JP7165621B2 - Variable valve mechanism for internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve mechanism that drives valves of an internal combustion engine and changes the driving state of the valves according to the operating conditions of the internal combustion engine.

The present applicant previously proposed a variable valve mechanism 51 for an internal combustion engine shown in FIG. 7 (Patent Document 1). In this variable valve mechanism 51, a cam 53 and two helical grooves 54 and 55 are provided on a camshaft 52, and a rocker arm body 57 is oscillatably supported on a rocker shaft 56 extending parallel to the camshaft 52. A rocker arm body 57 is provided with a roller shaft 58 extending parallel to a rocker shaft 56 . A roller 59 with which a cam 53 can contact is supported on the roller shaft 58 so as to be displaceable in the longitudinal direction of the rocker shaft. , 55 and a roller guide 63 (sliding contact portion) for holding both sides of the roller 59 is displaced in the rocker shaft length direction. provided as possible. Then, the entire link arm 60 is rotated by a rotating device (not shown) to engage one engaging arm 61 with one spiral groove 54, or the other engaging arm (not shown) is engaged with the other. By selecting whether to engage the spiral groove 55, the link arm 60 and the roller 59 are displaced in the rocker shaft longitudinal direction according to the selected spiral groove 54, 55, and the cam 53 comes into contact with the roller 59, or It is a mechanism that changes whether or not the rocker arm main body 57 abuts, thereby changing the rocking motion of the rocker arm body 57 .

JP 2014-224496 A

In the above-described variable valve mechanism 51, it is necessary to provide the roller guide 63 (which is a separate part from the rocker arm main body 57) that holds the side surface of the roller 59 so that it can be displaced in the axial direction together with the link arm 60. Therefore, the structure was complicated.

Therefore, the applicant displaces the rocker arm along with the roller in the rocker shaft length direction instead of displacing only the roller 59 with respect to the rocker arm main body 57 in the rocker shaft length direction. We are considering a plan to eliminate the need for roller guides. Further, the rocker arm of the same proposal is used as the first rocker arm, and a second rocker arm is provided below the first rocker arm to be pushed and rocked by the first rocker arm, and the second rocker arm is supported by a pivot.

However, in this proposal, when the first rocker arm is displaced in the rocker shaft length direction, there is a problem that the second rocker arm in contact with the first rocker arm moves along with it in the rocker shaft length direction and falls down.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to make it difficult for the second rocker arm to fall when the first rocker arm is displaced in the rocker shaft length direction.

The present invention
a first rocker arm (10) provided below the cam (3) and rocking when pressed by the cam (3);
a second rocker arm (10) provided below the first rocker arm (10) and rocking by being pressed by the first rocker arm (10);
A base end of the first rocker arm (10) is supported by a rocker shaft (9) so as to be displaceable in the rocker shaft longitudinal direction,
The proximal end of the second rocker arm (45) is supported by a pivot (46), and the distal end of the second rocker arm (45) is provided with a pad (48) for pressing the valve (V),
A variable valve mechanism in which when the first rocker arm (10) is displaced in the rocker shaft length direction, the rocking movement of the first rocker arm (10) changes and the rocking movement of the second rocker arm (45) also changes,
An internal combustion engine characterized in that the center of gravity (G) of the second rocker arm (45) is below an imaginary tangent line (L) drawn from the center (P) of the spherical portion of the pivot (46) to the pad portion (48). Variable valve mechanism.

According to the present invention, it is possible to prevent the second rocker arm from falling when the first rocker arm is displaced in the rocker shaft length direction.

FIG. 1 is a perspective view of the variable valve mechanism of the embodiment as seen from the front side (front side). FIG. 2 is a perspective view of the same mechanism as seen from the rear side (rear side). FIG. 3(a) is a perspective view of a first rocker arm and a link arm of the same mechanism, and FIG. 3(b) is a sectional view of the first rocker arm of the same mechanism cut at the position of the roller. FIG. 4(a) is a side sectional view of the mechanism cut at the boundary between the first rocker arm and the head, and FIG. 4(b) is a side sectional view of the mechanism cut at the link arm. FIG. 5 is a front view of the same mechanism, where (a) shows the roller displaced to the first cam position, and (b) shows the roller displaced to the second cam position. FIG. 6(a) is a front view and side sectional view of a second rocker arm of the same mechanism, and FIG. 6(b) is a front view and side sectional view of a second rocker arm of a comparative example. FIG. 7 shows a conventional variable valve mechanism, where (a) is a perspective view and (b) is a sectional view.

1. First Rocker Arm The first rocker arm may comprise a roller against which the cam abuts. The number of rollers may be one or more, but it is preferable to have two rollers on the left and right in terms of left-right balance.

2. The number of the second rocker arms may be one or more, but it is preferable to have two on the left and right in terms of left-right balance.
The second rocker arm may comprise a roller against which the first rocker arm abuts.

Next, embodiments of the present invention will be described with reference to the drawings. The structure, shape, number, and the like of each part in the embodiment are examples, and can be changed as appropriate without departing from the gist of the invention.
The variable valve mechanism 1 of the embodiment shown in FIGS. 1 to 6(a) is
a first rocker arm 10 which is provided below the cam 3 and rocks when pressed by the cam 3;
a second rocker arm 10 that is provided below the first rocker arm 10 and rocks when pressed by the first rocker arm 10,
The base end of the first rocker arm 10 is supported by the rocker shaft 9 so as to be displaceable in the rocker shaft longitudinal direction,
A base end portion of the second rocker arm 45 is supported by a pivot 46, and a pad portion 48 for pressing the valve V is provided at a tip end portion of the second rocker arm 45,
A variable valve mechanism in which when the first rocker arm 10 is displaced in the rocker shaft length direction, the rocking motion of the first rocker arm 10 changes and the rocking motion of the second rocker arm 45 changes,
The second rocker arm 45 is characterized in that the center of gravity G of the second rocker arm 45 is below an imaginary tangent line L drawn from the center P of the spherical portion of the pivot 46 to the pad portion 48 .

When the first rocker arm 10 is displaced in the rocker shaft length direction, the rocking motion of the first rocker arm 10 changes and the rocking motion of the second rocker arm 45 changes as follows.
The camshaft 2 is provided with a cam 3 and two spiral grooves 5 and 7,
A first rocker arm 10 including a roller 16 with which the cam 3 can come into contact is swingably supported on a rocker shaft 9 extending parallel to the camshaft 2,
A link arm 20 including two engagement arms 23 and 24 selectively engaged in the two spiral grooves 5 and 7 is displaceable in the rocker shaft length direction,
The two engaging arms 23 and 24 are rotated by the rotating device 40 to engage one engaging arm 23 in one spiral groove 5 or engage the other engaging arm 24 in the other spiral groove 7. By selecting whether to engage or not, the link arm 20 is displaced in the rocker shaft length direction according to the selected helical grooves 5 and 7, and the roller 16 is displaced in the rocker shaft length direction based on this displacement. It switches whether the cam 3 contacts or does not contact.
The roller 16 is positioned so as not to be substantially displaced relative to the rocker shaft 9 in the longitudinal direction of the rocker shaft.
Displacement of the link arm 20 in the rocker shaft length direction displaces the first rocker arm 10 together with the roller 16 in the rocker shaft length direction.
As described above, when the first rocker arm 10 is displaced in the rocker shaft length direction, the rocking motion of the first rocker arm 10 changes depending on whether the cam 3 contacts the roller 16 or not, and the second rocker arm 45 also changes.

Modes in which the cam 3 does not contact the roller 16 include a mode in which no other cam contacts the roller, a mode in which another zero-lift circular cam contacts the roller, and a mode in which another cam with a nose profile contacts the roller. In this embodiment, the cam 4 of another nose profile is in contact with the roller.

The lengthwise direction of the camshaft, the lengthwise direction of the rocker shaft, and the lengthwise direction of the roller shaft are all horizontal directions in FIG. 1 and are the same. Therefore, hereinafter, the direction toward the left in FIG. 1 viewed from the front side is referred to as an axial direction d1, and the direction toward the right is referred to as an axial direction d2. Moreover, left and right refer to left and right in FIG. FIG. 2 seen from the rear side appears left and right opposite to FIG.

[Cam, etc.]
A camshaft 2 is inserted between a cam support 27 of a cylinder head of an internal combustion engine and a cam cap 28 mounted on the cam support 27 with bolts 29 and is rotatably supported. Between the two cam supports 27 spaced apart from each other, the camshaft 2 has a first cam 3 and a second cam 4 as drive cams and a cam rail groove in order from the axial direction d1 side to the axial direction d2 side. The second spiral groove 7, the annular groove 6, the first spiral groove 5, and the first cam 3 and the second cam 4 as driving cams are provided side by side.

The two first cams 3 are composed of a base circle with a circular cross section and a nose projecting from the base circle and having a relatively high lift and a narrow operating angle, and are mainly used in a high speed rotation range.
The two second cams 4 are composed of a base circle with a circular cross section and a relatively low lift and wide working angle nose protruding from the base circle, and are mainly used in the low speed rotation range.

The annular groove 6 is a groove for locking the link arm 20 so that it cannot be displaced in the axial directions d1 and d2, and is an annular groove that does not shift in the axial direction.

The first spiral groove 5 is a groove for displacing the link arm 20 in the axial direction d1, and is provided on the side of the annular groove 6 in the axial direction d2. The first helical groove 5 extends from its base end to a predetermined position in the axial direction d1, d2 in the direction opposite to the rotational direction of the camshaft 2 without deviation. 2, it extends spirally in the axial direction d1 and merges with the annular groove 6. As shown in FIG. This helically extending portion is provided at a phase where the tip of the first engagement arm 23 engages when the first and second cams 3 and 4 act on the base circle.

The second spiral groove 7 is a groove for displacing the link arm 20 in the axial direction d2, and is provided on the side of the annular groove 6 in the axial direction d1. The second spiral groove 7 extends from its base end to a predetermined position in the axial direction d1, d2 in the direction opposite to the rotational direction of the camshaft 2 without deviation. 2, it extends spirally in the axial direction d2 and merges with the annular groove 6. As shown in FIG. This helically extending portion is provided at a phase where the tip of the second engagement arm 24 engages when the first and second cams 3 and 4 perform base circle action.

[First rocker arm]
A rocker shaft 9 extending parallel to the camshaft 2 is inserted through a cam support 27 of the cylinder head. A first rocker arm 10 is supported on the rocker shaft 9 between two cam supports 27 spaced apart from each other so as to be rockable in the rocker shaft circumferential direction and displaceable in axial directions d1 and d2.

The first rocker arm 10 is, as shown in FIG. 3 and the like, a dual first rocker arm in which lower portions of a left rocker arm 11 and a right rocker arm 12 are separated by a connecting portion 13 and connected. Each of the left and right first rocker arms 11 and 12 includes a base portion 14 fitted onto the rocker shaft 9 and supported as described above, a pair of side wall portions 17 and 17 spaced apart in the axial direction, and a pair of side wall portions 17 and 17 . and a bottom portion 18 connecting between the lower portions of 17 . Since the lateral length of the first rocker arm 10 is smaller than the length between the two cam supports 27, the first rocker arm 10 can be displaced between the two cam supports 27 in the axial directions d1 and d2.

Furthermore, each of the left and right first rocker arms 11 and 12 has a roller shaft 15 that spans between the pair of side wall portions 17 and 17, and a needle roller rotatably mounted on the roller shaft 15 in the roller shaft circumferential direction. and a roller 16 attached thereto. The roller 16 has a predetermined clearance (minimum gap for allowing the rotation of the roller 16) between the pair of first opposing surfaces f1, f1 of the pair of side wall portions 17, 17 which face each other in the rocker shaft length direction. It is attached to the roller shaft 15 as described above while being sandwiched between the rollers. Therefore, the roller 16 is positioned so as not to be substantially displaced relative to the rocker arms 11 and 12 in the axial direction of the rocker shaft (roller axial direction), and is displaced along with the rocker arm 10 in the longitudinal direction of the rocker shaft. .

[Second rocker arm]
The second rocker arm 45 is a roller rocker arm, the lengthwise base end of which is supported by a pivot 46, the lengthwise middle portion of which a roller 47 is rotatably attached, and the lengthwise end of which presses the valve V. A pad portion 48 is formed to meet the requirements. Two second rocker arms 45 are provided side by side below the first rocker arm 10 , and the respective rollers 47 are pressed by the lower surface of the rocking first rocker arm 10 . This pressing causes the second rocker arm 45 to swing and press the valve V. As shown in FIG.

As shown in FIG. 6( a ), the center of gravity G of the second rocker arm 45 is below the imaginary tangent line L drawn from the center P of the spherical portion of the pivot 46 to the pad portion 48 and is low. Therefore, when the first rocker arm 10 is displaced in the rocker shaft length direction, the second rocker arm 45 is less likely to move along with it in the rocker shaft length direction, and thus is less likely to fall.
On the other hand, like the second rocker arm 45' of the comparative example shown in FIG. If it is too high, when the first rocker arm 10' is displaced in the rocker shaft length direction, the second rocker arm 45' tends to move along with it in the rocker shaft length direction and fall down.

[Link arm]
As shown in FIG. 3 and the like, the link arm 20 protrudes forward from the tubular base 22 so as to be separated from each other in the axial direction when viewed from the front and form a V shape when viewed from the side. It includes a first engaging arm 23 and a second engaging arm 24 projecting upward.

The cylindrical base portion 22 has a predetermined clearance (allowing rotation of the link arm 20) between a pair of second opposing surfaces f2, f2 of the base portion 14 of the left rocker arm 11 and the base portion 14 of the right rocker arm 12, which face each other in the rocker shaft length direction. It is fitted on the rocker shaft 9 so as to be rotatable in the circumferential direction of the rocker shaft 9 while being sandwiched with a minimum gap between them. Therefore, the link arm 20 is substantially axially undisplaceable with respect to the first rocker arm 10 and axially displaceable together with the first rocker arm 10 and the roller 16 .

The thrust position of the first rocker arm 10 on the axial direction d1 side is determined by the contact of the left side surface of the base portion 14 of the left rocker arm 11 with the side surface of the left cam support 27 (or cam cap 28). The thrust position of 16 on the axial direction d1 side is also determined. In other words, the side surface of the cam support 27 (or the cam cap 28) regulates the displacement end of the first rocker arm 10 in the axial direction d1 in the thrust direction.
The thrust position on the axial direction d2 side of the first rocker arm 10 is determined by the contact of the right side surface of the base portion 14 of the right rocker arm 12 with the side surface of the right cam support 27 (or cam cap 28). The thrust position of 16 on the side of the axial direction d2 is also determined. In other words, the side surface of the cam support 27 (or the cam cap 28) regulates the thrust-direction one-sided heterogeneity of the first rocker arm 10 on the axial direction d2 side.

A plate-like pressed portion 25 is provided on the back surface of the cylindrical base portion 22, and the link arm 20 is rotated by selectively pressing the lower portion or the upper portion of the pressed portion 25 forward by the rotating device 40. move.

The first engagement arm 23 is formed such that its tip can be engaged with the first spiral groove 5 or the annular groove 6 .
The second engaging arm 24 is formed such that its tip can be engaged with the second spiral groove 7 or the annular groove 6 .

[Forcing structure]
The biasing structure 30 biasing the first rocker arm 10 to the thrust position in the axial direction d1 includes a convex latch 33 biased by a plate spring 31 attached to the back surface of the left cam support 27 with a bolt 32. , and a concave catch 34 formed in the base 14 of the left rocker arm 11 into which a convex latch 33 engages.
The biasing structure 30 that biases the first rocker arm 10 to the thrust position in the axial direction d2 includes a convex latch 33 that is biased by a plate spring 31 that is attached to the back surface of the right cam support 27 with a bolt 32. , and a concave catch 34 formed in the base 14 of the right rocker arm 12 into which a convex latch 33 engages.
Each convex latch 33 is formed by deforming the middle portion of the leaf spring 31 , but it may be attached to the leaf spring 31 .

When the first rocker arm 10 is determined at each thrust position in the axial direction d1, d2, each convex latch 33 engages each concave catch 34 to urge the first rocker arm 10 to each thrust position. Since the first rocker arm 10 is held at each thrust position by this urging, even if vibration or external force is applied to the valve mechanism at the timing when neither of the engaging arms 23, 24 engages with the spiral grooves 5, 7, Also, the first rocker arm 10 and the link arm 20 are not displaced to unintended positions.

[Rotation device]
As shown in FIGS. 2 and 4, the rotating device 40 includes a first electromagnetic solenoid 41 for pressing the lower portion of the pressed portion 25 forward to rotate the link arm 20 in the axial direction r1. , and a second electromagnetic solenoid 42 for pushing the upper portion of the pushed portion 25 forward to rotate the link arm 20 in the other axial circumferential direction r2. When each of the electromagnetic solenoids 41 and 42 is turned on, the rod is extended to press the link arm 20, and when turned off, the rod is retracted and the pressing is released.

The variable valve operation of the variable valve mechanism 1 of the embodiment constructed as described above will be described.
[1] When the roller 16 is displaced to the position where the second cam 4 abuts, the second electromagnetic solenoid 42 is turned on to press the upper portion of the pressed portion 25 forward, as indicated by the solid line in FIG. 4(b). Then, the link arm 20 is rotated in the other axial circumferential direction r2. Due to this rotation of the link arm 20 , the tip of the second engaging arm 24 is engaged with the second spiral groove 7 and the tip of the first engaging arm 23 is withdrawn from the annular groove 6 . As described above, the helically extending portion of the second helical groove 7 is in a phase where the second engaging arm 24 engages during the base circle action, so as shown in FIGS. , the link arm 20 is displaced along the second spiral groove 7 along the second spiral groove 7 in the other axial direction d2 as the camshaft 2 rotates, and pushes the first rocker arm 10 and the roller 16 to displace them in the same way. As a result, the two rollers 16 are displaced to a position where the two second cams 4 abut (and the first cam 3 does not abut), and the second engagement arm 24 enters the annular groove 6 so that the link arm 20 lateral positions are retained. Further, as described above, the thrust position of the first rocker arm 10 is determined by the contact between the first rocker arm 10 and the cam support 27, and the biasing structure 30 biases the first rocker arm 10 to the thrust position.

Then, the roller 16 is pressed by the second cam 4, the first rocker arm 10 swings, the second rocker arm 45 swings, and the two valves V are simultaneously lifted with a low lift and a wide operating angle. This valve mode is mainly used in the low speed range.

[2] When the roller 16 is displaced to the position where the first cam 3 abuts The first electromagnetic solenoid 41 is turned on to press the lower portion of the pressed portion 25 forward, and the two-dot chain line in FIG. As shown, the link arm 20 is rotated in one axial circumferential direction r1. Due to this rotation of the link arm 20 , the tip of the first engagement arm 23 is engaged with the first spiral groove 5 and the tip of the second engagement arm 24 is withdrawn from the annular groove 6 . As described above, the spirally extending portion of the first spiral groove 5 is in a phase in which the first engagement arm 23 engages during the base circle action. As the shaft 2 rotates, it is displaced along the first spiral groove 5 in one axial direction d1 during base circle action, pushing the first rocker arm 10 and the roller 16 to displace them in the same way. As a result, the two rollers 16 are displaced to a position where the two first cams 3 abut (and the second cam 4 does not abut), and the first engagement arm 23 enters the annular groove 6 so that the link arm 20 lateral positions are retained. Further, as described above, the thrust position of the first rocker arm 10 is determined by the contact between the first rocker arm 10 and the cam support 27, and the biasing structure 30 biases the first rocker arm 10 to the thrust position.

Then, the roller 16 is pressed by the first cam 3 to swing the first rocker arm 10, the second rocker arm 45 swings, and the two valves V are simultaneously lifted with a high lift and a narrow operating angle. This valve operating mode is mainly used in the high speed range.

According to this embodiment, the following effects are obtained.
(a) The thrust positions of the first rocker arm 10 and the roller 16 are controlled by a small number of members (the first rocker arm 10 itself and the cam support 27 or the cam cap 28) other than the spiral grooves 5 and 7 and the engagement arms 23 and 24. As a result, the durability of the spiral grooves 5, 7 and the engagement arms 23, 24 is increased, and the number of these members is small, so that the precision of the thrust position can be improved and the variation can be reduced. In addition, the fact that the number of the same members is small also makes it possible to reduce the cost by alleviating the tolerance reduction of the same members.
(a) It is possible to prevent the link arm 20 from being displaced to an unintended position at the timing when neither of the two engagement arms 23, 24 engages with the spiral grooves 5, 7.
(c) The structure is simplified because there is no need to displace the roller guide that holds the side of the roller (which is a separate part from the first rocker arm) in the axial direction together with the link arm as in the conventional example. do.
(d) The roller shaft 15 provided on the first rocker arm 10 can be shortened to substantially the same width as the roller width. When the roller shaft 15 is short in this manner, the deflection of the roller shaft 15 is small when a load is input to the roller 16, so that the rigidity of the mechanism is improved.
(e) Since the center of gravity G of the second rocker arm 45 is lower than the imaginary tangent line L drawn from the center P of the spherical portion of the pivot 46 to the pad portion 48, when the first rocker arm 10 is displaced in the rocker shaft length direction, The second rocker arm 45 is less likely to fall.

It should be noted that the present invention is not limited to the above-described embodiments, and can be modified and embodied without departing from the gist of the invention, for example, as follows.
(1) Use one first cam 3 and one second cam 4, and one roller 16;
(2) The number of rollers included in the first rocker arm 10 may be one or more, but preferably two on the left and right in terms of left-right balance.
(3) The rotating device is not particularly limited, and other than the electromagnetic solenoid, a hydraulic mechanism, an electric motor mechanism, or the like can be exemplified.

1 Variable Valve Mechanism 2 Camshaft 3 First Cam 4 Second Cam 5 First Spiral Groove 6 Annular Groove 7 Second Spiral Groove 9 Rocker Shaft 10 First Rocker Arm 11 Left Rocker Arm 12 Right Rocker Arm 13 Connecting Part 14 Base 15 Roller Shaft 16 Roller 17 Side wall 18 Bottom 20 Link arm 22 Cylindrical base 23 First engaging arm 24 Second engaging arm 25 Pressed portion 45 Second rocker arm 46 Pivot 47 Roller 48 Pad G Center of gravity of second rocker arm L Virtual tangent line P pivot sphere center V valve

Claims (1)

a first rocker arm (10) provided below the cam (3) and rocking when pressed by the cam (3);
a second rocker arm (10) provided below the first rocker arm (10) and rocking by being pressed by the first rocker arm (10);
A base end of the first rocker arm (10) is supported by a rocker shaft (9) so as to be displaceable in the rocker shaft longitudinal direction,
The proximal end of the second rocker arm (45) is supported by a pivot (46), and the distal end of the second rocker arm (45) is provided with a pad (48) for pressing the valve (V),
A variable valve mechanism in which when the first rocker arm (10) is displaced in the rocker shaft length direction, the rocking movement of the first rocker arm (10) changes and the rocking movement of the second rocker arm (45) also changes,
An internal combustion engine characterized in that the center of gravity (G) of the second rocker arm (45) is below an imaginary tangent line (L) drawn from the center (P) of the spherical portion of the pivot (46) to the pad portion (48). Variable valve mechanism.

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