JPH11324625A - Variable valve system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate restart of an internal combustion engine. SOLUTION: On the basis of a maximum lift position H, an 0-lift position L is set to a rod shaped link 17, and an intermediate lift position M is set to a ring shaped link 13, and a return spring 24 for energizing a control shaft 14 toward from the 0-lift position L to the intermediate lift position M. The control shaft 14 is moved to the intermediate lift position M by the return spring 24 even being every positions between the 0-lift position L and the intermediate lift position M when an actuator is released, and thereby a valve drops into an opening condition. It is thus possible to facilitate restart of an internal combustion engine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve mechanism for an internal combustion engine that can change valve timing and valve lift of intake and exhaust valves according to operating conditions of the internal combustion engine.

[0002]

2. Description of the Related Art A variable valve mechanism is known as a valve mechanism for an internal combustion engine.

The variable valve mechanism controls the valve timing (opening / closing timing) and the valve lift amount of the intake valve and the exhaust valve according to the operating conditions of the internal combustion engine. An improved and stable drivability is realized, and at the time of high speed and high load, the charging efficiency of the intake air is improved to secure a sufficient output.

FIG. 12 shows a conventional example,
The outline of the variable valve mechanism described in Japanese Patent No. 37305 is shown.

The variable valve mechanism shown in FIG. 1 has a camshaft 2 disposed substantially above the center of an upper deck of a cylinder head 1 and a cam 2a fixed to an outer peripheral surface of the camshaft 2. I have. A control shaft 3 is disposed obliquely above the camshaft 2 in parallel with the camshaft 2, and a rocker arm 5 is pivotally supported on the control shaft 3 via an eccentric cam 4. The above-described cam 2a is in contact with one end 5a of the rocker arm 5.

On the other hand, the above-mentioned cylinder head 1 is provided with an intake valve 6 slidably in the vertical direction.
Is urged upward by a valve spring 6c via a half-collet 6a and an upper retainer 6b attached to the upper end of the stem. These intake valves 6,
For the upper retainer 6b, the valve spring 6c, etc.,
A valve lifter 7 is mounted.

A swing cam 8 is provided above the valve lifter 7.
Are arranged. The swing cam 8 is swingably supported by a support shaft 9 arranged in parallel with the camshaft 2, and a cam surface 8 a at a lower end thereof is brought into contact with an upper surface of the valve lifter 7. Also, the upper end surface 8b of the swing cam 8
Is urged upward by a spring 10 so that one end 5
a is always in contact with the other end 5b of the rocker arm 5 which is in contact with the cam 2a.

In the variable valve mechanism having the above structure, the lift of the cam 2a is transmitted to the intake valve 6 via one end 5a and the other end 5b of the rocker arm 5, the swing cam 8, and the valve lifter 7. Is done.

The rotation of the control shaft 3 is controlled in a predetermined angle range by an actuator (not shown). By this rotation control, the center position of the eccentric cam 4 is controlled, so that the rocking fulcrum of the rocker arm 5 changes.

[0010] When the eccentric cam 4 is controlled to a predetermined forward / reverse rotation position, the rocking fulcrum of the rocker arm 5 changes.
As a result, the contact position of the cam surface 8a of the swing cam 8 with the upper surface of the valve lifter 7 changes, and the swing trajectory of the swing cam 8 changes, whereby the valve timing and valve lift of the intake valve 6 are variably controlled. It is supposed to.

[0011]

However, according to the above-described conventional variable valve mechanism, when the actuator is disengaged (for example, when the internal combustion engine is stopped or the actuator is out of order), the spring spring of the valve spring 6c is disengaged. The force generates a force that pushes the valve lifter 7 upward, and this force is transmitted to the eccentric cam 4 via the swinging cam 8 and the rocker arm 5, and the valve lift of the eccentric cam 4 is minimized. It will be urged to the turning position (upward in FIG. 12). For this reason, if a setting is made to include 0 lift (valve stop) in the variable range of the valve lift of the intake valve 6 due to performance requirements of the internal combustion engine, the intake valve 6 will be in the 0 lift state when the actuator is released. As a result, the internal combustion engine cannot be restarted because intake is impossible.

In this variable valve mechanism, the rocker arm 5 is connected to the eccentric cam 4 in the maximum valve lift state generally used in the maximum rotation speed range of the internal combustion engine where the rotational moment of inertia of the swing cam 8 is maximized. Since the design is not made in consideration of the relationship between the direction of the force vector to be applied and the rotational position of the eccentric cam 4, the eccentric cam 4 is not used in the maximum rotational speed range of the internal combustion engine where the eccentric cam 4 receives the maximum force. There has been a problem that the torque required to maintain the predetermined rotation position becomes excessive.

The present invention can solve the above-mentioned problem, that is, a variable valve mechanism in which the restart of the internal combustion engine is easy and the required torque for holding the eccentric cam in a predetermined rotation position is small. The purpose is to provide.

Further, the above-mentioned conventional example has the following disadvantages.

A cam 2a (see FIG. 12) and an oscillating cam 8 are provided on the camshaft 2 and the support shaft 9, respectively, and are individually located at positions greatly separated in the width direction of the internal combustion engine (the left-right direction in FIG. 12). Are located in Therefore, these cams 2
a and a large arrangement space for the oscillating cam 8 is required.

Since the cam 2a and the oscillating cam 8 are largely separated from each other in the width direction of the internal combustion engine, both ends 5a and 5b of the rocker arm 5 necessarily extend substantially in the width direction of the internal combustion engine. I have to get them out. Therefore, the mountability of the variable valve mechanism to the internal combustion engine is deteriorated and the weight is increased due to the increase in the size of the rocker arm 5 combined with the increase in the arrangement space.

Since the support shaft 9 is required in addition to the camshaft 2, the number of parts is increased and the camshaft 2 is increased.
The axial center of the shaft 9 and the support shaft 9 are likely to be displaced from each other, which may reduce the control accuracy of the valve timing.

Since the end 5b of the rocker arm 5 is configured to obtain the swing of the swing cam 8 by pressing the swing cam 8, the pressing point (contact position) of the rocker arm 5 is set to the swing cam 8 There is a risk of leaving from. Therefore, the position of the rocking fulcrum of the rocker arm 5 is restricted, and the rocking cam 8
, And therefore the valve timing and valve lift of the intake valve 6 cannot be set relatively large.

It is a second object of the present invention to provide a variable valve mechanism that has solved these disadvantages.

[0020]

According to a first aspect of the present invention, there is provided a camshaft rotatably driven by a crankshaft of an internal combustion engine, and a rotary cam fixed to an outer peripheral surface of the camshaft. A control shaft disposed substantially parallel to the camshaft, a control cam integral with the control shaft, a rocker arm supported swingably by the control cam, and swingable by the camshaft. A supported swinging cam, a ring-shaped link rotatably fitted to the rotating cam and connecting the rotating cam to one end of the rocker arm, and the other end of the rocker arm and the swinging cam. And an actuator for rotating the control shaft within a predetermined angle range, and an actuator for operating the internal combustion engine. Control means for controlling the driving according to the rotation of the camshaft, transmitting the rotation of the camshaft to the rocking cam as a rocking motion via the rotating cam, the ring-shaped link, the rocker arm, and the rod-shaped link. In a variable valve mechanism for an internal combustion engine, a valve is opened and closed and a swing angle of the swing cam is changed by rotation of the control cam accompanying rotation of the control shaft by the control means. Lift position stopper for stopping the control shaft at a zero lift position provided at one end of the rotation range, and a medium lift position for stopping the rotation of the control shaft at a medium lift position provided at the other end of the rotation range A stopper, provided between the zero lift position and the middle lift position within a rotation range of the control shaft. The control shaft is biased from the zero lift position to the middle lift position via a maximum lift position set on or near a line connecting the center of the control shaft and the center of the camshaft. A first urging member.

According to a second aspect of the present invention, in the first aspect of the invention, based on the maximum lift position, the zero lift position is set on the rod-like link side, and the middle lift position is on the ring-like link side. It is characterized by being set.

According to a third aspect of the present invention, in the first or second aspect of the present invention, l ₀ , l ₁ , l ₂ , l ₃ , l
₄ , l ₅ , l ₆ , θ ₃₄ , l ₀ : the length of a line connecting the center of the control cam and the center of the camshaft, l ₁ : the center of the camshaft and the center of the rotary cam line length connecting, l _2: the said ring-shaped links: the center of the rotating cam, the line length connecting the center of the connecting portion between the one end portion of the rocker arm and the ring-shaped link, l ₃ The length of a line connecting the center of the connecting portion with the one end of the rocker arm and the center of the control cam; l ₄ : the center of the control cam, the other end of the rocker arm and the rod-shaped link line length connecting the center of the connecting portion, l _5: center of the connecting portion of the center of the connection portion between the rod-shaped link and the other end of the rocker arm, and the swing cam and the rod-like link line length connecting the bets, l _6: the swing cam and the rod-like link And the center of the connecting portion of the line segment length connecting the center of the cam shaft, theta _34: when said l ₃ included angle between the l _4, and, these values, l ₄ sin ^{_{[cos -1 {l 0 2 +}} l 1 2 + l 2 2 -l 3 2 -2l 1 l 2} / {2l 0 (l 1 + l 2)}] = l 3 sin [θ 4 + cos -1 {(l 4 −l ₀ cos θ ₄ ) / √ (l ₀ ² + l ₄ ² -2 l ₀ l ₄ cos θ ₄ ) ＋ + cos ^-1 ｛l ₀ ² + l ₄ ² + l ₅ ² -l ₆ ² -2l ₀ l ₄ cos θ ₄ ｛/ ｛2l ₅ ｌ (l ₀ ² + l ₄ ² -2l ₀ l ₄ cos θ ₄ )｝] (1) where θ ₄ = θ ₃₄ −cos ⁻¹ ｛(l ₀ ² −l ₁ ²⁻ l ₂ ² + l ₃ ² −2l ₁ l ₂ ) / (2l ₀ l ₃ )}.

[0023] The invention of claim 4 is the invention of claim 1, 2, or 3.
In the invention, a second biasing member that biases the control shaft toward the maximum lift position is provided only when the control shaft is located on the zero lift position side from the maximum lift position. Features.

[0024]

According to the first aspect of the present invention, the control shaft can be moved to any position between the zero lift position and the middle lift position when the actuator is released, for example, when the internal combustion engine stops or the actuator fails. Even if there is,
The control shaft is arranged in the middle lift position by the first biasing member, that is, the valve lift is enabled, so that the internal combustion engine can be restarted.

According to the second aspect of the present invention, since the zero lift position and the middle lift position are set on the rod-like link side and the ring-like link side, respectively, based on the maximum lift position, the control shaft rotation angle change is prevented. Valve lift sensitive areas can be avoided.

According to the third aspect of the present invention, l ₀ to l ₆ , θ
₃₄ constitutes a link geometry that substantially satisfies the above-mentioned equation (1), so that the control shaft holding torque can be reduced at the time of the lift peak at the time of the maximum lift at which the maximum load acts on the control shaft.

According to the fourth aspect of the present invention, by providing the second urging member, the urging members (first and second urging members) of the control shaft from the zero lift position to the maximum lift position are provided. Improvement of the reaction force and reduction of the reaction force of the urging member (first urging member) in the normal operation state (between the middle lift position and the maximum lift position), and the load on the actuator in the normal operation state Reduction can be achieved at the same time.

[0028]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a diagram showing a schematic configuration of a variable valve mechanism according to the present embodiment. In this figure, since the position of each member in the front and back direction in the figure is not considered, all parts which are actually hidden by other members and cannot be seen are shown by solid lines.

The variable valve mechanism comprises the following members 11 to 24 as main constituent members. The following members are the camshaft 11 and the rotating cam 1 shown in FIG.
2, ring-shaped link 13, control shaft 14,
Control cam 15, rocker arm 16, rod-shaped link 1
7, swing cam 18, valve 19, actuator 20 shown in FIG. 10, control means 21, 0 lift position stopper 2
2. Middle lift position stopper 23, first biasing member 24
It is. The details will be described below in order.

The camshaft 11, as shown in FIG.
It is arranged with its longitudinal direction facing front and back in FIG. 1, and is rotationally driven by rotation of a crankshaft (both not shown) of the internal combustion engine. Center of the cam shaft 11 (the axial center) and c _1.

The rotating cam 12 is provided with the camshaft 11 described above.
The center c ₂ of the cam shaft 11
Fixed with offset from ₁ . Rotating cam 12, with the rotation of the cam shaft 11, and rotates with the eccentric about the center c ₁ of the cam shaft 11.

The ring-shaped link 13 is connected to the rotary cam 1 described above.
2 is a member for connecting the rocker arm 16 to a rocker arm 16 described later. The ring-shaped link 13 has a large diameter portion 13a and a small diameter portion 13a.
b, and the large-diameter portion 13a is
And the small diameter portion 13b is rotatably connected to one end 16a of the rocker arm 16. The ring-shaped link 13 transmits the eccentric rotation of the rotary cam 12 to the rocker arm 16 as a swinging motion. Small-diameter portion 1 of ring-shaped link 13
Center of the connecting portion between 3b and one end 16a of the rocker arm 16 (rotation center) and c _3. In addition, the ring-shaped link 1
Center of the large diameter portion 13a of the 3 coincides with the center c ₂ of the above-described rotary cam 12.

The control shaft 14 is disposed substantially parallel to the camshaft 11 described above. The center (axial center) of the control shaft 14 is defined as 14a. The rotation range and the like of the control shaft 14 will be described later in detail.

The control cam 15 is formed integrally with the control shaft 14 described above. Center c ₄ of the control cam 15 is offset from the center 14a of the control shaft 14. As will be described later, the control cam 15 rotates the control shaft 14 so that the center c ₄ is adjusted to the center 14 a of the control shaft 14 in accordance with the rotation angle.
It moves around the center. Coincides with the swing center of the rocker arm 16 to the center c ₄ of the control cam 15 is described below.

The rocker arm 16 is connected to the control cam 1 described above.
5 swingably supported. The small-diameter portion 13b of the above-mentioned ring-shaped link 13 is rotatably connected to one end 16a of the rocker arm 16, and the upper end 17a of a rod-shaped link 17 described later is turned to the other end. It is movably connected. The center of the connecting portion between the upper end 17a of the distal end portion 16b and the rod-shaped link 17 of the rocker arm 16 and c _5. The rocker arm 16 has one end 1 at the center c ₄ of the control cam 15 described above as a swing center.
6a and the other end 16b swing substantially up and down. The swing center at this time is moved by the rotation of the control shaft 14 described above. That is, when the center c ₄ of the control cam 15 is moved by the rotation of the control shaft 14, the moved point becomes the swing center of the rocker arm 16. By moving the rocking center of the rocker arm 16, the valve timing and the valve lift of the intake valve 19 are changed.

The rod-shaped link 17 connects the rocker arm 16 described above and a swing cam 18 described later. The rod-shaped link 17 is disposed substantially vertically, and connects the upper end 17a to the other end 16b of the rocker arm 16 so as to be freely rotatable, while swinging the lower end 17b as described below. The cam 18 is rotatably connected to a lower end 18b. The rod-shaped link 17 transmits the rocking motion of the rocker arm 16 as the rocking motion of the rocking cam 18.

The oscillating cam 18 is connected to the camshaft 11 described above.
And a valve lifter 19 a fitted to the valve 19. The swing cam 18 has an upper end portion 18.
a is fitted to the outer periphery of the camshaft 11 and supported swingably, and the lower end portion 17b of the rod-shaped link 17 is rotatably connected to the lower end portion 18b. The center of the connecting portion and c _6. Swing center of the swing cam 18 coincides with the center c ₁ of the cam shaft 11 described above. The swing cam 18 has a cam surface 18c formed at a lower end thereof in contact with an upper surface 19b of a valve lifter 19a. Swing cam 18 to the center c ₁ of the upper portion 18a, a lower end portion 18b is swung by a rod-like link 17 described above. Thereby, the valve 19 is moved up and down via the valve lifter 19a.

The structure for urging the valve 19 upward is the same as that of the conventional example shown in FIG. 12, and the description thereof will not be repeated.

As shown in FIG. 10, the actuator 20 is connected to one end of the control shaft 14 and rotates the control shaft 14 within a predetermined angle range. As the actuator 20, for example, a rotary hydraulic actuator or a stepping motor that rotates by a rotation angle proportional to the number of pulses of the operation signal can be used.

The control means 21 includes the above-described actuator 2
Connected to 0. The control means 21 controls the rotation angle of the control shaft 14 by controlling the rotation angle of the actuator 20 according to the operating state of the internal combustion engine (for example, at low speed and low load, at high speed and high load, etc.). The center c ₄ of the control cam 15 integrated with the control shaft 14, that is, the swing center of the rocker arm 16 is moved.

The zero lift position stopper 22 contacts an engagement member 25 protruding from the outer peripheral surface of the control shaft 14 to regulate one rotation limit of the control shaft 14. Zero lift position stopper 22
When the engagement member 25 comes into contact therewith, the valve 1
9 is set at a position where the valve lift amount (maximum lift amount) becomes zero.

The middle lift position stopper 23 abuts on the engaging member 25 of the control shaft 14 to regulate the other rotation limit of the control shaft 14. The middle lift position stopper 23 is set at a position where the valve lift amount (maximum lift amount) of the valve 19 is approximately halfway between 0 and the maximum when the engagement member 25 comes into contact therewith. In the present embodiment, the control shaft 14 is connected to the zero lift position L (FIG. 2) regulated by the zero lift position stopper 22 described above.
) And a middle lift position M regulated by the middle lift position stopper 23. The maximum lift position H at which the valve lift amount becomes the maximum at a predetermined position therebetween can be rotated in both forward and reverse directions. Is set.

The return spring 24 as the first biasing member is
For example, a return spring constituted by a torsion spring is used to move the control shaft 14 from the zero lift position L to the middle lift position M via the maximum lift position H.
It is urging toward. The spring force of the return spring 24 is set such that, when the actuator 20 is pulled out, the control shaft 14 is rotated to any position between the zero lift position L and the middle lift position M regardless of whether the control shaft 14 has been rotated to the middle lift position. M is set so that it can be moved to M.

According to the above-described embodiment, the rotary cam 1
2 is also used as a shaft for swingably supporting the swing cam 18, so that the arrangement space of the entire apparatus is reduced, the mountability on the engine is improved, and the valve timing is improved. Control accuracy is improved. The large diameter portion 13a of the ring-shaped link 13 is loosely fitted on the outer peripheral surface of the rotary cam 12, and the rocker arm 16
By connecting the swing cam 18 and the swing cam 18 with the rod-shaped link 17 as shown in FIG. 1, even if the valve timing and the valve lift amount are set relatively large, the swing cam 18 may come off. There is no. That is, it is possible to solve the above-mentioned problems described as the disadvantages of the conventional example shown in FIG.

Next, the features of the present embodiment will be described in detail with reference to FIG.

As described above, the control shaft 14 integrated with the control cam 15 is provided with the zero lift position stopper 22.
With the middle lift position stopper 23, both ends of the rotation range, that is, the 0 lift position L and the middle lift position M are set, and it is possible to rotate between them. In the meantime, the maximum lift position H is set. In other words, as the control shaft 14 rotates, the center c ₄ of the control cam 15, that is, the swing center of the rocker arm 16 moves from the zero lift position L to the middle lift position M around the center 14 a of the control shaft 14. The maximum lift position H is set between the 0 lift position L and the middle lift position M. In the present embodiment, the maximum lift position H is the center 14a of the control shaft 14, so as to position on a straight line or near the line connecting the center c ₁ of the cam shaft 11.

As described above, in the present embodiment,
Based on the maximum lift position H, a zero lift position L is set on the rod-like link 17 side.
The middle lift position M is set on the side.

The return spring 24 as the first biasing member acts to return the control shaft 14 from the zero lift position L to the middle lift position M when the actuator 20 is released.

Further, in this embodiment, in addition to these,
Thus, as shown in FIG.
15 center c_Four And the center c of the camshaft 11₁ Connect with
Line segment length is l₀ The center c of the camshaft 11₁ And ring
Center of the large diameter portion 13a of the link 13 (in the rotating cam 12)
Heart) c_Two L is the length of the line segment connecting₁ , Ring-shaped link 13
Center c of large diameter portion 13a_Two And connecting part (ring-shaped link 1
3 and one end 16a of the rocker arm 16
Center of connection c)_Three L is the length of the line segment connecting_Two ,Linking
Center of part c_Three And the center c of the control cam 15_Four Line segment connecting
L_Three The center c of the control cam 15_Four And connecting part (locker
The other end 16b of the arm 16 and the upper end of the rod-like link 17
Center c of the connecting portion with the portion 17a)_Five L is the length of the line segment connecting
_Four , The center of the connecting part c_Five And the connecting portion (of the rod-shaped link 17)
Connection between lower end 17b and lower end 18b of swing cam 18
Part) center c₆ L is the length of the line segment connecting_Five , The center of the connection
c₆And the center c of the camshaft 11₁ The length of the line segment connecting
l₆ And l above_Three And l_Four Is the included angle between₃₄When
When these₀ , L₁ , L_Two , L_Three , L_Four , L
_Five , L₆ , Θ₃₄Satisfies the above equation (1).
It is set to form link geometry.
Equation (1) is expressed as follows based on FIG.
Led.

First, at the time of the maximum lift, the vector A in FIG.
A resultant force vector B is examined link length for facing the center c ₁ of the cam shaft 11.

[0052] triangle for _{^{l 3 2 = l 0 2 +}} (l 1 + l 2) 2 -2l 0 (l 1 + l 2) cos θ 1 θ 1 = cos -1 [(l 0 2 + l 1 2 + l 2 2 + l ₃ ² -2l ₁ l ₂ ) / 2l ₀ (l ₁ + l ₂ )] l ₄ sin θ ₁ = l ₄ sin [cos ^-1 ｛(l ₀ ² + l ₁ ² + l ₂ ² + l ₃ ² -2 l ₁ l _2] ) / 2 l ₀ (l ₁ + l ₂ )}] (2) This is proportional to the absolute value of the x component of the vector A.

[0053] As for the triangle ^{_{(l 1 + l 2) 2}} = l 3 2 + l 0 2 -2l 3 l 0 cos θ 3 θ 3 = cos -1 {(l 3 2 + l 0 2 -l 1 2 -l 2 2 _{-2l 1 l 2) / 2l 0} l 3)} Therefore ^{_{θ 4 = θ 34 -cos -1 {}} (l 3 2 + l 0 2 -l 1 2 -l 2 2 -2l 1 l 2) / 2l 0 l 3 )} ... (3) The _{^{l 2 = l 4 2 + l}} 0 2 -2l 0 l 4 cos θ 4 ... (4) l = √ (l 4 2 + l 0 2 -2l 0 l 4 cos θ 4 from triangles) ... (5) Furthermore _{^{l 0 2 = l 4 2 +}} l 2 -2ll 4 cos θ ₅ above equation (4), when (5) by substituting _{organize, cos θ 5 = (l 4} -l 0 cos θ 4) / √ (l ₄ ² + l ₀ ² -2 l ₀ l ₄ cos θ ₄ ) θ ₅ = cos ^-1 ｛(l ₄ -l ₀ cos θ ₄ ) / √ (l ₄ ² + l ₀ ² -2l ₀ l ₄ cos θ ₄ )｝ (6) From the triangle, l ₆ ² = l ₅ ² + l ² -2ll ₅ cos θ ₅ ′ Substituting (4) and (5) into the above equation Cos θ ₅ ′ = (l ₄ ² + l ₅ ² + l ₀ ² −l ₆ ² −2l ₀ l ₄ cos θ ₄ ) / 2 l ₅ √ (l ₄ ² + l ₀ ² −2l ₀ l ₄ cos θ _{4 ^{) θ 5 '= cos -1 {}} (l 4 2 + l 5 2 + l 0 2 -l 6 2 -2l 0 l 4 cos θ 4) / 2l 5 √ (l 4 2 + l 0 2 -2l 0 l 4 cos θ ₄ )｝ (7) Therefore, from (3), (6) and (7), l ₃ sin φ = l ₃ sin {π- (θ ₄ + θ ₅ + θ ₅ ')} = l ₃ sin (θ _{4 + θ 5 + θ 5 ')} = l 3 sin [θ 4 + cos -1 {(l 4 -l 0 cos θ 4) / √ (l 4 2 + l 0 2 -2l 0 l 4 cos θ 4)} + cos -1 { _{^{(l 4 2 + l 5 2}} + l 0 2 -l 6 2 -2l 0 l 4 cos θ 4) / 2l 5 √ (l 4 2 + l 0 2 -2l 0 l 4 cos θ 4)}] ... (8) which Is proportional to the x component absolute value of the vector B.

[0054] at maximum lift, the resultant force acting on the control shaft 14 through the rocker arm 16 faces the vicinity of the center c ₁ of the cam shaft 11, to be a link geometry which satisfies (2) = (8) is necessary.
That is, it is sufficient that the above-described expression (1) is satisfied.

Next, the characteristic operation of the variable valve mechanism according to the present embodiment will be described.

The zero lift position L and the middle lift position M are set with the maximum lift position H interposed therebetween, and the control shaft 1 moves in the direction from the zero lift position L to the middle lift position M.
Since the return spring 24 for rotating the actuator ₄ is provided, the center c ₄ of the control cam 15 is set when the actuator 20 is pulled out when the internal combustion engine is stopped or the actuator 20 is out of order.
Regardless of the position, it is moved to the middle lift position M. Thus, when the actuator 20 is released, a valve lift that allows the internal combustion engine to be restarted can be ensured.

The 0-lift position L side from the maximum lift position H is used only when the 0-lift and the minimal lift are performed. Further, the middle lift position M side with respect to the maximum lift position H is used as a normal operation area (normal operation use area). Thus, with the maximum lift position H as a boundary,
By dividing the region to be used, a region where the valve lift is sensitive to a change in the control shaft rotation angle as shown in FIG. 3 can be avoided. The reason why such a valve lift sensitive region exists is that, as shown in FIG. 4, when the center c ₄ of the control cam 15 moves in the direction of arrow A, the center c ₄ and the center c ₁ of the cam shaft 11 move. Y
The axial distance increases to reduce the lift, but in the X-axis direction, the entire variable valve mechanism
Rotating clockwise around the center c1 of ₁ to increase the lift, the effect of reducing the lift in the Y-axis direction is reduced to the effect of the lift expansion in the X-axis direction. The lift amount can be controlled. On the other hand, the control cam 1
When the center c ₄ moves, the distance between the center c ₄ and the center c ₁ of the camshaft 11 in the Y-axis direction increases and acts to reduce the lift, and in addition, the variable valve mechanism in the X-axis direction. Since the whole is rotated counterclockwise around the center c ₁ of the camshaft 11 so as to further reduce the lift, the lift reduction effect in the X-axis direction is added to the lift reduction effect in the Y-axis direction. This is because the valve lift amount for a change in the shaft rotation angle becomes too large.

When the center c ₄ of the control cam 15 is on the middle lift position M side, it is on the return side of the return spring 24 and the return spring force is reduced. In the middle lift position M, the center c ₄ of the control cam 15 is reliably moved to the middle lift position M by the valve spring reaction force.

Further, as shown in FIGS. 5 (a), 5 (b) and 5 (c), in the variable valve mechanism of this embodiment, as the lift is enlarged, the rotation of the swing cam 18 at the lift peak is increased. The angular acceleration increases dramatically. Particularly, in the maximum lift position state, since the internal combustion engine is used at the maximum rotation, the load due to the rotational inertia moment of the swing cam 18 becomes very large, and the holding torque of the control shaft 14 becomes too large.

However, the center c _{1 of the} camshaft 11 is almost equal.
Since the center c ₄ of the control cam 15 across the direction of movement to the left and right, the maximum lift direction is necessarily substantially camshaft 11
The center c ₁ becomes direction, as further described above in equation (1) is almost _{satisfied, l 0, l 1, l} 2, l 3, l 4, l 5
, L ₆ , θ _34, the maximum lift at which the center c ₄ of the control cam 15 is substantially oriented in the direction of the center c _{1 of the} camshaft 11 as shown in FIG. , The absolute value of the X component of the force vector A exerted on the rocker arm 16 by the rod-shaped link 17 and the ring-shaped link 13
And the X component absolute value of the force vector B acting on
The resultant of the force vector A and the force vector B acting on the control shaft 14 is directed toward the center c ₁ of the camshaft 11. Accordingly, as shown in the present embodiment of FIG. 7A, unlike the reference example of FIG. 7B, when the input to the control shaft 14 is maximized, the arm R of the rotational moment can be eliminated. Therefore, the holding torque required for the control shaft 14 can be reduced as shown in FIG.

[Second Embodiment] The present embodiment shown in FIG. 9 will be described mainly with respect to portions different from the above-described first embodiment.

In addition to the return spring 24 for moving the control shaft 14 from the zero lift position L to the middle lift position M, the center c ₄ of the control cam 15 is shifted from the maximum lift position H to zero.
A return spring (for example, a toe) serving as a second urging member that generates a spring reaction force and urges the control shaft 14 in a direction from the zero lift position L to the maximum lift position H only when it is located on the lift position L side. (Shanal spring) 26. For example, when the center c ₄ of the control cam 15 exists between the 0 lift position L and the maximum lift position H,
As shown in 1, since the arm 26a of the return spring 26 returns in contact with the spring stopper 27, the return spring 26 is to generate a spring reaction force, said a medium lift position M is the center c ₄ of the control cam 15 When present between the maximum lift position H and the natural angle (or natural length) of the return spring 26, the arm 26a of the return spring 26
Without contact, the return spring 26 does not generate a spring reaction force.

The center c ₄ of the control cam 15 is at the zero lift position L
And the maximum lift position H, the control shaft 14 is reliably returned by overcoming the reaction force of the valve spring by using two return springs 24 and 26, while the normal operation state is used. When the center c ₄ of the control cam 15 exists between the middle lift position M and the maximum lift position H, the control shaft 14 is returned by the return spring 24 and the reaction force of the valve spring. This allows
The return spring reaction force of the control shaft 14 from the zero lift position L to the maximum lift position H is improved, and the return spring reaction force in a normal operation state (between the middle lift position M and the maximum lift position H) is reduced. It is possible to achieve both the reduction and the load on the actuator 20.

[Brief description of the drawings]

FIG. 1 is a view showing a variable valve mechanism according to a first embodiment of the present invention.

FIG. 2 shows a zero lift position L, a middle lift position M, a maximum lift position H, a center of a control cam (a rocking center of a rocker arm), a center of a cam shaft, and a first lift position in the first embodiment.
FIG. 5 is a diagram showing a positional relationship of a biasing member (return spring) and the like.

FIG. 3 is a diagram showing a valve lift change characteristic with respect to a control shaft rotation angle in the first embodiment.

FIG. 4 is a qualitative explanatory diagram of FIG. 3;

FIGS. 5A, 5B, and 5C are diagrams illustrating the swing characteristics of the swing cam according to the first embodiment.

FIGS. 6A and 6B are diagrams illustrating a link geometry according to the first embodiment.

FIG. 7A is a diagram illustrating a control shaft holding torque reducing effect according to the first embodiment. (B)
3A is a diagram showing a comparative example of FIG.

FIG. 8 is a diagram showing a calculation result of a control shaft holding torque in the first embodiment.

FIG. 9 shows a zero lift position L, a medium lift position M, a maximum lift position H, a center of a control cam (a rocking center of a rocker arm), a center of a cam shaft, and a first lift position in the second embodiment.
Urging member (return spring), second urging member (return spring)
FIG.

FIG. 10 is a perspective view showing a configuration of a zero lift position stopper, a middle lift position stopper, a first urging member (return spring), and the like in the first embodiment.

FIG. 11 is a perspective view showing a configuration of a zero lift position stopper, a middle lift position stopper, a first urging member (return spring), a second urging member (return spring), and the like in the second embodiment. .

FIG. 12 is a view showing a conventional variable valve mechanism.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Camshaft 12 ... Rotating cam 13 ... Ring link 14 ... Control shaft 14a ... Center of control shaft 15 ... Control cam 16 ... Rocker arm 17 ... Rod link 18 ... Swing cam 19 ... Valve 20 ... Actuator 21 ... Control means 22 ... 0 lift position stopper 23 ... medium lift position stopper 24 ... first urging member (return spring) 26 ... second biasing member (return spring) of c ₁ ... camshaft center c ₄ ... control cam Center (rocker arm swing center) L: 0 lift position M: middle lift position H: maximum lift position

Claims (4)

[Claims] A camshaft rotatably driven by a crankshaft of an internal combustion engine, a rotary cam fixed to an outer peripheral surface of the camshaft, a control shaft disposed substantially parallel to the camshaft, A control cam integral with the shaft, a rocker arm swingably supported by the control cam, a swing cam swingably supported by the camshaft, and rotatably fitted to the rotary cam. A ring-shaped link connecting the rotating cam and one end of the rocker arm, a rod-shaped link connecting the other end of the rocker arm and the swing cam, and turning the control shaft within a predetermined angle range. An actuator for moving the camshaft, and control means for driving and controlling the actuator in accordance with operating conditions of the internal combustion engine. The rotation is transmitted to the swing cam through the rotation cam, the ring-shaped link, the rocker arm, and the rod-shaped link as a swing motion to open and close a valve, and the rotation of the control shaft by the control unit is controlled. In the variable valve mechanism of the internal combustion engine, wherein the swing angle of the swing cam is changed by the rotation of the control cam, the control shaft is rotated at a zero lift position provided at one end of a rotation range. A zero lift position stopper to stop; a middle lift position stopper to stop the rotation of the control shaft at a middle lift position provided at the other end of the rotation range; and a zero lift position stopper within the rotation range of the control shaft.
The control shaft is provided between a lift position and the middle lift position, and passes the control shaft via a maximum lift position set on or near a line connecting the center of the control shaft and the center of the camshaft. A first urging member for urging from a zero lift position toward the middle lift position. 2. The system according to claim 1, wherein the zero lift position is set on the rod-like link side and the middle lift position is set on the ring-like link side based on the maximum lift position. Variable valve mechanism for an internal combustion engine. 3. The maximum lift l ₀ , l ₁ , l ₂ , l
₃ , l ₄ , l ₅ , l ₆ , θ ₃₄ , l ₀ : length of a line connecting the center of the control cam and the center of the cam shaft, l ₁ : the length of the center of the cam shaft and the rotation cam line length connecting the center, l _2: line length connecting the centers of the rotating cam, and a center of the connecting portion between the one end portion of the rocker arm and the ring-shaped link, l _3: the ring line length connecting the center of the connecting portion between the link and one end portion of the rocker arm, the center of the control cam, l _4: the center of the control cam, the rod-like and the other end of the rocker arm line length connecting the center of the connecting portion between the link, l _5: concatenation of the center of the connection portion between the rod-shaped link and the other end of the rocker arm, and the swing cam and the rod-like link line length connecting the center parts, l _6: the said rod-like link rocking And the center of the connecting portion of the cam, the line segment length connecting the center of the cam shaft, theta _34: when said l ₃ included angle between the l _4, and, these values, l ^{_{4 sin [cos -1 {l 0}} 2 + l 1 2 + l 2 2 -l 3 2 -2l 1 l 2} / {2l 0 (l 1 + l 2)}] = l 3 sin [θ 4 + cos -1 {( l ₄ −l ₀ cos θ ₄ ) / √ (l ₀ ² + l ₄ ² −2 l ₀ l ₄ cos θ ₄ ) ＋ + cos ⁻¹ ｛l ₀ ² + l ₄ ² + l ₅ ² −l ₆ ² -2l ₀ l ₄ cos θ ₄ ｝ / ｛2l ₅ √ (l ₀ ² + l ₄ ² −2l ₀ l ₄ cos θ ₄ )｝] (1) where, θ ₄ = θ ₃₄ −cos ⁻¹ ｛(l ₀ ² − ^{_{l 1 2 -l 2 2 + l}} 3 2 -2l 1 l 2) / (2l 0 l 3)} a, characterized in that it is configured so as to constitute a link geometry substantially satisfied claim 1 or 2, wherein Variable valve mechanism for an internal combustion engine. 4. A second urging member for urging the control shaft toward the maximum lift position only when the control shaft is located on the zero lift position side from the maximum lift position. The variable valve mechanism for an internal combustion engine according to claim 1, wherein: