JP2003161125A - Variable valve system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable valve system which enhances mechanical retentivity of a lifter guide member with respect to a cylinder head and surely prevents rotation of a following contact and a direct striking type valve lifter with respect to a solid cam. <P>SOLUTION: A direct striking type valve lifter 10 is reciprocated with a solid cam through the medium of a following contact 21 to open/close a valve. A guide part 33 of a lifter guide member 30 is engaged with a guided part 27 on the inside of the valve lifter 10, so as to guide the reciprocating movement of the valve lifter 10 and to prevent rotation of the following contact 21 and the valve lifter 10 with respect to the solid cam. A spring seat 31 for receiving a valve spring is provided to the lifter guide member 30, wherein an insertion part 35 is formed in the center part. The insertion part 35 is inserted into the valve guide 25. Mesh of serrations 36 and 37 provided to both the insertion part 35 and the valve guide 25 leads to prevention of rotation of the lifter guide member 30 with respect to the cylinder head 7. <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. 10 and 11, there is disclosed a variable valve mechanism in which a three-dimensional cam 100 reciprocates a direct-acting valve lifter 102 via a follower contact 101 to open and close a valve 103 with the valve lifter 102. Valve lifter 10
2 is formed in an inverted cup shape, and a lifter guide member 104 is inserted inside thereof. Lifter guide member 104
A guide 105 for preventing the follower contact 101 and the valve lifter 102 from rotating with respect to the three-dimensional cam 100;
Spring seat part 1 for receiving valve spring 106
07 and a cylindrical portion 110 fixed to the valve guide 109 fixed to the cylinder head 108 by press-fitting. However, according to the conventional variable valve mechanism, the lifter guide member 104 is fixed to the valve guide 109 by the cylindrical portion 110 having a perfect circular cross section. There is a problem that the mechanical holding force of the lifter guide member 104 with respect to 108 becomes insufficient. For this reason, when an excessive rotational force acts on the direct-drive valve lifter 102, the lifter guide member 104 rotates with respect to the cylinder head 108, and the follow-up contact 101 and the direct-drive valve lifter 102 rotate with respect to the three-dimensional cam 100. There was a possibility. [0004] It is an object of the present invention to provide a variable valve mechanism capable of reliably preventing rotation of a follower contact and a direct-acting valve lifter with respect to a three-dimensional cam by strengthening the mechanical holding 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, A direct-acting valve lifter, 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. A rotation preventing portion for preventing rotation of the valve lifter and a spring seat portion for receiving a valve spring are provided. An insertion portion to be inserted into the attachment portion is formed, and at least one of the insertion portion and the attachment portion is provided with a locking portion for locking the other, and the locking portion prevents the lid guide member from rotating with respect to the cylinder head. And Here, the mounting portion on the cylinder head side may be a part integrally formed with the cylinder head, or may be a separate part fixed to the cylinder head. In the latter case, for example, a valve guide for guiding the stem portion of the valve can be used as the mounting portion. The locking portion may be provided on both the insertion portion and the attachment portion, or may be provided on either one of them. Examples of the former locking portion include a shape portion that forms a locking structure by meshing teeth, a locking structure by fitting a concave portion and a convex portion, a locking structure by joining flat surfaces, and the like. Examples of the latter locking portion include a shape portion that forms a locking structure that bites into the other by press fitting, a locking structure that protrudes the other by press fitting, and the like. The variable valve mechanism according to the present invention can be applied to either one of an intake valve and an exhaust valve, but is preferably applied to both. An embodiment of a variable valve mechanism in which the present invention is applied to both an intake valve and an exhaust valve will be described below with reference to the drawings. Therefore, in the embodiment, simply referring to a valve means both an intake valve and an exhaust valve. [0008] As shown in FIGS.
In FIG. 1, a three-dimensional cam 2 in which the cam profile is continuously changed in the axial direction from the right low-rotation cam profile to the left high-rotation cam profile in FIG. 1 is formed. The three-dimensional cam 2 has a base circle portion 2a and a nose portion 2b.
Since the base circle portion 2a has the same radius in both the low-rotation cam profile and the high-rotation cam profile, the base circular portion 2a is a cylindrical surface having no inclination. But,
The nose portion 2b is inclined like a conical surface because the valve opening angle and the lift amount are small in the low rotation cam profile and the valve opening angle and the lift amount are large in the high rotation cam profile. 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 in accordance with an operating condition such as the rotational speed of the internal combustion engine. The displacement device 3 includes, for example, a guide portion of the camshaft 1 using splines and a camshaft 1 using hydraulic pressure.
(Both not shown), and are controlled by a control device (not shown) such as a microcomputer that operates based on a rotation sensor, an accelerator opening sensor, and the like of the internal combustion engine. 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, and a direct-hit valve lifter 10 is inserted into the lifter guide hole 8. It is inserted so that it can slide back and forth in the vertical direction. Immediately below the lifter guide hole 8, a valve guide 25 is fixed to the cylinder head 7, and a stem portion 4a of the valve 4 is provided inside the valve guide 25.
Are slidably inserted. A recess 26 is formed in the cylinder head 7 around the valve guide 25,
The lower end of a lifter guide member 30 that guides the reciprocating motion of the direct hit valve lifter 10 is fitted into the recess 26. 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. When the internal combustion engine is rotating at a low speed, 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 contacting the base circle portion 2a (see FIG. 3A), and swings by the same angle as the contact line angle when contacting the nose portion 2b (see FIG. 3B). 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. A pressing portion 12 for pressing the stem portion 4a is provided on the 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. In contact. At the base of the lifter guide member 30, a disc-shaped spring seat portion 31 for receiving the lower end of the valve spring 6 is provided. Then, the valve 4 is moved by the valve spring 6.
Are biased in the closing direction, and the direct-hit valve lifter 10 is biased toward the three-dimensional cam 2. At the lower end of the inner wall surface of the side wall portion 13, guided portions 27 are protruded at two locations approximately 180 degrees apart, and a guided portion 28 is provided at two locations without the guided portion 27. In the lifter guide member 30, guide portions 33 are formed at two places approximately 180 degrees apart from each other so as to rise from the outer peripheral edge of the spring seat portion 31. The guide part 33 is a side wall part 13
Of the guided portion 27, slides up and down in the vicinity of the inner wall surface of the side wall portion 13, and slidably engages with the side end surface of the guided portion 27. As a result, the guide portion 33 functions as a guide portion for guiding the reciprocating motion of the direct-hit type valve lifter 10, and the follower 2 contacts the three-dimensional cam 2.
The first and direct-acting valve lifters 10 function as rotation preventing portions for preventing rotation. The spring seat portion 31 of the lifter guide member 30 causes the recess 26
Is held in pressure contact with the bottom surface. Spring seat part 31
A stepped cylindrical insertion portion 35 is formed by squeezing upward at the center portion of the valve guide 25. This insertion portion 35 is inserted into an upwardly projecting portion of the valve guide 25, which is a mounting portion on the cylinder head 7 side. A serration 36 extending in the vertical direction is provided on the inner periphery of the insertion portion 35, and a serration 37 is provided on the outer periphery of the valve guide 25. Serration 36,
Reference numeral 37 denotes a locking portion that locks one of the other around the axis of the valve, and the lid guide member 30 is prevented from rotating with respect to the cylinder head 7 by engagement of these teeth. A member 24 for oil-sealing the stem portion 4a is attached to the upper end of the insertion portion 35. Therefore, according to the variable valve mechanism of the present embodiment, the following operational effects can be obtained. (A) The lifter guide member 30 has the serrations 36, 3
Since the rotation of the lifter guide member 30 with respect to the cylinder head 7 can be strengthened because the rotation of the lifter guide member 30 with respect to the cylinder head 7 is prevented by the engagement of the cylinder head 7. (B) Therefore, even when an excessive rotational force acts on the direct-hit valve lifter 10, there is no possibility that the lifter guide member 30 will rotate with respect to the cylinder head 7, and the follow-up contact 21 and the direct-hit type The rotation of the valve lifter 10 can be reliably prevented. (C) Since the serrations 36 and 37 are provided on both the insertion portion 35 and the valve guide 25, the lifter guide member 30 can be easily and quickly stopped without tools as compared with a detent structure by press fitting. Can be assembled. The present invention is not limited to the configuration of the above-described embodiment. For example, the structure for preventing the rotation of the lifter guide member 30 may be configured as follows. (1) As shown in FIG. 5 (a), the inner periphery of the insertion portion 35 is formed in a perfect circular cross section, the serration 37 is provided on the outer periphery of the valve guide 25 as a locking portion, and the lifter guide member 30 is provided.
At the time of assembling, as shown in FIG. 2B, the insertion portion 35 is press-fitted into the valve guide 25, and the pointed end of the serration 37 is cut into the inner peripheral surface of the insertion portion 35. Stopping against the head 7. (2) As shown in FIG.
5, a pair of flat portions 39 is provided on the inner periphery of the valve guide 25 and a pair of flat portions 4 is provided on the outer periphery of the valve guide 25.
0, and as shown in FIG.
To prevent the lifter guide member 30 from rotating around the cylinder head 7. (3) As shown in FIG. 7A, a plurality of (for example, four) ridges 41 are provided on the inner periphery of the insertion portion 35 as locking portions.
The outer periphery of the valve guide 25 is formed in a perfect circular cross section, and when the lifter guide member 30 is assembled, as shown in FIG.
The lifter guide member 30 is prevented from rotating with respect to the cylinder head 7 by press-fitting the insertion portion 35 into the valve guide 25 and making the tip of the ridge 41 bite into the outer peripheral surface of the valve guide 25. (4) As shown in FIG.
5, a plurality of (for example, four) concave stripes 42 are provided on the inner periphery of the valve guide 25, and the outer periphery of the valve guide 25 is formed in a perfect circular cross section. ), The insertion portion 35 is pressed into the valve guide 25,
The lifter guide member 30 is prevented from rotating with respect to the cylinder head 7 by protruding several portions of the valve guide 25 into the concave streak 42. (5) As shown in FIG.
Serrations 44 are provided on the outer periphery of the cylindrical mounting portion 43 projecting from
The serrations 45 are provided on the inner periphery of the lower large diameter portion of the insertion portion 35, and the lifter guide member 30 is prevented from rotating with respect to the cylinder head 7 by the engagement of the serrations 44, 45. Since the variable valve mechanism of the present invention is constructed as described above, the mechanical holding force of the lifter guide member with respect to the cylinder head is strengthened, so that the follower contact and the direct contact with the three-dimensional cam can be improved. It has an excellent effect that the rotation of the hammer 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 showing a structure for preventing a direct-acting valve lifter and a lifter guide member from rotating 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 perspective view showing a modification of the rotation preventing structure. FIG. 6 is a perspective view showing another modification of the rotation preventing structure. FIG. 7 is a perspective view showing another modification of the rotation preventing structure. FIG. 8 is a perspective view showing another modification of the rotation preventing structure. FIG. 9 is a sectional view showing another modification of the rotation preventing structure. FIG. 10 is a cross-sectional view showing a conventional variable valve mechanism. FIG. 11 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-drive valve lifter 21 Follow-up contact 25 Valve guide 30 Lifter guide member 31 Spring seat part 33 Guide part 35 Insertion part 36 Serration 37 Serration 39 Flat part 40 Flat part 41 Convex ridge 42 Concave ridge 43 Cylindrical mounting part 44 Serration 45 Serration

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Norio Kato             10 Hamadashita, Nakahata-cho, Nishio-shi, Aichi Pref.             Otics (72) Inventor Katsuhiko Motosugi             10 Hamadashita, Nakahata-cho, Nishio-shi, Aichi Pref.             Otics (72) Inventor Shinichiro Kikuoka             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Inside the car company F term (reference) 3G016 AA06 AA19 BA34 BA36 BB04                       BB06 CA16 CA50 CA52 CA57                       DA01 DA17 GA00                 3G018 AB07 BA04 BA24 DA17 DA18                       DA69 DA83 EA03 EA04 EA24                       FA03 FA06 FA07 GA00

Claims (1)

Claims: 1. A three-dimensional cam having a cam profile continuously changed in an axial direction, a displacement device for displacing the three-dimensional cam in an axial direction, and a contact line angle associated with rotation of the three-dimensional cam. A follower contact that contacts the three-dimensional cam while following the change; a direct-acting valve lifter that opens and closes a valve by being reciprocated by the three-dimensional cam through the follower contact; and biases the valve in a closing direction. A valve spring, and a lifter guide member for guiding reciprocal movement of the direct-acting valve lifter, wherein the lifter guide member has a follow-up contact to the three-dimensional cam and a rotation preventing portion for preventing rotation of the direct-acting valve lifter; A spring seat portion for receiving a spring, and an insertion portion to be inserted into the mounting portion on the cylinder head side is formed substantially at the center of the spring seat portion; A locking portion for locking the other in at least one of the insertion portion and the mounting portion is provided, a variable valve mechanism, characterized in that the lid guide member prevented from rotating relative to the cylinder head by the locking portion.