JPH03156110A - Variable valve system for engine - Google Patents

Abstract

PURPOSE:To perform smooth movement of a cam shaft in good response by providing each of shafts, which support roller followers so as to be rotatable to each of rocker arms, in an approximately rectangular direction to the cam shaft. CONSTITUTION:Roller followers 21, 22 which are put in rolling contact with an open valve cam 2 and a close valve cam 3 are provided on an open valve rocker arm 5 and a close valve rocker arm 15. Shafts 24, 26 which support the roller followers 21, 22 so as to be rotatable to each of rocker arms 5, 15 are provided in an approximately rectangular direction to a cam shaft 1. In this way, when the cam shaft 1 is moved to an axis to vary a valve timing, the roller followers 21, 22 can be put in rolling contact with the faces of solid cams 2, 3 via the shafts 24, 26 which are approximately rectangular to the cam shaft 1, therefore to reduce friction on the rolling contact faces and perform smooth movement of the cam shaft 1.

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 pulp timing of intake and exhaust valves of an engine according to operating conditions.

(Prior Art) In general, there is a device in which the pulp timing of the intake and exhaust valves of an engine can be changed according to the operating conditions to improve the intake and exhaust efficiency, for example, in the low speed range and the high speed range. This method has been proposed in, for example, Japanese Patent No. -96310.

In order to change the pulp 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 the driving conditions, for example, the valve opening period and lift can be reduced in the low speed range, and the valve opening period and lift can be increased in the high speed range. This improves intake and exhaust efficiency in the area.

(Problem to be Solved by the Invention) However, according to the conventional valve train, the intake and exhaust valves are opened by cams, but the valves are closed by using the biasing force of the valve spring, so the three-dimensional cam is used as the axis. A large driving force was required when moving in a direction. Particularly during valve lift, the pulp spring applies a large frictional force, so an actuator that can overcome this frictional force is required to move the three-dimensional cam, and it is difficult to switch with good response.

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, and The cam and the valve-closing cam are composed of three-dimensional cams whose cam profile changes in the axial direction, and a drive means is provided to displace the camshaft in the axial direction. A valve rocker arm is brought into contact with a valve shaft of an intake valve or an exhaust valve in a downward direction, and a valve closing rocker arm, which is swingable according to the valve closing cam, is also moved in a upward direction with respect to the valve shaft. In the variable valve system of the engine to be locked, each of the rocker arms is provided with a roller 7t lower that rolls into contact with each of the three-dimensional cams, and a rotating shaft that rotatably supports the roller followers with respect to each of the rocker arms is approximately provided on the camshaft. installed in orthogonal directions.

(Operation) Based on the above MII precept, the intake valve or the exhaust valve is pushed open by the valve opening port 7 arm which is driven by the valve opening cam,
It is pulled up by the valve closing a7 arm which follows the valve opening cam and operates to open and close.

When changing the pulp 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 lower roller 7t of the valve-opening and valve-closing rocker arms with respect to the cam changes, and the intake valve or exhaust valve is lifted with different characteristics of the cam profile.

When the three-dimensional cam moves in the axial direction, the roller follower is able to roll on the cam surface via the rotating shaft that is substantially orthogonal to the camshaft, reducing the 7 luxitan in this part and reducing the movement of the camshaft. It can be done smoothly.

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 roller follower against the cam is low, and the contact friction force is reduced even if the roller follower does not shift as the cam rotates. There is no increase in wear on the roller follower and cam surfaces, and high durability can be maintained.

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

! In the lS1 diagram, 1 in the figure is a camshaft, and this camshaft 1 has one valve opening cam 2 located above the pulp (intake valve or exhaust valve) 4 of each cylinder, and a valve opening cam 2 located above the pulp (intake valve or exhaust valve) 4 of each cylinder. Two valve-closing cams 3 are integrally formed on both sides of the cam 2.

The valve-opening port 7 force 7-m 5, which contacts the valve-opening cam 2 via the roller follower 21, brings its swinging tip 5a into contact with the end of the valve shaft 4a of the pulp 4, and its swinging The movable base end is swingably supported by a pivot (spherical receiver) 7 via a screw 6, and the pulp 4 is pushed down by the rotational position of the camshaft 1.

On the other hand, the valve-closing port 7 arm 15 is swingably connected to the valve-opening rocker arm 5 via a support shaft 16 at its intermediate portion, and is attached to a portion that branches from the intermediate portion into two. One of the swinging lights 1115 contacts the two valve-closing cams 3 via the roller follower 22, while the other swinging light 1115
a contacts the retainer 17 attached to the valve stem 4a from below (
(locked) and pulls up the pulp 4 depending on the rotational position of the camshaft 1.

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

By changing the screwing position of the threaded part 6a of the above-mentioned Anoyasto Screw 6, the swinging center position of the valve opening rocker arm 5 is adjusted. Fixed. Note that the pivot 7 is inserted into the support hole 9a of the ring head 9 and receives a load, and the lubricating oil guided to the support hole 9a through the oil gear gallery 19 causes the spherical receiving portion 1 of the screw 6 to
Lubricate the area before contact with 1.

By the way, as shown in FIG. 12, the valve-opening cam 2 and the valve-closing cam 3 formed on the camshaft 1 are formed of three-dimensional cams whose cam profile changes continuously in the axial direction. That is, depending on the axial position of the camshaft 1, the cam profile that contacts the rockers 7-m 5 and 15 differs little by little, 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, the valve opening period and lift are both small, whereas in a high speed range, both the valve opening period and lift are large. At low speeds, valve overlap is eliminated to improve fuel efficiency and exhaust composition, while at high speeds, intake and exhaust efficiency is increased to improve maximum engine output.

The roller follower 21 connects to the rotating shaft 2 via a bearing 23.
4, and this rotating shaft 24 is fixed to the valve opening rocker arm 5 in a direction perpendicular to the camshaft 1.

Each roller 7 lower 22 is similarly rotatably supported by a rotating shaft 26 via a bearing 25, and this rotating shaft 26 is fixed to the valve-closing rocker arm 15 in a direction perpendicular to the camshaft 1.

Each roller follower 21, 22 has a circular cross section perpendicular to each rotating shaft 24, 26, and constitutes a rotary body that can be moved in accordance with the movement of each cam 2.3 in the axial direction.

Each roller follower 21, 22 is formed into a spindle shape whose diameter decreases toward both ends, and whose cross section is arcuate in the same direction as the rotating shaft 24, 26, to ensure smooth rotation of each cam 2, 3. I can do it.

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.

On the other hand, when the camshaft 1 is driven in the axial direction via the actuator by a signal from the controller depending on the operating conditions of the engine, the valve opening and closing valves contact each roller follower 21, 22 of each rocker arm 5, 15. Valve cam 2
The cam profiles of and 3 change, and the valve timing changes accordingly.

In other words, the valve timing changes so that the valve opening period and lift of valve 4 are reduced in the low engine speed range, and the valve opening period and lift of valve 4 are increased in the high speed range, and the optimum valve characteristics according to each operating condition are achieved. It is guaranteed.

When the three-dimensional cams 2, 3 move in the axial direction, each roller follower 21.
It becomes possible to make rolling contact on the cam surface via the camshaft 1, reducing the 7 yen of this part and allowing smooth movement of the camshaft 1.

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.

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 roller follower 21, 22 that elbows the cam 2, 3 is low, and the rotation of the cams 2, 3 is affected. Even if the roller followers 21, 22 are not transferred, the contact frictional force does not increase, there is little wear on the roller followers 21, 22 and the cam surfaces, and there are almost no problems such as fluctuations in valve clearance due to wear.

(Effect of the invention) As described above, according to the present investigation, the cam profile of the three-dimensional cam changes by displacing the camshaft 7 in the axial direction,
It is possible to freely change the valve timing of the intake or exhaust valve according to the operating conditions, and in this case,
Since each rotating shaft that rotatably supports the roller follower relative to each rocker arm is provided in a direction substantially perpendicular to the camshaft 7, the movement of the camshaft 7 can be performed smoothly with good response, and as a result, the camshaft can be driven easily. It is also possible to make the mechanism smaller and lighter.

In addition, 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 roller follower with the cam is low, and the roller followers make contact even if they do not transfer as the cam rotates. Frictional force does not increase and high durability and reliability can be maintained.

[Brief explanation of the drawing]

PIS1 diagram is a sectional view showing an embodiment of the present invention, PltJ2
The figure shows the plane l of the three-dimensional cam. 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... Roller follower, 24.
26...Rotation axis.

Claims (1)

[Claims] A camshaft that rotates in synchronization with engine rotation is provided with a valve-opening cam and a valve-closing cam, respectively, and these valve-opening cams and valve-closing cams are composed of three-dimensional cams whose cam profiles change in the axial direction. , a driving means for displacing the camshaft in the axial direction is provided, and a swingable valve opening rocker arm is driven by the valve opening cam to press down against the valve shaft of the intake valve or the exhaust valve. In a variable valve system for an engine, in which a swingable valve closing rocker arm is similarly locked in a lifting direction with respect to a valve shaft by following the valve closing cam, each of the rocker arms is attached to each of the three-dimensional cams. A variable valve system for an engine, characterized in that a roller follower that rotates in contact is provided, and a rotating shaft that rotatably supports the roller follower with respect to each rocker arm is provided in a direction substantially perpendicular to the camshaft.