JP2003254022A - Variable valve system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely stop the rotations of a follow-up contact and direct hitting valve lifters for a solid cam by increasing the rotation stopping force of a lifter guide member applied to a cylinder head in a variable valve system. <P>SOLUTION: The direct hitting valve lifter 10 is reciprocatingly moved by the solid cam 2 through the follow-up contact 21 to open and close a valve 4. The lifter guide member 30 comprises two rotation stopping part 33 for stopping the rotation of two adjacent direct hitting valve lifters 10 relative to the solid cam 2 and a connection part 31 for connecting two rotation stopping parts 33 to each other. The lifter guide member 30 is locked to the cylinder head 7 by engaging the connection part 31 with two valve guides 25 for guiding two valves 4 opened and closed by two direct hitting valve lifters 10. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable operation in which a valve timing and a lift amount are continuously or stepwise changed from a low rotation to a high rotation of an internal combustion engine. It relates to a valve mechanism. 2. Description of the Related Art JP-A-10-196331 discloses that
As shown in FIGS. 7, 8 and 9, the three-dimensional cam 100 juxtaposed to the camshaft 99 makes the following contact 101
A variable valve actuation mechanism that reciprocates a direct-acting valve lifter 102 through the valve lifter 102 to open and close a valve 103 with the valve lifter 102 is disclosed. The valve lifter 102 is formed in an inverted cup shape, and a lifter guide member 104 is inserted inside thereof. The lifter guide member 104 has a three-dimensional cam 1
00 follower 101 and valve lifter 102
Rotation preventing portion 105 for preventing rotation of the cylinder, connecting portion 107 for receiving valve spring 106, and cylinder head 10
And a cylindrical portion 110 fixed to the valve guide 109 fixed by press-fitting. [0003] However, according to the conventional variable valve mechanism, the lifter guide member 104 is formed by a relatively small-diameter cylindrical portion 110 having a circular section 110 with a relatively small diameter.
, There is a problem that the rotation preventing force of the lifter guide member 104 against the valve guide 109 becomes insufficient. For this reason, the direct hit type valve lifter 10
When an excessive rotational force acts on the valve guide 109,
The lifter guide member 104 rotates with respect to the three-dimensional cam 10.
0 and follow-up contact 101 and direct-acting valve lifter 10
2 could rotate. SUMMARY OF THE INVENTION An object of the present invention is to provide a variable valve mechanism capable of reliably preventing rotation of a follow-up contact and a direct-acting valve lifter with respect to a three-dimensional cam by strengthening the rotation preventing force of a lifter guide member with respect to a cylinder head. It is in. In order to achieve the above object, a variable valve mechanism according to the present invention comprises a three-dimensional cam in which a cam profile is continuously changed in an axial direction, and a three-dimensional cam in an axial direction. The valve is opened and closed by reciprocating via the follower contact by the three-dimensional cam, the follower contacting the three-dimensional cam while following the change of the contact line angle accompanying the rotation of the three-dimensional cam, Direct-acting valve lifter, a valve guide fixed to the cylinder head for guiding the valve slidably, a valve spring for urging the valve in the closing direction, and a lifter guide member for guiding the reciprocating motion of the direct-acting valve lifter And the lifter guide member connects the two rotation preventing portions to each other to prevent rotation of two adjacent directly-driven valve lifters with respect to the three-dimensional cam, and connects the two rotation preventing portions. A connection part, and the lifter guide member is prevented from rotating with respect to the cylinder head by engaging the connection part with two valve guides for guiding two valves that are opened and closed by two direct-acting valve lifters. I do. The structure of the rotation preventing portion is not particularly limited. However, the structure of the direct hit type valve lifter is different from the rotation preventing portions having various shapes such as ridges, grooves, and holes provided on the side wall portion of the direct hitting valve lifter. Examples of members having various shapes such as a plate shape and a rod shape that allow reciprocation and engage so as to prevent rotation can be exemplified. [0007] The positions of the two rotation preventing portions provided on the lifter guide member are not particularly limited, and may be any positions. The shape of the connecting portion is not particularly limited, and may be 2
It suffices if there is a portion that can be engaged with two valve guides and has a portion where two rotation preventing portions are attached and a portion where two valve springs are received. Also, the outer peripheral edge shape of the connecting portion is
There is no particular limitation, and examples include a square, a circle, an ellipse, and a shape containing a curve. The cross-sectional shape of the outer diameter of the valve guide and the planar shape of the hole of the lifter guide member engaging with the outer diameter of the valve guide are not particularly limited. Examples include polygons, a combination of a circumference and a plane, and a perfect circle having a perfect circle and a ridge on the outer periphery. The variable valve mechanism according to the present invention can be applied to either an intake valve or an exhaust valve, but is preferably applied to both. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a variable valve mechanism in which the present invention is applied to two adjacent direct-acting valve lifters in both an intake valve and an exhaust valve arranged side by side on a camshaft will be described. This will be described with reference to the drawings. Therefore, in the embodiment, simply referring to a valve means both an intake valve and an exhaust valve. In addition, one of the two direct hitting valve lifters 10 is directly hitting type valve lifter 10A,
The other is a direct hit type valve lifter 10B. When it is simply referred to as the direct hit type valve lifter 10, it refers to both. Similarly, the rotation preventing unit 33 also includes the rotation preventing unit 33A on the side of the direct hit valve lifter 10A and the rotation preventing unit 3 on the side of the direct hit valve lifter 10B.
3B, and simply refer to both the rotation preventing portions 33. As shown in FIG. 1, a camshaft 1 has
In FIG. 1, three-dimensional cams 2 whose cam profiles are continuously changed in the axial direction are arranged in parallel from the right low rotation cam profile to the left high rotation cam profile. The three-dimensional cam 2 includes a base circular portion 2a and a nose portion 2b. The base circular portion 2a has the same radius in both the low-rotation cam profile and the high-rotation cam profile, and thus has a cylindrical surface without inclination. However, the nose portion 2b has a small valve opening angle and a small lift amount in the low rotation cam profile, and has a large valve opening angle and the large lift amount in the high rotation cam profile. I have. At the end of the camshaft 1, there is provided a displacement device 3 for continuously or stepwise displacing the camshaft 1 in the axial direction according to the operating condition such as the rotation speed of the internal combustion engine. The displacement device 3 includes, for example, a rotation preventing portion of the camshaft 1 using a spline and a driving portion of the camshaft 1 using a hydraulic pressure (both are not shown), and a rotation sensor and an accelerator opening sensor of an internal combustion engine. It is controlled by a control device (not shown) such as a microcomputer that operates based on the above. As shown in FIGS. 2 and 3, below the three-dimensional cam 2, a relief recess 15 for releasing the rotation trajectory of the three-dimensional cam 2 and a lifter guide hole 8 are formed in the cylinder head 7. A direct-hit valve lifter 10 is slidably inserted into the guide hole 8. Lifter guide hole 8
Right below the cylinder head 7, the valve guide 2
5, the stem 4a of the valve 4 is slidably inserted and guided inside the valve guide 25. A member 24 for oil-sealing the stem portion 4a is attached to the upper end of the valve guide 25. The direct hit type valve lifter 10 is formed in an inverted cup shape from an end wall portion 11 and a side wall portion 13. A semi-cylindrical inner surface seat 19 is formed on the upper surface of the end wall portion 11, and a half-divided cylindrical follow contact 21 is swingably supported on the inner surface seat 19. The follower contact 21 has a flat contact surface 23 and contacts the three-dimensional cam 2 at the contact surface 23 while following a change in the contact line angle accompanying the rotation of the three-dimensional cam 2. The valve 4 is opened and closed by the reciprocating motion of the direct hit type valve lifter 10 in the vertical direction via the follower contact 21 by the three-dimensional cam 2, and the lifter guide member 30 guides the reciprocating motion of the direct hit type valve lifter 10. It has become. A pressing portion 12 for pressing the stem portion 4a is provided on a lower surface of the end wall portion 11, and a shim 9 for adjusting valve clearance is interposed between the pressing portion 12 and the stem portion 4a. (Instead of the shim 9, the valve clearance can be adjusted by changing the thickness of the pressing portion 12.) A valve retainer 5 is attached to the upper end of the stem portion 4a, and the upper end of the valve spring 6 contacts the lower surface thereof. The valve 4 is urged in the closing direction by the valve spring 6, and the direct-acting valve lifter 10 is urged toward the three-dimensional cam 2. The lifter guide member 30 includes connecting portions 31 and 2
And three rotation preventing parts 33. The connecting portion 31 is a base portion of the lifter guide member 30 and has a shape in which both ends in the longitudinal direction are rounded in a semicircular shape.
Concatenate. The hole 32 of the connecting portion 31 has two valves 4 opened and closed by two direct-acting valve lifters 10.
The connecting portions 31 are press-fitted into the valve guides 25 and are engaged with the outer diameters of the two valve guides 25 for guiding each other. Further, the lower ends of the two valve springs 6 are received and pressed and held by the spring force of the valve springs 6. The two rotation preventing portions 33 prevent rotation of two adjacent directly-hit valve lifters 10 with respect to the three-dimensional cam 2, and are curved from the semicircular outer peripheral edges of both ends in the longitudinal direction of the connecting portion 31. It has a plate shape, and the rotation preventing portions 33A and 33B are provided so as to face each other on the connecting portion 31. At the lower end of the inner wall surface of the side wall portion 13 of the direct hit type valve lifter 10A, there are provided two rotation preventing portions 27 which are ridges extending in the longitudinal direction of the side wall portion 13 at positions where the rotation preventing portions 33A can enter.
Is provided on the short arc side between the two rotation preventing portions 27. Rotation prevention unit 33
A enters the inside of the side wall portion 13 from the entry portion 28 and moves up and down in a state of being close to the inner wall surface of the side wall portion 13 so as to allow reciprocation with the side end surface of the rotation prevention portion 27 and prevent rotation. Are slidably engaged. Direct-acting valve lifter 1
Similarly, at the lower end of the inner wall surface of the side wall portion 13 of 0B, a rotation-prevented portion 27 is protrudingly provided at two places, and an entry portion 28 is provided, and the rotation-prevention portion 33B enters from the entered portion 28. , Is slidably engaged with the side end surface of the rotation-prevented portion 27. As a result, the lifter guide member 30 is prevented from rotating with respect to the cylinder head 7 without shifting to either side. The variable valve mechanism according to the present embodiment operates as follows. First, at the time of low rotation of the internal combustion engine, the low rotation cam profile on the right side of the three-dimensional cam 2 corresponds to the following contact 21 as shown in FIG. The follower contact 21 does not tilt when coming into contact with the base circle portion 2a, and as shown in FIG.
When it comes into contact with the nose portion 2b, it swings by the same angle as the contact line angle. The direct-acting valve lifter 10 reciprocates based on the low-rotation cam profile to open and close the exhaust-side and intake-side valves 4 with a small valve opening angle and a small lift, thereby increasing low-speed torque and improving fuel efficiency. Let it. When the internal combustion engine is rotating at a high speed, the direct-acting valve lifter 10 reciprocates based on the left high-rotation cam profile to open and close the exhaust-side and intake-side valves 4 with a large valve opening angle and a large lift amount. And increase the high-speed output. As described above, according to the variable valve mechanism of the present embodiment, the following effects can be obtained. (A) By engaging the lifter guide member 30 with two adjacent valve guides 25, the cylinder head 7
Since the anti-slipping and anti-rotation are performed, the rotation inhibiting force of the lifter guide member 30 can be enhanced. (B) For this reason, even when an excessive rotational force acts on the direct-hit valve lifter 10, there is no possibility that the lifter guide member 30 rotates with respect to the valve guide 25, and the following contact 21
In addition, the rotation of two adjacent directly-driven valve lifters 10 can be reliably prevented. (C) If the lifter guide member 30 is engaged with and fixed to two adjacent valve guides 25, the lifter guide member 30
Is completed, there is no need to provide a recess in the cylinder head 7 and engage the lifter guide member 30. It should be noted that the present invention is not limited to the configuration of the above-described embodiment, and may be embodied with the following modifications without departing from the spirit of the invention. (1) As shown in FIG. 6A, the rotation preventing portion 33A and the rotation preventing portion 33B have the same direction, and the rotation preventing portion 33A is a semicircular outer peripheral edge of the longitudinal end of the connecting portion 31. And the rotation preventing portions 33B are formed so as to rise from an intermediate portion of the connecting portion 31.
A rotation preventing portion 33 for preventing the rotation of the valve lifter A and the direct hit valve lifter 10B. (2) As shown in FIG.
The rotation preventing portions 33A are provided at two locations with respect to 0A, and the rotation inhibiting portions 33B are also provided at two locations with respect to the direct hit valve lifter 10B. (3) Also, as shown in FIG.
To be rod-shaped. Since the variable valve mechanism of the present invention is constructed as described above, the force for preventing rotation of the lifter guide member with respect to the cylinder head is strengthened, and the follower contact and direct hit with the three-dimensional cam are achieved. It has an excellent effect that the rotation of the valve lifter can be reliably prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a variable valve mechanism according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of a direct-acting valve lifter in the variable valve mechanism. FIG. 3 is a sectional view of the variable valve mechanism. FIG. 4 is a sectional view showing an operation of the variable valve mechanism. FIG. 5 is a sectional view showing the operation of the variable valve mechanism. FIG. 6 is a perspective view showing a modification of the rotation prevention structure. FIG. 7 is a perspective view showing a conventional variable valve mechanism. FIG. 8 is a sectional view showing a conventional variable valve mechanism. FIG. 9 is an exploded perspective view showing a main part of the variable valve mechanism. [Description of Signs] 1 Camshaft 2 Solid cam 3 Displacement device 4 Valve 6 Valve spring 7 Cylinder head 10 Direct-hit valve lifter 21 Follow-up contact 30 Lifter guide member 31 Connecting portion 33 Rotation preventing portion

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Norio Ishikawa             10 Hamada-shi, Nakahata-machi, Nishio-shi, Aichi Pref.             Otics F term (reference) 3G016 AA06 AA19 BA19 BB04 BB06                       CA16 CA20 CA52 DA01 GA00                 3G018 AB07 AB18 BA04 DA17 DA83                       FA01 FA06 FA07 GA00

Claims (1)

1. A three-dimensional cam in which a cam profile is continuously changed in an axial direction, a displacement device for displacing the three-dimensional cam in an axial direction, and a contact line angle accompanying rotation of the three-dimensional cam. A follow-up contact that contacts the three-dimensional cam while following a change in the position, a direct-hit valve lifter that opens and closes a valve by being reciprocated by the three-dimensional cam through the follow-up contact, and is fixed to the cylinder head. A valve guide that slidably guides the valve, a valve spring that biases the valve in a closing direction, and a lifter guide member that guides the reciprocating motion of the direct-hit valve lifter, wherein the lifter guide member includes: It is provided with two rotation preventing portions for preventing rotation of two adjacent directly-driven valve lifters with respect to the three-dimensional cam, and a connecting portion for connecting the two rotation preventing portions. A variable valve, wherein the lifter guide member is prevented from rotating relative to a cylinder head by engaging the connecting portion with two valve guides for guiding two valves opened and closed by the two direct-acting valve lifters. mechanism.