JP2006200391A - Valve lift variable device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable valve lift mechanism for an internal combustion engine capable of suitably reducing an operating force related to variable valve lift operation.
A variable valve lift device includes a control shaft and a rocker shaft that are arranged in parallel with an intake camshaft, and an intermediate drive mechanism that is pivotally supported by the rocker shaft. The intermediate drive mechanism includes a substantially cylindrical slider gear 30 fitted on the outer peripheral surface of the rocker shaft, and an input arm 31 and an output arm that are supported by the rocker shaft by being splined to the slider gear 30. It is comprised by. In the spline engaging portion of the slider gear 30 and the input arm 31, the external helical spline 30a of the slider gear 30 and the internal helical spline 31a of the input arm 31 are in line contact.
[Selection] Figure 5

Description

  The present invention relates to a variable valve lift device for an internal combustion engine that makes a lift integral value of an engine valve variable through conversion of linear displacement into torsional displacement by a helical spline mechanism.

  As a device applied to an on-board internal combustion engine, the valve lift amount and valve operating angle of the engine valve (intake / exhaust valve) are made variable. In other words, the lift amount from the valve opening to the valve closing is integrated into the crank angle. There is known a valve lift variable device that makes the lift integral value variable. Conventionally, devices of Patent Documents 1 and 2 have been proposed as this type of variable valve lift.

  The valve lift variable devices described in these documents mediate transmission of the pressing force from the camshaft cam of the internal combustion engine to the engine valve, and change the transmission mode to change the lift integral value of the engine valve. I am doing so. Then, the transmission mode of the pressing force is changed through conversion of linear displacement into twist displacement by the helical spline mechanism 100 as shown in FIG.

  The helical spline mechanism 100 is provided for each cylinder on a rocker shaft 101 arranged in parallel with a camshaft, and includes an input arm 102, an output arm 103, and a slider gear 104. The input arm 102 is pivotally supported by the rocker shaft 101 so as to be able to swing when the cam of the camshaft is pressed. Similarly, the output arm 103 is pivotally supported by the rocker shaft 101 and drives the engine valve to open and close according to the swing. Inside the input arm 102 and the output arm 103, a slider gear 104 is accommodated in a state in which the rocker shaft 101 is supported so as to be linearly displaceable in the axial direction.

  On the inner circumferences of the input arm 102 and the output arm 103, internal helical splines 102a and 103b are formed, respectively. On the outer periphery of the slider gear 104, external helical splines 104a and 104b that are engaged with the internal helical splines 102a and 103b, respectively, are formed. The teeth of the internal helical spline 102a of the input arm 102 and the external helical spline 104a of the slider gear 104 engaged therewith are the external teeth of the internal helical spline 103b of the output arm 103 and the slider gear 104 engaged therewith. The inclination direction is different from that of the helical spline 104b.

The slider gear 104 is linearly displaced along the axis of the rocker shaft 101 by an electric or hydraulic actuator. When the slider gear 104 is linearly displaced in this way, the input arm 102 and the output arm 103 are rotated in the direction around the axis of the rocker shaft 101 through the spline engagement. However, the rotation at this time is performed so as to cause relative torsional displacement between the input arm 102 and the output arm 103 due to the difference in the inclination direction of the tooth traces as described above. Through the relative twisting of the input arm 102 and the output arm 103, the transmission mode of the cam pressing force to the engine valve changes, and the lift integral value of the engine valve is changed.
JP 2003-129810 A JP 2003-129812 A

  As shown in FIG. 9, the spline engagement in the helical spline mechanism 100 as described above reduces the surface pressure acting on the tooth surface during transmission of the pressing force, and increases the durability of the helical spline. It is common to form them so that they are in surface contact with each other. In the example of FIG. 9, the external helical spline 104a of the slider gear 104 is formed in an involute tooth shape, and the inter-tooth portion of the internal helical splines 102a and 103b of the input arm 102 or the output arm 103 is the external helical spline 104a. , 104b are formed in the same shape.

  In general, the helical spline mechanism 100 is often used for the generation of torsional displacement in a situation where a high moment acts on an object, and in such a scene, the setting of the tooth shape giving priority to durability is certainly effective. However, with such a tooth shape setting, an increase in the operating force of the helical spline mechanism 100 is unavoidable.

  By the way, when employed in a variable valve lift device for an internal combustion engine such as a vehicle, the helical spline mechanism 100 is also required to have high operability because it is operated in conjunction with a rapid change in the engine operating condition. It is also difficult to increase the output of the actuator that drives it due to restrictions on mounting space and fuel efficiency. Therefore, although it is desired to reduce the operating force of the helical spline mechanism 100, there is a limit to the reduction of the operating force as long as the tooth shape is set.

  The present invention has been made in view of such a situation, and a problem to be solved is to provide a variable valve lift mechanism for an internal combustion engine that can suitably reduce an operating force related to variable valve lift operation. There is.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
According to a first aspect of the present invention, there is provided a variable valve lift device for an internal combustion engine in which a lift integral value of an engine valve is variable through conversion of linear displacement into torsional displacement by the helical spline mechanism. The gist of this is that it is in line contact with the external helical spline.

  When the spline engaging portion of the helical spline mechanism is in surface contact, it becomes difficult to spread the lubricating oil over the entire contact surface, and there is a possibility that a part of the oil film may be cut off. As a result, the frictional force of the spline engaging portion increases, leading to an increase in the operating force of the helical spline mechanism. In that respect, in the above configuration, since the internal helical spline and the external helical spline are brought into line contact at the spline engaging portion of the helical spline mechanism, lubricating oil can be easily supplied to the contact portion between the helical splines. can do. Accordingly, it is possible to more reliably enjoy the effect of reducing the frictional force due to the lubricating oil, and the operating force related to the variable valve lift operation can be suitably reduced.

  According to a second aspect of the present invention, there is provided a variable valve lift device for an internal combustion engine in which a lift integral value of an engine valve is variable through conversion of linear displacement into torsional displacement by the helical spline mechanism. One of the contact surface of the external tooth helical spline and the contact surface of the external helical spline with respect to the internal helical spline is a flat surface and the other is a curved surface.

  In the above configuration, since one of the contact surfaces of the spline engaging portion of the helical spline mechanism is a flat surface and the other is a curved surface, they come into line contact. Therefore, also with the above configuration, the operating force related to the variable valve lift operation can be suitably reduced.

  According to a third aspect of the present invention, there is provided a variable valve lift device for an internal combustion engine in which a lift integral value of an engine valve is made variable through conversion of linear displacement into torsional displacement by the helical spline mechanism, and the internal helical spline of the helical spline mechanism. In addition, the gist of the invention is that either one of the helical splines and the external tooth helical spline has a trapezoidal tooth profile and the other has an involute tooth profile.

  In the helical spline mechanism of the variable valve lift device having the above-described configuration, the contact surface of the helical spline that is a trapezoidal tooth shape of the spline engaging portion is a flat surface, and the contact surface of the helical spline that is an involute tooth shape is a curved surface. , They come into line contact. Therefore, also with the above configuration, the operating force related to the variable valve lift operation can be suitably reduced.

  In this way, when the spline engagement is a line contact, the contact surface pressure becomes high, and there is a risk of causing uneven wear. In that respect, if each tooth of the internal helical spline and the external helical spline is formed at an equal pitch as described in claim 4, the force acting on each tooth becomes substantially equal and an extremely high surface. Since it can suppress that a pressure arises, the increase in the said uneven wear can be suppressed.

  In addition, each said structure is the input arm which has the said internal-tooth helical spline as described in Claim 5, for example, and rock | fluctuates according to the input of the press of the cam of the cam shaft of the said internal combustion engine, The input arm And an output arm that has the internal helical spline having a different inclination direction of the tooth trace, is coaxially arranged with the input arm and is swingably arranged to press the engine valve in response to the swing. A slider having external helical splines that are respectively engaged with the internal helical splines of the input arm and the output arm, and arranged so as to be linearly displaceable in the axial direction of the swing shaft of the input arm and the output arm. And a variable valve lift device for an internal combustion engine having a helical spline mechanism configured to include a gear.

Hereinafter, an embodiment in which the variable valve lift of the present invention is applied to an in-vehicle internal combustion engine (hereinafter referred to as an engine) will be described with reference to FIGS.
FIG. 1 shows a side structure of a valve system of an engine to which a variable valve lift is applied. As shown in the figure, the engine is provided with an intake camshaft 11 for driving an intake valve 10. The intake camshaft 11 has an intake cam 11a and rotates in synchronization with an engine crankshaft (not shown). As the intake camshaft 11 rotates, a pressing force for opening and closing the intake valve 10 is transmitted from the intake cam 11a to the intake valve 10. The exhaust valve has the same configuration as the intake valve 10 and will not be described below.

  Further, the engine is provided with a variable valve lift 12 that varies the valve lift amount and the valve operating angle of the intake valve 10. The variable valve lift 12 is disposed between the intake valve 10 and the intake camshaft 11. In the variable valve lift 12, the valve lift amount and the valve operating angle of the intake valve 10 are controlled to increase as the engine changes from the low load operation state to the high load operation state. By increasing the lift integral value of the intake valve 10 in this way, the intake air amount of the engine can be increased.

  Next, the detailed structure of the variable valve lift 12 will be described in detail with reference to FIGS. FIG. 2 is an exploded perspective view showing the internal structure of the variable valve lift 12.

  As shown in FIGS. 1 and 2, the variable valve lift 12 includes a control shaft 20 and a rocker shaft 21 that are arranged in parallel with the intake camshaft 11, and an intermediary as a helical spline mechanism that is pivotally supported by the rocker shaft 21. And a drive mechanism 23. The mediating drive mechanism 23 is for transmitting the pressing force by the intake cam 11 a to the intake valve 10 and changing the transmission mode through drive control of the control shaft 20.

  The intermediary drive mechanism 23 includes a substantially cylindrical slider gear 30 fitted on the outer peripheral surface of the rocker shaft 21, and an input arm 31 and an output that are pivotally supported on the rocker shaft 21 by being spline-engaged with the slider gear 30. The arm 32 is configured. A roller 34 is rotatably attached to the input arm 31. The roller 34 is biased so as to be pressed against the intake cam 11a by a coil spring (not shown) fixed to the engine.

  The output arm 32 includes a base circle portion 35 and a nose 36 having a substantially triangular shape, and a concave cam surface 36 a is formed on the lower surface of the nose 36. Between the output arm 32 and the intake valve 10, a rocker arm 37 that transmits the swing of the output arm 32 to the intake valve 10 is provided. One end of the rocker arm 37 is supported by an adjuster 39, and the other end is disposed so as to contact the intake valve 10. A roller 38 is rotatably attached to a substantially central portion of the rocker arm 37. The roller 38 is urged so as to be pressed against the output arm 32 by the valve spring 10 a of the intake valve 10.

  In the intermediate drive mechanism 23 configured in this manner, the intake cam shaft 11 rotates and the intake cam 11 a presses the roller 34, whereby the input arm 31 and the output arm 32 swing around the rocker shaft 21. By swinging the output arm 32 in this way, the swing is transmitted from the nose 36 to the roller 38 and the rocker arm 37, whereby the intake valve 10 is opened and closed.

Next, a structure for changing the relative position between the input arm 31 and the output arm 32 in the variable valve lift 12 will be described in detail with reference to FIG.
As shown in the figure, the rocker shaft 21 is disposed so as to penetrate the input arm 31 and the output arms 32 disposed on both sides thereof. In the slider gear 30 fitted to the rocker shaft 21, an external helical spline 30a is formed on the outer wall at the center in the longitudinal direction, and an external helical spline 30b is formed on the outer walls at both ends in the longitudinal direction. Yes. The teeth 40 forming the external helical splines 30a and 30b are all arranged on the outer wall of the slider gear 30 at an equal pitch.

  An internal helical spline 31 a formed on the inner wall of the input arm 31 is engaged with the external helical spline 30 a of the slider gear 30. Further, the external helical spline 30 b of the slider gear 30 is engaged with an internal helical spline 32 b formed on the inner wall of the output arm 32. The teeth 41 forming the internal helical splines 31a and 32b are arranged at equal pitches on the inner walls of the input arm 31 and the output arm 32, respectively. In the slider gear 30, the external helical spline 30a is formed in an inclined direction opposite to the tooth trace of the external helical spline 30b. The internal helical spline 31a of the input arm 31 is formed in an inclined direction opposite to the tooth trace of the internal helical spline 32b of the output arm 32.

  On the other hand, a control shaft 20 is inserted inside the rocker shaft 21. Then, a pin 107 is inserted into the elongated hole 105 formed in the slider gear 30 extending in the circumferential direction and the elongated hole 106 formed in the rocker shaft 21 extending in the axial direction, and one end of the pin 107 is engaged with the control shaft 20. By stopping, the slider gear 30 and the control shaft 20 are connected (see FIG. 8). Here, the long hole 106 of the rocker shaft 21 is for allowing displacement of the control shaft 20 in the axial direction, and the long hole 105 of the slider gear 30 allows displacement of the slider gear 30 in the circumferential direction. Is to do.

  Then, the control shaft 20 is linearly displaced in the axial direction, and the slider gear 30 is linearly displaced in the same direction in conjunction therewith, so that the external helical splines 30a and 30b and the internal helical splines 31a and 32b are engaged. The input arm 31 and the output arm 32 are rotationally displaced in opposite directions with respect to their swinging directions. Thus, the linear displacement of the control shaft 20 is converted into the torsional displacement of the input arm 31 and the output arm 32, so that the relative position between the input arm 31 and the output arm 32 is changed, and the intake cam 11a to the intake valve 10 is changed. The transmission mode of the pressing force is changed. Such linear displacement in the axial direction of the control shaft 20 is realized by, for example, drive control of an actuator using an electric motor.

  Further, a lubricating oil passage 45 is constituted by a gap between the inner wall surface of the rocker shaft 21 and the control shaft 20. A part of the lubricating oil discharged from the engine oil pump is supplied to the lubricating oil passage 45. The lubricating oil supplied to the lubricating oil passage 45 passes through an oil supply port (not shown) between the external helical splines 30a and 30b of the slider gear 30 and the internal helical splines 31a and 32b of the input arm 31 and the output arm 32. Pressure is supplied to the meshing portion, that is, the spline engagement portion between the slider gear 30 and the input arm 31 and output arm 32.

  FIG. 3A shows the state of the variable valve lift 12 when the relative position difference between the input arm 31 and the output arm 32 is small, and FIG. 3B shows the same valve when the relative position difference is large. Each state of the variable lift device 12 is shown. Here, the sandwiching angle θ shown in FIGS. 3A and 3B is C for the axis of the control shaft 20, P for the contact position between the roller 34 and the intake cam 11 a, and the output arm 32 and roller 38. When the contact position with Q is Q, the angle between the straight line connecting CP and the straight line connecting CQ is shown. 3A, the contact position where the rocker arm 37 and the nose 36 come into contact with the swing of the input arm 31 and the output arm 32 due to the depression of the intake cam 11a is shown in FIG. It is set as the use range α. Similarly, in the state of FIG. 3B, the contact position is set as a use range α shown in FIG.

  FIG. 4 shows the relationship among the lift amounts of the intake cam 11a, the output arm 32, and the intake valve 10 for the state of FIG. 3A and the state of FIG. 3B, respectively. As shown in FIGS. 3 and 4, the larger the difference between the relative positions of the input arm 31 and the output arm 32, the more the contact position between the rocker arm 37 and the nose 36 is set within the cam surface 36 a of the nose 36. The distance from the axis of the rocker shaft 21 shifts to the larger side. Therefore, as the relative position difference increases, the input arm 31 and the output arm 32 are greatly swung with respect to the depression of the intake cam 11a. Then, the rocker arm 37 is greatly swung, and accordingly, the valve lift amount and the valve operating angle of the intake valve 10 change so as to increase, and as a result, the intake valve 10 is greatly opened. Conversely, as the relative position difference between the input arm 31 and the output arm 32 becomes smaller, the output arm 32 becomes smaller and the valve lift amount and the valve operating angle of the intake valve 10 become smaller.

FIG. 5 shows a cross-sectional structure of a spline engaging portion between the slider gear 30 and the input arm 31 and the output arm 32.
As shown in the figure, each tooth 40 forming the external helical spline 30a of the slider gear 30 has an involute tooth profile. Thereby, each tooth 40 of the external helical spline 30a has a tooth surface 40a as a contact surface that comes into contact with the internal helical spline 31a of the input arm 31 in a smooth curved surface shape. On the other hand, each tooth 41 forming the internal helical spline 31a of the input arm 31 has a trapezoidal tooth profile. Thereby, the tooth-tooth surface 41a contact | abutted by the external-tooth helical spline 30a of the slider gear 30 is formed in the planar shape of the internal-tooth helical spline 31a.

  In the spline engaging portion between the slider gear 30 and the input arm 31, the tooth surface 40a of each tooth 40 of the external helical spline 30a and the tooth surface 41a of each tooth 41 of the internal helical spline 31a are in line contact. . Therefore, in the spline engaging portion, both tooth surfaces 40a and 41a are provided between the tooth surface 40a of each tooth 40 of the external helical spline 30a and the tooth surface 41a of each tooth 41 of the internal helical spline 31a. A gap E is formed except for the contact portion where the line contacts. By spreading the lubricating oil in the gap E thus formed, the frictional force generated when the external helical spline 30a and the internal helical spline 31a slide is effectively reduced. In addition, since the tooth profile of each said tooth | gear 40 and 41 is formed in the same shape also about the spline engaging part of the slider gear 30 and the output arm 32, the description is abbreviate | omitted below.

According to the variable valve lift device 12 of the present embodiment described above, the following effects can be obtained.
(1) If the spline engaging portion of the mediation drive mechanism 23 is in surface contact, it becomes difficult to spread the lubricating oil over the entire contact surface, and there is a risk that a portion of the oil film may be cut off. As a result, the frictional force of the spline engaging portion is increased, and the operating force of the mediation drive mechanism 23 is increased. In that respect, according to the present embodiment, the external helical splines 30a and 30b of the slider gear 30 and the internal helical splines 31a and 32b of the input arm 31 and the output arm 32 in the spline engaging portion of the intermediate drive mechanism 23. Are in line contact with each other. For this reason, lubricating oil can be easily supplied to the contact part of external-tooth helical spline 30a, 30b and internal-tooth helical spline 31a, 32b, and it can enjoy more reliably the reduction effect of the frictional force by lubricating oil. It becomes possible. Therefore, the operating force related to the variable valve lift operation, that is, the operating force required to operate the mediation drive mechanism 23 can be suitably reduced. Therefore, since the actuator can be reduced in output and reduced in size, it is possible to reduce power consumption and improve fuel efficiency by reducing the amount of oil supplied and hydraulic pressure. Furthermore, in the variable valve lift device 12 mounted on the engine, the installation space can be easily secured.

  (2) The external tooth helical splines 30a and 30b of the slider gear 30 have involute tooth shapes. Further, the internal helical splines 31a and 32b of the input arm 31 and the output arm 32 that are spline-engaged with the slider gear 30 have trapezoidal tooth shapes. In this case, in the spline engaging portion, the tooth surface 40a of each tooth 40 of the external helical splines 30a and 30b is curved, while the tooth surface 41a of each tooth 41 of the internal helical splines 31a and 32b is planar. Therefore, the external helical splines 30a and 30b and the internal helical splines 31a and 32b can be more reliably brought into line contact. For this reason, lubricating oil can be more easily supplied to the contact part of the external helical splines 30a, 30b and the internal helical splines 31a, 32b, and the effect of reducing the frictional force by the lubricating oil can be enjoyed more reliably. It becomes possible.

  (3) When the external helical splines 30a and 30b of the slider gear 30 and the internal helical splines 31a and 32b of the input arm 31 and the output arm 32 are in line contact, the contact is greater than when they are in surface contact. Since the pressure becomes high, there is a possibility that uneven wear occurs on the tooth surfaces 40a, 41a of the teeth 40, 41. In this respect, according to the present embodiment, the teeth 40 of the external helical splines 30a, 30b are arranged at equal pitches on the outer wall of the slider gear 30, and the teeth 41 of the internal helical splines 31a, 32b are respectively input. Arranged at equal pitches on the inner walls of the arm 31 and the output arm 32. For this reason, the force acting on each tooth 40 of the external helical splines 30a, 30b and each tooth 41 of the internal helical splines 31a, 32b can be made almost uniform, and the occurrence of extremely high surface pressure is prevented. can do. Therefore, the increase in the partial wear which arises in the tooth surfaces 40a and 41a of each tooth | gear 40 and 41 can be suppressed.

In addition, the said embodiment can also be changed and implemented as follows.
As shown in FIG. 6, the tooth profile of each tooth 40 forming the internal helical splines 31a and 32b of the input arm 31 and the output arm 32 may be changed to an involute tooth profile. Even in this case, the internal helical splines 31 a and 32 b of the input arm 31 and the output arm 32 can be brought into line contact with the external helical splines 30 a and 30 b of the slider gear 30.

  Further, the tooth shape of each tooth 41 forming the internal helical splines 31a and 32b of the input arm 31 and the output arm 32 is changed from an involute tooth shape to a trapezoidal tooth shape, and external helical splines 30a and 30b of the slider gear 30 are formed. The tooth profile of each tooth 40 may be changed from a trapezoidal tooth profile to an involute tooth profile.

  The tooth shape of each tooth 40 forming the external helical splines 30a, 30b of the slider gear 30 is not limited to a trapezoidal tooth shape, and may be changed to an arbitrary rectangular tooth shape such as a tooth shape having a U-shaped cross section.

  Further, the tooth profile of each tooth 41 formed by the internal helical splines 31a and 32b of the input arm 31 and the output arm 32 is not limited to the involute tooth profile, for example, a cycloid tooth profile, an octoid tooth profile, a linenka tooth profile, a Gleason tooth profile, etc. If 41a has a smooth curved surface shape, it can also be changed to an arbitrary tooth profile.

  As shown in FIG. 7, the number of teeth of the external helical splines 30a and 30b of the slider gear 30 may be changed to an arbitrary number of teeth as necessary. In this case, guide grooves 47 are formed on the inner walls of the input arm 31 and the output arm 32 so as to correspond to the teeth 40 forming the external helical splines 30a, 30b.

  -You may change so that each tooth | gear 40 which forms the external-tooth helical splines 30a and 30b may be arrange | positioned in the outer wall of the slider gear 30 at unequal pitch. Similarly, the teeth 41 forming the internal helical splines 31a and 32b may be changed so as to be arranged at unequal pitches on the inner walls of the input arm 31 and the output arm 32, respectively.

  If the valve lift variable device 12 is a device that can change the lift integral values of the intake valve 10 and the exhaust valve through conversion of linear displacement into twisted displacement by the mediation drive mechanism 23, the overall structure can be changed as appropriate. Good. Even in this case, the operating force related to the variable valve lift operation can be suitably reduced.

The side view which shows the side structure of the valve operating system of the internal combustion engine applied about one Embodiment of this invention. The disassembled perspective view of the mediation drive mechanism of the valve lift variable apparatus of the embodiment. (A), (B) is a side view which shows the operation | movement aspect of a valve lift variable apparatus. The graph which shows the relationship between each lift amount of an intake cam, an output arm, and an intake valve in the valve lift variable apparatus. Sectional drawing which shows the cross-section of the spline engaging part in the mediation drive mechanism of the valve lift variable apparatus. Sectional drawing which shows the cross-section of the spline engaging part in the mediation drive mechanism about another embodiment of this invention. Sectional drawing which shows the cross-section of the spline engaging part in the mediation drive mechanism about another structural example of a valve lift variable apparatus. Sectional drawing which shows the perspective cross-section of the mediation drive mechanism of the conventional valve lift variable apparatus. Sectional drawing which shows the cross-section of the spline engaging part in a common mediation drive mechanism.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Intake valve (engine valve), 11 ... Intake cam shaft, 11a ... Cam, 12 ... Valve lift variable device, 23 ... Mediation drive mechanism (helical spline mechanism), 30 ... Slider gear, 30a, 30b ... External helical spline 31 ... Input arm, 31a ... Internal tooth helical spline, 32 ... Output arm, 32b ... Internal tooth helical spline, 40 ... Tooth, 40a ... Tooth surface (contact surface), 41 ... Tooth, 41a ... Tooth surface (contact) surface).

Claims (5)

In a valve lift variable device for an internal combustion engine in which the lift integral value of an engine valve is variable through conversion of linear displacement into torsional displacement by a helical spline mechanism,
The variable valve lift device for an internal combustion engine, wherein the internal helical spline of the helical spline mechanism is in line contact with the external helical spline. In a valve lift variable device for an internal combustion engine in which the lift integral value of an engine valve is variable through conversion of linear displacement into torsional displacement by a helical spline mechanism,
One of the contact surface of the internal helical spline of the helical spline mechanism with the external helical spline and the contact surface of the external helical spline with the internal helical spline is a flat surface, and the other is a curved surface. A variable valve lift device for an internal combustion engine. In a valve lift variable device for an internal combustion engine in which the lift integral value of an engine valve is variable through conversion of linear displacement into torsional displacement by a helical spline mechanism,
One of the internal helical spline and the external helical spline of the helical spline mechanism has a trapezoidal tooth shape, and the other has an involute tooth shape, and the variable valve lift device for the internal combustion engine.   4. The variable valve lift device for an internal combustion engine according to claim 1, wherein each tooth of the internal helical spline and the external helical spline is formed at an equal pitch. 5. The helical spline mechanism is
An input arm having the internal helical spline and swinging in response to an input of a cam press of a camshaft of the internal combustion engine;
The input arm has the internal helical spline in which the inclination direction of the tooth line is different, and is coaxially arranged with the input arm so as to be swingable and presses the engine valve according to the swing. An output arm;
A slider gear having external helical splines engaged with the internal helical splines of the input arm and output arm, respectively, and arranged so as to be linearly displaceable in the axial direction of the swing shaft of the input arm and output arm. When,
The variable valve lift device for an internal combustion engine according to claim 1, comprising:

Images