are shown in FIG. Pin 41 reaches point C 'as shown by the dashed line. The pivotal movement of the pin 41 from the point B to the point C 'pushes up the push rod 35 by an axial component of the push rod 35, swings the rocker arm 33, lifts the valve 30 by the maximum lift amount L', and opens the exhaust port. open. As described above, the pivot point of the link member 42 (pin 4
When the point 3) is at the point A ', the movement of the pin 41 is from the point B to the point C' of the arc a ', and the swing trajectory from the point B to the point C' is in the axial direction of the push rod 35. Since the push rod 35 is greatly inclined and the component in the axial direction of the push rod 35 is small, the lift amount of the push rod 35 is small, and the lift amount of the valve 30 is also small (low lift state). FIG. 8 shows valve lift curves in the high lift state of the valve shown in FIG. 6 and the low lift state shown in FIG. A curve HL is a valve lift curve in a high lift state, and a curve LL is a valve lift curve in a low lift state. The curve HL (high lift state) has a maximum lift amount L of 12 mm, has a smooth tapered shape gradually tapered, and the cam has a rotation angle of 296 ° 26 to produce a substantial lift except for tappet clearance of 0.16 mm. ′, And the rotation angle excluding the buffer curve portion with a lift amount of 1 mm or less is 200
°. On the other hand, the curve LL (low-lift state) has a maximum lift amount L 'of about 3.2 mm, which is sufficiently smaller than the curve HL (high-lift state), but the rotation angle of the cam causing the substantial lift is 258 ° 50'. The rotation angle is 184 ° 4 except for the buffer curve portion with a lift amount of 1 mm or less.
4 ′, each of which indicates an angle close to the curve HL (high-lift state), and thus the overall shape is a mountain shape approximating a trapezoid. In the low lift state, the curve LL has a mountain shape close to a trapezoid because the swing of the pin 41 with respect to the push rod 35 from the point B to the point C 'in FIG. Near the end, the axial component of the push rod 35 is large, and the lift amount is rapidly increased / decreased. The other reason is that the axial component of the push rod 35 is extremely small and there is no change in the lift amount. As described above, even in the low lift state, even if the lift curve has a shape close to a trapezoid and the maximum lift amount is sufficiently reduced, the buffer curve portion does not become extremely low, and the valve is quickly opened and closed. Intake and exhaust efficiency can be improved. Since the tappet clearance changes very little between the high lift state and the low lift state, the tappet sound can be reduced. Since the pivot pin 45 is pivoted, the pivot position of the pivot point (pin 43) of the link member can be continuously changed to any point on the arc around the point B of the points A to A '. Accordingly, any intermediate state between the high lift state and the low lift state can be formed, and fine engine operation control can be performed. Next, the second embodiment will be described with reference to FIGS.
0 will be described. FIGS. 9 and 10 are views corresponding to FIGS. 6 and 7 in the first embodiment. In the second embodiment, the link member 42 in the first embodiment is moved to the rocker arm side, and the basic structure is the same. Since the link member 53 is located on the rocker arm 55 side, the connecting arm 52 becomes long, and the push rod 54 becomes short and is pivotally attached to the rocker arm 55. FIG. 9 shows that the pivot point of the link member 53 is at the point A and is in a high lift state, and the rotation of the cam 50 causes the driven lever 51 to rotate.
And the swinging end of the link member 53 swings from the point B to the point C via the connecting arm 52, moves the push rod 54 largely in the longitudinal direction, and swings the rocker arm 55 to the maximum lift amount of the valve 56. L is large. On the other hand, in FIG.
The pivot point moves from point A to point A 'and is in a low lift state, and the swing end of the link member 53 swings from point B to point C', and the push rod 54 slightly moves in the longitudinal direction. Valve
The maximum lift amount L 'of 56 is small. The second embodiment has the same basic structure as the first embodiment, and has the same operation and effect. Next, a third embodiment will be described with reference to FIGS. The third embodiment is provided with a new driven lever 61 in which the driven lever 36 in the first embodiment is modified to also serve as the connecting arm 40, and other members are substantially the same. The driven lever 61 has a contact surface 61a in contact with the cam 60 and a contact surface 61b in contact with the swing end of the link member 62. The driven lever 61 swings by rotation of the cam 60 and is pushed by the contact surface 61b to pivot the link member 62. It swings around a fulcrum (point A or point A '). FIG. 11 shows that the pivot point of the link member 62 is at the point A and the link member 62 is in the high-lift state,
The swing end of 62 swings greatly from point B to point C, and the push rod 63 also moves greatly in the longitudinal direction, and the maximum lift amount L of the valve 65 lifted via the rocker arm 64 is large. On the other hand, in FIG. 12, the pivot point of the link member 62 shifts from the point A to the point A ′ and is in a low lift state, and the swing end of the link member 62 slightly swings from the point B to the point C ′, The movement is slight, and the maximum lift amount L 'of the valve 65 is small. Next, a fourth embodiment will be described with reference to FIGS. In this example, the link member 73 is located on the rocker arm 74 side, and the driven lever 71 directly acts on the push rod 72, the push rod 72 swings the link member 73, and the link member 73 is directly locked. arm
Acts in contact with the contact surface 74a of 74. FIG. 13 shows that the pivot point of the link member 73 is at the point A and is in a high lift state, and the driven lever 71 which swings by rotation of the cam 70 pushes the push rod 72 to swing the link member 73 around the point A. The rocking end of the link member 73 swings from the point B to the point C, and swings largely in the rocking direction of the rocker arm 74, so that the maximum lift amount L of the valve 75 is large. On the other hand, in FIG. 14, the pivot point of the link member 73 shifts from the point A to the point A ′ and is in a low lift state, and the swing end of the link member 73 swings from the point B to the point C ′ and the rocker arm 74 swings. The valve 75 slightly swings in the direction, and the maximum lift amount L 'of the valve 75 is small. Next, a fifth embodiment will be described with reference to FIGS. This embodiment is an example in which the cam 80 is located near the rocker arm 83. The cam 80 directly acts on the link member 81, and the rocking of the link member 81 swings the rocker arm 83 via the short push rod 82. Move. FIG. 15 shows a state in which the pivot point of the link member 81 is at the point A and is in a high lift state, and the swing end of the link member 81 which swings by rotation of the cam 80 swings from the point B to the point C to push the push rod. The maximum lift amount L of the valve 84, which largely moves 82 in the longitudinal direction and lifts through the rocker arm 83, is large.
On the other hand, in FIG. 16, the pivot point of the link member 81 is shifted from the point A to the point A '.
And the swinging end of the link member 81 swings from the point B to the point C 'to move the push rod 82 slightly in the longitudinal direction, and the maximum lift amount L' of the valve 84 becomes small. Next, a sixth embodiment will be described with reference to FIGS. In this embodiment, the push rod 82 in the fifth embodiment is eliminated, and the link member 91 swings directly on the contact surface 92a of the rocker arm 92. FIG. 17 shows that the pivot point of the link member 91 is at the point A and the link member 91 is in the high lift state.
91 is pivoted about the point A, and the pivot end of the link member 91 is at the point B
To the point C, that is, the rocker arm 92 swings largely in the swing direction, and the maximum lift L of the valve 93 is large. On the other hand, in FIG. 18, the pivot point of the link member 91 shifts from the point A to the point A 'and is in a low lift state, and the swing end of the link member 91 swings from the point B to the point C', that is, the swing of the rocker arm 92. Swings slightly in the direction, and the maximum lift amount L 'of the valve 93 is increased.
Is small. FIG. 19 shows a valve lift curve in the sixth embodiment. A curve HL is a valve lift curve in a high lift state, and a curve LL is a valve lift curve in a low lift state. A curve HL (high lift state) has a maximum lift amount L of 12 mm and has a smooth tapered shape gradually tapering, while a curve LL (low lift state) has a maximum lift amount L.
´ is about 3.2 mm, which is gentle at the beginning of opening but sharp when closing, and has a curved shape similar to that of closing in the high-lift state. Therefore, the maximum lift can be sufficiently reduced without lowering the buffer curve, and the change in tappet clearance can be kept small. According to the present invention, when the pivot point of the link member is displaced by the pivot point moving means, the swing locus of the link member with respect to the rocker arm can be changed. The rocker arm swings accordingly to open and close the valve, so the maximum lift can be reduced sufficiently without lowering the buffer curve, improving the intake and exhaust efficiency with a smooth valve opening and closing movement. Can be achieved. Further, the change in tappet clearance can be suppressed to a small value, and the generation of tappet noise can be suppressed. The valve lift can be easily changed by moving the pivot point along an arc centered on the swinging point of the link member when the base circle of the cam is acting.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side sectional view of an engine to which a valve train according to one embodiment of the present invention is applied. FIG. 2 is a sectional view taken along line II-II in FIG. FIG. 3 is a perspective view of a link mechanism of the valve train in the first embodiment. FIG. 4 is a perspective view of the link mechanism in another state. FIG. 5 is a bottom view of the same. FIG. 6 is a side view of a main part of the same valve apparatus in a high lift state. FIG. 7 is a side view of a main part of the same valve apparatus in a low lift state. FIG. 8 is a view showing a valve lift curve in the first embodiment. FIG. 9 is a side view of a main part of the valve train in a high lift state according to the second embodiment. FIG. 10 is a side view of a main part in the low lift state. FIG. 11 is a side view of a main part of a valve train in a high lift state according to a third embodiment. FIG. 12 is a side view of main parts in the low lift state. FIG. 13 is a side view of a main portion of the valve train in a high lift state according to a fourth embodiment. FIG. 14 is a side view of main parts in the low lift state. FIG. 15 is a side view of a main part of the valve train in a high lift state according to a fifth embodiment. FIG. 16 is a side view of the main parts in the low lift state. FIG. 17 is a side view of a main portion of the valve train in a high lift state according to a sixth embodiment. FIG. 18 is a side view of main parts in the low lift state. FIG. 19 is a view showing a valve lift curve in the sixth embodiment. [Description of Signs] 1 ... Engine, 2 ... Crankcase, 3 ... Cylinder block, 4 ... Cylinder, 5 ... Cylinder head, 6 ...
Piston, 7 ... connecting rod, 8 ... crankshaft, 9
... Camshaft, 10 ... Cam, 11,12 ... Sprocket, 13
... chain, 14 ... head cover, 15 ... spark plug, 16 ...
Injector, 20 ... intake port, 21 ... exhaust port, 22
... valve seat, 23 ... valve guide, 30 ... valve, 31 ... valve spring retainer, 32 ... valve spring, 33 ... rocker arm, 34 ... rocker shaft, 35 ... push rod, 36 ... driven lever, 37 ... fixed support shaft, 38 ... pin, 40 ... connecting arm, 41 ... pin, 42 ... link member, 43 ... pin, 44 ...
Pivoting lever, 45: rotating pin, 50: cam, 51: driven lever, 52: connecting lever, 53: link member, 54: push rod, 55: rocker arm, 56: valve, 60: cam, 61
... follower lever, 62 ... link member, 63 ... push rod,
64: rocker arm, 65: valve, 70: cam, 71: driven lever, 72: push rod, 73: link member, 74: rocker arm, 75: valve, 80: cam, 81: link member, 82: push rod 83, rocker arm, 84, valve, 90, cam, 91, link member, 92, rocker arm, 93, valve.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-125913 (JP, A) JP-A-60-228716 (JP, A) JP-A-62-99606 (JP, A) 180611 (JP, U) J. 40-22809 (JP, Y1) (58) Field surveyed (Int. Cl. ⁷ , DB name) F01L 13/00 301 F01L 1/18

Claims (1)

(1) In a valve operating device for an internal combustion engine in which a valve is opened and closed by a rocker arm that is oscillated based on rotation of a cam, the oscillating center is a movable pivot point. And a pivot point moving means for moving a pivot point of the link member, and the pivot point moving means is operated by a base circle of the cam.
When the link member swings around an arc
A pivot point can be moved along , the link member swings based on the rotation of the cam around the pivot point moved by the pivot point moving means, and the link member swings based on the swing of the link member. A continuously variable valve lift mechanism characterized by rocking a rocker arm.