JPH0571321A - Variable valve system for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a valve actuator for an internal combustion engine which varies both the quantity of valve lifting and the operating angle through a lever for shifting the rocking fulcrum of a rocker arm. CONSTITUTION:A link 5 is provided, which couples the fulcrum shaft 6 of a lever 2 with the middle of a rocker arm 1 rotatably, and the top 21a of the junction in contact with the rocker arm 1 of the lever 2 is made in circular cross section coaxial with the fulcrum shaft 6, and also the junction part 11 in contact with the valve 8 of the rocker arm 1 is made in circular cross section coaxial with the fulcrum shaft 6. Moreover, a chip 35, which has a spherical junction part 36, is provided as a body separate from the rocker arm 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve operating system for switching the lift characteristic of an intake valve or an exhaust valve according to the operating condition of an internal combustion engine.

[0002]

2. Description of the Related Art As a variable valve operating device of this type, there has been a device shown in FIG. 6 for example (SAE paper 896081).
reference).

Explaining this, a cam 47 that rotates in synchronism with the engine, a rocker arm 41 that contacts the cam 47 and the intake valve 48, a lever 42 that is swingably joined to a back surface 49 of the rocker arm 41, and a lever 42. A pivot 46, one end of which is rotatably supported, and a control cam 43, which changes the rotational position of a lever 49 according to the operating state.
With.

As one end of the rocker arm 41 is pushed up by the rotation of the cam 47, the rocker arm 41 swings while moving the portion contacting the lever 2 to the left as shown by the broken line in the figure, and at the other end. The intake valve 48 is pushed down.

Further, the swinging fulcrum of the rocker arm 41 is moved by switching the turning position of the lever 42 between the high lift position approaching the cam 47 and the low lift position moving away from the cam 47 via the control cam 43. do it,
The valve lift amount L of the intake valve 8 is adjusted.

[0006]

However, in such a conventional device, even if the valve lift amount L of the intake valve 8 can be adjusted by changing the rotational position of the lever 42, the lift start initial stage can be adjusted. In addition, since the rocker ratio does not completely become zero, there is a problem that the crank angle range in which the intake valve 8 is open (hereinafter referred to as operating angle) does not change. For this reason, for example, the operating angle of the intake valve 8 becomes unnecessarily large in the low rotation speed range, and the intake charging efficiency is lowered.

In view of the above points, the present invention has an object to provide a variable valve operating system for an internal combustion engine in which both a valve lift amount and an operating angle are variable via a lever which moves a rocking fulcrum of a rocker arm. To do.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a cam that rotates in synchronism with an engine, a rocker arm that contacts the cam and an intake valve or an exhaust valve, a lever that swingably joins to the back surface of the rocker arm, and a lever. A variable valve operating device for an internal combustion engine, comprising: a fulcrum shaft having one end rotatably supported; a means for switching a lever between a high lift position that approaches a cam and a low lift position that moves away from the cam, in the middle of the fulcrum shaft and the rocker arm. A pivotally connected link is provided in the cam base shackle to connect the tip of the lever connecting the point where the lever contacts the rocker arm at the low lift position and the point where the lever contacts the rocker arm at the high lift position. Formed in a concentric arc-shaped cross section centering on the fulcrum shaft, and forming a joint of the rocker arm in contact with the valve in a concentric arc-shaped cross section centering on the fulcrum shaft. .

Further, a tip which is formed as a separate body is attached to the rocking end of the rocker arm, and a joint portion which comes into contact with the intake valve end portion of the tip is formed into a spherical shape having an arc cross section concentric with the fulcrum shaft.

[0010]

When the lever is in the high lift position where it approaches the cam, the rocker arm swinging fulcrum approaches the cam, so that the valve lift amount increases. When the lever is switched to the low lift position where the lever is relatively far from the cam, the rocking fulcrum of the rocker arm is far from the cam, so that the valve lift amount is small.

When the lever is in the low lift position, even if the part of the cam contacting the rocker arm moves from the base circle part to the lift part and one end of the rocker arm is lifted, the part of the rocker arm contacting the lever is centered on the fulcrum axis. The rocker arm rotates about a fulcrum shaft via a link while it is at the tip of the joint portion of the lever having a concentric arc-shaped cross section. Since the joint portion of the rocker arm that is in contact with the valve also has a concentric arc cross section centered on the fulcrum axis, the distance between the fulcrum axis and the valve does not change at this time, and the valve is kept in the fully closed position. When the portion where the rocker arm contacts comes out of the tip of the joint portion of the lever having an arc-shaped cross section, the rocker arm swings to open the valve. That is, when the lever is in the low lift position, even if one end of the rocker arm starts to be lifted, the valve opening does not immediately start, so that a relatively small operating angle is obtained.

As the lever rotates from the low lift position to the high lift position, the range in which the rocker arm contacts the tip of the joint portion of the lever having an arcuate cross section becomes smaller, so that the base circle portion moves to the lift portion. When one end of the rocker arm is lifted, the rocker arm swings and opens the valve earlier than in the low lift position, so that a relatively large operating angle is obtained.

When the lever rotates about the fulcrum shaft between the high lift position and the low lift position while the rocker arm is in contact with the base circle part of the cam, the portion of the lever contacting the rocker arm is concentric with the fulcrum shaft. Since it is the tip of the joint of the lever having an arcuate cross section, the valve is kept in a fully closed state without rocking the rocker arm.

Further, by providing the tip having the spherical joint portion separately from the rocker arm, the rocker arm can be easily processed.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the cylinder head 31 is provided with an intake valve 8 for opening and closing the intake port 30, and a valve spring 32 for urging the intake valve 8 in a valve closing direction is interposed via a retainer 33. To be done.

On the cylinder head 9, there are provided a cam 7 that rotates in synchronization with engine rotation, and a rocker arm 1 that follows the cam 7 and pushes down the intake valve 8 against the valve spring 32. A roller follower 10 that is rotatably contacted with a cam 7 is connected to one end of the rocker arm 1, and a joint portion 11 that is in contact with a valve end portion 8a of an intake valve 8 is formed at the other end.

A rear surface 12 of the rocker arm 1 is curved to have a barrel-shaped cross section, and a lever 2 for swingably joining the rear surface 12 is provided. The rocker arm 1 swings as the roller follower 10 moves up and down in accordance with the cam 7 while moving the contact point to the lever 2 to the right side in FIG. 1, and the intake valve 8 passes through the valve spring 32. Open and close.

One end of the lever 2 is rotatably supported by a fulcrum shaft 6, and a control cam 3 contacting the upper surface 22 of the lever 2 is provided as means for switching the rotational position of the lever 2. The lever 2 is pressed against the control cam 3 via a spring 4. The control cam 3 is rotationally driven in accordance with the operating state via an actuator (not shown) and its control device, and holds the lever 2 at a low lift position away from the cam 7 as shown by the solid line in the figure, for example, in the low speed and low load region. The lever 2 is continuously or stepwise rotated counterclockwise in response to an increase in the load or the number of revolutions, and in the high-speed high-load region, the lever 2 is moved to the high lift position approaching the cam 7 as shown by the broken line in the figure. By holding it, the valve lift amount of the intake valve 8 is increased.

A link 5 connecting the fulcrum shaft 6 and the rocker arm 1 is provided. One end of the link 5 is rotatably connected to the lever 2 coaxially via a fulcrum shaft 6, and the other end of the link 5 is rotatably connected to the middle of the rocker arm 1 via a pin 13. The center O of the fulcrum shaft 6 is arranged on the central axis I of the intake valve 8. In this case, the links 5 are provided as a pair so as to sandwich the rocker arm 1 and the lever 2.

The lever 2 is held at the high lift position as shown by the broken line in the figure, and a relatively large valve lift amount of the intake valve 8 is obtained, and the base circle portion 7b of the cam 7 is fixed to the roller follower 10. 2 shows the point where the lever joint portion 21 contacts the rocker arm 1 in the fully closed state where
When A ₂ as shown in, is formed in a cylindrical surface having a concentric arcuate cross section joining tip 21a of the distal end side from the point A ₂ of the lever joint portion 21 around the fulcrum shaft 6, and the rocker arm 1 A joint portion 11 in contact with the intake valve end portion 8a is formed in a cylindrical surface shape having a concentric arc cross section centered on the fulcrum shaft 6 as well. Regarding the center O of the fulcrum shaft 6, the joint end 21a of the lever 2 is curved with a radius R ₁ , and the joint 11 of the rocker arm 1 is curved with a larger radius R ₂ .

Next, the operation will be described.

When the lever 2 is in the high lift position shown by the broken line, as shown in FIG. 2, the point A ₂ of the lever 2 is in the fully closed state where the base circle portion 7b of the cam 7 is in contact with the roller follower 10. It touches point E on rocker arm 1. When the contact point for the roller follower 10 moves from the base circle section 7b to the lift section 7c as the cam 7 rotates, the contact point of the lever 2 for the rocker arm 1 is point A when the valve is opened.
_The rocker arm 1 swings and pushes down the intake valve 8 while moving to the right side in the drawing on the joint portion 21 extending in a plane from ₂ . That is, the lowering of the lever 2 causes the rocker arm 1 to move.
Since the swing fulcrum of the intake valve 8 is lowered, the lift characteristic of the intake valve 8 has a relatively large valve lift amount L _{1 as} shown in FIG.
In addition, since the rocker arm 1 starts to swing by the lift portion 7c of the cam 7, the intake valve 8 starts to open at the same time, so that a relatively large operating angle C ₁ is obtained.

On the other hand, when the lever 2 is rotated upward through the control cam 3 from the high lift position shown by the broken line to the low lift position shown by the solid line by the angle θ, the base follower of the cam 7 is provided to the roller follower 10. In the fully closed state in which 7b is in contact, the joint end 21a of the lever 2 having an arcuate cross section is brought into sliding contact with the point E of the rocker arm 1 to rotate, so that the intake valve 8 is fully closed without rocking the rocker arm 1. Kept in.

When the lever 2 is in the low lift position shown by the solid line, the point on the tip 21a of the joint portion having the arc-shaped cross section of the lever 2 in the fully closed state where the base circle portion 7b of the cam 7 is in contact with the roller follower 10. A ₁ touches point E on rocker arm 1. As the cam 7 rotates, the roller follower 10
Contacts to the base circle portion 7b to the lift portion 7c
When the contact point of the lever 2 with respect to the rocker arm 1 moves to the right side in the figure from the point A ₁ to the point A ₂ on the joint end 21a having an arcuate cross section, the point E of the rocker arm 1 becomes the fulcrum shaft when the valve is opened. While the rocker arm 1 rotates about the fulcrum shaft 6, the point H (see FIG. 1) of the rocker arm 1 rotates about the fulcrum shaft 6 via the link 5, so that the rocker arm 1 itself rotates about the fulcrum shaft 6. become. At the same time, the contact point of the rocker arm joint 11 with respect to the point V on the intake valve end 8a also shifts from the point U ₁ to the point U ₂ , but the rocker arm joint 11 is also formed in an arcuate cross section about the fulcrum axis O. Therefore, the distance between the fulcrum shaft O and the intake valve end portion 8a does not change, and the intake valve 8 is kept fully closed. The contact point of the rocker arm 1 with respect to the lever 2 is a joint end 21a having an arc-shaped cross section.
When the contact point is disengaged from above, the contact point moves to the right side in the drawing on the joint portion 21 extending in a plane from the point A _2, so that the rocker arm 1 swings to push down the intake valve 8. That is, since the rocking fulcrum of the rocker arm 1 rises as the lever 2 rises, the lift characteristic of the intake valve 8 obtains a relatively small valve lift amount L ₂ as shown in FIG.
Even if the rocker arm 1 starts to swing due to the lift portion 7c, the opening of the intake valve 8 does not immediately start, so that a relatively small operating angle C ₂ is obtained.

In this embodiment, the operating angle C ₂ is maximized when the lever 2 comes closest to the cam 7 and the maximum valve lift L ₁ is obtained. Reduce the formed area, lever 2
May approach the cam 7 to some extent and the valve lift amount may reach an intermediate value, and the operating angle may be maximized. In this case, the valve lift amount increases as the lever 2 approaches the cam 7, but the operating angle gradually increases until the valve lift amount reaches an intermediate value, but the operating angle maintains a maximum constant value after the intermediate value. It will be.

Next, in another embodiment shown in FIG. 5, a tip 35, which is separately formed, is attached to the rocking end of the rocker arm 1 by press fitting, and the tip 35 is in contact with the intake valve end 8a. Similarly, 36 is formed in a spherical shape having a concentric arc cross section of radius R ₂ with respect to the fulcrum shaft 6. In this case, the rocker arm 1 can be easily processed by providing the tip 35 as a separate body.

[0028]

As described above, according to the present invention, the cam that rotates in synchronization with the engine, the rocker arm that contacts the cam and the intake valve or the exhaust valve, the lever on which the back surface of the rocker arm is swingably joined, and the lever. In a variable valve operating system for an internal combustion engine, a fulcrum shaft rotatably supporting one end of the lever, and means for switching a lever between a high lift position approaching a cam and a low lift position moving away from the cam are provided. A link that rotatably connects is provided, and the tip of the joint that contacts the rocker arm of the lever is formed in a concentric arc section with the fulcrum shaft, and the joint that contacts the valve of the rocker arm is formed in a concentric arc section with the fulcrum shaft. Therefore, both the valve lift amount and the operating angle are changed according to the turning position of the lever to maintain high filling efficiency or exhaust efficiency depending on the number of rotations. Can.

Further, since the chip having the spherical joint is provided separately from the rocker arm, the rocker arm can be easily processed and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a valve operating system showing an embodiment of the present invention.

FIG. 2 is also an operation explanatory diagram.

FIG. 3 is a valve lift characteristic diagram when the lever is also at a high lift position.

FIG. 4 is a valve lift characteristic diagram when the lever is at the low lift position.

FIG. 5 is a cross-sectional view of a valve train according to another embodiment.

FIG. 6 is a front view of a valve operating system showing a conventional example.

[Explanation of symbols]

 1 rocker arm 2 lever 3 control cam 5 link 6 fulcrum shaft 7 cam 7a base circle part 7b lift part 8 intake valve 11 rocker arm joint part 12 rocker arm rear face 21 lever joint part 21a lever joint tip 35 tip 36 joint part

Claims (2)

[Claims] 1. A cam that rotates in synchronism with an engine, a rocker arm that contacts the cam and an intake valve or an exhaust valve, a lever that swingably connects to the back surface of the rocker arm, and one end of the lever is rotatably supported. A variable valve operating system for an internal combustion engine, comprising a fulcrum shaft, and means for switching a lever between a high lift position approaching a cam and a low lift position moving away from the cam,
A rotatably connected link is provided in the middle of the fulcrum shaft and the rocker arm, and the lever contacts the rocker arm at the low lift position and the lever contacts the rocker arm at the high lift position in the cam base cycle. Characterized in that the tip of the joint portion of the lever connecting the two is formed in a concentric arc-shaped cross section around the fulcrum shaft, and the joint portion of the rocker arm in contact with the valve is formed in a concentric arc-shaped cross section around the fulcrum shaft. Variable valve device for internal combustion engine. 2. A tip, which is formed as a separate body, is attached to the rocking end of the rocker arm, and a joint portion in contact with the end portion of the intake valve of the tip is formed into a spherical shape having a concentric arc cross section with the fulcrum shaft. The variable valve operating system for an internal combustion engine according to claim 1.