JP2003049620A - Variable valve system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a rotation inhibiting structure of a lifter body and a cam terminal with a simple constitution, to easily grind an outer peripheral face of a sidewall part and secure the accuracy, and to dispense with machining a recessed groove of a lifter guide hole. SOLUTION: This variable valve system comprises a solid cam, its displacement device 3 and a direct strike-type valve lifter 10, the direct strike-type valve lifter 10 is composed of the lifter body 11 and a following contact mechanism including the cam terminal 21. A rotation inhibiting pin 30 extended inside of the lifter body 11 is stood on a cylinder head 7b, a bulge part 15 inwardly bulging, is formed on a part of the sidewall part 13, and the bulge part 15 is provided with a fitting groove 16 for fitting the rotation inhibiting pin 30 in a state of being slidable in the reciprocating direction of the lifter body 11, and being restricted in the rotating direction of the lifter body 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve mechanism that changes valve timing and lift according to operating conditions of an internal combustion engine, and more particularly to a rotation preventing structure for a direct drive valve lifter.

[0002]

2. Description of the Related Art A variable valve mechanism using a three-dimensional cam whose cam profile changes continuously in the axial direction and a direct-acting valve lifter having a cam contactor that contacts the three-dimensional cam (for example, Japanese Patent Publication No. -45803, Japanese Patent Publication No. 6-847
According to Japanese Unexamined Patent Publication No. 22), the valve timing and the lift amount are continuously changed from the low rotation speed to the high rotation speed of the internal combustion engine, and precise control according to the operating condition of the internal combustion engine can be performed. This variable valve mechanism is provided with a rotation blocking structure that prevents the cam contactor from rotating with respect to the three-dimensional cam. However, in the rotation blocking structure described in the above publication, the number of parts is increased and the rigidity is lowered. There is a problem (pointed out in JP-A-2000-136704, which will be described later).

Therefore, the present applicant has previously proposed, as a rotation preventing structure capable of solving the above-mentioned problems, as shown in FIG. 7, on the outer peripheral surface of the end wall portion 118 of the inverted cup-shaped lifter body 107 of the direct hit type valve lifter. A convex portion 125 that prevents rotation of the lifter body 107 with respect to the cylinder head 109 is integrally provided, and a concave groove 126 into which the convex portion 125 is slidably fitted is provided in a part of the guide hole 110 of the cylinder head 109. It has been proposed (Japanese Patent Laid-Open No. 2000-136704). According to this variable valve mechanism, the number of parts can be reduced and the rigidity can be increased.

[0004]

However, according to the rotation preventing structure of FIG. 7, since the convex portion 125 is provided outside the end wall portion 118, the convex portion 125 interferes with the side wall portion 119.
It became difficult to grind the outer peripheral surface of the, and it was also difficult to secure the accuracy of the surface. Further, it is necessary to form the concave groove 126 in a part of the guide hole 110, and it takes a lot of time and labor to process the groove.

Therefore, an object of the present invention is to realize a rotation preventing structure for a lifter body and a cam contactor with a simple structure, to facilitate grinding of the outer peripheral surface of the side wall portion and to ensure accuracy, and to lifter guides. An object of the present invention is to provide a variable valve mechanism that can eliminate the groove processing of holes.

[0006]

In order to achieve the above object, a variable valve mechanism according to the present invention comprises a three-dimensional cam whose cam profile is continuously changed in the axial direction and an operation such as the rotational speed of an internal combustion engine. A variable valve mechanism comprising: a displacement device for axially displacing the solid cam depending on the situation; and a direct-acting valve lifter for opening and closing a valve by reciprocating based on a cam profile of the solid cam. The direct hitting valve lifter is a lifter body having an end wall portion and a cylindrical side wall portion, and is provided on the end wall portion so as to follow the change of the contact line angle due to the rotation of the solid cam and to form the solid cam. A follow-up contact mechanism including a cam contactor (cam contactor) that makes contact with the cylinder head, a rotation prevention pin extending inward of the lifter body is provided upright in the cylinder head, and a part of a side wall portion of the lifter body is inwardly extended. Expansion A fitting portion that is fitted to the rotation preventing pin so as to be slidable in the reciprocating direction of the lifter body and constrained in the rotating direction of the lifter body. It is characterized in that a groove is provided.

Here, the position of the bulging portion may be anywhere on the inner circumference of the side wall portion, and may be provided in a direction advantageous for disposing peripheral members such as a retainer. The position of the bulging portion may be anywhere in the entire height of the side wall portion, but it is preferable to provide the bulging portion at or near the lower end of the opening. The width of the bulging portion is not particularly limited, but is preferably about 1/20 to 1/2 of the inner peripheral length of the side wall portion. Further, the number of the rotation preventing pin, the bulge portion and the fitting groove is only one each, but may be plural.

The bulging portion is not particularly limited in terms of its bulging amount, but it is preferable that the bulging portion bulges inward by 3 to 8 mm as measured from the outer peripheral surface of the side wall portion. If it is less than 3 mm, it becomes difficult to form the fitting groove, and if it exceeds 8 mm, it interferes with the valve spring.

The bulging portion is not particularly limited in its forming method, but the following modes can be exemplified. (1) A bulging portion formed by bending a part of the lower edge of the opening of the side wall portion deeper inward than the remaining portion. (2) A bulging portion formed by forming a part of the side wall portion to be thicker inward than the remaining portion.

The center of the pressing portion for pressing the valve protruding from the lower surface of the end wall portion bulges from the center of the end wall portion so that the rotation prevention pin and the bulging portion are less likely to interfere with the valve spring. It is preferable that the portion is located at a position shifted to the side opposite to the side where the portion is located. The shift amount is not particularly limited, but is preferably about 0.1 to 3.0 mm.

The solid cam is preferably one in which the cam profile is continuously changed in the axial direction from the low rotation cam profile to the high rotation cam profile.

[0012] The valve timing phase, the valve opening angle and the lift amount in the low rotation cam profile, and the valve timing phase in the high rotation cam profile,
The valve opening operating angle and the lift amount can be appropriately set according to the requirements of each internal combustion engine. However,
In many cases, the low rotation cam profile has a small valve opening angle and lift amount, and the high rotation cam profile has a large valve opening angle and lift amount.

When the three-dimensional cam is displaced stepwise by the displacement device, it may be changed in two steps, but in that case, it is preferable to be able to adjust the displacement in two steps. More preferably, the solid cam is displaced in at least three steps. Most preferably, the solid cam is continuously displaced. The displacement device is not limited to a specific structure, and may be one using hydraulic pressure, electromagnetic force, or the like.

The follow-up contact mechanism is not particularly limited, but is composed of a semi-cylindrical inner surface seat provided at the center of the lifter bridge and a cam contactor fitted to the semi-cylindrical inner surface seat so as to be able to roll. preferable. The cam contact may be a replacement part for adjusting the valve clearance. In addition, the roller mechanism with cam contactor shown in Japanese Patent Laid-Open No. 9-296714 can be applied.

The variable valve mechanism of the present invention can be applied to either the intake valve or the exhaust valve, but is preferably applied to both.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments 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, the term “valve” simply means both the intake valve and the exhaust valve.

First, FIGS. 1 to 4 show a variable valve mechanism according to a first embodiment. The camshaft 1 has a low rotation cam profile on the left side to a high rotation cam profile on the right side in FIGS. Up to this point, the three-dimensional cam 2 having the cam profile continuously changed in the axial direction is formed. The three-dimensional cam 2 is composed of 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 is a non-inclined cylindrical surface. However, the nose part 2b
Has a small valve opening angle and lift amount in the low rotation cam profile, and has a large valve opening angle and lift amount in the high rotation cam profile, and therefore is inclined like a conical surface.

At the end of the camshaft 1, there is provided a displacement device 3 for continuously displacing the camshaft 1 and the solid cam 2 in the axial direction according to the operating conditions such as the number of revolutions of the internal combustion engine. The displacement device 3 includes, for example, a guide portion of the camshaft 1 using a spline and a drive portion of the camshaft 1 using hydraulic pressure (all are not shown), and a rotation sensor of an internal combustion engine, an accelerator opening sensor, etc. Is controlled by a control device (not shown) such as a microcomputer that operates based on the above.

A guide hole 8 is formed in the cylinder head 7a below the cam shaft 1, and the valve 4 is reciprocally moved up and down in the illustrated example based on the cam profile of the three-dimensional cam 2 in the guide hole 8. A direct-type valve lifter 10 for opening and closing is arranged slidably. An escape recess 9 is formed on the upper surface of the cylinder head 7a to allow the rotational trajectory of the three-dimensional cam 2 to escape (see FIG. 3A). The stem portion 4a of the valve 4 is inserted and guided by a valve guide 25 fixed to the cylinder head 7b below the valve lifter 10.

The direct-acting valve lifter 10 includes a lifter body 11 having a disk-shaped end wall portion 12 and a cylindrical side wall portion 13 (skirt portion), and a three-dimensional cam 2 provided on the end wall portion 12.
And a follow-up contact mechanism including a cam contactor 21 that comes into contact with the three-dimensional cam 2 while following the change in the contact line angle due to the rotation of the.

A pressing portion 14 for pressing the end portion of the stem portion 4a is provided on the lower surface of the end wall portion 12, and a shim for adjusting the valve clearance is provided between the pressing portion 14 and the end portion of the valve 4. May be interposed. A valve spring 6 is mounted between a valve retainer 5 attached near the upper end of the valve 4 and a spring seat 27 abutted against an annular recess 26 on the upper surface of the cylinder head 7b.

The follow-up contact mechanism will be described in detail. At the center of the upper surface of the end wall portion 12, a raised portion 18 which is long in the direction perpendicular to the axis of the three-dimensional cam 2 is integrally formed, and the raised portion 18 extends in the same direction. An extending semi-cylindrical inner surface seat 19 is provided as a recess. Further, an engaging recess 20 is provided at a substantially central portion in the longitudinal direction of the semi-cylindrical inner surface seat 19. The cam contactor 21 is of a half-columnar shape including a semi-cylindrical surface 22 that swingably contacts the semi-cylindrical inner surface seat 19 and a flat contact surface 23 that contacts the solid cam 2. A fan-shaped engaging convex portion 24 is integrally provided at a central portion in the longitudinal direction of the semi-cylindrical surface 22, and the engaging convex portion 24 is engaged with the engaging concave portion 20 and is swingably sandwiched. With this engagement, with the end face in the longitudinal direction of the cam contactor 21 appearing,
Movement of the cam contactor 21 in the longitudinal direction is restricted. The cam contactor 21 follows the change of the contact line angle accompanying the rotation of the three-dimensional cam 2 by swinging at a small angle, and the contact surface 2
3 contacts the solid cam 2.

Now, in the present embodiment, the upper end portion is a round bar-shaped rotation preventing pin 30 extending into the inside of the lifter body 11 (specifically, immediately inside the side wall portion 13 so that it can be fitted into a fitting groove described later). Is erected by being inserted and fixed in the mounting hole 31 of the cylinder head 7b. Further, a part of the lower edge of the opening of the side wall portion 13 is bent deeper inward than the remaining portion, so that a bulge portion 15 that bulges inward is provided over substantially half the circumference of the side wall portion 13. The bulging portion 15 bulges inward by about 4 mm as measured from the outer peripheral surface of the side wall portion 13 at the central portion in the circumferential direction, and the bulging amount gradually decreases as the distance from the central portion increases. Since it is preferable that the height of the side wall portion 13 is uniform over the entire circumference, the height of the side wall portion 13 before bending as described above is made longer than the remaining portion at the portion which will be the bulging portion 15 and then bent. The height of the rear side wall portion 13 is made uniform around the entire circumference. A semi-circle is fitted in the central portion of the bulging portion 15 so as to be slidable in the reciprocating direction of the lifter body 11 with respect to the rotation blocking pin 30 and to be restrained in the rotating direction of the lifter body 11. -Shaped fitting groove 16
Is recessed from the inner edge. By this fitting, the cam contactor 21 and the lifter body 11 can be prevented from rotating with respect to the three-dimensional cam 2, and the correct positional relationship between the three-dimensional cam 2 and the cam contactor 21 can be maintained. The shapes of the rotation blocking pin 30 and the fitting groove 16 can be changed appropriately.

Further, in the present embodiment, the pressing portion 14 is positioned so that the center Q of the pressing portion 14 is shifted from the center P of the end wall portion 12 to the side opposite to the side where the bulging portion 15 is located. The stem portion 4a and the center of the valve spring 6 are similarly shifted. The shift amount a is, for example, about 1.2 mm. With this shift,
The inner space of the lifter body 11 becomes relatively large on the side where the bulging portion 15 is present, and the rotation blocking pin 30 and the bulging portion 15 are separated from the outer diameter of the valve spring 6 with a margin, so that they interfere with the valve spring 6. It's getting harder. In particular, this shift method is preferable in the lifter body 11 in which the difference between the inner diameter of the side wall portion 13 and the outer diameter of the valve spring 6 is small.

According to the variable valve mechanism of the first embodiment configured as described above, the valve timing and the lift amount are continuously or stepwise changed by displacing the three-dimensional cam 2 in the axial direction, Precise control according to the operating condition of the internal combustion engine can be performed, and thus various characteristics such as torque, output, fuel consumption, and cleanliness of exhaust gas can be maximized over the entire rotation range.

The rotation of the cam contactor 21 and the lifter body 11 is caused by the engagement of the rotation prevention pin erected on the cylinder head 7b and the fitting groove 16 of the bulging portion 15 which bulges inward of the side wall portion 13. Can be prevented, the following effects can be obtained. The structure is simple and the number of parts is small. Since it is not necessary to provide a convex portion unlike the conventional one on the outer side of the end wall portion 13, the outer peripheral surface of the side wall portion 13 can be easily ground and the accuracy of the surface can be secured easily. Since it is not necessary to form the concave groove in the guide hole 8 unlike the conventional case, the concave groove machining can be eliminated and the labor of the machining can be greatly reduced. It should be noted that the processing of the mounting hole 31 is simple and does not take much time.

Next, FIGS. 5 and 6 show a variable valve mechanism according to a second embodiment, in which the bulging portion 15 forms a part of the side wall portion 13 inwardly of the remaining portion so as to have a thicker wall (for example, a cold portion). It differs from the first embodiment only in that it is formed by forging) and that the circumferential length of the bulging portion 15 is about 1/6 to 1/8 of the inner circumference of the side wall portion 13. ing. Although the height of the bulging portion 15 of the first embodiment is equal to the thickness of the side wall portion 13, the height of the bulging portion 15 of the present embodiment can be made larger than the thickness of the side wall portion 13. It is also possible to extend to the end wall portion 12 as shown by the two-dot chain line in FIG. The fitting groove 16 is recessed from the inner side so as to penetrate the bulging portion 15 from the bottom to the top, but when the height of the bulging portion 15 is large, the fitting groove 16 ends halfway from the bottom of the bulging portion 15. It may be recessed from the inside. Also according to this embodiment, the same effect as that of the first embodiment can be obtained.

The present invention is not limited to the above-described embodiment, and is embodied by appropriately changing the configuration and shape of the rotation stopping member and the configuration and shape of other parts without departing from the spirit of the invention. You can also

[0029]

Since the variable valve mechanism of the present invention is constructed as described above, the rotation preventing structure for the lifter body and the cam contactor can be realized with a simple structure, and the outer peripheral surface of the side wall portion can be prevented. It has an excellent effect that it is possible to facilitate the grinding process and ensure the accuracy, and to eliminate the concave groove process of the lifter guide hole.

[Brief description of drawings]

FIG. 1 is a perspective view showing a variable valve mechanism according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of a direct drive type valve lifter of the variable valve mechanism.

FIG. 3A is a plan view of the direct-acting type valve lifter,
(B) is a bottom view.

FIG. 4 is a sectional view of the variable valve mechanism.

5A and 5B show a direct-acting valve lifter of a variable valve mechanism according to a second embodiment, FIG. 5A is an exploded perspective view, and FIG. 5B is a bottom view.

FIG. 6 is a sectional view of the variable valve mechanism.

FIG. 7 is a perspective view showing a conventional variable valve mechanism.

[Explanation of symbols]

2 three-dimensional cam 3 Displacement device 4 valves 10 Direct hit type valve lifter 11 Lifter body 12 End wall 13 Side wall 14 Pressing part 15 Bulging part 16 Fitting groove 21 Cam contactor 30 rotation prevention pin

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Norio Kato             10 Hamadashita, Nakahata-cho, Nishio-shi, Aichi Stock Association             Company Otics (72) Inventor Katsuhiko Motosugi             10 Hamadashita, Nakahata-cho, Nishio-shi, Aichi Stock Association             Company Otics F-term (reference) 3G016 AA06 AA19 BA19 BA27 BA33                       BA34 BA36 BB04 BB06 CA05                       CA21 CA50 DA01 GA01                 3G018 AB02 AB16 BA04 BA09 BA10                       DA17 DA83 DA85 FA01 FA06                       FA07 GA14 GA17

Claims (5)

[Claims] 1. A three-dimensional cam whose cam profile is continuously changed in the axial direction, and a displacement device which displaces the three-dimensional cam in the axial direction according to operating conditions such as the rotational speed of an internal combustion engine.
In a variable valve mechanism including a direct-acting valve lifter that opens and closes a valve by reciprocating based on a cam profile of the solid cam, the direct-acting valve lifter has an end wall portion and a cylindrical side wall portion. A lifter body, and a follow-up contact mechanism provided on the end wall portion and including a cam contactor that comes into contact with the three-dimensional cam while following the change in the contact line angle accompanying the rotation of the three-dimensional cam, the cylinder head A rotation prevention pin extending inward of the lifter body is erected on the upper side of the lifter body, and a bulging portion that bulges inward is provided on a part of the side wall portion. A variable valve mechanism, wherein a fitting groove is provided so as to be slidable in a reciprocating direction and restrained in a rotating direction of a lifter body. 2. The variable valve mechanism according to claim 1, wherein the bulging portion bulges inward by 3 to 8 mm as measured from the outer peripheral surface of the side wall portion. 3. The variable valve mechanism according to claim 1, wherein the bulging portion is formed by bending a part of an opening lower edge of the side wall portion deeper inward than the remaining portion. 4. The variable valve mechanism according to claim 1, wherein the bulging portion is formed by forming a part of the side wall portion inwardly of the remaining portion so as to have a wall thickness. 5. The center of a pressing portion for pressing a valve protrudingly provided on the lower surface of the end wall portion is shifted from the center of the end wall portion to the side opposite to the side where the bulging portion is located. The variable valve mechanism according to any one of claims 1 to 4, wherein the variable valve mechanism is located at.