JP2004150301A - Adjustable valve system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adjustable valve system for an internal combustion engine capable of continuously changing the driving phase and the valve lift quantity of an intake or an exhaust valve. <P>SOLUTION: This adjustable valve system 10 is provided with a cam shaft 20, a rocker shaft 21 and a rocker arm mechanism 23 for transmitting action of a cam 22 formed in the cam shaft 20 to a valve 11. The rocker arm mechanism 23 includes a first arm 31 for driving the valve 11, a second arm 32, a third arm 33, and a variable mechanism for turning the rocker shaft 21. The first arm 31 is supported by the rocker shaft 21 freely to rock. The second arm 32 is driven by the cam 22 to rock around a universal joint part 26 as a support point on the rocker shaft 21 side. The third arm 33 is displaced with the rock of the second arm 32 to drive the first arm 31. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a variable valve train for an internal combustion engine that can change the drive phase and valve lift of an intake or exhaust valve.
[0002]
[Prior art]
It is known that the phase or lift amount of a valve of an intake / exhaust system is changed in accordance with the operation state of an internal combustion engine in order to reduce exhaust gas or reduce fuel consumption of an internal combustion engine such as an automobile engine. As a variable valve operating device therefor, a vane type variable phase operating device that continuously changes a cam phase by hydraulic pressure is known.
[0003]
There is also known a cam-switching type valve train that switches a plurality of types of cams in accordance with the operating state of an internal combustion engine to adjust a valve driving phase and a lift amount to an operating state.
[0004]
Alternatively, there has been known a mechanical type continuously variable valve operating device that uses a gear driven by a stepping motor, an intermediate lever, a return spring, and the like to change a driving phase and a lift amount of a valve. (For example, see Patent Document 1 below)
[0005]
[Patent Document 1]
Japanese Patent No. 3245492
[Problems to be solved by the invention]
The vane type variable phase valve apparatus can shift the valve driving phase by changing the position of the vane, but cannot change the valve lift.
[0007]
On the other hand, a cam switching type valve operating device and a mechanical type continuously variable valve operating device can shift the lift amount and the phase, but the cam switching type valve operating device requires a plurality of types of cams, so parts are required. The number is large and the structure is complicated. Further, in the mechanical type continuously variable valve operating device, a mechanism for changing the lift amount and a mechanism for shifting the phase are separately required, which complicates the structure and increases the size.
[0008]
In the case of a conventional general continuous phase variable valve operating device, if the closing timing of the intake valve is retarded, the valve opening start timing is also retarded. For this reason, there is a problem that the valve overlap between the intake and the exhaust is reduced or eliminated, and the fuel consumption is deteriorated due to the pumping loss.
[0009]
SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a variable valve operating device capable of continuously changing a valve driving phase and a valve lift with a relatively simple configuration.
[0010]
[Means for Solving the Problems]
As described in claim 1, the variable valve device of the present invention has a camshaft rotatably provided in an internal combustion engine, a rocker shaft, and a rocker arm mechanism. The rocker arm mechanism includes a first arm swingably supported by the rocker shaft and capable of driving the intake or exhaust valve, a second arm driven by the cam and swinging about the rocker shaft side as a fulcrum, A third arm that is swingably provided on a support shaft disposed near the rocker shaft and is displaced by the swing of the second arm to drive the first arm; and a third arm that is disposed on the rocker shaft side of the second arm. A variable mechanism for displacing the fulcrum.
[0011]
The rotation phase of the second arm with respect to the cam is advanced or retarded according to the position of the fulcrum of the second arm displaced by the variable mechanism, so that the cam is driven via the second arm and the third arm. The drive phase of the first arm is advanced or retarded.
[0012]
In a preferred embodiment of the present invention, as described in claim 2, the third arm has a transmission surface portion, and the transmission surface portion converts a swing amount of the second arm to drive the first arm. A converter is provided that changes the distance from the center of the support shaft to the transmission surface.
[0013]
The variable mechanism displaces the fulcrum of the second arm by rotating the rocker shaft as described in, for example, claim 3 and changes a contact portion of the second arm with the cam. The rotational phase of the second arm with respect to the cam is changed by moving the cam in the circumferential direction of the base circle of the cam.
[0014]
In a preferred aspect of the present invention, as described in claim 4, the transmission surface portion includes a non-conversion portion in which a distance from the center of the support shaft to the transmission surface portion does not substantially change in a rotation direction of the third arm. A rotation amount substantially equivalent to the predetermined angle from the start of the rotation of the second arm in a state where the rotation phase of the second arm with respect to the cam is advanced by a predetermined angle by the variable mechanism, is canceled by the non-converting portion. Like that.
[0015]
In a preferred embodiment of the present invention, as described in claim 5, the second arm is rotatably supported at a base end thereof by a connecting member provided on the rocker shaft side, and is provided on a part of the second arm. The contact portion provided contacts the cam, the operating portion provided on the other end of the second arm contacts the third arm, and the contact portion of the second arm provided on the third arm is connected to the cam. A spring for urging the third arm so as to displace the second arm in a direction in which the second arm is brought into contact with the third arm.
[0016]
In a preferred embodiment of the present invention, a bifurcated shaft fitting portion is formed on the first arm, and a part of the second arm is inserted between the bifurcated shaft fitting portions. Is located. Alternatively, as described in claim 7, a bifurcated base end may be formed in the second arm, and a part of the first arm may be located between the base ends.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. A variable valve device 10 shown in FIG. 1 is for opening and closing an intake valve 11 constituting an intake system of an internal combustion engine (an example of an automobile engine). The intake valve 11 is urged by a valve spring 12 in a direction to close the intake passage 13. Note that a valve operating device similar to the variable valve operating device 10 may be provided on the exhaust valve side.
[0018]
The variable valve operating device 10 includes a camshaft 20 rotatably provided on a cylinder head (not shown) of an internal combustion engine, a rocker shaft 21, and a cam 22 formed on the camshaft 20. And a rocker arm mechanism 23 for driving the opening and closing of the arm.
[0019]
The camshaft 20 and the rocker shaft 21 are arranged so as to be parallel to each other. The camshaft 20 rotates in a direction indicated by an arrow R1 in FIG. 1 according to rotation of a crankshaft (not shown) of the internal combustion engine.
[0020]
The rocker shaft 21 is capable of swinging, that is, reciprocatingly rotating in a direction indicated by an arrow R2 in FIG. The rocker shaft 21 swings in the direction of the arrow R2 by the variable mechanism 25 shown in FIG. A connection member 27 having a spherical universal joint 26 such as a stud bolt is attached to the rocker shaft 21.
[0021]
The rocker arm mechanism 23 includes a first arm 31, a second arm 32, and a third arm 33 described below.
The first arm 31 is supported by the rocker shaft 21 so as to be relatively rotatable (swingable). An adjusting screw 35 is provided on the first arm 31. When the camshaft 20 rotates in the direction indicated by the arrow R1, the tip of the adjusting screw 35 drives the valve 11 in the valve opening direction. The adjustment screw 35 can be adjusted so that there is no play between the first arm 31 and the valve 11. In the vicinity of the adjusting screw 35, a force transmitting portion 37 including a force transmitting member 36 such as a roller is provided.
[0022]
As shown in FIG. 2, the first arm 31 has an end 40 on which the adjusting screw 35 is provided, and shaft fitting portions 41 and 42 through which the rocker shaft 21 is inserted. The shaft fitting portions 41 and 42 are formed in a shape that branches off from the end portion 40 in a forked shape.
[0023]
A second arm 32 is provided between the rocker shaft 21 and the camshaft 20. The second arm 32 has a base end portion 50 that swingably fits into the universal joint portion 26 and an operating portion 51 that comes into contact with a relay portion 66 of the third arm 33 described later.
[0024]
A contact portion 53 having a cam follower 52 such as a roller that rolls on the cam 22 is provided between the base end portion 50 and the operating portion 51. Therefore, the second arm 32 swings about the center C1 of the universal joint 26 on the rocker shaft 21 side as the cam 22 rotates.
[0025]
That is, when the rocker shaft 21 is swung in the direction of the arrow R <b> 2 by the variable mechanism 25, the base end 50 of the second arm 32 is displaced in the circumferential direction of the rocker shaft 21. Due to the displacement in the circumferential direction, the rotation phase of the second arm 32 with respect to the cam 22 can be changed to the retard side or the advance side.
[0026]
At least a portion of the second arm 32 is located between the shaft fitting portions 41 and 42 in a state where the contact portion 53 of the second arm 32 is in contact with the base circle 22b of the cam 22.
[0027]
According to the configuration in which a part of the second arm 32 is sandwiched between the shaft fitting portions 41 and 42 in this manner, the contact portion between the second arm 32 and the cam 22 or the contact between the second arm 32 and the third arm 33 is formed. Even when an unbalanced load occurs in the contact portion or the like, the second arm 32 can be prevented from being displaced in the axial direction of the rocker shaft 21, and a problem such as uneven wear can be prevented.
[0028]
A support shaft 60 is arranged near the rocker shaft 21 in parallel with the rocker shaft 21. The third arm 33 functioning as a transmission cam is swingably provided on the support shaft 60. The third arm 33 is urged by a spring 61 in a counterclockwise direction in FIG. 1, that is, in a direction in which the contact portion 53 of the second arm 32 contacts the cam 22.
[0029]
The third arm 33 is provided with a transmission surface section 65 that contacts the force transmission section 37 of the first arm 31 and a relay section 66 that contacts the operating section 51 of the second arm 32. The transmission surface portion 65 functioning as a cam surface is displaced in the rotation direction of the third arm 33, that is, in the circumferential direction of the support shaft 60, as the second arm 32 swings.
[0030]
Therefore, when the second arm 32 swings, the contact position between the force transmitting portion 37 and the transmitting surface portion 65 is displaced in the circumferential direction of the support shaft 60. That is, when the second arm 32 is swung toward the third arm 33 around the universal joint 26 by the protrusion 22 a of the cam 22, the transmission is performed when the third arm 33 is rotated clockwise via the relay 66. When the first arm 31 rotates in the direction of the arrow R3 by the surface portion 65, the valve 11 is opened.
[0031]
More specifically, the transmission surface portion 65 includes a non-converting portion 70 in which the distance from the center C2 of the support shaft 60 does not change and the distance from the center C2 of the support shaft 60 increases toward the distal end portion 33a of the third arm 33. And a conversion unit 71. That is, the transmission surface portion 65 is formed such that the distance from the center C2 of the support shaft 60 changes with respect to the rotation direction of the third arm 33 so as to drive the first arm 31 by converting the swing amount of the second arm 32. ing.
[0032]
On the other hand, when the rotation phase of the contact portion 53 of the second arm 32 with respect to the cam 22 is advanced by a predetermined angle by the variable mechanism 25, the non-converting portion 70 extends from the start of swinging of the second arm 32 to substantially the predetermined angle. The cam surface shape is such that the swing amount of the cam can be canceled.
[0033]
Next, the operation of the variable valve train 10 will be described.
FIG. 1 shows a state where the rocker shaft 21 is driven by the variable mechanism 25 to the retard side from the neutral position N by an angle θ1. In this case, the contact portion 53 of the second arm 32 is displaced with respect to the cam 22 by an angle α to the retard side (left side in FIG. 1) from the neutral point P1. Further, the operating portion 51 of the second arm 32 is displaced to the left in FIG.
[0034]
In this state, when the camshaft 20 rotates in the direction of the arrow R1 and the convex portion 22a of the cam 22 pushes up the contact portion 53 of the second arm 32 as shown in FIG. Pivoted counterclockwise about the center C1. Therefore, the operating section 51 of the second arm 32 pushes the relay section 66, and the third arm 33 rotates clockwise. As a result, the conversion unit 71 of the transmission surface unit 65 presses the force transmission unit 37, so that the first arm 31 rotates and the valve 11 opens.
[0035]
In this case, as shown in FIG. 1, since the force transmitting unit 37 is located near the conversion unit 71 before the valve is opened, the third arm 33 that functions as a transmission cam when the third arm 33 rotates clockwise. Of the transmission surface 65 of the arm 33, the non-converting portion 70 in contact with the force transmitting portion 37 is shortened, and as a result, the converting portion 71 is elongated.
[0036]
Therefore, while the cam angle is small, the first arm 31 starts to be driven in a direction to open the valve 11, and the first arm 31 is moved in the direction of arrow R3 while the force transmitting section 37 contacts the conversion section 71 over a long range. Pressed. Therefore, the valve lift amount H1 (shown in FIG. 3) is large.
[0037]
Therefore, as shown by the curve L1 in FIG. 4, the valve lift is large, and the peak of the valve lift is retarded. In this case, the driving of the valve is suitable for a large amount of intake air with high rotation and high load.
[0038]
FIG. 5 shows a state where the rocker shaft 21 is driven to the neutral position N by the variable mechanism 25. In this case, the contact portion 53 of the second arm 32 is in contact with the cam 22 at the neutral point P1. Further, the third arm 33 is slightly rotated counterclockwise by slightly displacing the operating portion 51 of the second arm 32 to the right in FIG. 5 as compared to FIG. Therefore, as compared with the state shown in FIG. 1, the non-converting portion 70 in contact with the force transmitting portion 37 of the transmitting surface portion 65 of the third arm 33 functioning as the transmitting cam is slightly longer, and as a result, the converting portion 71 is slightly shorter. Become.
[0039]
In this state, when the camshaft 20 rotates and the convex portion 22a of the cam 22 pushes up the contact portion 53 of the second arm 32 as shown in FIG. 6, the second arm 32 moves the center C1 of the universal joint portion 26. It rotates counterclockwise as a fulcrum. Therefore, the operating section 51 of the second arm 32 pushes the relay section 66, and the third arm 33 rotates clockwise. As a result, the conversion unit 71 of the transmission surface unit 65 presses the force transmission unit 37, so that the first arm 31 rotates and the valve 11 opens.
[0040]
In other words, when the valve is closed as shown in FIG. 5, the distance from the force transmission unit 37 in contact with the transmission surface 65 to the conversion unit 71 is slightly longer. That is, after passing through the non-converting section 70 longer than in FIG. 1, the force transmitting section 37 and the converting section 71 come into contact with each other. Therefore, when the third arm 33 rotates clockwise, the third arm 33 rotates clockwise while the force transmission unit 37 is pressed by the conversion unit 71 over a medium length. Therefore, the valve lift amount becomes a moderate valve lift amount H2 (shown in FIG. 6) and the driving phase of the valve becomes neutral as shown by a curve L2 in FIG. Is driven.
[0041]
FIG. 7 shows a state where the rocker shaft 21 is driven by the variable mechanism 25 from the neutral position N to the advance side by an angle θ2. In this case, the contact portion 53 of the second arm 32 is displaced from the cam 22 by an angle β on the advance side (the right side in FIG. 1) from the neutral point P1. Further, since the operating portion 51 of the second arm 32 is displaced rightward in FIG. 7 and the third arm 33 is displaced counterclockwise, the third arm 33 that functions as a transmission cam is different from the state shown in FIG. Of the transmission surface 65 of the arm 33, the non-converting portion 70 in contact with the force transmitting portion 37 becomes longer, and as a result, the converting portion 71 becomes shorter.
[0042]
In this state, when the camshaft 20 rotates and the protrusion 22a of the cam 22 pushes up the contact portion 53 of the second arm 32 as shown in FIG. 8, the second arm 32 moves the center C1 of the universal joint 26. It rotates counterclockwise as a fulcrum. Therefore, the operating section 51 of the second arm 32 pushes the relay section 66, and the third arm 33 rotates clockwise. As a result, the conversion unit 71 of the transmission surface unit 65 presses the force transmission unit 37, so that the first arm 31 rotates and the valve 11 opens.
[0043]
In this case, since the period (distance) of the non-converting portion 70 in contact with the force transmitting portion 37 in the transmitting surface portion 65 of the third arm 33 functioning as a transmitting cam is long, the third arm 33 swings with the third arm 33. When the arm 33 rotates clockwise, the distance over which the force transmission unit 37 moves on the conversion unit 71 is short. Therefore, the rotation amount of the first arm 31 is small, and the valve lift amount H3 (shown in FIG. 8) is reduced. Therefore, as shown by the curve L3 in FIG. 4, the valve drive phase is advanced, and the valve lift is reduced, so that the valve is driven at a low speed and suitable for a small intake amount with a low load.
[0044]
If the variable valve operating device 10 having the above configuration is applied to an intake system, the open side of the intake valve 11 can be fixed and the closed side can be continuously changed, so that a high expansion ratio cycle can be achieved.
[0045]
Further, it is possible to reduce fuel consumption by synergistic action with inertial intake. Inertial intake means that pressure pulsation generated by the intake action of the piston causes inertia in intake air in the intake pipe. By using this inertial intake and starting to close the intake valve 11 at the peak timing of intake pulsation, fresh air continues to flow into the cylinder even after the piston passes the bottom dead center, and volume efficiency can be increased. . Since the peak timing of the pulsation varies depending on the engine speed, the intake air amount can be increased by starting to close the intake valve 11 in accordance with the peak timing.
[0046]
In the variable valve operating device 10 of the embodiment, the rocker shaft 21 is moved by the variable mechanism 25 based on the phase from the start to the end of the valve opening of the curve L1 in FIG. In the case where the second arm 32 is driven, the period in which the second arm 32 is advanced with respect to the cam 22 is canceled by extending the period in which the third arm 33 is in contact with the non-converting section 70 and the force transmitting section 37. The valve opening start timing can be made substantially constant.
[0047]
Therefore, according to the variable valve operating device 10, the valve closing timing can be changed while the valve opening start timing is fixed. Therefore, by changing the valve closing timing in accordance with the pulsation of the inertia intake air, the intake air amount can be changed. And the effect of reducing fuel consumption is obtained.
[0048]
In addition, by optimally controlling the amount of air, a favorable combustion state is achieved, and unburned substances and the like are reduced, and the exhaust gas component is improved.
[0049]
In the case of a conventional general continuous phase variable valve operating device, if the closing timing of the intake valve is retarded, the opening start timing is also retarded. For this reason, valve overlap of intake and exhaust is reduced or eliminated, and pumping loss occurs.
[0050]
On the other hand, according to the variable valve apparatus 10 of the embodiment, the valve closing timing can be retarded with the valve opening start timing fixed, so that the valve closing timing is delayed while maintaining the valve overlap. By squaring, the effect of increasing the amount of intake air can be obtained. Therefore, an effect of reducing fuel consumption can be obtained.
[0051]
In general, when the air becomes excessive at a low load, the exhaust temperature decreases. However, according to the variable valve apparatus 10 of the embodiment, the intake air amount can be controlled according to the operating state of the engine. By reducing the temperature, the exhaust gas temperature can be increased. For this reason, the catalyst is activated and the catalyst functions effectively. In this case, since the exhaust gas can be purified by the catalyst, the engine body can be set in a state of good fuel economy even if the exhaust gas component is slightly deteriorated. As a result, the fuel efficiency of the engine body is improved, and the exhaust gas is purified by the catalyst, so that both high fuel efficiency and purification of the exhaust gas can be achieved. Also, according to the variable valve apparatus 10, by reducing the amount of intake air at a low load, there is no need to provide an intake or exhaust throttle for controlling the amount of intake air, and cost can be reduced.
[0052]
FIG. 9 shows a variable valve train 10A according to a second embodiment of the present invention. In the variable valve operating device 10A, forked portions 32a and 32b are formed on the base end 50 side of the second arm 32. In a state where the second arm 32 is in contact with the base circle 22b (shown in FIG. 1) of the cam 22, at least a part of the first arm 31 is located between the forked portions 32a and 32b. Other configurations, operations, and effects are the same as those of the variable valve device 10 of the first embodiment, and thus, the same reference numerals are given to the portions common to both, and the description will be omitted.
[0053]
According to the configuration in which a part of the first arm 31 is sandwiched between the forked portions 32a and 32b as in the second embodiment, the contact portion between the second arm 32 and the cam 22, or the second arm 32 and the second Even when an eccentric load is generated at a contact portion between the third arm 33 and the like, the second arm 32 can be prevented from being displaced in the axial direction of the rocker shaft 21, thereby preventing problems such as uneven wear.
[0054]
FIG. 10 shows a variable valve train 10B according to a third embodiment of the present invention. The variable valve operating device 10B differs from the variable valve operating device 10 of the first embodiment in that the shaft fitting portion 31a of the first arm 31 is not bifurcated. Other configurations, operations, and effects are the same as those of the variable valve device 10 of the first embodiment, and thus, the same reference numerals are given to the portions common to both, and the description will be omitted.
[0055]
By setting the second arm 32 to be able to advance with respect to the cam 22 from the state shown in FIG. 7, the cylinder can be brought into the cylinder rest state (the valve lift amount is extremely small or zero) as indicated by L4 in FIG. Thus, an effect of reducing fuel consumption can be obtained.
[0056]
【The invention's effect】
According to the first aspect of the invention, the drive phase of the intake or exhaust valve can be continuously changed according to the position of the fulcrum by displacing the fulcrum on the rocker shaft side of the second arm by the variable mechanism. it can.
[0057]
According to the second aspect of the present invention, by providing the transmission portion of the third arm with the conversion portion whose distance from the center of the support shaft changes, the swing amount of the second arm is converted by the third arm. To the first arm. For this reason, by moving the position of the fulcrum on the rocker shaft side of the second arm by the variable mechanism, the lift amount of the intake or exhaust valve can be changed.
[0058]
According to the third aspect of the present invention, the drive phase of the intake or exhaust valve can be continuously changed by the variable mechanism that displaces the fulcrum around the axis of the rocker shaft.
[0059]
According to the invention described in claim 4, even if the rotational phase of the second arm with respect to the cam is advanced by a predetermined angle by the variable mechanism, the swing amount of the substantially predetermined angle from the start of the swing of the second arm by the non-converting portion. By canceling, the valve opening start timing can be made substantially the same regardless of the valve lift amount.
[0060]
According to the fifth aspect of the present invention, by providing the spring for urging the third arm, the positions of the second arm and the third arm can be maintained so that the second arm always contacts the cam. it can.
[0061]
According to the invention described in claim 6 and claim 7, even if an unbalanced load is generated at a contact portion between the second arm and the cam or a contact portion between the second arm and the third arm, the second position is maintained. The displacement of the arm in the axial direction of the rocker shaft can be prevented.
[Brief description of the drawings]
FIG. 1 is a front view of a variable valve apparatus according to a first embodiment of the present invention when a valve is closed in a state where a phase is retarded.
FIG. 2 is a plan view of a part of the variable valve apparatus shown in FIG. 1;
FIG. 3 is a front view of the variable valve apparatus shown in FIG. 1 when the phase is retarded and the valve is opened.
FIG. 4 is a view showing a relationship between a cam angle and a valve lift of the variable valve operating device shown in FIG. 1;
FIG. 5 is a front view of the variable valve apparatus shown in FIG. 1 in a phase neutral state when the valve is closed.
FIG. 6 is a front view of the variable valve operating device shown in FIG. 1 when the valve is opened in a phase neutral state.
FIG. 7 is a front view of the variable valve operating device shown in FIG. 1 when the valve is closed in a state where the phase is advanced.
FIG. 8 is a front view of the variable valve apparatus shown in FIG. 1 when the phase is advanced and the valve is opened.
FIG. 9 is a plan view of a part of a variable valve apparatus according to a second embodiment of the present invention.
FIG. 10 is a plan view of a part of a variable valve apparatus according to a third embodiment of the present invention.
[Explanation of symbols]
10, 10A, 10B Variable valve device 11 Valve 20 Camshaft 21 Rocker shaft 22 Cam 23 Rocker arm mechanism 25 Variable mechanism 26 Universal joint 27 Connecting member 31 First arm 32 Second Arm 33, third arm 37, force transmitting section 60, support shaft 61, spring 65, transmitting surface section 70, non-converting section 71, converting section

Claims (7)

A camshaft rotatably provided in the internal combustion engine,
A rocker shaft provided in the internal combustion engine,
A rocker arm mechanism driven by a cam formed on the camshaft to open and close an intake or exhaust valve,
The rocker arm mechanism includes:
A first arm swingably supported by the rocker shaft and capable of driving the intake or exhaust valve;
A second arm driven by the cam and swinging around the rocker shaft side as a fulcrum;
A third arm that is swingably provided on a support shaft disposed near the rocker shaft and is displaced by the swing of the second arm to drive the first arm;
A variable mechanism for displacing the fulcrum on the rocker shaft side of the second arm;
A variable valve train for an internal combustion engine, comprising: The third arm has a transmission surface portion that is displaced by the swing of the second arm and is in contact with the first arm to drive the first arm,
The transmission surface portion includes a conversion portion that changes a distance from the center of the support shaft to the transmission surface portion to convert the swing amount of the second arm to drive the first arm. The variable valve train for an internal combustion engine according to claim 1. The variable mechanism displaces the fulcrum by rotating the rocker shaft, and moves a contact portion of the second arm with the cam in a circumferential direction of a base circle of the cam, thereby forming the cam. 3. The variable valve train for an internal combustion engine according to claim 2, wherein a rotation phase of the second arm with respect to the rotation angle is changed. The transmission surface portion has a non-conversion portion in which a distance from the center of the support shaft to the transmission surface portion does not substantially change in a rotation direction of the third arm.
In a state where the rotation phase of the second arm with respect to the cam is advanced by a predetermined angle by the variable mechanism, a swing amount substantially equivalent to the predetermined angle from the start of swing of the second arm is canceled by the non-converting portion. The variable valve train for an internal combustion engine according to claim 3, wherein: The second arm has a base end rotatably supported by a connecting member provided on the rocker shaft side,
A contact portion provided on a part of the second arm contacts the cam, and an operating portion provided on the other end of the second arm contacts the third arm, and
A spring provided on the third arm and biasing the third arm so as to displace the second arm in a direction in which the contact portion of the second arm comes into contact with the cam. The variable valve train for an internal combustion engine according to claim 1. The first arm has a shape in which a shaft fitting portion through which the rocker shaft is inserted is branched into a forked shape from an end on the valve side,
The variable valve train of an internal combustion engine according to claim 5, wherein a part of the second arm is located between the forked shaft fitting portions. The second arm has a shape in which the base end side is branched into a forked shape from the operation section side,
The variable valve train of an internal combustion engine according to claim 5, wherein a part of the first arm is located between the forked base ends.

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