JP3995913B2 - Variable valve mechanism - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable valve mechanism that changes a lift amount and a working angle of a valve continuously or stepwise in accordance with an operating state of an internal combustion engine.
[0002]
[Prior art]
Since the normal valve mechanism does not change the lift amount or operating angle of the valve even if the operating status of the internal combustion engine changes, it must balance various characteristics such as the output of the internal combustion engine, torque, fuel consumption, and exhaust gas cleanliness. I can't. In view of this, various variable valve mechanisms for changing the valve lift or operating angle continuously or stepwise in accordance with the operating conditions of the internal combustion engine have been conventionally considered.
[0003]
[Problems to be solved by the invention]
However, with a normal roller rocker arm, the cam profile is fixed, and the lift amount and working angle cannot be changed according to the driving situation. Further, since the sublift amount cannot be changed, it is impossible to control the internal EGR.
[0004]
Therefore, the object of the present invention is to solve the above-mentioned problems, change the sub-lift amount and operating angle of the valve continuously or stepwise over the entire operating state of the internal combustion engine, perform precise control, and have a simple structure. An object of the present invention is to provide a variable valve mechanism that can obtain high reliability and can improve fuel efficiency by enabling optimal control of internal EGR.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the variable valve mechanism according to the present invention is such that the rocker arm has a rocking center portion at one end portion and a cam corresponding portion at a central portion in the length direction. The seesaw arm is pivotally attached to the cam-corresponding part of the rocker arm at the center so that the seesaw arm can swing at the center, and a first sliding contact part and a second sliding contact part are provided at one end and the other end of the seesaw arm, respectively. A camshaft with a main cam that forms a sub-nose and a main nose following the sub-nose is rotatably supported, and a control shaft with a sub-lift controller can be rotated above the second sliding contact part A phase change device is provided that changes the sub-lift amount and operating angle of the valve by changing the phase of the control shaft continuously or stepwise according to the operating condition of the internal combustion engine. . The cam-corresponding portion means a portion that corresponds to the cam via the seesaw arm and is pressed.
[0006]
Although the rocker arm and the seesaw arm may swing in different planes, it is preferable that the rocker arm and the seesaw arm swing in the same plane in terms of space efficiency.
[0007]
The first sliding contact portion or the second sliding contact portion may be a fixed hard tip or a rotatable roller. However, in consideration of sliding resistance and wear, at least one (preferably both) of the first sliding contact portion and the second sliding contact portion is preferably a roller that is rotatably attached to the seesaw arm.
[0008]
The phase change device is not particularly limited, and examples thereof include a device including a helical spline mechanism, a drive unit using hydraulic pressure, and a control device such as a microcomputer.
[0009]
Here, the following two types of rocker arms are conceivable, but the present invention is embodied in the type (1).
(1) A type that has a rocking center at one end of the rocker arm, a cam-corresponding portion at the center, and a valve pressing portion at the other end. (So-called swing arm)
(2) Type that has a rocking center at the center of the rocker arm, a cam corresponding part at one end, and a valve pressing part at the other end.
[0010]
When the rocker arm and the seesaw arm swing in the same plane, the present invention is preferably embodied in the above type (1) because the seesaw arm does not protrude from the rocker arm and has good space efficiency. That is, the rocker arm is a type that has a rocking center at one end, a cam corresponding portion at the center, and a valve pressing portion at the other end, and the seesaw arm is pivotally attached to the cam corresponding portion. Is preferred.
[0011]
The following two modes can be exemplified as the swing center portion.
(A) A mode in which the rocking center is a concave spherical surface supported by a pivot.
(B) A mode in which the rocking center portion is a shaft hole portion in which the seesaw arm is pivotally supported.
[0012]
An adjuster for preventing a gap from being formed between the cam sliding contact portions and the cams may be connected to the swing center portion. The structure of the adjuster is not particularly limited, and includes an inner member engaged so as to be able to contact and separate, a bottomed hole formed in the cylinder head, and a lost motion spring that urges the inner member and the bottomed hole in the separation direction. A mechanical adjuster (mechanical adjuster) can be exemplified. More specifically, a cup-shaped inner member whose side peripheral walls engage with each other on the opening side, 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.
[0013]
In the aspect (a), it is preferable that a tappet clearance adjusting mechanism is provided between the swing center portion and the pivot support member. For example, in the above aspect (a), a tappet clearance adjustment mechanism can be exemplified in which a male screw provided on the pivot is screwed into a female screw provided on the pivot support member so that the screwing amount can be adjusted.
[0014]
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.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
A variable valve mechanism according to a first embodiment of the present invention will be described below with reference to FIGS.
As shown in FIGS. 1 and 2, a swing arm type rocker arm 1 is used for the variable valve mechanism, and one end of the rocker arm 1 is supported by a pivot 3 with a concave spherical surface portion 2 formed in the same portion. It becomes the rocking | fluctuation center part which becomes. The other end portion of the rocker arm 1 is divided into two forks, and a valve pressing portion 4 is recessed at the lower end of each tip, and the valve pressing portion 4 presses the base end portion of the valve 5.
[0016]
A seesaw arm arrangement hole 6 formed in the cam corresponding part of the center of the rocker arm 1 is provided with a center part of a seesaw arm 7 formed in a substantially V shape, and the seesaw arm 7 swings around an axis perpendicular to the arm side wall. It is pivotally mounted. Therefore, the rocker arm 1 and the seesaw arm 7 swing in the same plane.
[0017]
The male screw provided at the lower shaft portion of the pivot 3 is screwed into the female screw provided on the pivot support member 8 so that the screwing amount can be adjusted, thereby constituting a tappet clearance adjusting mechanism.
[0018]
One end side of the seesaw arm 7 extends to the valve pressing portion 4 side in the case of the rocker arm 1, and a first roller 9 as a first sliding contact portion is disposed in a fork formed at one end portion of the seesaw arm 7. Is pivotally mounted about an axis perpendicular to the fork sidewall. The other end side of the seesaw arm 7 extends to the swinging central portion side in the case of the rocker arm 1, and a second roller 10 as a second sliding contact portion is disposed in the fork formed at the other end portion. 10 is rotatably mounted around an axis perpendicular to the fork side wall.
[0019]
Above the first roller 9, one camshaft 23 having a main cam 20 that presses the first roller 9 is rotatably supported and arranged so as to extend in a direction perpendicular to the rocking surface of the rocker arm 1. Has been.
[0020]
The main cam 20 includes a base circle 20a, a sub nose 21, and a main nose 22 following the sub nose 21, and the sub nose 21 includes a nose gradually increasing portion 21a in which a protruding amount gradually increases and a nose 21b having a maximum protruding amount as a sub. The main nose 22 includes a nose gradually increasing portion 22a in which the protruding amount further increases from the nose 21b, a nose 22b having the maximum protruding amount, and a nose gradually decreasing portion 22c in which the protruding amount gradually decreases.
[0021]
Above the second roller 10, a control shaft 31 having a sub-lift controller 30 that presses the second roller 10 is rotatably supported so as to extend in a direction perpendicular to the rocking surface of the rocker arm 1. It is arranged.
[0022]
The sublift controller 30 includes a base circle 30c, a cancel recess 30a that is recessed with respect to the base circle 30c, a cancel start portion 30d in which the recess amount gradually increases from the base circle 30c toward the cancel recess 30a, and the cancel recess 30a. To the base circle 30c, and the amount of dent gradually decreases.
[0023]
The phase of the control shaft 31 (in this embodiment, the relative phase of the sub-lift controller 30 with respect to the main cam 20) is continuously or stepwise (preferably three or more stages, more preferably four or more stages) depending on the operating condition of the internal combustion engine. A phase change device (not shown) for changing the sub-lift amount and the operating angle of the valve 5 is provided instead of the multi-stage.
[0024]
The phase change device is configured such that a piston provided with a helical spline moves in the axial direction while rotating at a predetermined angle by hydraulic pressure, and the rotation acts on the control shaft 31, whereby the relative phase of the sub-lift controller 30 with respect to the main cam 20. And is controlled by a control device such as a microcomputer based on detection values from a rotation sensor of an internal combustion engine, an accelerator opening sensor, or the like.
[0025]
The variable valve mechanism configured as described above operates as follows.
First, FIG. 2 (a) → (b) → FIG. 3 (a) → (b) shows the phase relationship between the main cam 20 and the sub-lift controller 30 and the operation due to the operation under the condition that the maximum sub-lift amount is required. ing.
2A, when the second half of the base circle 20a of the main cam 20 is in sliding contact with the first roller 9, and the second half of the base circle 30c of the sublift controller 30 is in sliding contact with the second roller 10, The first roller 9 is in the uppermost position. At this time, the pivoting portion of the seesaw arm 7 is at the uppermost position, and the rocker arm 1 is not pressed by the seesaw arm 7, so that the lift amount L of the valve 5 is zero.
As shown in FIG. 2B, since the relative phase between the main cam 20 and the sublift controller 30 is controlled so as to realize the maximum sublift amount, the nose 21b passes through the nose gradually increasing portion 21a on the first roller 9. Even if comes in sliding contact, the second half of the base circle 30 c is still in sliding contact with the second roller 10. At this time, the first roller 9 is pressed and displaced in the downward direction, and the second roller 10 pivotally attached to the other end of the seesaw arm 7 cannot abut against the base circle 30c, so that the seesaw arm 7 rotates in the clockwise direction. The pivoting portion is displaced downward while swinging. The rocker arm 1 swings due to the displacement of the seesaw arm 7, and the lift amount L of the valve 5 is generated and increased to reach the maximum sub lift amount Lsmax.
[0026]
From FIG. 2B to FIG. 3A, that is, when the first roller 9 is pressed by the nose gradually increasing portion 22a, the second roller 10 receives the cancel start portion 30d, the cancel concave portion 30a, and the sub lift controller 30. Since it enters the cancellation end portion 30b and rises to slightly raise the pivoting portion of the seesaw arm 7, the lift amount L of the valve 5 by the nose gradually increasing portion 22a is partially canceled, and the lift acts slightly behind.
As shown in FIG. 3A, when the first roller 9 receives maximum pressure by the nose 22b, the base circle 30c comes into sliding contact with the second roller 10. At this time, the lift amount L of the valve 5 increases and reaches the maximum main lift amount Lmmax.
As shown in FIG. 3 (b), when the base circle 30c continues to be in sliding contact with the second roller 10 and the base circle 20a comes into sliding contact with the first roller 9 via the nose gradually decreasing portion 22c, the seesaw arm 7 is in FIG. Returning to the same position as in a), the rocker arm 1 also swings to the uppermost position, so that the lift amount L of the valve 5 decreases to zero.
[0027]
Next, FIG. 4 (a) → (b) → (c) shows the phase relationship between the main cam 20 and the sub lift controller 30 and the operation due to the operation under the condition that the minute sub lift amount is required.
As shown in FIG. 4A, when the latter half of the base circle 20a is in sliding contact with the first roller 9 and the latter half of the base circle 30c is in sliding contact with the second roller 10, the first roller 9 is in the uppermost position. . At this time, the pivoting portion of the seesaw arm 7 is at the uppermost position, and the rocker arm 1 is not pressed by the seesaw arm 7, so that the lift amount L of the valve 5 is zero.
As shown in FIG. 4B, the relative phase between the main cam 20 and the sublift controller 30 is controlled so as to realize a small sublift amount, so that the middle of the nose gradually increasing portion 21a slides on the first roller 9. In the middle of increasing the sub-lift amount of the valve 5 in contact with the second roller 10, the cancel start portion 30 d starts to slide. When the nose 21b comes into sliding contact with the first roller 9 before long, the second roller 10 enters the cancel start portion 30d close to the cancel recess 30a and slightly rises, and slightly raises the shaft attachment portion of the seesaw arm 7, so that the nose 21b The sub-lift amount of the valve 5 is partially canceled (reduced), and the sub-lift amount Ls of the valve 5 becomes minute.
[0028]
4B to 4C, that is, when the first roller 9 is pressed by the nose gradually increasing portion 22a, the second roller 10 enters the cancel recess 30a and the cancel end portion 30b and rises. Compared with the period from 2 (b) to FIG. 3 (a), the cancellation amount of the lift amount L is small and the lift delay is also small.
As shown in FIG. 4C, when the first roller 9 receives the maximum pressure by the nose 22b, the base circle 30c comes into sliding contact with the second roller 10, and the lift amount L of the valve 5 becomes the maximum main lift amount Lmmax. .
[0029]
Note that, in an operating situation where an intermediate sub-lift amount between FIGS. 2, 3, and 4 is required, the phase relationship between the main cam 20 and the sub-lift controller 30 intermediate between FIGS. It is produced continuously or stepwise by the phase change device, and an intermediate lift amount is obtained continuously or stepwise as shown in FIG.
[0030]
Next, FIGS. 5 (a) → (b) → (c) show the phase relationship between the main cam 20 and the sublift controller 30 and the operation due to the operation under the condition that the sublift stop is required.
As shown in FIG. 5A, when the first roller 9 is in sliding contact with the latter half of the base circle 20a and the second roller 10 is in sliding contact with the latter half of the base circle 30c, the first roller 9 is in the uppermost position. . At this time, the seesaw arm 7 is at the uppermost position, and the rocker arm 1 is not pressed by the seesaw arm 7, so that the lift amount L of the valve 5 becomes zero.
As shown in FIG. 5B, since the relative phase between the main cam 20 and the sublift controller 30 is controlled so as to realize the sublift pause, when the nose gradually increasing portion 21a starts to slidably contact the first roller 9 In addition, the cancel start portion 30d starts to slidably contact the second roller 10. When the nose 21b comes into sliding contact with the first roller 9 eventually, the second roller 10 enters the cancel recess 30a and rises to raise the shaft-attached portion of the seesaw arm 7. Therefore, the sub-lift amount of the valve 5 by the nose 21b is all Canceled (subtracted), the sub-lift amount Ls of the valve 5 does not occur.
[0031]
5B to 5C, that is, when the first roller 9 is pressed by the nose gradually increasing portion 22a, the base circle 30c is in sliding contact with the second roller 10, so that the lift amount L is canceled and lifted. There is virtually no delay.
As shown in FIG. 5C, when the first roller 9 is subjected to the maximum pressure by the nose 22b, the base circle 30c comes into sliding contact with the second roller 10, and the lift amount L of the valve 5 becomes the maximum main lift amount Lmmax. .
[0032]
Next, a second embodiment of the variable valve mechanism embodying the present invention will be described with reference to FIG. 7 only for parts different from the first embodiment. FIG. 7 is obtained by adding a mechanical adjuster 40 as an adjuster to the variable valve mechanism of the first embodiment.
[0033]
The mechanical adjuster 40 has a bottomed hole 43 formed in the cup-shaped inner member 41 and the cylinder head 42 in which the side peripheral walls engage with each other so that the opening side faces each other and can be contacted and separated, and the inner member 41. The inner member comprises a coil spring as a lost motion spring 44 that is installed in a compressed state between the inner bottom surface of the cup and the inner bottom surface of the bottomed hole 43 and biases the inner member 41 from the bottomed hole 43 in the separating direction. 41 slides while being guided inside the bottomed hole 43 of the cylinder head 42.
[0034]
In the first embodiment, depending on the shape, size, relative position of the main cam 20, the sub lift controller 30 or the seesaw arm 7, the relative phase of the main cam 20 and the sub lift controller 30, or the like, there may be a gap between the roller and the cam. However, in this embodiment, by adding the mechanical adjuster 40, the lost motion spring 44 separates the inner member 41 and the bottomed hole 43 and raises the pivot 3 as shown in FIG. And thus the rocker arm 1 is prevented from falling.
[0035]
In addition, this invention is not limited to the structure of the said embodiment, For example, as follows, it can also change and actualize in the range which does not deviate from the meaning of invention.
(1) Change the configuration and control method of the phase change device as appropriate.
(2) Use a rocker arm with a rocking center at the center.
[0036]
【The invention's effect】
The variable valve mechanism according to the present invention changes the sub-lift amount and operating angle of the valve continuously or stepwise over the entire operating state of the internal combustion engine, and can perform precise control, and has a simple structure and high reliability. In addition to being able to optimally control the internal EGR, the fuel efficiency is improved , and the seesaw arm has an excellent effect that it is difficult to protrude from the rocker arm and has good space efficiency .
[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 a cross-sectional view showing the operation of the mechanism when a maximum sub-lift amount is required.
FIG. 3 is a cross-sectional view showing the operation following FIG. 2;
FIG. 4 is a cross-sectional view showing the operation of the mechanism when a minute sublift amount and operating angle are required.
FIG. 5 is a cross-sectional view showing the operation of the mechanism when sublift suspension is necessary.
FIG. 6 is a graph showing the lift amount and working angle of the valve obtained by the same mechanism.
FIG. 7 is a cross-sectional view showing a variable valve mechanism according to a second embodiment of the present invention.
[Explanation of symbols]
1 Rocker arm 5 Valve 7 Seesaw arm 9 First roller 10 as first sliding contact portion Second roller 20 as second sliding contact portion Main cam 21 Sub nose 22 Main nose 23 Cam shaft 30 Sub lift controller 31 Control shaft

Claims (4)

The rocker arm has a rocking center at one end and a cam-corresponding portion at the center in the length direction.
A seesaw arm is pivotally attached to the cam corresponding portion at the central portion in the length direction so as to be swingable at the central portion,
A first sliding contact portion and a second sliding contact portion are provided at one end and the other end of the seesaw arm, respectively.
A camshaft provided with a main cam having a sub nose and a main nose following the sub nose above the first sliding contact portion is rotatably supported.
A control shaft provided with a sub-lift controller is rotatably supported above the second sliding contact portion,
A variable valve mechanism provided with a phase change device that changes the sub-lift amount and operating angle of the valve by changing the phase of the control shaft continuously or stepwise according to the operating condition of the internal combustion engine.   The variable valve mechanism according to claim 1, wherein the rocker arm and the seesaw arm swing in the same plane.   The variable valve mechanism according to claim 1 or 2, wherein at least one of the first sliding contact portion or the second sliding contact portion is a roller rotatably mounted on the seesaw arm. The variable valve mechanism according to claim 1, 2 or 3, wherein the sub-lift controller includes a cancel recess recessed with respect to the base circle for partially canceling the lift amount of the valve.

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