JP2001041017A - Variable valve mechanism - Google Patents

Abstract

(57) [Problem] To provide a variable valve mechanism having a simple structure that is compact, has high rigidity, and is excellent in durability. SOLUTION: A first rocker arm (for low speed) 10 that is swingably supported by a rocker shaft 30 and driven by a first cam 41 to open an intake valve is provided with a piston 50 that is controlled to move forward and backward by hydraulic pressure. Incorporate. The second rocker arm (for high speed) 20 which is provided adjacent to the first rocker arm and is driven by a second cam 42 having a larger lift than the first cam, engages with the piston. The projection 21 is extended. An engagement portion 51 is provided on the side of the piston to selectively engage with the engagement protrusion. In addition, by incorporating the piston into the substantially central boss of the first rocker arm, the driving force is transmitted in one direction.

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 for varying the opening / closing timing and lift of intake and exhaust valves according to the number of revolutions of an internal combustion engine, and more particularly to a variable valve mechanism having a compact and highly rigid structure. .

[0002]

2. Related Art In order to improve the output performance of an internal combustion engine, a variable valve mechanism for changing the opening / closing valve timing and lift amount of an intake / exhaust valve in accordance with the rotation speed is used. This type of variable valve mechanism is disclosed in, for example, Japanese Patent No. 2779429.
As disclosed in Japanese Unexamined Patent Publication, a low-speed rocker arm driven by a low-speed cam with its tip linked to a valve, and a high-speed rocker arm driven by a high-speed cam having a larger lift than the low-speed cam. A cam (low speed cam or high speed cam) acting on the valve is switched by connecting or disconnecting each rocker arm using a connection mechanism driven by hydraulic pressure.

More specifically, the variable valve mechanism has a structure in which low-speed and high-speed rocker arms are swingably supported on a rocker shaft. Then, a piston incorporated in the high-speed rocker arm and driven forward and backward by hydraulic pressure is selectively engaged with an engaging portion extending from the low-speed rocker arm toward the high-speed rocker arm. Incidentally, when the piston is not driven, the engagement (connection) of both rocker arms is released, and the high-speed rocker arm swings independently of the low-speed arm, and only the swing of the low-speed rocker arm acts on the intake valve. On the other hand, when the piston is hydraulically driven, the swing of the high-speed rocker arm with a large lift amount is applied to the low-speed rocker arm, so that the swing of the high-speed rocker arm acts on the valve via the low-speed rocker arm.

[0004]

By the way, as the performance of the internal combustion engine becomes higher, it is required that the rigidity of each rocker arm be made sufficiently high. However, in the above-described conventional variable valve mechanism, since the piston is incorporated in the high-speed rocker arm, the high-speed rocker arm becomes heavy and its rigidity is likely to be impaired. Further, the low-speed rocker arm has a structure (swing arm structure) in which a cam contact portion is provided between a linking portion (valve side) with the valve and a swing shaft thereof.
A coupling mechanism for the two rocker arms is provided on the opposite side of the valve from the low-speed rocker arm. For this reason, the driving force transmitted from the high-speed cam to the high-speed rocker arm is transmitted back to the low-speed rocker arm via the coupling mechanism, so that the transmission path of the driving force is long, and in this respect, the rigidity is reduced. It is a factor.

Further, the lubricating environment in the valve operating mechanism tends to be severe, and a problem may occur in the durability of a rocker bush that is incorporated in a rocker shaft and supports a rocker arm. Especially with the addition of the variable mechanism,
Problems such as narrowing of the width of the rocker arm and occurrence of a twisting load due to the offset of the weighted point occur. Further, since the swing angle of the high-speed rocker shaft is larger than that of the low-speed rocker shaft, the wear resistance (durability) of the shaft portion (support portion) tends to be a problem.

The present invention has been made in view of such circumstances, and an object thereof is to provide a variable valve mechanism having a simple structure that is compact, has high rigidity, and is excellent in durability.

[0007]

In order to achieve the above object, a variable valve mechanism according to the present invention is swingably supported by a rocker shaft and driven by a first cam. A first rocker arm (low-speed rocker arm) that opens an intake valve or an exhaust valve incorporates a piston that is controlled to move forward and backward by hydraulic pressure. On the other hand, a first rocker arm is provided adjacent to the first rocker arm, and the first cam is provided. A second rocker arm (a high-speed rocker arm) driven by a second cam having a large lift amount is provided with an engagement protrusion which can be engaged with the piston. The hydraulic pressure is applied to the side of the piston. An engagement portion is provided which engages with the engagement protrusion at a position where the engagement protrusion is received and moved, and is released from engagement with the engagement protrusion at a position where the hydraulic pressure is released and returned.

That is, the present invention incorporates a piston for controlling the engagement with the high-speed rocker arm in the boss portion on the low-speed rocker arm side, thereby simplifying the structure of the high-speed rocker arm and reducing its inertial mass. However, the rigidity of the high-speed rocker arm is sufficiently increased, thereby realizing a variable valve mechanism that simplifies the entire structure and improves durability and reliability.

In a preferred aspect of the present invention, one end of the first rocker arm opposite to the rocker shaft as a swing axis is linked to the valve, and the other end is the first link.
And a so-called double-arm type structure having a contact portion with the cam, and a structure in which a cylinder in which the piston is incorporated is provided in a central boss portion. The driving force from the second rocker arm acts in a direction to press the piston toward the valve side, and the driving force acts on the valve in one direction via the piston in the shortest path, thereby providing overall strength and rigidity. It is characterized by increasing.

[0010] More preferably, the second rocker arm is directly supported on the rocker shaft by providing the first rocker arm with a shaft portion for swingably supporting the second rocker arm. Compared to the second case
Of the first rocker arm with respect to the rocker shaft is widened to increase the durability of the rocker bush attached to the supporter. It is characterized by:

According to a fourth aspect of the present invention, the piston is mounted on the cylinder so as to be able to move forward and backward in a detent structure so as to be stable with the engaging projection extending from the second rocker arm. And secure engagement is realized.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a variable valve mechanism according to an embodiment of the present invention will be described with reference to the accompanying drawings, particularly a variable valve mechanism for driving an intake valve. FIG. 1 is an exploded perspective view showing an overall schematic configuration of a variable valve mechanism according to this embodiment, and FIG. 2 is a top view showing an assembled state thereof. In the figure, reference numeral 10 denotes a first low-speed rocker arm that is swingably supported on the rocker shaft 30, and reference numeral 20 denotes a second high-speed rocker arm that is provided adjacent to the first rocker arm 10 and that can swing freely. The first rocker arm 10 has a boss 11 that is supported by a rocker shaft 20.
, The arms 12 and 13 are respectively extended on both sides thereof, and the tip of one arm 12 is used as a link with an intake valve (not shown). The roller 14 which comes into contact with the cam 41 is rotatably mounted. The first rocker arm 10 is driven by the first cam 41, swings according to the cam profile, and opens and drives the intake valve via the adjustment screw 15 mounted on the linking section.

A cylinder 16 is formed on the boss 11 at a substantially right angle to the rocker shaft 20, and a piston 50 is mounted on the cylinder 16 so as to be movable forward and backward. The piston 50 is driven by receiving a hydraulic pressure supplied through the inside of the rocker shaft 20 as described later. When the piston 50 is not driven, the piston 50 is pressed by a return spring 61 described later and positioned at a lower portion of the cylinder portion 16. When driven by hydraulic pressure, it is positioned above the cylinder 16 against the return spring.

In particular, on the side of the piston 50, there is provided an engagement groove 51 which forms an engagement portion with the second rocker arm 20. This engagement groove 51 is provided in the second
The first and second rocker arms 10 and 2 selectively engage with engagement projections 21 extending from the rocker arms 20 of the first and second rocker arms.
It plays a role in controlling the connection of 0 and the disconnection. In particular, the engagement groove 51 opens a part of the wall surface of the cylinder portion 16 and faces the opening portion 17 formed in the boss portion 11 and engages with the engagement protrusion 21 fitted into the opening portion 17. It is provided as follows. The opening 17 is located on the side opposite to the intake valve, that is, the roller 14 driven by the first cam 41.
It is opened toward the side of the arm 13 on which is mounted.

Incidentally, the engaging groove 51 is formed in the cylinder portion 1.
6, a deep groove 52 that allows the engagement projection 21 to pass when the piston 50 is positioned at a lower portion (when not driven), and a state where the piston 50 is positioned at an upper portion of the cylinder portion 16 (when driven). And a shallow groove 53 which abuts on the engaging projection 21 to block the passage therethrough. The engagement protrusion 21 is selectively fitted into the deep groove portion 52 or the shallow groove portion 53 in accordance with the position of the piston 50 at the time of driving / non-driving, and selectively receives the pressing force by the engagement protrusion 21. ing.

On the other hand, the second rocker arm 20 has a boss portion 22 supported on a shaft portion 18 provided on the side of the first rocker arm 10, and an arm 23 extending from the boss portion 22 is provided on the second rocker arm 20. The roller 24 is rotatably mounted. The roller 24 has a second cam 42 having a cam profile having a larger lift amount than the first cam 41.
Abut. Also, the second rocker arm 20 is
The roller 24 is rotationally urged by a return spring 62 which engages with an end of the thick portion 25 formed on the upper portion of the second cam 2 in a direction in which the roller 24 comes into contact with the second cam 42, thereby.
In accordance with the cam profile of the cam 41.

Above the arm 23, the above-mentioned engaging projection 21 is extended toward the first rocker arm 10 side. The engagement protrusion 21 is provided on the second rocker arm 20.
Of the second cam 42
Has a shape in which the pressing piece 26 is extended in a direction in which the pressing piece 26 is rotationally urged. This pressing piece 26 (engaging projection 21) fits the boss 22 of the second rocker arm 20 to the shaft 18 of the first rocker arm 10 as shown in FIG. When assembled with each other, as shown in FIG. 3, the first rocker arm 20 swings the second rocker arm 20 by contacting the shallow groove 353 of the engagement groove 51 provided in the piston 50 through the opening 17 described above. It plays the role of communicating to 10.

Each of the return springs 61 and 62 is composed of a torsion coil spring.
Is mounted on the upper surface of the boss portion 11. The return spring 61 has its working end connected to the piston 50 as shown in FIG.
To a concave spring receiving portion 54 formed on the top of
The piston 50 is provided to press against the bottom of the cylinder portion 16. As shown in FIG. 4, the return spring 62 has its working end connected to the thick portion 2 of the second rocker arm 20.
The second rocker arm 20 is provided so as to rotate and bias the second rocker arm 20 toward the roller 24.

The spring support member 63 is provided with a guide piece 64 which is located at a support portion of the return spring 61 and protrudes toward the cylinder 16. This guide piece 64
Is located along the wall surface of the cylinder portion 16 and is engaged with a slit groove 56 formed in the peripheral wall of the piston 50 in the vertical direction.
In cooperation with the return spring 61 engaged with the cylinder part 1
It functions as a detent structure for defining the mounting direction of the piston 50 with respect to 6. With such a detent structure, the piston 50 moves in and out of the cylinder 16 only in a state where the engagement groove 51 faces the opening 17.

According to the variable valve mechanism configured as described above, when the internal combustion engine is rotating at a low speed and no hydraulic pressure is supplied to the cylinder portion 16 through the inside of the rocker shaft 30, that is, when the piston 50 is not driven, As shown in FIG. 5, the piston 50 receives the urging force of the return spring 61 and is positioned at the bottom of the cylinder 16. Then, with the rotation of the first and second cams 41 and 42, the first
When the first rocker arm 10 and the second rocker arm 10 are driven to swing, respectively, the first rocker arm 10
And drives the intake valve through the adjusting screw 15 to open the intake valve. At this time, the lift amount of the second cam 42 is large, and the first rocker arm 10
Even if the swing width of the second rocker arm 20 is larger than that of the second rocker arm 20, the engagement protrusion 2
Since the first pressing piece 26 only enters into the deep groove 52 of the piston 50 as shown in FIG. 5, the second rocker arm 20 swings independently of the first rocker arm 10. Therefore, the swing of the second rocker arm 20 does not affect the first rocker arm 10.

On the other hand, when a hydraulic pressure is supplied to the cylinder portion 16 through the inside of the rocker shaft 30, the piston 50 receives the hydraulic pressure and, as shown in FIG. The shallow groove 53 of the engagement groove 51 faces the engagement protrusion 21. In this state, when the first and second rocker arms 10 and 20 are respectively oscillated with the rotation of the first and second cams 41 and 42, the first rocker arm 10 basically becomes the first rocker arm 10. It swings according to the cam profile of the cam 41 and operates to open the intake valve via the adjustment screw 15. However, at this time, the lift amount of the second cam 42 is large, the second rocker arm 20 swings more than the first rocker arm 10, and the engagement protrusion 21 extended from the second rocker arm 20 is moved. Piston 50
Is pressed. As a result, the first rocker arm 10 largely swings by receiving the pressing force from the second rocker arm 20 in addition to the swing of itself, and the large swing causes the intake air to flow through the adjustment screw 15. The valve is driven to open. In other words, the swing of the second rocker arm 20 acts on the adjusting screw 15 via the first rocker arm 10, and the operation of the intake valve is defined by the cam profile of the second cam 42.

The variable valve mechanism constructed as described above and driven to open the intake valve in accordance with the cam profile of the first or second cam 41, 42 is characterized in particular by the first and second rockers. Arm 10,2
A piston 50 having a function of connecting and disconnecting the first rocker arm 10 is incorporated into the boss portion 11 of the first rocker arm 10, and an engagement protrusion 21 extending from the second rocker arm 20 is selectively engaged with the piston 50. It is in the point which was made. At the same time, by mounting the piston 50 on the upper portion of the boss 11 which is substantially the center of the first rocker arm 10, a driving point to which driving force is applied from the first and second cams 41 and 42, and the adjusting screw 15 The connecting mechanism is positioned at an intermediate point of the operation point at which the second rocker arm 20 is mounted.
Is transmitted to the first rocker arm 10 smoothly and with the shortest path.

With such a structure, the second rocker arm 20 driven by the second cam 41 having a large lift can be simplified in its structure and reduced in mass because the piston 50 is not mounted. Therefore, the rigidity of the second rocker arm 20 that swings at a higher speed than that of the first rocker arm 10 can be sufficiently increased. In addition, the return spring 62 is reduced by the weight of the second rocker arm 20.
Can be reduced by reducing the spring force required for the device. Therefore, as described above, the second rocker arm 20 is stably and reliably rotated only by the simple structure of the torsion coil spring (return spring 62) mounted on the first rocker arm 10 side via the spring support member 63. Can be energized.

Also, for the first rocker arm 10,
The connecting portion (piston 50) with the second rocker arm 20 is incorporated into the boss 11 at substantially the center, and the pressing force applied from the engaging projection 21 is transmitted as it is to the adjusting screw 15 side in front of it. The driving force from the second rocker arm is not transmitted back at the end of the arm as in the case of the first embodiment, so that the transmission path of the driving force can be minimized and its rigidity can be sufficiently increased. Furthermore, piston 5
Since the piston 0 itself is also provided on its side to receive the pressing force from the engagement projection 21, the rigidity of the piston 50 itself can be sufficiently increased. Therefore, it is possible to increase the overall rigidity of the variable valve mechanism and increase the operation reliability thereof.

Further, according to the above-described structure, since the second rocker arm 20 is supported by the shaft portion 18 of the first rocker arm 10, the second rocker arm 20 swings at an angle larger than that of the first rocker arm 10 with respect to the rocker shaft 30. Although the first rocker arm 10 moves, the first rocker arm 10 itself also swings by the first cam 41, so that the swing angle with respect to the first rocker arm 10 can be sufficiently reduced. Therefore, the load on the second rocker arm 20 to be supported by the shaft portion 18 can be reduced, and its durability can be increased.

Also, for the first rocker arm 10,
Since a wide area including the shaft portion 18 can be used as a support portion for the rocker shaft 30, the support load can be reduced. In particular, the surface pressure of the bush 31 made of copper, lead alloy, or the like, which is mounted on the rocker shaft 30 and supports the first rocker shaft 10, reduces the surface pressure, thereby reducing fatigue and improving its durability. Can be

The present invention is not limited to the above embodiment. For example, the advance / retreat width of the piston 50 may be determined according to the thickness of the pressing portion 26 of the engagement protrusion 21, so that the piston 50 can reliably contact the pressing portion 26, and can reliably escape from the contact with the pressing portion 26. It is enough to set to. Also, the mechanism for preventing the rotation of the piston 50 can be realized only by the engagement between the return spring 61 and the concave spring receiving portion 54 formed on the top of the piston 50.

Further, the second rocker arms 20, 20 are arranged on both sides of the first rocker arm 10, respectively.
These second rocker arms 20, 20 may be respectively driven by second cams 42, 42 having different lift amounts. In this case, the piston 50 is provided with engagement grooves corresponding to the engagement protrusions 21 extending from the second rocker arms 20, respectively.
0 is controlled in three stages: lower, middle, and higher.
It is also possible to configure so as to selectively engage with each of the engagement protrusions 21 and 21. Further, the case where the intake valve is driven has been described as an example, but the present invention can be similarly applied to the case where the exhaust valve is driven. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0029]

As described above, according to the first aspect of the present invention, the rigidity of the second rocker arm that swings at a high speed is increased, and the second rocker arm is provided with a piston provided on the boss portion of the second rocker arm. Since the driving force from the second rocker arm is reliably received, it is possible to simplify the overall configuration and realize a highly reliable operation variable valve mechanism with sufficiently increased rigidity.

According to the second aspect of the present invention, since the driving force transmission paths are arranged in one direction and minimized, the overall rigidity can be increased also in this regard, and the reliability thereof can be improved. it can. Further, according to the third aspect of the present invention, the support area of the first rocker arm with respect to the rocker shaft can be widened to enhance its durability, and the support structure itself of the second rocker arm can be simplified.

According to the fourth aspect of the present invention, there is a great effect in practical use such as the unintended rotation of the piston can be prevented and the pressing force from the engaging projection can be reliably received. Can be

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an overall schematic configuration of a variable valve mechanism according to an embodiment of the present invention.

FIG. 2 is a view for explaining the assembling of a first rocker arm and a second rocker arm shown in FIG. 1;

FIG. 3 is a top view of the variable valve mechanism shown in FIG. 1;

FIG. 4 is a diagram showing an assembled state of a second rocker arm in the variable valve mechanism shown in FIG. 1;

FIG. 5 is a partial cross-sectional view showing an assembled state of a first rocker arm in the variable valve mechanism shown in FIG. 1, showing a non-driven state of a piston.

FIG. 6 is a partial cross-sectional view showing an assembled state of a first rocker arm in the variable valve mechanism shown in FIG. 1, showing a driving state of a piston.

[Explanation of symbols]

 Reference Signs List 10 First rocker arm (for low speed) 11 Boss part 15 Adjuster screw (coupling part with intake valve) 16 Cylinder part 18 Shaft part 20 Second rocker arm (for high speed) 21 Engagement projection 30 Rocker shaft 41 First cam 42 Second cam 50 Piston 51 Engagement groove 52 Deep groove 53 Shallow groove 61 Return spring (for piston) 62 Return spring (for second rocker arm)

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Kazuhisa Tokimatsu F-term (reference) 3G016 AA06 AA19 BA36 BB18 BB22 CA04 CA06 CA13 CA27 CA29 CA46 CA52 DA22 GA00 GA01

Claims (4)

[Claims] 1. A tip is linked to an intake valve or an exhaust valve,
A first rocker arm pivotally supported by a rocker shaft and driven by a first cam; and a first rocker arm provided adjacent to the first rocker arm.
A second rocker arm driven by a second cam having a larger lift amount than the first cam, and a hydraulic pressure supplied through the inside of the rocker shaft mounted on a cylinder formed on a boss of the first rocker arm. A piston that receives and moves back and forth in the cylinder; an engagement protrusion that extends from the second rocker arm and is provided to be able to engage with the piston; and a piston that is provided on a side surface of the piston and receives hydraulic pressure. The second rocker arm is engaged with the first rocker arm at the position where the hydraulic pressure is released, and the engagement with the engagement protrusion is performed at the position where the hydraulic pressure is released and returned. A variable valve mechanism, comprising: an engaging portion for releasing the force. 2. The first rocker arm has a rocker shaft that supports the first rocker arm as a swing axis, and an intake valve or an exhaust valve linked to one end opposite to the first rocker arm, and the first cam connected to the other end. The variable valve mechanism according to claim 1, further comprising a contact portion provided with a boss portion, wherein a boss portion into which the piston is incorporated is provided at a central portion thereof. 3. The variable valve mechanism according to claim 1, wherein the first rocker arm includes a shaft that swingably supports the second rocker arm. 4. The variable valve mechanism according to claim 1, wherein the piston is mounted on the cylinder so as to be able to move forward and backward in a detent structure.