JP2002309918A - Variable valve system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable valve system to continuously or gradually change a lift amount and an operation angle of a valve throughout the whole operation situation of an internal combustion engine and to effect precise control, and also the system simple in structure and capable of obtaining high reliability. SOLUTION: A seesaw arm 7 has its central part rockably axially mounted on the cam corresponding part of a rocker arm 1, and a first roller 8 and a second roller 9 are situated at one end part and the other end part of the seesaw arm 7, respectively. A first rotation cam 20 and a second rotation cam 30 to press the rollers 8 and 9, respectively, are rotatably situated. A phase changing device is provided to change a lift amount and an operation angle of a valve 5 by continuously or gradually changing the phase of the second rotary cam 30 to the first rotary cam 20 according to the operation situation of the internal combustion engine.

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 the valve lift and valve operating angle continuously or stepwise according to the operating condition of an internal combustion engine.

[0002]

2. Description of the Related Art In a normal valve operating mechanism, since the valve lift or valve operating angle does not change even when the operating condition of the internal combustion engine changes, various factors such as the output, torque, fuel consumption, and exhaust gas cleanness of the internal combustion engine are used. The characteristics cannot be compatible. In view of the above, various variable valve mechanisms that continuously or stepwise change the valve lift or valve operating angle in accordance with the operating conditions of an internal combustion engine have been proposed.

[0003]

However, in the case of a conventional small-step variable valve operating mechanism, for example, in which the internal combustion engine is changed in two or three stages between a low rotation region and a high rotation region, the entire operating condition is not improved. However, there are problems such as the inability to perform precise control over time, the occurrence of a valley in the torque characteristics at the switching point, and the difficulty in increasing reliability. Further, the conventional continuously variable type valve operating mechanism has a problem that only one of the valve lift and the operating angle can be changed, and it is difficult to enhance the reliability.

Accordingly, an object of the present invention is to solve the above-mentioned problems, to continuously or stepwise change the valve lift and valve operating angle over the entire operation state of the internal combustion engine, and to achieve precise control and structure. Is to provide a variable valve mechanism that is simple and can obtain high reliability.

[0005]

In order to achieve the above object, a variable valve mechanism according to the present invention has a seesaw arm pivotally mounted on a cam-corresponding portion of a rocker arm at the center thereof so as to be swingable. A first cam sliding contact portion and a second cam sliding contact portion are provided at one end and the other end of the first rotating cam and the second rotating cam respectively pressing the first cam sliding contact portion and the second cam sliding contact portion. A phase change device that rotatably provides a rotary cam and changes the valve lift and operating angle by changing the phase of the second rotary cam with respect to the first rotary cam continuously or stepwise according to the operating condition of the internal combustion engine. It is characterized by having provided. The cam corresponding portion means a portion corresponding to and pressed against the cam via the seesaw arm.

The rocker arm and the seesaw arm may swing in different planes, but it is preferable that the rocker arm and the seesaw arm swing in the same plane for space efficiency.

The first cam sliding contact portion or the second cam sliding contact portion may be a fixed hard tip or a rotatable roller. However, in consideration of sliding resistance and wear, at least one of the first cam sliding contact portion or the second cam sliding contact portion (preferably both)
Is preferably a roller rotatably mounted on a seesaw arm.

Here, the rocker arm may be any of the following types. (1) The rocker arm has a swing center at one end, a cam corresponding portion at the center, and a valve pressing portion at the other end (so-called swing arm). (2) The rocker arm has a swing center at the center, a cam corresponding portion at one end, and a valve pressing portion at the other end.

When the rocker arm and the seesaw arm swing in the same plane, the present invention is preferably embodied in the above-mentioned type (1) in that the seesaw arm does not protrude from the rocker arm and the space efficiency is good. That is, the rocker arm has a swing center at one end,
It is preferable that the cam corresponding portion is provided at the center and the valve pressing portion is provided at the other end, and the seesaw arm is mounted on the cam corresponding portion.

As the swing center, the following two embodiments can be exemplified. (A) A mode in which the swing center portion is a concave spherical portion supported by a pivot. (B) A mode in which the swing center portion is a shaft hole portion on which the seesaw arm is rotatably supported.

An adjuster for preventing a gap from being formed between each cam sliding contact portion and the cam may be connected to the swing center portion. Although the structure of the adjuster is not particularly limited, the inner member and the bottomed hole formed in the cylinder head that can be brought into contact with and separated from each other, and a lost motion spring that biases the inner member and the bottomed hole in the separating direction are provided. And mechanical adjusters (mechanical adjusters). More specifically, a cup-shaped inner member whose side peripheral walls are engaged inward and outward with the opening sides facing each other, a bottomed hole formed in the cylinder head, a cup inner bottom surface and a bottomed hole of the inner member. And a coil spring as a lost motion spring installed in a compressed state therebetween.

It is preferable that a tappet clearance adjusting mechanism using a screw is provided between the swing center portion and the adjuster. For example, in the above mode (a), a tappet clearance adjustment mechanism in which a male screw provided on a pivot is screwed into a female screw provided on an adjuster so as to adjust the screwing amount can be exemplified.

Although the phase changing device is not particularly limited, a device having a helical spline mechanism, a drive unit using hydraulic pressure, and a control device such as a microcomputer can be exemplified.

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

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a variable valve mechanism embodying the present invention will be described with reference to FIGS. A swing arm type rocker arm 1 is used for the variable valve mechanism. One end of the rocker arm 1 is a swing center portion in which a concave spherical portion 2 formed on the rocker arm 1 is supported by a pivot 3. The other end of the rocker arm 1 is bifurcated, and a valve pressing portion 4 is formed at a lower portion of each end to press a valve 5.

A center portion of a seesaw arm 7 formed in a substantially V shape is disposed in a seesaw arm arrangement hole 6 formed in a cam corresponding portion at the center of the rocker arm 1.
Is pivotally mounted about an axis perpendicular to the arm side wall. Therefore, the rocker arm 1 and the seesaw arm 7 swing in the same plane.

One end of the seesaw arm 7 is the rocker arm 1
A first roller 8 (which functions as a base roller in the present embodiment) as a first cam sliding contact portion is disposed in a fork formed at one end of the first roller 8 to extend obliquely upward toward the center of the swinging motion. The first roller 8 is rotatably mounted on an axis perpendicular to the fork side wall. The other end of the seesaw arm 7 extends obliquely upward toward the valve pressing portion 4, and a fork formed at the other end has a second roller 9 as a second cam sliding contact portion (in this embodiment, as an additional roller). The second roller 9 is rotatably mounted on an axis perpendicular to the side wall of the fork.

Above the first roller 8, a first rotary cam 20 is provided.
(It functions as a base rotating cam in this embodiment.) Is rotatably mounted on the shaft, and presses the first roller 8 which is the first cam sliding contact portion.

The first rotary cam 20 has a base circle 20a,
A nose gradually increasing portion 20b having a gradually increasing protrusion amount, a nose 20c having a substantially equal protrusion amount and continuing at a wide angle, and a nose gradually decreasing portion 20d having a gradually decreasing protrusion amount.

Above the second roller 9, a second rotary cam 30 is provided.
(In this embodiment, it functions as an additional rotating cam.) Is rotatably mounted on the shaft, and the second roller 9 serving as the second cam sliding contact portion.
Is pressed.

The second rotary cam 30 has a base circle 30a,
A nose gradually increasing portion 30b having a gradually increasing protrusion amount, a nose 30c having a substantially equal protrusion amount and continuing at a wide angle, and a nose gradually decreasing portion 30d having a gradually decreasing protrusion amount.

The second rotating cam 3 with respect to the first rotating cam 20
0 is a phase in which the lift amount and operating angle of the valve 5 are changed by changing the relative phase continuously or stepwise (preferably three or more steps, more preferably four or more steps) according to the operating condition of the internal combustion engine. A change device (not shown) is provided.

In the phase changing device, the piston provided with the helical spline moves in the axial direction while rotating at a predetermined angle by hydraulic pressure, and the rotation acts on the second rotating cam 30, whereby the second rotating cam 30 is moved relative to the first rotating cam 20. The structure is such that the relative phase of the two-rotation cam 30 is changed, and is controlled by a control device such as a microcomputer based on a detection value from a rotation sensor or an accelerator opening sensor of the internal combustion engine.

The variable valve mechanism configured as described above
It works as follows. First, FIG. 2 (a) → (b) → FIG.
(A) → (b) shows the phase relationship between the first rotating cam 20 and the second rotating cam 30 under an operating condition that requires the maximum lift amount and the maximum operating angle, and the operation by the phase relationship. FIG.
As shown in (a), the base circle 20 of the first rotary cam 20
When the first half of a is oriented to the first roller 8 (oriented with a gap in the present embodiment, but slidably contacted in a second embodiment described later), the second half of the base circle 30a of the second rotary cam 30. Slides on the second roller 9. As shown in FIG. 2B, when the rear half of the base circle 20a is oriented to the first roller 8 (same as above), the nose gradually increasing portion 30b or the nose 30
The first half of c is in sliding contact with the second roller 9. At this time, the lift of the valve 5 has not yet occurred. As shown in FIG. 3A, when the first half of the nose 20 c slides on the first roller 8, the second half of the nose 30 c slides on the second roller 9.
At this time, the first roller 8 receives the maximum pressing force by the first rotating cam 20, and the second roller 9 receives the maximum pressing force by the second rotating cam 30. Accordingly, the seesaw arm 7 that supports the first roller 8 and the second roller 9 together is also subjected to the maximum pressing, and the rocker arm 1 that supports the seesaw arm 7 also swings to the maximum. At that time, the lift amount L of the valve 5 is generated and increased to reach the maximum value Lmax, and the operating angle also becomes maximum (see FIG. 6). As shown in FIG.
When the rear half of the roller c slides on the first roller 8, the nose gradually decreasing part 30d or the first half of the base circle 30a
In sliding contact with At this time, since the second roller 9 is raised and the seesaw arm 7 is also raised, the lift amount L of the valve 5 is reduced to zero.

Next, FIGS. 4A to 4B show the phase relationship between the first rotating cam 20 and the second rotating cam 30 under an operating condition where a small lift amount and a small operating angle are required, and the action by the phase relationship. Is shown. As shown in FIG. 4A, when the nose gradually increasing portion 20b or the initial portion of the nose 20c slides on the first roller 8 to increase the lift amount of the valve by 5 degrees, the nose gradually decreasing portion 30d becomes the second roller. 9 and the second roller 9 starts to move upward, so that the lift amount L and the operating angle of the valve 5 are both very small (see FIG. 6). FIG. 4 (b)
As soon as the nose 20c slides on the first roller 8, the base circle 30a slides on the second roller 9 and the second roller 9 rises. As a result, the seesaw arm 7 and the rocker arm 1 also rise, so that the lift amount of the valve 5 decreases to zero.

Under an operating condition requiring a lift amount and a working angle intermediate between those shown in FIGS. 2, 3 and 4, the first rotary cam 20 and the intermediate rotary cam 20 shown in FIGS. Second rotating cam 30
Is made continuously or stepwise by the phase changing device, and as shown in FIG. 6, an intermediate lift amount / working angle is obtained continuously or stepwise.

Next, FIGS. 5A to 5B show the phase relationship between the first rotating cam 20 and the second rotating cam 30 in an operating condition in which the lift needs to be stopped, and the operation thereof. As shown in FIG. 5A, before the nose gradually increasing portion 20b is oriented to the first roller 8, the nose gradually decreasing portion 30d starts slidingly contacting the second roller 9, so that the lift amount L and the working angle of the valve 5 are Both become 0, and the lift stops. FIG.
As shown in (b), even when the nose 20c starts sliding on the first roller 8, the valve 5 does not lift because the base circle 30a is oriented to the second roller 9.

Next, a second embodiment of the variable valve mechanism according to the present invention will be described with reference to FIG. FIG. 7 shows a variable valve mechanism of the first embodiment in which a mechanical adjuster 40 is added as an adjuster.

The mechanical adjuster 40 has a cup-shaped inner member 41 and a bottomed hole 43 formed in a cylinder head 42 whose side peripheral walls are engaged with the inside and outside so as to be in contact with and separated from each other with their opening sides facing each other. A coil spring as a lost motion spring 44 which is installed in a compressed state between the inner bottom surface of the cup of the member 41 and the inner bottom surface of the bottomed hole 43 and urges the inner member 41 away from the bottomed hole 43; The inner member 41 is guided and slid inside the bottomed hole 43 of the cylinder head 42.

In the first embodiment, a gap may be formed between the roller and the cam as described above. In this embodiment, however, the addition of the mechanical adjuster 40 allows the lost motion spring 44 to move the inner member 41 as shown in FIG. In addition, since the pivot 3 is lifted by separating the bottomed hole 43, it is possible to prevent a gap from being formed in each part, and thus the rocker arm 1.
To prevent falling.

It should be noted that the present invention is not limited to the configuration of the above-described embodiment, and may be embodied with modifications as follows, for example, without departing from the spirit of the invention. (1) The configuration and control method of the phase change device are appropriately changed. (2) A rocker arm having a swing center in the center.

[0032]

Since the variable valve mechanism of the present invention is constructed as described above, the valve lift and valve operating angle can be changed continuously or stepwise over the entire operation state of the internal combustion engine, thereby achieving precise Control is possible, and the structure is simple and high reliability can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view showing the operation of the mechanism when the maximum lift amount and operating angle of FIG. 1 are required.

FIG. 3 is a sectional view showing an operation subsequent to FIG. 2;

FIG. 4 is a cross-sectional view showing the operation of the same mechanism when the minute lift and operating angle of FIG. 1 are required.

FIG. 5 is a cross-sectional view showing the operation of the mechanism when the lift stop of FIG. 1 is required.

FIG. 6 is a graph showing a valve lift and a valve operating angle obtained by the variable valve mechanism according to the first embodiment;

FIG. 7 is a sectional view showing a variable valve mechanism according to a second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 rocker arm 3 pivot 5 valve 7 seesaw arm 8 first roller 9 as first cam sliding contact portion 9 second roller 20 as second cam sliding contact portion 20 first rotating cam 20a base circle 20b nose gradually increasing portion 20c nose 20d nose gradually decreasing portion Reference Signs List 30 second rotating cam 30a base circle 30b nose gradually increasing portion 30c nose 30d nose gradually decreasing portion 40 mechanical adjuster

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuji Yoshihara 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Manabu Tateno 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F Terms (reference) 3G016 AA08 AA19 BA03 BA06 BA18 BA28 BB11 BB18 BB22 BB26 CA28 DA04 DA08 DA22 GA01 GA06 3G018 AB04 AB17 BA09 BA17 CA06 CA19 DA05 DA13 DA19 DA29 EA01 FA01 FA02 GA03 GA14

Claims (3)

[Claims] 1. A seesaw arm is pivotally attached to a cam corresponding portion of a rocker arm at a central portion thereof so as to be swingable, and a first cam sliding contact portion and a second cam sliding contact are respectively provided at one end and the other end of the seesaw arm. A first rotating cam and a second rotating cam that respectively press the first cam sliding contact portion and the second cam sliding contact portion are provided rotatably, and the phase of the second rotating cam with respect to the first rotating cam is changed. A variable valve mechanism provided with a phase changing device that changes a valve lift and a valve operating angle continuously or stepwise according to the operating condition of an internal combustion engine. 2. The variable valve mechanism according to claim 1, wherein the rocker arm and the seesaw arm swing in the same plane. 3. The variable valve mechanism according to claim 1, wherein at least one of the first cam sliding portion and the second cam sliding portion is a roller rotatably mounted on the seesaw arm.