JPH03156112A - Variable valve system for engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a variable valve device that changes the valve timing of intake and exhaust valves of an engine according to operating conditions.

(Prior Art) Generally, a device for improving the intake and exhaust efficiency in low speed ranges and high speed ranges by changing the valve timing of intake and exhaust valves of an engine according to operating conditions is disclosed in Japanese Patent Laid-Open No. 55 This method has been proposed in, for example, Japanese Patent No. -96310.

In order to change the valve timing, we created a three-dimensional cam whose cam profile changes in the axial direction of the camshaft.
By moving this in the axial direction according to driving conditions, for example, the valve opening period and lift can be reduced in low speed ranges, and the valve opening period can be reduced in high speed ranges, thereby reducing fuel consumption and exhaust composition in low speed ranges. , which improves exhaust efficiency at high speeds.

(Problem to be Solved by the Invention) However, in the conventional valve train, since the cam surface is inclined in the axial direction, the cam contact portion (cam follower) such as the rocker arm of the intake and exhaust valve becomes a point contact. Countermeasures against wear due to high surface pressure were required, and it was difficult to ensure sufficient durability.

The present invention aims to solve these conventional problems.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a camshaft that rotates in synchronization with engine rotation with a valve opening cam and a valve closing cam, respectively. The swingable valve opening port 2 arm brought into contact via the cam follower is brought into contact with the valve shaft of the intake valve or exhaust valve in the downward direction, and the valve closing cam is contacted via the cam 7 arm. Like the swingable valve closing rocker arm that is in contact with the valve shaft, it locks in the lifting direction, but these valve opening cams and valve closing cams are composed of three-dimensional cams whose cam profile changes in the axial direction. A driving means for displacing the camshaft in the axial direction is provided, and at least one of the cams 71a is swingably supported with respect to each Ronca arm via a rotating shaft substantially orthogonal to the camshaft.

(Operation) Based on the above configuration, the intake valve or the exhaust valve is pushed open by the valve-opening rocker arm that follows the valve-opening cam, and is pulled up by the valve-closing rocker arm that follows the valve-closing cam to open and close.

When changing the valve timing of the intake valve or exhaust valve, the three-dimensional cam is moved in the axial direction together with the camshaft. As a result, the contact position of each cam follower of the valve-opening and valve-closing rocker arms with respect to the cam changes, and the different characteristics of the cam profiles cause the intake valve or exhaust valve to close.

When the three-dimensional cam rotates or moves in the axial direction, the cam followers are able to swing along the inclined cam surface via the rotation axis approximately perpendicular to the camshaft, and come into linear contact with each other. In addition to reducing surface pressure on the camshaft and suppressing wear, the camshaft can move smoothly.6 Because there is no valve spring that biases the intake or exhaust valve toward the cam in the valve-closing direction, each cam follower relative to the cam The contact pressure is low, the contact friction force associated with the rotation of the cam does not increase, there is little wear on the cam follower and cam surface, and high durability can be maintained.

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

In FIG. 1, 1 in the figure is a camshaft, and this camshaft 1 has one valve opening cam 2 located above the valve (intake valve or exhaust valve) 4 of each cylinder, and a valve opening cam 2 located above the valve (intake valve or exhaust valve) 4 of each cylinder. Two valve-closing cams 3 are integrally formed on both sides of the valve-closing cam 2.

The valve-opening rocker arm 5, which contacts the valve-opening cam 2 via the cam follower 21, has its swinging tip 5a aligned with the valve 4.
is brought into contact with the end of the valve shaft 4a, and its swinging base end is connected to a pivot (spherical receiver) via an adjustment screw 6.
7, and the valve 4 is pushed down depending on the rotational position of the camshaft 1.

On the other hand, the valve-closing rocker arm 15 is swingably connected to the valve-opening rocker arm 5 through a support shaft 16 at its intermediate portion, and has a cam follower attached to a portion that branches from the intermediate portion. 22, the other swinging tip 15a contacts (locks) a retainer 17 attached to the valve shaft 4a from below, and rotates the camshaft 1 (depending on the position). Pull up valve 4.

Note that when the valve-opening cam 2 pushes down the valve 4, the valve-opening cam 3 does not prevent this, and the valve-closing cam 3 pushes down the valve 4.
Each of the valve opening cams 2 is formed with a cam profile so as not to interfere with the lifting of the valve, and thereby the vertical movement of the valve 4 is both driven by the cam without the need for a valve spring.

By changing the hinge position of the threaded portion 6a of the above-mentioned Anoyast Suffleyu 6, the swing center position of the valve opening rocker arm 5 is adjusted to 113I, and the adjustment screw 6 is adjusted to the threaded portion 6a.
It is fixed with a locking nut 8 that is screwed into the locking nut 8. Note that the bot 7 is inserted into the support hole 9a of the cylinder rad 9 to receive a load, and also passes through the oil gear lary 19 to the support hole 9.
The lubricating oil guided to a lubricates the contact surface of the anoyasto souffle 6 with the spherical receiving part 11.

By the way, as shown in FIG. 2, the valve-opening cam 2 and the valve-closing cam 3 formed on the Moeki camshaft 1 are formed of three-dimensional cams whose cam profile changes continuously in the axial direction. That is, the cam profile that contacts the rocker arms 5 and 15 differs little by little depending on the axial position of the camshaft 1, and the opening period and lift amount of the valve 4 can be gradually changed. Each cam profile is set so that, depending on the axial position of the camshaft 1, for example, in a low engine speed range, both the valve opening period and the lift are small, whereas in a high speed range, both the valve opening period and the lift are large. This eliminates the valve opening in the low speed range to improve fuel efficiency and exhaust composition, while in the high speed range the intake and exhaust efficiency is increased to improve maximum engine output.

A cam follower 21 connected to the valve-closing rocker arm 4 is swingably supported via a rotating shaft 24.
is fixed to the lock valve rocker arm 5 in a direction perpendicular to the camshaft 1.

Each cam 7 oro 72 connected to the valve closing rocker arm 15
2 is the same (it is swingably supported via a rotating shaft 26, and this rotating shaft 26 is fixed to the valve-closing rocker arm 15 in a direction perpendicular to the camshaft 1).

Each cam follower 21, 22 contacts each cam 2, 3 7
The lower surfaces 21a and 22a are curved in an arc shape in the direction of the rotation axis, and have a straight cross section in the direction orthogonal to the rotation axis, allowing each cam 2.3 to rotate smoothly.

An actuator for moving the camshaft 1 in the axial direction is connected to one end (not shown) of the camshaft 1, and signals representative of various operating conditions such as engine speed, load, and temperature are input to the controller, and based on these signals, A target value of the camshaft 1 in the axial direction is calculated.

Next, the effect will be explained.

As the camshaft 1 rotates, the valve opening cam 2 pushes down the valve 4 via the rocker arm 5 and opens the valve.
Subsequently, the valve 4 is pulled up by the valve closing cam 2 via the rocker arm 15 and closed.

In this way, all opening and closing of the valve 4 is performed by the cams 2 and 3, eliminating the need for conventional valve springs, so the valve 4 can be opened and closed stably without surging even in high-speed ranges. be able to.

Since each rotating shaft 16° 26 that supports each cam 7 arm 21, 22 in a swingable manner with respect to each rocker 7-m 5° 15 is provided in a direction substantially perpendicular to the camshaft 1, the cam followers 21, 22 As shown in Fig. 3, when it hits the base circle portion of the three-dimensional cams 2 and 3, it is kept approximately horizontal and comes in linear contact with each cam surface, while as shown in Fig. M4, the When the inclined I]7F portion 1 hits, it swings about the rotating shaft 16.26 by the inclination angle θ of the cam surface and comes into linear contact with the cam surface. As a result, each cam 7t lower 21, 22 and each three-dimensional cam 2, 3 are always in linear sliding contact and the contact pressure between them is kept low, and the contact friction force against the cam follower does not increase as the cam rotates, resulting in a high Durability and M compliance can be maintained.

On the other hand, when the camshaft 1 is driven in the axial direction via the actuator by a signal from the controller according to the operating conditions of the engine, the valve-opening valve contacts the lower 21, 22 of each cam 7t of each rocker arm 5, 15; The cam profiles of the valve-closing cams 2 and 3 change, and the valve timing changes accordingly.

In other words, in the low engine speed range, the opening period of valve 4 is 7.
The valve timing is changed so that the valve opening period becomes smaller and the valve opening period becomes larger in the high-speed range, thereby ensuring optimal valve characteristics according to each operating condition.

When the three-dimensional cams 2 and 3 move in the axial direction, each cam follower 21 and 22 rotates around the rotation axis 24 that is substantially orthogonal to the camshaft 1.
．． 26, it is possible to swing along the inclined cam surface, and the camshaft 1 makes linear contact at this part to reduce the surface pressure and suppress wear, and also allows the camshaft 1 to move smoothly. I can do it.

Therefore, even if the driving force for displacing the camshaft 1 in the axial direction is small, the camshaft 1 moves smoothly and the valve timing can be switched with good response.

Furthermore, since there is no valve spring that biases the intake or exhaust valve toward the cam in the valve closing direction, the contact pressure of each cam follower 21, 22 with respect to the cams 2 and 3 is low, and the cam 2
．． The contact friction force against the cam followers 21, 22 does not increase with the rotation of the valve 3, the cam followers 21, 22 and the cam surfaces suffer little wear, and problems such as fluctuations in valve clearance due to wear hardly occur.

(Effects of the Invention) As described above, according to the present invention, the cam profile of the three-dimensional cam changes by displacing the camshaft in the moving direction,
The valve timing of the intake or exhaust valve can be changed freely according to the operating conditions, and in this case,
Since each rotating shaft that swingably supports the cam follower with respect to each rocker arm is provided in a direction substantially perpendicular to the camshaft, the cam follower makes linear contact with the three-dimensional cam,
The contact pressure between the two is low, and the contact friction force against the cam 7t lower does not increase as the cam rotates, allowing high durability and reliability to be maintained.

In addition, since there is no valve spring that biases the intake or exhaust valve toward the cam in the valve closing direction, the camshaft can move smoothly and with good response.As a result, the TFT mechanism that drives the camshaft can be made smaller. It can also be made lighter.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, and Fig. #IJ2 is a plan view of a three-dimensional cam. FIGS. 3 and 4 are sectional views showing the operation, respectively. 1...Camshaft, 2...Valve opening cam, 3...
Valve closing cam, 4... Valve (intake, exhaust valve), 5...
Rocker arm, 9... Schilling head, 15... Rocker arm, 21.22... Cam follower, 24.2
6...Rotation axis. Figure 1

Claims (1)

[Claims] A camshaft that rotates in synchronization with engine rotation is provided with a valve-opening cam and a valve-closing cam, and a swingable valve-opening rocker arm that contacts the valve-opening cam via a cam follower is connected to the intake valve or exhaust valve. Similarly to the swingable valve-closing rocker arm, which is brought into contact with the valve shaft of the valve in the downward direction and contacted with the valve-closing cam via a cam follower, the valve shaft is locked in the upward direction with respect to the valve shaft. These valve-opening cams and valve-closing cams are composed of three-dimensional cams whose cam profiles change in the axial direction, and drive means for displacing the camshafts in the axial direction are provided, while at least one of the cam followers is attached to each rocker arm. A variable valve device for an engine, characterized in that the variable valve device is swingably supported via a rotating shaft substantially orthogonal to the camshaft.