Variable valve system mechanism

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a variable valve mechanism that continuously or stepwise changes the overlap angle and lift amount from low rotation to high rotation of an internal combustion engine.

【0002】

[Conventional technology]

Conventionally, various valve operating mechanisms have been known that change the valve timing and the lift amount in two stages depending on whether the internal combustion engine is rotating at a low speed or at a high speed. 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 large lift amount to swing the swing arm. .. According to the variable valve operating mechanism, various characteristics such as output, torque, fuel consumption, and cleanliness of exhaust gas are considerably improved as compared with a general valve operating mechanism.

【0003】

[Problems to be Solved by the Invention]

However, the variable valve mechanism also has the following problems. Since the valve timing or lift amount is only changed in two stages between low rotation and high rotation, it is difficult to precisely control the valve timing or lift amount according to the operating conditions of the internal combustion engine. In addition, a valley may occur in the torque characteristics at the switching point between low rotation and high rotation.

【0004】

Since two cams are required for one valve, there is a problem that the structure becomes complicated and it is difficult to make it compact. In addition, since the mainstream type of switching mechanism is to move the pins with high hydraulic pressure, it does not switch smoothly with a single operation, abnormal noise is generated during switching, and some parts are worn out, resulting in accuracy. There was a problem of lack of reliability. Further, there is a problem that a high hydraulic source is required to improve the switching response.

【0005】

Therefore, an object of the present invention is to solve the above-mentioned problems and continuously or stepwise change the overlap angle and the lift amount from the time of low rotation to the time of high rotation of the internal combustion engine to change the operating condition of the internal combustion engine. Precise control can be performed according to the above, and various characteristics such as output, torque, fuel consumption, and cleanliness of exhaust gas can be improved to the maximum over the entire rotation range, and the above changes can be performed smoothly and quietly. Furthermore, it is an object of the present invention to provide a new variable valve mechanism that can be made so that one cam can be used for one valve, and the structure can be simplified and made compact.

【0006】

[Means for solving problems]

In order to achieve the above object, the variable valve mechanism of the present invention includes a rocker shaft, an eccentric shaft portion provided by shifting the axis of a part of the rocker shaft, and a shaft support swingably provided on the eccentric shaft portion. The first arm, which is pressed by the cam and swings, is swayably supported by the rocker shaft, and the first arm is engaged so as to be relatively displaceable, and swings in response to the swing of the first arm. The second arm that opens and closes the valve by moving and the eccentric shaft part are rotated continuously or stepwise according to the operating conditions such as the rotation speed of the internal combustion engine, so that the first arm is rotated in the circumferential direction of the cam. It is characterized by being equipped with an arm displacement device for displacement.

【0007】

The engagement between the first arm and the second arm is not limited to a specific means, and the following means can be exemplified. B) Engagement by fitting the long holes provided relative to the first arm and the second arm and the engagement pin. By "relatively" is meant that one of the first arm and the second arm may be provided with an elongated hole and the other may be provided with an engaging pin. B) Engagement by contact between the roller provided relative to the first arm and the second arm and the contact surface. By "relatively" is meant that a roller may be provided on either one of the first arm and the second arm, and a contact surface may be provided on the other arm.

【0008】

When the first arm is displaced stepwise by the arm displacement device, it may be changed in two steps, but it is preferable to displace it in three or more steps. More preferably, the first arm is continuously displaced. The arm displacement device is not limited to a specific structure, and can be exemplified by using a hydraulic force, an electromagnetic force, or the like.

【0009】

The following can be exemplified as the second arm. 1) A swing arm in which one end is swingably supported by a rocker shaft, the central portion is engaged with the first arm, and the other end is provided with a valve pressing portion. 2) A rocker arm whose central portion is swingably supported by a rocker shaft, one end of which is engaged with the first arm, and the other end of which is provided with a valve pressing portion.

【0010】

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

【0011】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an example of an embodiment of the variable valve mechanism according to the present invention will be described with reference to the drawings.

【0012】

First, FIGS. 1 to 6 show the variable valve mechanism of the first embodiment. As shown in FIGS. 1 and 2, this variable valve mechanism is applied to both the intake side (right side) and the exhaust side (left side), and the structures on both sides are symmetrical. Therefore, most of the following structural explanations are common to the variable valve mechanisms on both sides. Note that FIGS. 3 to 5 show only the variable valve mechanism on the exhaust side for convenience.

【0013】

The cam shaft 1 is formed with a cam 2 including a base circle portion 2a and a nose portion 2b of a predetermined cam profile. An eccentric ring-shaped eccentric shaft portion 4 is extrapolated to a part of the rocker shaft 3 arranged diagonally downward of the camshaft 1, and the key 5 is press-fitted into both the key grooves of the rocker shaft 3 and the eccentric shaft portion 4. It is fixed. The axis 3a of the rocker shaft 3 and the axis 4a of the eccentric shaft portion 4 are offset from each other.

【0014】

The eccentric shaft portion 4 is pivotally supported by a first arm 6 that is pressed by the cam 2 and swings. The first arm 6 is provided with a hard pad 8 which is pivotally supported by an eccentric shaft portion 4 in an insertion hole 7 formed at one end and the cam 2 is in sliding contact with the upper surface of the other end.

【0015】

On both sides of the eccentric shaft portion 4 of the rocker shaft 3, a second arm 10 integrally formed from the bifurcated arm body 11 and its connecting portion 12 in a Π shape is oscillatingly supported. The second arm 10 is pivotally supported by the rocker shaft 3 in an insertion hole 13 formed at one end of the arm body 11, the central portion is engaged with the first arm 6, and two valves are connected to the connecting portion 12 at the other end. It is a swing arm provided with a pressing portion 14.

【0016】

The first arm 6 is engaged with the central portion of the arm body 11 so as to be relatively displaceable. Therefore, the second arm 10 swings in response to the swing of the first arm 6, and opens and closes the two exhaust valves 18 or the two intake valves 19 at the same time. In the engagement between the first arm 6 and the second arm 10, the central portion of the engaging pin 15 inserted and supported by both arm bodies 11 of the second arm 10 is penetrated in the middle portion of the first arm 6. It is an engagement by slidably fitting into the elongated hole 16. This slide allows the displacement of the first arm 6.

【0017】

On the rocker shaft 3, the eccentric shaft portion 4 is continuously or stepwise rotated together with the rocker shaft 3 according to the operating conditions such as the rotation speed of the internal combustion engine, so that the first arm 6 is moved in the circumferential direction of the cam 2. An arm displacement device 17 for displacement is connected. FIG. 5 is an explanatory view showing a locus in which the pad 8 is displaced in the circumferential direction of the cam 2 when the first arm 6 is displaced, and the pad 8 is displaced in the range of the θ angle. The arm displacement device 17 consists of a helical spline mechanism and a drive unit using hydraulic pressure (details are not shown), and is operated by a control device such as a microcomputer based on the detected values from the rotation sensor of the internal combustion engine, the accelerator opening sensor, and the like. It is designed to be controlled.

【0018】

The variable valve mechanism configured as described above operates as follows. First, at low rotation of the internal combustion engine, as shown in FIG. 1, the arm displacement device 17 moves the rocker shaft 3 and the eccentricity so that the axis 4a of the eccentric shaft portion 4 is closer to the valve side than the axis 3a of the rocker shaft 3. The shaft portion 4 is rotated to displace the first arm 6 toward the valve. In order to obtain the displacement locus of the pad 8 as described above, it is preferable to angle the pad 8 so that the axis 4a is obliquely downward from the axis 3a.

【0019】

In the case of this embodiment, since both cams 2 are counterclockwise, when the first arm 6 on the exhaust side (left side) is displaced to the valve side, the pad 8 is located on the advancing side of the cam 2 and is on the intake side (right side). ), When the first arm 6 is displaced toward the valve, the pad 8 is located on the lagging side of the cam 2. Further, the distance from the axis 3a of the rocker shaft 3 to the center of the pad 8 becomes longer, and the ratio (arm ratio) of the distance from the axis 3a of the rocker shaft 3 to the valve pressing portion 14 with respect to the same distance becomes smaller. , The lift amount of the valves 18 and 19 by the second arm 10 becomes small. Therefore, as shown in the curve L of FIG. 6, the exhaust valve 18 and the intake valve 19 open and close with a small overlap angle and a lift amount to stabilize idling and improve fuel efficiency.

【0020】

Further, at high rotation of the internal combustion engine, as shown in FIG. 2, the arm displacement device 17 is set to the rocker shaft 3 and the rocker shaft 3 so that the axis 4a of the eccentric shaft portion 4 is on the opposite valve side from the axis 3a of the rocker shaft 3. The eccentric shaft portion 4 is rotated to displace the first arm 6 toward the anti-valve side. In order to obtain the displacement locus of the pad 8 as described above, it is preferable to angle the pad 8 so that the axis 4a is obliquely upward from the axis 3a.

【0021】

When the first arm 6 on the exhaust side is displaced to the anti-valve side, the pad 8 is located on the lagging side of the cam 2, and when the first arm 6 on the intake side is displaced to the anti-valve side, the pad 8 is on the advancing side of the cam 2. Located in. Further, the distance from the axis 3a of the rocker shaft 3 to the center of the pad 8 becomes shorter, and the ratio (arm ratio) of the distance from the axis 3a of the rocker shaft 3 to the valve pressing portion 14 with respect to the same distance becomes larger. , The lift amount of valves 18 and 19 by the second arm 10 becomes large. Therefore, as shown in the curve H of FIG. 6, the exhaust valve 18 and the intake valve 19 open and close with a large overlap angle and a lift amount to increase the output.

【0022】

Then, even in the middle of the process from the low rotation speed to the high rotation speed, the arm displacement device 17 continuously rotates the rocker shaft 3 and the eccentric shaft portion 4 according to the operating conditions such as the rotation speed and the accelerator opening degree. Displace the first arm 6. Therefore, as shown in the curve M of FIG. 6, the exhaust valve 18 and the intake valve 19 open and close with an intermediate overlap angle and a lift amount to generate an output according to the operating condition.

【0023】

As described above, according to the variable valve mechanism of the first embodiment, the overlap angle and the lift amount are continuously changed from the time of low rotation to the time of high rotation of the internal combustion engine to adjust the operating condition of the internal combustion engine. Precise control can be performed accordingly, and various characteristics such as output, torque, fuel consumption, and cleanliness of exhaust gas can be improved to the maximum over the entire rotation range. In particular, the torque increases over the entire rotation range and no valleys occur. It also improves fuel economy. Further, the displacement of the first arm 6 makes it possible to make the change smoothly and quietly, and further, it is possible to use only one cam for one valve (two in this embodiment). Can be simplified and made compact.

【0024】

Next, FIGS. 7 to 10 show the variable valve mechanism of the second embodiment. This variable valve mechanism only replaces the pad 8 with the roller 24 and replaces the fitting of the elongated hole 16 with the engaging pin 15 with the contact between the roller 25 and the contact surface 22. , It is different from the first embodiment.

【0025】

That is, a roller receiving portion 21 connecting between the bifurcated arm main bodies 11 is formed in the lower part of the second arm 10, and the upper surface of the roller receiving portion 21 is a gently curved contact surface 22. A mounting hole 23 is formed in the other end of the first arm 6 in the vertical direction, and the mounting hole 23 includes an upper roller 24 with which the cam 2 abuts and a lower roller 25 with a contact surface 22. , And the rollers 24 and 25 are rotatably shaft-mounted on the side wall of the first arm 6. The lower roller 25 is rotatably contacted with the contact surface 22, so that the first arm 6 is rotatably engaged with the central portion of the second arm 10 so as to be relatively displaceable. Others are the same as those of the first embodiment, and reference numerals are given to FIGS. 7 to 10 in common, and the description thereof will be omitted.

【0026】

The variable valve mechanism of the present embodiment basically operates in the same manner as that of the first embodiment. First, when the internal combustion engine rotates at a low speed, the first arm 6 is displaced toward the valve as shown in FIG. As a result, the exhaust valve 18 and the intake valve 19 open and close with a small overlap angle and lift amount as shown in the curve L of FIG. 6, stabilizing idling and improving fuel efficiency.

【0027】

Further, when the internal combustion engine rotates at a high speed, the first arm 6 is displaced to the anti-valve side as shown in FIG. As a result, the exhaust valve 18 and the intake valve 19 open and close with a large overlap angle and lift amount, as shown in the curve H of FIG. 6, to increase the output.

【0028】

Then, in the middle of the process from the low rotation speed to the high rotation speed, the exhaust valve 18 and the intake valve 19 open and close with an intermediate overlap angle and lift amount as shown in the curve M of FIG. Generates output according to.

【0029】

Therefore, the same effect as that of the first embodiment can be obtained by this embodiment as well. Moreover, since the cam 2 abuts on the rotatable upper roller 24 and the lower roller 25 abuts on the abutting surface 22 and rolls, friction loss at both abutting portions can be reduced. The displacement can be performed smoothly.

【0030】

The present invention is not limited to the configuration of the above embodiment, and can be modified and embodied as follows, for example, within a range that does not deviate from the gist of the invention. (1) Displace the first arm 6 in stages. (2) Change the configuration and control method of the arm displacement device 17 as appropriate. (3) As the second arm, use a rocker arm instead of the swing arm.

【0031】

[Effect of the invention]

Since the variable valve mechanism of the present invention is configured as described above, the overlap angle and the lift amount are continuously or stepwise changed from the low rotation speed to the high rotation speed of the internal combustion engine to continuously or stepwise change the internal combustion engine. Precise control can be performed according to the operating conditions of the engine, and various characteristics such as output, torque, fuel consumption, and cleanliness of exhaust gas can be improved to the maximum over the entire rotation range. In addition, the change can be performed smoothly and quietly, and one cam can be used for one valve, which has an excellent effect of simplifying the structure and making it compact. Play.

[Simple explanation of drawings]

[Figure 1]

It is a front view which shows the variable valve mechanism (at the time of low rotation of an internal combustion engine) which concerns on 1st Embodiment of this invention.

[Figure 2]

It is a front view which shows the variable valve mechanism (at the time of high rotation of an internal combustion engine).

[Fig. 3]

It is a perspective view of the variable valve mechanism.

[Fig. 4]

It is an exploded perspective view of the variable valve mechanism.

[Fig. 5]

It is explanatory drawing which shows the displacement locus of the pad of the 1st arm in the variable valve mechanism.

[Fig. 6]

It is a graph which shows the valve timing and the lift amount by the variable valve mechanism.

[Fig. 7]

It is a front view which shows the variable valve mechanism (at the time of low rotation of an internal combustion engine) which concerns on the 2nd Embodiment of this invention.

[Fig. 8]

It is a front view which shows the variable valve mechanism (at the time of high rotation of an internal combustion engine).

[Fig. 9]

It is a perspective view of the variable valve mechanism.

[Fig. 10]

It is an exploded perspective view of the variable valve mechanism.

[Explanation of symbols]

1 camshaft 2 cam 3 Rocker shaft 3a axis 4 Eccentric shaft 4a axis 5 keys 6 First arm 7 Insertion hole 8 pads 10 Second arm 11 Arm body 12 Connection 13 Insertion hole 14 Valve pressing part 15 Engagement pin 16 long hole 17 Arm displacement device 18 Exhaust valve 19 Intake valve 21 Roller receiver 22 Contact surface 23 Mounting holes 24 roller 25 roller