JP2002371816A - Variable valve mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable valve mechanism capable of continuously or stepwisely changing lift amount of a valve, an operation angle and lift timing of the valve by rotating one camshaft without remarkably changing a conventional driving system. SOLUTION: This mechanism is provided with a lift control device for changing an oscillation starting angle of a first interposing arm 20 and changing lift amount and the operation angle of the valve 5 by a rotating cam 40 by journaling a control shaft 10 in the vicinity of a rocker arm 1, attaching the first interposing arm 20 to the control shaft 10, providing the control shaft 10 with a projecting part 11, attaching a second interposing arm 30 to the projecting part 11, journaling the camshaft 41 forming the rotating cam 40, and rotating the control shaft 10 and the projecting part 11 at small angles.

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 order to achieve various characteristics such as the output, torque, fuel consumption, and cleanliness of exhaust gas of an internal combustion engine, the valve lift or operating angle of a valve is continuously or stepwise changed according to the operating condition of the internal combustion engine. Various types of variable valve mechanisms have been considered. As a typical example, the rocker arm is rocked by rotating two camshafts, and the rocking angle of the rocker arm is changed by relatively changing the phase of the two camshafts, thereby increasing the valve lift or acting. There is known one in which the angle is changed continuously.

[0003]

However, in order to rotate two camshafts as in the above-mentioned typical example, a conventional drive system that rotates one camshaft is greatly changed. There was a problem that it was difficult to drive.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and to rotate a single camshaft without largely changing the conventional drive system, to adjust the valve lift, valve operating angle and valve lift timing. An object of the present invention is to provide a variable valve mechanism that can be changed continuously or stepwise.

[0005]

To achieve the above object, a variable valve mechanism according to the present invention supports a control shaft in the vicinity of a rocker arm so as to be rotatable at a small angle, and a cam corresponding portion of the rocker arm is mounted on the control shaft. A first intervening arm having a pressing surface for pressing the control shaft is swingably mounted independently of the small-angle rotation of the control shaft, and protrudes from the control shaft in the radial direction of the control shaft to be small together with the control shaft. An angle-rotating projection is provided, and a protrusion of the projection includes a cam sliding portion and a pressing portion that presses the first interposed arm, and the distance between the cam sliding portion and the pressing portion is the length of the second interposed arm. The second intervening arm that changes in the direction is pivotally mounted on a shaft, and the rocker arm is pushed through the second sliding arm and the first intermediate arm in that order by pressing the cam sliding contact portion. A single camshaft, which forms a rotary cam that lifts the valve by pressing, is rotatably supported, and the control shaft and the protruding portion are continuously or stepwise within one rotation according to the operating condition of the internal combustion engine. By rotating the second intervening arm in the length direction by rotating it by a small angle within the range, the swing start angle of the first intervening arm is changed, and thus the pressing surface of the first intervening arm contacts the cam corresponding portion. A lift control device is provided which changes the position and the operating angle of the valve by the rotating cam by changing the position in the length direction of the first intervening arm. In addition, the cam corresponding part means a part corresponding to and pressed against the rotating cam via the second interposed arm and the first interposed arm. In addition, the small angle rotation refers to a rotation in which the rotation angle does not reach 360 degrees.

The cam corresponding portion, the cam sliding portion or the pressing portion may be a fixed hard tip, a rotatable roller or a rotatable rotating member. However, in consideration of sliding resistance and wear, at least one (preferably any two, most preferably all) of the cam corresponding portion, the cam sliding contact portion, and the pressing portion is rotatably mounted on the rocker arm. It is preferable that a roller or a roller rotatably mounted on the second interposed arm or a rotating member rotatably mounted on the second interposed arm be used.

As the control shaft, a control shaft provided with at least one protruding portion for pivotally attaching the second interposed arm can be exemplified. Specifically, one or two protrusions are provided on the control shaft through an opening provided in the upper part of the first intervention arm, or in the length direction of the control shaft of the first intervention arm. One of which is formed at one end outside or one at the both ends outside is formed.

When the roller and the rotating member are provided coaxially,
The tip of the second intervening arm and the upper part of the rotating member are formed in a fork shape, the rollers are sandwiched by the fork of the rotating member, and the rollers are sandwiched by the fork at the tip of the second intervening arm. The torsional stress may not be generated in the arm. Further, the rollers may be held by a fork at the distal end of the second intervening arm, and the rollers may be held by a fork above the rotating member. In this case, the lower surface of the rotating member and the contact surface of the rotating member of the first intervening arm are formed flat so that the rotating member does not rotate and come into contact with the cam.
It is desirable that the lower surface of the rotating member always contact the first intervening arm.

The rocker arm, the first interposed arm and the second interposed arm may swing in different planes, but preferably swing in the same plane for space efficiency.

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) A 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.

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.

In the above mode (a), it is preferable that a tappet clearance adjusting mechanism is provided at the center of the swing. For example, a tappet clearance adjustment mechanism in which a male screw provided on the pivot is screwed into a female screw provided on the pivot support member so that the screw amount can be adjusted.

Although the lift control device is not particularly limited, a lift control device including 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 An embodiment of a variable valve mechanism embodying the present invention will be described below 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 recessed at the lower portion of each end, so that the valve pressing portion 4 presses the base end of the valve 5.

A first roller 7 as a cam corresponding portion is provided in a roller arrangement hole 6 formed in the center of the rocker arm 1.
It is arranged so as to slightly protrude from the upper surface of the rocker arm 1,
The first roller 7 is rotatably mounted on an axis orthogonal to the arm side wall.

A male screw provided at the lower part of the shaft of the pivot 3 is screwed into a female screw provided on the pivot support member 8 so that the screwing amount can be adjusted, thereby forming a tappet clearance adjusting mechanism.

In the vicinity of above the first roller 7, a substantially cylindrical control shaft 10 is rotatably supported by a small angle.

The control shaft 10 has a first interposed arm 20 having a pressing surface 23 for pressing the first roller 7.
However, it is pivotally mounted independently of the small angle rotation of the control shaft. The first intervention arm 20 has a substantially cylindrical portion 21 through which the control shaft 10 is inserted.
And an arm portion 22 extending from the cylindrical portion 21 toward the valve pressing portion 4 of the rocker arm 1. Further, the first intervening arm 20 is urged by a member (not shown) in a direction in which the arm portion 22 rises.

The lower surface of the arm 22 is a pressing surface 23 for pressing the first roller 7 and is formed as a concave surface having a radius of curvature larger than the radius of the first roller 7. Even if the contact position of the pressing surface 23 with respect to the roller 7 changes in the length direction of the first intervention arm 20, the pressing surface 23
Presses the first roller 7 in a direction substantially perpendicular to the first roller 7. A flat portion 24 extending tangentially from the cylindrical portion 21 is formed above the pressing surface 23.

On the upper surface of the cylindrical portion 21 of the first interposed arm 20, an opening 25 extending in the circumferential direction from near the boundary between the flat portion 24 and the cylindrical portion 21 to near the opposite side of the control shaft 10 is provided. .

The control shaft 10 is provided with a protrusion 11 which projects in the radial direction of the control shaft 10 and rotates by a small angle together with the control shaft 10. The protruding portion 11 is provided at the opening 25 of the first intervention arm 20.
The protrusion 11 is engaged with the opening 25 through the protrusion, and the protrusion 11 and the control shaft 10 are within the allowable range.
, The first intervening arm 20 can swing.

At the protruding end of the protruding portion 11, a second intervening arm 30 having a second roller 34 as a cam sliding contact portion and a rotating member 33 as a pressing portion for pressing the first intervening arm 20 is provided.
Is pivotally mounted on a fork piece 31 formed at the base end of the second intervening arm 30 so as to be able to swing while holding the protruding end of the protruding portion 11 therebetween.

The second roller 34 and the substantially trapezoidal rotating member 33 are attached to the inner wall of a fork formed at the upper end of the rotating member 33 with the second roller 34 slightly protruding and sandwiched therebetween. Are arranged coaxially perpendicular to the inner wall of the fork piece 32 formed at the tip of the second intervening arm 30, and are rotatably or rotatably mounted around its axis. The second roller 34 and the rotating member 33 can rotate or rotate independently of each other.

The rotating member 33 has a flat surface formed at the lower end, and forms a sliding portion 33a which can slide on the flat portion 24 of the first interposed arm 20. As described above, since the first intervening arm 20 is constantly urged in the direction in which the arm portion 22 rises, the rotating member 33 is
Is always in contact with the plane portion 24. Also,
The upper end side of the rotating member 33 is formed so that the second roller 34 projects at a wide angle so that the second roller 34 functions as a cam sliding portion. Therefore, the distance between the second roller 34 and the sliding portion 33a of the rotating member 33 changes in the length direction of the second intervening arm 30, and becomes maximum at the center position of the second roller.

Above the tip of the second intervening arm 30, the valve 5 is lifted by pressing the rocker arm 1 through the second intervening arm 30 and the first intervening arm 20 by pressing the second roller 34 in that order. A camshaft 41 having a rotating cam 40 to be rotated is rotatably supported.
The rotary cam 40 has a base circle 40a, a nose gradually increasing portion 40b whose projection amount gradually increases, and a nose 40c whose maximum projection amount.
And a nose gradually decreasing portion 40d whose projection amount gradually decreases.

Control shaft 10 and protrusion 11
A lift control device (not shown) for continuously or stepwise (preferably in three or more stages, more preferably in four or more stages) a small angle within a rotation within one rotation of the internal combustion engine is provided. It is connected to the control shaft 10. Control shaft 1 by lift control device
When the 0 and the protrusion 11 are rotated by a small angle, the second intervening arm 30 is displaced in the length direction. At this time, the second roller 34 and the rotating member 33 of the second intervening arm 30 move between the rotating cam 40 and the first intervening arm 20 while changing the contact position with the rotating cam 40 or the first intervening arm 20, respectively. Change the distance. Thereby, the swing angle of the first intervening arm 20 can be changed, and the contact position of the pressing surface 23 of the first intervening arm 20 with the first roller 7 is set in the longitudinal direction of the first intervening arm 20. By changing them, the lift amount and the operating angle of the valve 5 by the rotary cam 40 are changed.

In the lift control device, for example, a piston provided with a helical spline moves in the axial direction while rotating at a predetermined angle by hydraulic pressure, and the rotation rotates the control shaft 10 by a small angle to raise the protruding portion 11. The angle is changed within one rotation, 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.

With the above configuration, when the rotary cam 40 presses the second roller 34, the variable valve mechanism of this embodiment
The second intervening arm 30 swings around the shaft attachment portion with the protrusion 11, and the rotating member 33 presses the first intervening arm 20 while changing the contact position between the sliding portion 33 a and the flat portion 24. As a result, the first intervening arm 20 swings, and the rocker arm 1 swings by pressing the first roller 7 with the pressing surface 23 while changing the contact position of the first intervening arm 20 with the first roller 7. The valve 5 is lifted.

At this time, the control shaft 10
Is rotated by a small angle, the second intervening arm 30 acts to move the rotating cam 40 and the first intervening arm 20 apart by the second roller 34 and the rotating member 33. At this time, the first intervening arm 20 swings in the direction in which the arm portion 22 is lowered, so that the swing start angle of the first intervening arm 20 can be changed. Then, the contact position of the first interposed arm 20 with respect to the first roller 7 changes in the longitudinal direction of the first interposed arm 20. Specifically, when the swing start angle of the first interposed arm 20 is high, the first roller The contact position of the first roller 7 is on the distal end side of the arm 22 when the swing start angle of the first interposed arm 20 is low.

The variable valve mechanism configured as described above
It works as follows. First, FIGS. 3A to 3B show the position of the protruding portion 11 under an operating condition that requires the maximum lift amount and the maximum operating angle, and the operation thereof. FIG.
As shown in (a), in an operating condition that requires a maximum lift amount and a maximum working angle, the second roller 34 and the rotating member 33 are retracted as much as possible between the rotating cam 40 and the first intervention arm 20. Is controlled so that Therefore, the swing start angle of the first interposed arm 20 when the second roller 34 is in sliding contact with the base circle 40a of the rotating cam 40 is the lowest. At this time, the first roller 7 is in contact with the cylindrical portion 21 of the first intervening arm 20, and the valve 5 is not lifted because the first roller 7 is at the uppermost position. However, since the contact position of the first roller 7 is close to the pressing surface 23, the contact position of the first roller 7 shifts to the pressing surface 23 as soon as the first intervening arm 20 starts swinging. Then, the rocker arm 1 is depressed and the valve 5 is lifted. As shown in FIG. 3B, when the second roller 34 is pressed by the nose 40c via the nose gradually increasing portion 40b, the rotating member 33 always moves the sliding portion 33a to the flat portion of the first intervention arm 20. 24, presses the first intervening arm 20 while rotating with respect to the second intervening arm 30. The second roller 34 also swings about the shaft attachment portion at the upper end of the protrusion 11 to allow downward displacement of the second roller 34. At this time, the first intervention arm 20 swings to the maximum, and the contact position of the first intervention arm 20 with respect to the first roller 7 shifts from the cylindrical portion 21 to the tip of the pressing surface 23,
The rocker arm 1 swings to the maximum depressed position, and the lift amount L of the valve 5 is generated and increased to reach the maximum value Lmax, and the operating angle is also maximized. As described above, even if the contact position changes, the pressing surface 23 formed in the concave curved surface presses the first roller 7 in a direction substantially perpendicular to the concave surface.
0 has almost no longitudinal stress component, and no load is applied between the cylindrical portion 21 and the control shaft 10.

Next, FIGS. 4A to 4B show the protruding portions 11 under an operating condition requiring a small lift amount and a small operating angle.
And the effect of the position. As shown in FIG. 4A, in an operation condition where a small lift amount and a small operating angle are required, the second roller 34 and the rotating member 33
It is controlled so as to be in a state of being greatly separated from between the zero and the first intervention arm 20. Therefore, the second roller 34
Is in the vicinity of the uppermost position when the first arm 20 is in sliding contact with the base circle 40a of the rotating cam 40. At this time, the first roller 7 is in contact with the cylindrical portion 21 of the first intervening arm 20, and the valve 5 is not lifted because the first roller 7 is at the uppermost position. As shown in FIG. 4B, when the second roller 34 is pressed by the nose 40c via the nose gradually increasing portion 40b, the second roller 34 is moved to the control shaft 10 and the camshaft 4
1, the amount of pressing on the first intervening arm 20 is smaller than in FIG. 3B, and the amount of swing of the first intervening arm 20 is also smaller. At this time, the contact position of the first interposed arm 20 with respect to the first roller 7 is only slightly shifted from the cylindrical portion 21 to the pressing surface 23, so that the pressing amount of the first roller 7 is very small and the lift amount L of the valve 5 is small. And the operating angle are both very small (see FIG. 6).

It should be noted that the lift amount intermediate between FIG. 3 and FIG.
In an operating condition requiring a working angle, the angle of the projecting portion 11 intermediate between FIGS. 3 and 4 is continuously or stepwise made by the lift control device, as shown in FIG. A large lift amount and operating angle can be obtained continuously or stepwise.

Next, FIGS. 5A to 5B show the position of the protruding portion 11 and the operation thereof under an operating condition in which the lift must be stopped. As shown in FIG. 5A, in an operation condition in which a lift stop is required, the second roller 34 and the rotating member 33 are separated from the rotating cam 40 and the first intervening arm 20 to the maximum extent. The rising angle of the protruding portion 11 is controlled so as to be as follows. Therefore, when the second roller 34 is in sliding contact with the base circle 40a of the rotary cam 40, the swing start angle of the first interposed arm 20 is at the uppermost position. At this time, the first roller 7 is in contact with the cylindrical portion 21 of the first intervening arm 20, and the valve 5 is not lifted since the first roller 7 is at the uppermost position. As shown in FIG. 5B, when the second roller 34 is pressed by the nose 40c via the nose gradually increasing portion 40b, the second roller 34 is at a maximum distance from the control shaft 10 and the camshaft 41. Therefore, the amount of pressing on the first intervening arm 20 is
As compared with (b), the swing amount of the first intervening arm 20 is further reduced. At this time, the contact position of the first intervention arm 20 against the first roller 7 is shifted from the cylindrical portion 21 to the pressing surface 2.
Since it moves in the direction of 3, but stays on the cylindrical portion 21, the pressing amount of the first roller 7 is 0, and the valve 5 is in the lift rest state.

Next, a second embodiment of the variable valve mechanism according to the present invention will be described with reference to FIG. FIG. 7 differs from the variable valve mechanism of the first embodiment in that a projection 11 that does not penetrate the first interposed arm 20 is provided on the control shaft 10.

In the first embodiment, one protruding portion 11 is provided on the control shaft 10 through the opening 25 formed in the first intervening arm 20, but in this embodiment, both sides of the first intervening arm 20 are provided. The protrusions 11 are provided one by one on the surface. Since the length of the protruding portion 11 is shortened in order to reduce the size of the entire mechanism, the second intervening arm 30
A relief surface 26 is formed in the first intervening arm 20 for releasing the contact of the base end of the first intervening arm 20 with the first intervening arm 20.

In the first embodiment, the protruding portion 11 is held by the fork piece 31 formed at the base end of the second intervening arm.
The two protruding portions 11 provided on the second arm 30 sandwich the second intervening arm 30, so that the base end of the second intervening arm 30 does not need to be formed in a fork shape, and serves as a stalk attachment portion 35.

In the first embodiment, the projecting portion 11 is
Are engaged, the protruding portion 11 restricts the swingable range of the first interposed arm 20. However, in the present embodiment, the first interposed arm 20 is not restricted by the protrudable portion 11 so that the swingable range is controlled. Easier to do.

Next, a third embodiment of the variable valve mechanism according to the present invention will be described with reference to FIG. FIG. 8 shows the variable valve mechanism of the second embodiment with the second roller 34 removed.

In the second embodiment, the second roller 34 as the cam sliding portion is axially mounted so as to protrude from the tip of the second intervening arm 30. On the upper side of the fork piece 32, a cam sliding contact surface 36 which is pressed by the rotating cam 40 is formed. The cam sliding surface 36 is formed so as to move away from the second intervening arm 30 as it approaches the distal end from the base end of the second intervening arm 30.

Since the second roller 34 is omitted, the number of parts can be reduced. Further, the rotating member 33 does not need to form a fork at its upper end for holding the second roller 34.

Note 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) The configuration and control method of the lift control device are appropriately changed. (2) A rocker arm having a swing center in the center. (3) The pressing portion is a rotatable roller. (4) The pressing portion and the cam sliding portion are provided on different shafts. (5) The pressing portion and the cam sliding portion are coaxially provided.

[0043]

Since the variable valve mechanism of the present invention is constructed as described above, one cam shaft is rotated without greatly changing the conventional drive system, and the valve lift and operating angle of the valve are controlled. Can be changed continuously or stepwise.

[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 perspective view showing a state in which a cam shaft and a rotary cam of the variable valve mechanism are omitted, and a second intervening arm is removed from a protruding portion.

FIG. 3 is a cross-sectional view showing the operation of the same mechanism when the maximum lift amount and operating angle of FIG. 1 are required.

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 the valve lift and valve operating angle obtained by the mechanism.

FIG. 7 is a perspective view showing a state in which a camshaft and a rotary cam of a variable valve mechanism according to a second embodiment of the present invention are omitted, and a second interposed arm is removed from a protruding portion.

FIG. 8 is a perspective view showing a state in which a camshaft and a rotary cam of a variable valve mechanism according to a third embodiment of the present invention are omitted, and a second interposed arm is removed from a protruding portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rocker arm 5 Valve 7 First roller 20 as cam corresponding part 20 First intervention arm 10 Control shaft 22 Arm part 23 Pressing surface 24 Flat part 25 Opening 11 Projection 30 Second intervention arm 33 Rotating member as pressing part 34 Second roller as cam sliding contact part 40 Rotating cam 41 Camshaft

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nori Sugiura 10 Hamadashita, Nakahata-cho, Nishio-shi, Aichi Prefecture Inside OTICS Co., Ltd. (72) Inventor Manabu Tateno 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3G018 AB04 AB16 BA17 DA11 DA15 DA85 FA01 FA06 FA07 GA14

Claims (3)

[Claims] A first interposition arm having a pressing surface for pressing a cam corresponding portion of the rocker arm on the control shaft; and a small angle rotation of the control shaft. The control shaft is provided so as to be swingable independently of the control shaft, and the control shaft is provided with a protrusion protruding in a radial direction of the control shaft and rotating at a small angle together with the control shaft. A pressing portion for pressing the first intervening arm, and a distance between the cam sliding portion and the pressing portion is pivotally mounted on a second intervening arm that changes in the length direction of the second intervening arm, A circuit that lifts the valve by pressing the rocker arm through the second intervening arm and the first intervening arm in that order by pressing the cam sliding contact portion. 1 formed with the cam
This camshaft is rotatably supported, and the second intervening arm is rotated by rotating the control shaft and the protruding portion at a small angle within one rotation continuously or stepwise according to the operating condition of the internal combustion engine. Changing the swing start angle of the first interposed arm through displacement in the length direction, and thereby changing the contact position of the pressing surface of the first interposed arm against the cam corresponding portion in the length direction of the first interposed arm. A variable valve mechanism provided with a lift control device for changing a lift amount and a working angle of the valve by the rotating cam. 2. The at least one of the cam corresponding portion, the cam sliding portion, and the pressing portion is a roller rotatably mounted on the rocker arm, or rotatably mounted on the second interposed arm. 2. The variable valve mechanism according to claim 1, wherein the variable valve mechanism is a rotating member rotatably mounted on the second interposed arm. 3. The variable valve mechanism according to claim 1, wherein at least one projection is provided on the control shaft.