JP2536898B2 - Valve forced opening / closing device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a valve forced opening / closing device for forcibly opening / closing an intake valve or an exhaust valve of an internal combustion engine.

(Prior Art) In order to improve the followability of intake and exhaust valves during high-speed rotation of an engine, a cam opening cam and a valve closing cam are formed on the cam shaft, and these are used without the help of the valve spring. There is known a desmodromic valve opening / closing device in which an intake valve and an exhaust valve are forcibly opened and closed by a cam (see, for example, USP 4,471,729, JP-A-60-32910, 3).
2911, Jitsuko Sho 53-51928, etc.).

By forcibly opening and closing the intake valve and the exhaust valve by each cam, the influence of surge of the valve spring in the high rotation speed range is eliminated, and the high speed rotation of the internal combustion engine is achieved.

(Problems to be Solved by the Invention) By the way, when such a valve forced opening / closing device is applied to a multi-valve internal combustion engine having two intake valves and two exhaust valves in each cylinder, a valve-opening cam is provided for each valve. Since it is necessary to provide a cam for closing the valve, the structure of the valve train becomes extremely complicated.

Also, even if a rocker arm is used to transmit the movement of each cam to the valve, at least one of the two rocker arms is displaced in the axial direction of the camshaft with respect to the valve in order to prevent mutual interference. Have to let
The valve-opening force or valve-closing force is not correctly transmitted to the valve in the sliding direction, which causes "twisting" of the rocker arm or valve shaft.

Considering that the valve forced opening / closing device was originally developed for the purpose of increasing the rotation speed of the internal combustion engine, such a `` twist '' could induce vibration or wear in the high rotation range, or This causes deterioration of the durability and reliability of the valve train, such as deterioration of followability, which is a major obstacle to its practical application.

An object of the present invention is to provide a valve forced opening / closing device that solves such a problem.

(Means for Solving the Problem) In order to achieve this object, the present invention provides an internal combustion engine having at least two intake valves or exhaust valves for one cylinder, in which a camshaft is provided above the two valves. A valve-opening cam that is located and pushes open each valve, and a single valve-closing cam that is located between these valve-opening cams and that pulls up each valve is provided, while a valve that is connected to two valves A forcible driver is provided, the valve forcible driver is hung from the valve closing cam via the bridge portion, and lifters are respectively arranged on the valve forcible driver so as to contact the valve shafts of the respective valves. Contact with the valve opening cam.

(Operation) Each valve opening cam pushes each valve through the lifter by the rotation of the cam shaft, and lifts in the valve opening direction.

In this valve opening process, the valve closing cam also displaces the valve forced drive body in the valve opening direction so that the lift of each valve is not hindered.

After the valve is fully opened, the valve closing cam displaces the valve forced drive body in the direction to pull up each valve, and at this time the valve opening cam escapes.
The valve lifts in the closing direction.

Each valve is pressed against each valve opening cam from directly above in the valve opening stroke, and is lifted by the valve forced driving body suspended in the valve closing cam located in the middle of each valve in the valve closing stroke. Both are well-balanced and stably driven.

(Embodiment) In FIG. 1, 1 is a camshaft that is rotationally driven in synchronization with engine rotation, and 2A and 2B are 2 for each cylinder.
These are intake valves or exhaust valves (hereinafter simply referred to as valves) provided individually.

The camshaft 1 is provided with valve opening cams 3A and 3B located right above the valves 2A and 2B.

A valve closing cam 4 is provided intermediate the valve opening cams 3A and 3B. The profiles of these cams 3A (3B) and 4 are as shown in FIG. 2, and the cams 3A and 3B for valve opening are shown.
Press the valves 2A, 2B to open, and at this time, the valve closing cam 4 does not hinder the lift of the valves 2A, 2B in the opening direction, and conversely opens the valves 2A, 2B with the valve closing cam 4. For cam
3A and 3B are formed so as not to prevent lift of the valves 2A and 2B in the closing direction.

The valves 2A and 2B, which are also shown in FIGS. 3 and 4, are suspended by the valve forced drive member 5 that straddles the valve closing cam 4.

In the forced valve drive body 5, bottomed cylindrical portions 6A, 6B provided at positions corresponding to the respective valves 2A, 2B slide in guide holes 8A, 8B formed in the cylinder head 7 coaxial with the valves 2A, 2B. It is freely inserted.

The valves 2A and 2B penetrating the bottoms of the cylindrical portions 6A and 6B are locked through a conical collet 9, and the valve forced drive body 5 is lifted to integrally lift the valves 2A and 2B. Both cylindrical parts 6A,
6B are connected to each other by a support plate 10, and are formed on a support wall 11 extending in a mountain shape on both sides of the support plate 10, and are connected by a shim plate 12 to bridge the apex of the support wall 11 to form a bridge portion. . The shim plate 12 is detachably coupled with a bolt 13, and the inner surface of the shim plate 12 contacts the valve closing cam 4.

Support walls 11 on both sides of the valve forced drive body 5 and a lower support plate 10
The cam shaft 1 is inserted into a space surrounded by the upper shim plate 12, and the valve compulsory driving body 5 is suspended by the valve closing cam 4.

Cylindrical lifters 15 are slidably inserted into the cylindrical portions 6A and 6B, respectively, and inner bottoms of the lifters 15 are valves 2A and 2B.
Abutting on each shaft end.

Further, the top surface of the lifter 15 contacts the valve opening cams 3A and 3B, and the valves 2A and 2B are driven by the cams 3A and 3B via the lifter 15.

A valve cap may be provided on the contact surface between the lifter 15 and the valves 2A and 2B.

A valve spring 16 is interposed between the cylinder head 7 and the lower surface of each of the cylindrical portions 6A and 6B of the valve forced drive body 5 to enhance the adhesion of the valves 2A and 2B in the low rotation range. However, this valve spring 16 is basically a valve 2A, 2B
Since it is closed by the valve closing cam 4, the spring load may be much weaker than the conventional one.

 It is configured as described above, and the operation will be described below.

In the opening stroke of the valves 2A and 2B as the camshaft 1 rotates, the valves 2A and 2B are pushed down by the valve opening cams 3A and 3B via the lifter 15, and the valve forced drive body 5 is closed at this time. The cam 4 displaces the valves 2A and 2B integrally in the valve opening direction and does not prevent the valves 2A and 2B from opening.

In the closing stroke after the valves 2A and 2B are fully opened, the valve closing cam 4 pulls up the valve forced drive body 5, and the valves 2A and 2B start to lift in the valve closing direction integrally with this. At this time, the valve opening cams 3A and 3B escape from the maximum lift area and do not prevent the valves 2A and 2B from being lifted. After that, the valve 2 is closed by the valve closing cam 4 through the valve forced drive body 5.
A and 2B are raised to the maximum and completely closed.

During the valve opening process of the valves 2A and 2B, the valves 2A and 2B are pushed down by the valve opening cams 3A and 3B immediately above the valves 2A and 2B, so that the valves 2A and 2B lift smoothly.

In addition, during the valve closing process of valves 2A and 2B,
By the valve forced drive body 5 suspended on the valve closing cam 4 located in the middle of 3B, both the valves 2A and 2B are lifted in a left-right balanced state, and the valve forced drive body 5 is the valve 2A,
Since it is guided by the guide holes 8A and 8B of the cylinder head 7 which is coaxial with 2B, it moves smoothly without tilting.

As a result, the opening and closing of the valves 2A and 2B is extremely stable, and in addition, without causing irregular vibrations in the high rotation range,
A reliable operation is guaranteed.

(Effect of the Invention) As described above, according to the present invention, the valve opening cam is provided directly above the two valves, but the valve closing is common to the two valve opening cams. Since it is performed by the valve forced drive body suspended on the valve closing cam, the structure of the valve system can be simplified and the balance for driving each valve is good, and `` twisting '' will occur on the valve shaft etc. , Stable operation is ensured even in the high rotation range, and vibration and wear are reduced,
It also improves durability and reliability.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 2 is an explanatory view of a valve opening / closing cam, FIG. 3 is a plan view of a valve forced drive body, and FIG. 4 is an exploded side view thereof. It is a figure. 1 ... Cam shaft, 2A, 2B ... valve, 3A, 3B ... valve opening cam, 4 ... valve closing cam, 5 ... valve forced driving body, 7 ...
… Cylinder head, 12 …… Shim plate, 15 …… Lifter.

Claims (1)

(57) [Claims] 1. In an internal combustion engine having at least two intake valves or exhaust valves for one cylinder, a camshaft is provided with cams for opening valves which are located above the two valves and open the respective valves. And a single valve-closing cam that is located between these valve-opening cams and that pulls up each valve is provided, while 2
A valve forced drive unit connected to two valves is provided, and the valve forced drive unit is hung from the valve closing cam via its bridge portion,
A valve forced opening / closing device for an internal combustion engine, further comprising: a lifter disposed on the valve forced driving body so as to come into contact with a valve shaft of each valve, and brought into contact with the valve opening cam.