JP2008128020A - Variable valve mechanism for internal combustion engine - Google Patents

Abstract

An object of the present invention is to increase the travel region of a swing cam 9 relative to a crown surface 10a of a valve lifter 10 while preventing the valve lifter 10 from falling down during first contact.
A variable valve mechanism (1) has a swing cam (9) for pushing down a valve lifter (10) against which an end surface (21a) of a valve stem (21) of an intake valve (11) abuts, and a crown surface center (P) of the valve lifter (10) and a shaft of the valve stem. The hearts R are configured to coincide. The first contact position on the crown surface 10a of the valve lifter 10 where the swing cam 9 first contacts the valve lifter 10 when the intake valve 11 is opened is offset to the cam base circle side of the swing cam 9. . Further, the offset amount from the crown surface center P of the valve lifter 10 at the first contact position is set to be equal to or less than the radius of the end surface of the terminal portion 21 a of the valve stem 21.
[Selection] Figure 2

Description

  The present invention relates to a variable valve mechanism for an internal combustion engine.

In Patent Document 1, a drive shaft that is rotationally driven by a crankshaft of an engine and has a drive cam fixed to the outer periphery thereof, and a swing that is swingably provided on the drive shaft and that opens and closes an engine valve via a valve lifter. A rocker arm whose one end is rotatably linked to the drive cam via a link arm and whose other end is linked to the end of the swing cam; and a swing fulcrum of the rocker arm is variable. There is disclosed a variable valve operating apparatus including a variable mechanism and a control unit that controls the variable mechanism according to an engine operating state. The variable valve device disclosed in Patent Document 1 variably controls the rocking fulcrum of the rocker arm to change the rocking position of the rocking cam with respect to the top surface of the valve lifter, thereby increasing the lift amount of the engine valve. The swing center of the swing cam is disposed so as to be offset by a predetermined amount toward the base circle side of the swing cam with respect to the axis of the valve lifter.
JP 11-336521 A

  However, in this Patent Document 1, since there is substantially no limit on the offset amount of the swing center of the swing cam from the center of the valve lifter crown to the cam base circle side, the engine valve is used when the offset amount is large. When the swing cam is first brought into contact with the valve lifter when the valve is opened, the valve lifter may fall to the cam base circle side. That is, when the swing cam first comes into contact with the valve lifter, the valve lifter may fall down, resulting in the occurrence of uneven wear and sound vibration performance.

  Accordingly, the present invention provides a variable valve for an internal combustion engine that is configured to have a swing cam that pushes down a valve lifter that abuts the end surface of the valve stem of the engine valve and that can continuously vary the valve lift characteristics of the engine valve. An internal combustion engine in which a first contact position on the valve lifter crown surface where the swing cam first contacts the valve lifter when the engine valve is opened is offset to the cam base circle side of the swing cam In this variable valve mechanism, the offset amount of the first contact position from the center position of the crown surface of the valve lifter is set to be equal to or less than the radius of the end face of the end portion of the valve stem. As a result, the stress acting on the valve lifter from the swing cam during the first contact when the swing cam first contacts the valve lifter when the engine valve is opened can be supported by the valve stem.

  According to the present invention, since the stress acting on the valve lifter at the time of the first contact can be directly supported by the valve stem directly below, the valve lifter can be prevented from falling at the time of the first contact, and the partial wear caused by the fall of the valve lifter, Generation of vibration and lifter hitting sound can be prevented.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view schematically showing a variable valve mechanism 1 according to the present invention. The variable valve mechanism 1 mechanically interlocks with the rotation of a crankshaft (not shown) to open and close the intake valve 11 and the lift characteristic of the intake valve 11 as the control shaft 12 rotates. A lift operating angle variable mechanism (VEL) that continuously changes both the valve lift amount and the operating angle of the intake valve 11 is shown. Since the variable valve mechanism 1 is known from, for example, the above-mentioned Patent Document 1, only the outline thereof will be described.

  The variable valve mechanism 1 is rotatably supported by a cam bracket (not shown) at the upper part of the cylinder head, and is fixed to the drive shaft 2 by press-fitting or the like on the drive shaft 2 extending in the cylinder row direction above the intake valve 11. A drive eccentric shaft portion 3 that rotates integrally with the drive shaft 2, and a control shaft 12 that is rotatably supported by the same cam bracket at a position above the drive shaft 2 and arranged in parallel with the drive shaft 2. A control eccentric shaft portion 18 that is fixed to the control shaft 12 by press-fitting or the like and rotates integrally with the control shaft 12, and a rocker arm 6 as an intermediate member that is swingably supported by the control eccentric shaft portion 18; And a swing cam 9 having a uniform thickness attached to the drive shaft 2 so as to be swingable. The drive eccentric shaft portion 3 and one end of the rocker arm 6 are linked by an arm-shaped first link 4, and the other end of the rocker arm 6 and the swing cam 9 are linked by a second link 8 having a ring shape at one end. Has been.

  The drive shaft 2 is driven by a crankshaft of an engine via a timing chain or timing belt (not shown), and rotates around the shaft mechanically interlocking with the crankshaft. The drive eccentric shaft portion 3 has a circular outer peripheral surface, and the center of the outer peripheral surface is eccentric from the axis of the drive shaft 2 by a predetermined amount. The rocker arm 6 is supported by a control eccentric shaft portion 18 so that the rocker arm 6 can swing. A first link 4 is connected to one end of the rocker arm 6 via a connecting pin 5, and a second link 8 is connected to the other end via a connecting pin 7. The control eccentric shaft portion 18 is eccentric by a predetermined amount from the axis of the control shaft 12. Therefore, the rocking center of the rocker arm 6 changes according to the angular position of the control shaft 12.

  The tip of the swing cam 9 and the second link 8 are connected via a connecting pin 17. An arc-shaped base circle surface 9a and a cam surface 9b extending in a predetermined curve from the base circle surface are continuously formed on the lower surface of the swing cam 9, and these base circle surfaces are formed. 9a and the cam surface 9b are configured to face and contact the upper surface of the valve lifter (tuppet) 10 in accordance with the swing position of the swing cam 9. That is, the base circle surface 9a is a section where the lift amount becomes 0 as a base circle section, and when the swing cam 9 swings and the cam surface 9b contacts the valve lifter 10, the intake valve 11 becomes the valve spring reaction force. The intake valve 11 is lifted gradually by being pushed down. That is, when the intake valve 11 is opened, the intake valve 11 gradually lifts after the first contact when the cam surface 9b of the swing cam 9 first contacts the valve lifter 10.

  The crown surface center P of the valve lifter 10 and the axis R of the valve stem 21 are configured to coincide with each other.

  As shown in FIG. 1, the control shaft 12 is configured to rotate within a predetermined rotation angle range by a control shaft actuator 13 provided on one end side of the control shaft 12. The control shaft actuator 13 is composed of an electric motor such as a servo motor, for example, and has a function of holding the rotation angle position of the control shaft 12. The control shaft actuator 13 and the machine are connected to the control shaft 12 via a worm gear mechanism 15 that is a mechanical interlocking mechanism. Are linked together.

  The worm gear mechanism 15 is fixed to the output shaft 13 a of the control shaft actuator 13, is fixed to the one end of the control shaft 12 by press fitting or the like, and is rotated together with the control shaft 12. And a worm wheel 15b. A worm gear that meshes with the worm 15a is formed on the outer periphery of the worm wheel 15b.

  The rotational angle positions of the control shaft 12 and the control eccentric shaft portion 18 are detected by a control shaft sensor 14 such as a potentiometer. Based on the detection signal of the control axis sensor 14, the control device (control means) 19 outputs a control signal to the control axis actuator 13, and the closed loop control is performed so that the rotational angle position of the control axis 12 becomes the target value. .

  The operation of the variable valve mechanism 1 will be briefly described. When the drive shaft 2 rotates, the swing cam 9 swings via the drive eccentric shaft portion 3, the first link 4, the rocker arm 6, and the second link 8. To do. The valve lifter 10 is pressed by the swing cam 9, and the intake valve 11 is opened and closed against the spring force of a valve spring (not shown). Further, when the angle position of the control shaft 12 is changed by the control shaft actuator 13, the initial position of the rocker arm 6 is changed, and the valve lift characteristic by the swing cam 9 is continuously changed. That is, the lift and the operating angle can be continuously expanded and contracted simultaneously. Depending on the layout of each part, for example, the opening timing and closing timing of the intake valve 11 change substantially symmetrically as the lift and operating angle change.

  The drive shaft 2 and the control shaft 12 extending in the cylinder row direction are shared by a plurality of cylinders constituting the cylinder row, whereas they are components of the variable valve mechanism 1 (lift operating angle variable mechanism). A certain swing cam 9, rocker arm 6, first link 4, second link 8 and the like are provided independently for each cylinder constituting the cylinder row.

  In the first embodiment of the present invention, as shown in FIG. 2, the crown of the valve lifter 10 at the first contact position, which is the contact position of the swing cam 9 with the crown surface 10a of the valve lifter 10 at the time of the first contact described above. The offset amount L from the surface center P has a length equal to or less than the radius (D / 2) of the end surface 21a end surface of the valve stem 21 of the intake valve 11 on the cam base circle side (right side in FIG. 2) of the swing cam 9. It is set to be. That is, the offset amount L from the crown surface center P position of the valve lifter 10 at the first contact position to the cam base circle side (right side in FIG. 2) of the swing cam 9 is the radius (D of the end portion 21a of the valve stem 21). / 2) It is set to be the following. In other words, the offset amount L of the swing center Q of the swing cam 9 from the position of the crown surface center P of the valve lifter 10 is set to be equal to or less than the radius (D / 2) of the end surface 21a of the valve stem 21. ing. Here, D is the diameter of the end face of the terminal portion 21a.

  By offsetting the first contact position with respect to the crown surface center P of the valve lifter 10, the area on the crown surface 10a of the valve lifter 10 with which the cam surface 9b of the oscillating cam 9 contacts is enlarged. The travel area on the crown surface 10a is increased, the maximum valve lift amount is increased, and the output is improved.

  In such a first embodiment, the position of the first contact is limited to a position directly above the end surface of the terminal portion 21a of the valve stem 21 of the intake valve 11, so that the swing cam 9 acts on the valve lifter 10 during the first contact. The stress to be supported can be supported by the valve stem 21. That is, since the stress acting on the valve lifter 10 at the time of the first contact can be directly supported by the valve stem 21 directly below, the first contact position is offset from the crown surface center P of the valve lifter 10 to act on the valve lifter 10 at the time of the first contact. The moment around the center P of the crown surface (around the axis R of the valve stem 21) can be effectively suppressed.

  Therefore, the valve lifter 10 can be prevented from falling at the time of the first contact, and the partial wear caused by the fall of the valve lifter 10 while expanding the travel area of the cam surface 9b of the swing cam 9 relative to the crown surface 10a of the valve lifter 10, Generation of vibration and lifter hitting sound can be prevented.

  Hereinafter, although other embodiment of this invention is described, the same name and code | symbol are attached | subjected about the same component, and the overlapping description is abbreviate | omitted.

  FIG. 3 shows a second embodiment of the present invention. In the second embodiment, in consideration of the valve clearance Vc, an offset amount L from the crown surface center P position of the valve lifter 10 at the first contact position to the cam base circle side (right side in FIG. 3) of the swing cam 9. Has been determined.

  That is, in the second embodiment, the offset amount L from the crown surface center P position of the valve lifter 10 at the first contact position to the cam base circle side (right side in FIG. 3) of the swing cam 9 is It is set to be equal to or shorter than the length obtained by adding the valve clearance Vc to the radius (D / 2) of the end surface 21a of the valve stem 21.

  In the second embodiment as well, the first contact position is limited to a position immediately above the end face of the terminal portion 21a of the valve stem 21 of the intake valve 11 as in the first embodiment described above. The effect can be obtained as in the first embodiment. Furthermore, in the second embodiment, the allowable range of the offset amount L is wider than that of the first embodiment described above by the valve clearance Vc. The travel area on the crown surface 10a of the valve lifter 10 by the cam surface 9b of the moving cam 9 can be increased, and the maximum valve lift amount can be further increased.

  4 and 5 show a third embodiment of the present invention. In the third embodiment, the width of the swing cam 9, that is, the thickness of the swing cam 9 in the direction perpendicular to the paper surface in FIG. 4 is made smaller than the radius (D / 2) of the end surface 21 a of the valve stem 21. Is set. The offset amount L from the crown surface center P of the valve lifter 10 at the first contact position to the cam base circle side (the right side in FIG. 4 and the upper side in FIG. 5) of the swing cam 9 is the terminal portion 21a of the valve stem 21. It is set in consideration of the radius (D / 2) of the end face and the offset amount C of the swing cam 9 in the cylinder row direction of the internal combustion engine. Here, the offset amount C of the swing cam 9 in the cylinder row direction of the internal combustion engine is a value (for example, about 1 mm) sufficiently smaller than the radius (D / 2) of the end surface of the terminal portion 21a of the valve stem 21.

  Specifically, in the third embodiment, the offset amount from the crown surface center P of the valve lifter 10 at the first contact position to the cam base circle side (the right side in FIG. 4 and the upper side in FIG. 5) of the swing cam 9. L is set so as to satisfy the following expression (1).

[Equation 3] L ≦ {(D / 2) ² −C ² } ^1/2 (1)
The reason why the swing cam 9 is offset from the crown surface center P in the cylinder row direction is that the valve lifter 10 rotates around the crown surface center P when the cam surface 9b of the swing cam 9 contacts the valve lifter 10. In order to prevent the cam surface 9b from contacting only a part of the crown surface 10a. That is, by offsetting the swing cam 9 from the crown surface center P in the cylinder row direction, the contactable range with the cam surface 9b on the crown surface 10a is expanded, and uneven wear on the crown surface 10a is prevented. It is.

  Also in the third embodiment, the first contact position is limited to a position immediately above the end surface of the terminal portion 21a of the valve stem 21 of the intake valve 11 as in the first embodiment described above. The effect can be obtained similarly to the first embodiment.

  6 and 7 show a fourth embodiment of the present invention. In the fourth embodiment, the width of the swing cam 9, that is, the thickness of the swing cam 9 in the direction perpendicular to the plane of FIG. 6 is set to be smaller than the radius (D / 2) of the end surface 21 a of the valve stem 21. Has been. In the fourth embodiment, the offset amount L from the crown surface center P of the valve lifter 10 at the first contact position to the cam base circle side (the right side in FIG. 6 and the upper side in FIG. 7) of the swing cam 9 is The radius (D / 2) of the end surface of the terminal portion 21a of the valve stem 21, the offset amount C of the rocking cam 9 in the cylinder row direction of the internal combustion engine, and the valve clearance Vc are set. Here, the offset amount C of the swing cam 9 in the cylinder row direction of the internal combustion engine is a value (for example, about 1 mm) sufficiently smaller than the radius (D / 2) of the end surface of the terminal portion 21a of the valve stem 21.

  More specifically, in the fourth embodiment, the offset amount from the crown surface center P of the valve lifter 10 at the first contact position to the cam base circle side (the right side in FIG. 6 and the upper side in FIG. 7) of the swing cam 9. L is set so as to satisfy the following expression (2).

[Expression 4] L ≦ {(D / 2) ² −C ² } ^1/2 (2)
Also in the fourth embodiment, the first contact position is limited to a position immediately above the end surface of the terminal portion 21a of the valve stem 21 of the intake valve 11 as in the first embodiment described above. The effect can be obtained similarly to the first embodiment.

  Further, in the fourth embodiment, the allowable range of the offset amount L is wider than the third embodiment described above by the valve clearance Vc. The travel area on the crown surface 10a of the valve lifter 10 by the cam surface 9b of the moving cam 9 can be increased, and the maximum valve lift amount can be further increased.

  The technical idea of the present invention that can be grasped from the above embodiment will be listed together with the effects thereof.

  (1) A variable valve mechanism for an internal combustion engine that is configured to have a swing cam that pushes down a valve lifter that abuts the end face of the valve stem of an engine valve and that can continuously vary the valve lift characteristics of the engine valve. Thus, when the engine valve is opened, the first contact position on the valve lifter crown surface where the swing cam first contacts the valve lifter is offset toward the cam base circle side of the swing cam. In the valve mechanism, an offset amount of the first contact position from the center position of the crown surface of the valve lifter is set to be equal to or less than the radius of the end face of the terminal portion of the valve stem. As a result, the stress acting on the valve lifter from the swing cam during the first contact when the swing cam first contacts the valve lifter when the engine valve is opened can be supported by the valve stem. That is, since the stress acting on the valve lifter at the time of the first contact can be directly supported by the valve stem immediately below, it is possible to prevent the valve lifter from falling down at the time of the first contact. The occurrence of lifter hitting sound can be prevented.

  (2) A variable valve mechanism for an internal combustion engine that has a swing cam that pushes down a valve lifter that abuts the end face of the valve stem of the engine valve and that can continuously vary the valve lift characteristics of the engine valve. Thus, when the engine valve is opened, the first contact position on the valve lifter crown surface where the swing cam first contacts the valve lifter is offset toward the cam base circle side of the swing cam. In the valve mechanism, the offset amount of the first contact position from the center position of the crown surface of the valve lifter is set to be equal to or less than the length obtained by adding the valve clearance to the radius of the end surface of the valve stem. As a result, the stress acting on the valve lifter from the swing cam during the first contact when the swing cam first contacts the valve lifter when the engine valve is opened can be supported by the valve stem.

  (3) A variable valve mechanism for an internal combustion engine that has a swing cam that pushes down a valve lifter that abuts the end face of the valve stem of the engine valve and that can continuously vary the valve lift characteristics of the engine valve. Thus, when the engine valve is opened, the first contact position on the valve lifter crown surface where the swing cam first contacts the valve lifter is offset toward the cam base circle side of the swing cam. In the valve mechanism, an offset amount L from the crown surface center position of the valve lifter at the first contact position to the cam base circle side of the swing cam is an offset amount C of the swing cam in the cylinder row direction of the internal combustion engine. The radius D / 2 of the end face of the end portion of the valve stem is set. As a result, the stress acting on the valve lifter from the swing cam during the first contact when the swing cam first contacts the valve lifter when the engine valve is opened can be supported by the valve stem.

(4) In the variable valve mechanism for the internal combustion engine according to (3), specifically, the offset amount L is L ≦ {(D / 2) ² −C ² } ^1/2. Is set.

(5) In the variable valve mechanism for the internal combustion engine described in (3), specifically, the offset amount L is L ≦ Vc + {(D / 2) ² −C ² } ^1/2. Is set to

The perspective view which shows schematic structure of the variable valve mechanism of the internal combustion engine which concerns on this invention. Explanatory drawing which showed typically the state which looked at the positional relationship of the valve lifter and rocking cam in 1st Embodiment of this invention from the cylinder row direction of the internal combustion engine. Explanatory drawing which showed typically the state which looked at the positional relationship of the valve lifter and rocking cam in 2nd Embodiment of this invention from the cylinder row direction of the internal combustion engine. Explanatory drawing which showed typically the state which looked at the positional relationship of the valve lifter and rocking cam in 3rd Embodiment of this invention from the cylinder row direction of the internal combustion engine. Explanatory drawing which showed typically the tolerance | permissible_range of the 1st contact position in 3rd Embodiment of this invention. Explanatory drawing which showed typically the state which looked at the positional relationship of the valve lifter and rocking cam in 4th Embodiment of this invention from the cylinder row direction of the internal combustion engine. Explanatory drawing which showed typically the tolerance | permissible_range of the 1st contact position in 4th Embodiment of this invention.

Explanation of symbols

9 ... Oscillating cam 10 ... Valve lifter 21 ... Valve stem

Claims (5)

A variable valve mechanism for an internal combustion engine that is configured to have a swing cam that pushes down a valve lifter that abuts the end face of the valve stem of the engine valve, and that can continuously vary the valve lift characteristics of the engine valve,
A variable valve mechanism for an internal combustion engine in which the first contact position on the valve lifter crown surface where the swing cam first contacts the valve lifter when the engine valve is opened is offset to the cam base circle side of the swing cam In
The variable valve mechanism for an internal combustion engine, wherein an offset amount of the first contact position from the center position of the crown surface of the valve lifter is set to be equal to or less than the radius of the end face of the end portion of the valve stem. A variable valve mechanism for an internal combustion engine that is configured to have a swing cam that pushes down a valve lifter that abuts the end face of the valve stem of the engine valve, and that can continuously vary the valve lift characteristics of the engine valve,
A variable valve mechanism for an internal combustion engine in which the first contact position on the valve lifter crown surface where the swing cam first contacts the valve lifter when the engine valve is opened is offset to the cam base circle side of the swing cam In
An internal combustion engine characterized in that an offset amount of the first contact position from a central position of the crown surface of the valve lifter is set to be equal to or less than a length obtained by adding a valve clearance to a radius of a terminal portion end surface of the valve stem. Variable valve mechanism. A variable valve mechanism for an internal combustion engine that is configured to have a swing cam that pushes down a valve lifter that abuts the end face of the valve stem of the engine valve, and that can continuously vary the valve lift characteristics of the engine valve,
A variable valve mechanism for an internal combustion engine in which the first contact position on the valve lifter crown surface where the swing cam first contacts the valve lifter when the engine valve is opened is offset to the cam base circle side of the swing cam In
An offset amount L from the crown contact center position of the valve lifter at the first contact position to the cam base circle side of the swing cam is an offset amount C of the swing cam in the cylinder row direction of the internal combustion engine, and the valve stem. And a radius D / 2 of the end face of the terminal portion of the internal combustion engine. The variable valve mechanism for an internal combustion engine according to claim 3, wherein the offset amount L is set so as to satisfy the following expression (1).
[Formula 1] L ≦ {(D / 2) ² −C ² } ^1/2 (1) The variable valve mechanism for an internal combustion engine according to claim 3, wherein the offset amount L is set so as to satisfy the following expression (2), where Vc is a valve clearance.
[Expression 2] L ≦ Vc + {(D / 2) ² −C ² } ^1/2 (2)

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