JPH1018821A - Variable valve gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maximumly improve characteristics such as a torque, an output, fuel consumption performance, clean property of exhaust gas in all rotational areas by continuously or steppedly varying a valve timing and a lifting rate from the low rotation area to the high rotation area of an internal combustion engine, thereby performing accurate control according to operation conditions of the internal combustion engine. SOLUTION: A variable valve gear has a cam shaft 1 provided with a solid cam 2 whose profile is continuously varied in an axial direction, a displacement device 3 which continuously displaces the cam shaft 1 in the axial direction according to an operation condition, a swing arm 6 or a rocker arm which opens and closes a valve 5 through oscillation based on the profile of the solid cam 2. The swing arm 6 is provided with a follow-up contact mechanism 10 composed of a semi-cylindrical inner seat and a follow-up contact part 14 being in contact with the solid cam 2 while following up variation of the contact linear angle, and rollably fitted to the seat.

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 which changes a valve timing and a lift continuously or stepwise from a low rotation to a high rotation of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, various valve operating mechanisms have been known in which a valve timing (including a valve opening operating angle and a phase) and a lift amount are changed in two stages between a low rotation and a high rotation of an internal combustion engine. ing. For example, there is a variable valve mechanism of a type that switches between a low rotation cam having a small valve opening angle and a lift amount and a high rotation cam having a large valve opening angle and a lift amount to swing a swing arm. . In this type, at the time of low rotation, as shown by the solid line in FIG. 12, both the left exhaust valve and the right intake valve reduce the valve opening angle and the lift amount, give swirl to the intake air, increase the low speed torque, and , Improving fuel economy. Also, at the time of high rotation, as shown by the broken line in FIG. 12, the exhaust valve and the intake valve both increase the valve opening operation angle and the lift amount, increase the intake air amount, and increase the high-speed output.

In addition, the camshaft on the intake side is rotated at a constant angle by a displacement device using a helical spline at a low rotation speed and a high rotation speed of the internal combustion engine, so that the valve opening operation angle and the lift amount are kept unchanged. There is a variable valve mechanism of a type in which only the timing phase is changed and the direct-acting valve lifter is pressed by the intake cam. In this type,
At low rotation, as shown by the solid line in FIG. 13, the valve timing phase of the right intake valve is shifted to the left exhaust valve side, the valve overlap is increased, the intake early closing effect is obtained, and the low speed torque is increased. While improving fuel economy. Also, at the time of high rotation, as shown by a broken line in FIG.
The phase of the valve timing of the intake valve is shifted in the direction away from the exhaust valve on the left to reduce valve overlap, increase intake time, and increase high-speed output.

According to these conventional variable valve mechanisms, various characteristics such as torque, output, fuel efficiency, and cleanliness of exhaust gas are considerably improved as compared with a general valve mechanism. In FIG.
The torque characteristics of the internal combustion engine obtained by these conventional variable valve operating mechanisms are indicated by dashed-dotted lines, and the torque characteristics of the internal combustion engine obtained by a general valve operating mechanism having no variability are indicated by broken lines. On the other hand, the torque increases over the entire rotation range. In addition, depending on the setting, the fuel efficiency is up to 8 ~
It is said to improve by about 10%.

[0005]

However, the following problems still remain in these conventional variable valve mechanisms. In any of the above types, since the valve timing or the lift amount is only changed in two stages between the time of low rotation and the time of high rotation, precise control according to the operating condition of the internal combustion engine has been difficult. As shown by the dashed line in FIG. 7, a valley may occur in the torque characteristic at the switching point between the low rotation and the high rotation. This phenomenon tends to appear particularly when a setting is made with emphasis on a high rotation range (for example, 8000 rpm or more).

When changing only the phase of the valve timing while keeping the valve opening operation angle and the lift amount as they are, if the valve opening operation angle is made large by giving importance to the output during high rotation, the valve opening operation angle at low rotation is Torque is sacrificed, idling becomes unstable, and if the valve opening angle is made small with emphasis on torque at low rotation, output at high rotation will be sacrificed.
There was a trade-off problem.

[0007] When switching between a low rotation cam having a small valve opening angle and a lift amount and a high rotation cam having a large valve opening angle and a large lift amount, the above trade-off problem can be solved. Two cams and two ~
Since three arms are required, the structure becomes complicated,
There was a problem that it was difficult to make it compact. In addition, since the switching mechanism is mainly of the type that moves the pin with high hydraulic pressure, it does not switch smoothly with a single operation, generates abnormal noise at the time of switching, and wears out partly, And lack of reliability. Further, there is a problem that a high hydraulic pressure source is required in order to increase the switching response.

[0008] Therefore, an object of the present invention is to solve the above-mentioned problems and to operate the internal combustion engine by changing the valve timing and the lift amount continuously or stepwise from low rotation to high rotation of the internal combustion engine. Precise control according to the situation can be performed, so that various characteristics such as torque, output, fuel consumption, cleanness of exhaust gas, etc. can be maximized over the entire rotation range, and the change is smooth and quiet. The present invention provides a novel variable valve mechanism capable of simplifying the structure and reducing the size by using only one three-dimensional cam and one arm for one valve. It is in.

[0009]

In order to achieve the above object, a variable valve mechanism according to the present invention has a cam profile continuously changed in the axial direction from a cam profile for low rotation to a cam profile for high rotation. A camshaft provided with a three-dimensional cam, a displacement device for continuously or stepwise displacing the camshaft in the axial direction according to an operating condition such as the rotation speed of the internal combustion engine, and a cam profile of the three-dimensional cam. An arm for swinging the valve to open and close the valve, wherein the arm has a semi-cylindrical inner seat, and is fitted to the semi-cylindrical inner seat so as to be able to roll, and a change in a contact line angle accompanying rotation of the three-dimensional cam. A follow-up contact mechanism comprising a follow-up contact portion that comes into contact with the three-dimensional cam while following the above.

Here, the valve timing phase, valve opening duration and lift amount in the low rotation cam profile and the valve timing phase, valve opening angle and lift amount in the high rotation cam profile are determined for each internal combustion engine. Can be set as appropriate according to the requirements in.
However, in many cases, the cam profile for low rotation has a small valve opening angle and lift amount, and the cam profile for high rotation has a large valve opening angle and lift amount.

When the camshaft is displaced in a stepwise manner by the displacement device, the camshaft may be changed in two steps. In such a case, it is preferable that the displacement in the two steps can be adjusted. More preferably, the camshaft is displaced in at least three stages. Most preferably, the camshaft is continuously displaced. The displacement device is not limited to a specific structure, but may be a device using hydraulic pressure, electromagnetic force, or the like.

The following can be exemplified as the arm. 1) One end is pivotally supported on the rocker shaft,
A swing arm having a valve pressing portion at the other end and a roller mechanism with a follow-up contact portion at the center. 2) A swing arm having one end pivotally supported by a pivot, a valve pressing portion at the other end, and a roller mechanism with a follow-up contact portion at the center. 3) A rocker arm having a roller mechanism with a follow-up contact portion at one end, a valve pressing portion at the other end, and an intermediate portion pivotally supported by a rocker shaft.

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

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a variable valve mechanism in which the present invention is applied to both an intake valve and an exhaust valve will be described below with reference to the drawings. Therefore, in the embodiment, simply referring to a valve refers to both an intake valve and an exhaust valve.

FIGS. 1 to 7 show a variable valve mechanism according to a first embodiment. A camshaft 1 has a camshaft from a low-speed cam profile on the right to a high-speed cam profile on the left in FIG. A three-dimensional cam 2 whose profile is continuously changed in the axial direction is formed. The three-dimensional cam 2 includes 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 has a cylindrical surface without inclination. However, since the nose portion 2b has a small valve opening action angle and a lift amount in the low rotation cam profile and has a large valve opening action angle and the lift amount in the high rotation cam profile, the nose portion 2b is inclined like a conical surface. I have.

At the end of the camshaft 1, there is provided a displacement device 3 for continuously displacing the camshaft 1 in the axial direction according to the operating condition such as the rotation speed of the internal combustion engine. The displacement device 3 includes a guide portion of the camshaft 1 using splines and a driving portion of the camshaft 1 using hydraulic pressure (both are not shown), and is based on a rotation sensor, an accelerator opening sensor, etc. of the internal combustion engine. The operation is controlled by a control device (not shown) such as a microcomputer which operates in a controlled manner.

A swing arm 6 that opens and closes a valve 5 by swinging based on the cam profile of the three-dimensional cam 2 is rotatably mounted on a rocker shaft 4 disposed obliquely below the cam shaft 1. I have. The swing arm 6 has an insertion hole 7 for the rocker shaft 4 at the right end, a male threaded pin 8 as a valve pressing portion and a fixing nut 9 at the left end, and the upper surface of the central portion is configured as follows. A follow-up contact mechanism 10 is provided.

On the upper surface of the central portion of the swing arm 6, a protruding portion 11 which is long in a direction perpendicular to the axis of the three-dimensional cam 2 is formed.
A semi-cylindrical inner seat 12 extending in the same direction is recessed in the raised portion 11, and both ends of the seat 12 are closed by closed walls 13. The semi-cylindrical inner seat 12 includes a semi-cylindrical surface 15 that comes into contact with the semi-cylindrical inner seat 12 in a slidable manner and a flat contact surface 16 that contacts the three-dimensional cam 2. Part 1
4 is fitted so as to be able to roll. Follow contact 14
Is adapted to contact the three-dimensional cam 2 on the contact surface 16 while following a change in the contact line angle accompanying the rotation of the three-dimensional cam 2 by a small-angle roll motion.

The variable valve mechanism according to the present embodiment operates as follows. First, when the internal combustion engine is running at a low speed, the camshaft 1 is displaced leftward by the displacement device 3 as shown in FIG. 4, and the right low-speed cam profile of the three-dimensional cam 2 corresponds to the following contact portion 14. I do. Then, FIG.
When the base circle portion 2a comes into contact with the contact surface 16 of the follow-up contact portion 14, the contact line angle is parallel to the axis of the three-dimensional cam 2 as shown in FIG. The base circle portion 2a contacts the base circle portion 2a without tilting. Further, as shown in FIG. 4B, when the nose portion 2b contacts the contact surface 16 of the follow-up contact portion 14, the contact line angle is inclined by a predetermined angle with respect to the axis of the three-dimensional cam 2, so that the follow-up contact portion 14 Rolls by the same angle, and the contact surface 16
Makes good contact with the nose portion 2b.

As described above, the following contact portion 14 is
The roller makes a small-angle roll motion for each rotation of, and contacts the three-dimensional cam 2 while following the change in the contact line angle, and is pressed by the nose portion 2b. Therefore, the swing arm 6 swings based on the cam profile for low rotation, and as shown by the curve L in FIG. While increasing the torque,
Improve fuel economy.

When the internal combustion engine is rotating at a high speed, the camshaft 1 is displaced rightward by the displacement device 3 as shown in FIG. 14 corresponds to. Then, as shown in FIGS. 5 (a) and 5 (b), the follow-up contact portion 14
Rolls once for each rotation of, contacts the three-dimensional cam 2 while following the change in the contact line angle, and is pressed by the nose portion 2b. Accordingly, the swing arm 6 swings based on the cam profile for high rotation, opens and closes the valve 5 with a large valve opening angle and lift amount as shown by a curve H in FIG. Enhance.

The camshaft 1 is continuously displaced by the displacement device 3 in accordance with the operating conditions such as the number of revolutions and the degree of opening of the accelerator, even during the period from the low rotation to the high rotation. Among them, the cam profile of the intermediate portion corresponds to the following contact portion 14. Accordingly, the swing arm 6 swings based on the cam profile, and opens and closes the valve 5 at an intermediate valve opening angle and lift amount as shown by a curve M in FIG. Generate output.

As described above, according to the variable valve mechanism of the present embodiment, the valve timing and the lift amount are continuously changed from the low rotation to the high rotation of the internal combustion engine, and the operating condition of the internal combustion engine is changed. , And various characteristics such as torque, output, fuel efficiency, and cleanliness of exhaust gas can be maximized over the entire rotation range. FIG. 7 shows the torque characteristic of the internal combustion engine obtained by the present embodiment by a solid line, but the torque increases over the entire rotation range with respect to the conventional variable valve mechanism shown by the dashed line. There are no valleys. Further, depending on the setting, it is considered that the fuel efficiency can be improved by about 15 to 20% at the maximum.

Further, the change can be made smoothly and quietly by the displacement of the camshaft 1, and further, only one three-dimensional cam 2 and one swing arm 6 can be used for one valve 5. In addition, the structure can be simplified and the size can be reduced.

FIGS. 8 and 9 show a variable valve mechanism according to the second embodiment. Only at the point where the right end of the swing arm 6 is swingably supported by a pivot 19 with a hydraulic adjuster 18 is shown. This is different from the first embodiment.

FIGS. 10 and 11 show a variable valve mechanism according to the third embodiment, which differs from the first embodiment only in that a rocker arm 20 is used instead of a swing arm. The rocker arm 20 has a follow-up contact mechanism 10 on the lower surface on the right end, a male threaded pin 8 and a fixing nut 9 as a valve pressing portion on the left end, and an insertion hole 7 for the rocker shaft 4 at an intermediate portion. . The camshaft 1 and its three-dimensional cam 2 are located below the following contact mechanism 10. The rocker arm 20 swings like a seesaw unlike the swing arm, but otherwise exerts the same operation as the first embodiment.

The same effects as in the first embodiment can be obtained by the variable valve mechanisms of the second and third embodiments.

It should be noted that the present invention is not limited to the configuration of the above-described embodiment, and may be embodied with, for example, the following changes without departing from the spirit of the invention. (1) The camshaft 1 is displaced stepwise. (2) The configuration and control method of the displacement device 3 are appropriately changed.

[0029]

Since the variable valve mechanism of the present invention is configured as described above, the valve timing and the lift amount can be changed continuously or stepwise from the low rotation to the high rotation of the internal combustion engine. Thus, it is possible to perform precise control in accordance with the operation state of the internal combustion engine, and thereby it is possible to maximize various characteristics such as torque, output, fuel efficiency, cleanness of exhaust gas, etc. over the entire rotation range, The change can be performed smoothly and quietly, and further, one valve and one arm can be used for one valve, so that the structure can be simplified and the size can be reduced. It has the effect.

[Brief description of the drawings]

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

FIG. 2 is a front view of the variable valve mechanism.

FIG. 3 is a plan view of the variable valve mechanism.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 2 when the internal combustion engine is running at a low speed.
It is a line sectional view.

FIG. 5 is a sectional view taken along line IV-IV of FIG. 2 when the internal combustion engine is rotating at a high speed.
It is a line sectional view.

FIG. 6 is a graph showing valve timing and lift amount by the variable valve mechanism.

FIG. 7 is a graph showing torque characteristics of an internal combustion engine obtained by the variable valve mechanism in comparison with a conventional example.

FIG. 8 is a front view showing a variable valve mechanism according to a second embodiment.

FIG. 9 is a sectional view taken along line IX-IX of FIG. 8;

FIG. 10 is a front view showing a variable valve mechanism according to a third embodiment.

11 is a sectional view taken along line XI-XI in FIG.

FIG. 12 is a graph showing valve timing and lift amount by a conventional variable valve mechanism.

FIG. 13 is a graph showing valve timing and lift by another conventional variable valve mechanism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Camshaft 2 Solid cam 3 Displacement device 4 Rocker shaft 5 Valve 6 Swing arm 8 Male screw pin 10 Following contact mechanism 12 Semicylindrical inner surface seat 14 Following contact part 15 Semicylindrical surface 16 Contact surface 18 Hydraulic adjuster 19 Pivot 20 Rocker arm

Claims (4)

[Claims] 1. A camshaft having a three-dimensional cam in which a cam profile is continuously changed in an axial direction from a low-rotation cam profile to a high-rotation cam profile, and according to an operating condition such as a rotation speed of an internal combustion engine. A displacement device that displaces the camshaft continuously or stepwise in the axial direction; and an arm that opens and closes a valve by swinging based on a cam profile of the three-dimensional cam, wherein the arm has a semi-cylindrical inner surface. A follow-up contact mechanism comprising a seat and a follow-up contact portion that is fitted to the semi-cylindrical inner surface seat so as to be able to roll and that contacts the three-dimensional cam while following a change in a contact line angle accompanying the rotation of the three-dimensional cam is provided. A variable valve mechanism. 2. The arm is pivotally supported at one end by a rocker shaft, and has a valve pressing portion at the other end.
The variable valve mechanism according to claim 1, wherein the swing arm includes a roller mechanism having a follow-up contact portion at a central portion. 3. The swing arm according to claim 1, wherein one end of the arm is swingably supported by a pivot, the other end has a valve pressing portion, and the central portion has the roller mechanism with the follow-up contact portion. 2. The variable valve mechanism according to 1. 4. The rocker arm having the roller mechanism with a follow-up contact portion at one end, a valve pressing portion at the other end, and an intermediate portion pivotally supported by a rocker shaft. Item 7. The variable valve mechanism according to Item 1.