JPH0730884Y2 - Valve forced opening / closing device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) 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) A valve opening cam and a valve closing cam are formed on a rotating camshaft in order to improve the followability of the intake and exhaust valves at high speed.
There is known a desmodromic valve opening / closing device in which intake and exhaust valves are forcibly opened and closed by these cams without the aid of a valve spring.

FIG. 3 shows an example of a valve opening / closing device of this type, in which rocker arms 5 and 6 are pivotally mounted on a rocker shaft 4 corresponding to a cam 2 for opening a valve and a cam 3 for closing a valve formed on a camshaft 1. The tip of the valve-opening rocker arm 5 which is supported and slides on the valve-opening cam 2 slides on the valve-closing cam 3 from above through the adjustment screw 7 to the valve shaft end 9 of the intake valve (or exhaust valve) 8. The tip end of the valve closing rocker arm 6 is brought into contact with the retainer 11 fixed to the valve shaft 10 from below.

Therefore, when the camshaft 1 rotates, the tip ends of the rocker arms 5 and 6 follow the valve opening cam 2 and the valve closing cam 3 first, and are pushed down by the valve opening rocker arm 5 to push the intake valve 8
When the rocker arms 5 and 6 are opened, the tip ends of the rocker arms 5 and 6 are moved upward and are pulled by the valve closing rocker arm 6 to close the intake valve 8.

Further, as shown in FIG. 4, an intake valve (or an exhaust valve) is provided through a retainer 15 having first and second flanges in which a first rocker arm 13 slidingly contacting a valve opening cam 12 is screwed to a valve shaft 14 and having upper and lower flanges.
The second rocker arm 18 that engages with the valve closing cam 17 is brought into contact with the first rocker arm 13 in the valve closing direction.

Therefore, when the cam shaft 19 rotates, the valve opening cam
The first rocker arm 13 moves downward following 12 and the intake valve 16 is opened first, and then the second rocker arm 18 following the valve closing cam 17 moves the first rocker arm 13 upward. The intake valve 8 can be closed.
-6611, JP-A-60-32910, 32911, JP-B-53-5192
(See Publication No. 8).

(Problems to be solved by the invention) However, in the case of FIG. 3, since the clearance between the valve closing rocker arm 6 and the retainer 11 fixed to the valve shaft 10 (valve closing side clearance) cannot be adjusted, for example, If the valve closing rocker arm 6 and the retainer 11 have variations in size and wear, the clearance with the retainer 11 increases and noise and vibration occur, and the valve 8 does not completely adhere to the valve seat. is there.

Further, in the structure shown in FIG. 4, the first rocker arm 13 is engaged with the valve shaft 14 through the retainer 15 having upper and lower flanges. In this case, the lower flange and the rocker arm 13 are joined by screwing the retainer 15. Even if the clearance (valve opening side clearance) can be adjusted, the retainer 15 and the rocker arm 13
If there is dimensional variation or wear on the valve, it is unavoidable that the clearance with the upper flange (clearance on the valve-closing side) will increase, and noise and vibration will still occur and the valve 16
Has a problem in that it does not adhere to the valve seat.

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

(Means for Solving the Problems) The present invention is directed to a camshaft that uses a valve-opening rocker arm for intake and an exhaust valve that opens an exhaust valve, and a valve-closing rocker arm for intake and exhaust. In a valve forced opening / closing device for an internal combustion engine having a valve-closing cam that operates, the valve-closing rocker arm is sucked and engaged with a retainer fixed to the valve shaft of the exhaust valve, and the valve-closing rocker arm is provided at the center thereof. One end of the pivot is pivotally supported so that one end contacts the cam and the other end abuts the retainer. The pivot is attached to the cylinder head through a screw so that the height of the pivot can be adjusted. With respect to the center line of the screw portion, the center of the cam shaft was set on a line that was substantially symmetrical to the center line of the intake and exhaust valves.

(Operation) Therefore, by raising or lowering the height of the pivot, the cam and valve clearance through the valve closing rocker arm can be easily adjusted, and at this time, the pivot almost sucks.
Since it is located at the geometrically symmetrical center of the exhaust valve and the camshaft, the initial rocker ratio (arm ratio) of the valve closing rocker arm is maintained regardless of whether the pivot is up or down, and the cam and valve clearance can be adjusted according to the valve characteristics. It can be performed in a state close to the design value.

(Embodiment) FIGS. 1 and 2 show an embodiment applied to an internal combustion engine having two intake valves and two exhaust valves per cylinder.
Is a camshaft that is rotationally driven by the engine, 31 is an intake valve or exhaust valve (hereinafter referred to as a valve) in which only one of the two is provided for each cylinder, and 32 is a cam between the camshaft 30 and the valve 31. A rocker shaft arranged in a somewhat upper position parallel to the shaft 30.

A valve opening cam 33 and a valve closing cam 34 are formed on the cam shaft 30 so as to be substantially adjacent to each other. Correspondingly, one end of the rocker shaft 32 is in sliding contact with the valve opening cam 33 from above. The valve opening rocker arm 35 is rockably supported via the boss portion 35a. The cam shaft 30 and the rocker shaft 32 are supported by bearings (not shown).

Also, below the rocker shaft 32, the cylinder head 36
A pivot 37 having a spherical tip is erected so that the height can be adjusted by a screw 37b formed on the shaft portion 37a and a lock nut 38. The pivot 37 has a substantially Y-shaped valve-closing rocker arm 39 whose one end is in sliding contact with the valve-closing cam 34 from below.
However, the spherical concave portion 39a formed in the central portion is engaged with the distal spherical portion 37c of the pivot 37 so as to be swingably supported.

The valve opening cam 33 is formed in a profile having a high position portion 33a at one position in the circumferential direction and the valve closing cam 34 is formed in a profile having a low position portion 34a at one position in the circumferential direction. It is set by the cycle and the sliding contact position of the rocker arms 35, 39.

On the other hand, the two valves 31 are slidably supported in the valve axis direction via the valve guides 40, and the collets 42 are fitted into the grooves 41a formed in the upper portion of the valve shaft 41, respectively. The retainer 43 is attached via the.

Then, the corresponding tip portions 45a, 45b of the Y-shaped rocker arm 35 for opening the valve are attached to the valve shaft ends 44 of both valves 31 from above via the adjusting screws 46 attached to the tip portions 45a, 45b, respectively. On the other hand, the corresponding tip portions 47a and 47b of the Y-shaped valve closing rocker arm 39 are brought into contact with the lower surfaces of the retainers 43 mounted on the valve shafts 41 of both valves 31 from below.

The adjusting screw 46 is screwed into the tip end portions 45a and 45b of the valve opening rocker arm 35, and after adjusting the clearance with the valve shaft end 44, is fixed by the lock nut 48.

Each tip portion 47a, 47b of the valve closing rocker arm 39 is formed, for example, in a U shape so as to contact the retainer 43 while sandwiching the valve shaft 41, and the contact surface with the retainer 43 is a smooth convex curved surface. It is formed.

With this configuration, when the valve 31 is open, the valve opening cam
33, the tip end portions 45a, 45b, 47a, 47b of the valve opening rocker arm 35 and the valve closing rocker arm 39 follow the valve closing cam 34, and the tip portions 45a, 45b of the valve opening rocker arm 35 move downward. While both valves 31 are opened via the adjusting screw 46 of
When the valve 31 is closed, the same valve opening cam 33 and valve closing cam 34 are used.
Following the above, the rocker arm 35 for opening the valve and the rocker arm for closing the valve
The respective tip portions 45a, 45b, 47a, 47b of 39 are moved upward, and the both valves 31 are closed via the retainer 43 that abuts on the tip portions 47a, 47b of the valve closing rocker arm 39.

Then, each clearance between the tip end portions 45a, 45b of the valve opening rocker arm 35 and the valve shaft ends 44 of both valves 31 can be adjusted by the adjusting screw 46, respectively, and the tip end portions 47a, 47b of the valve closing rocker arm 39 can be adjusted. Each clearance between each valve 31 and each retainer 43 can be adjusted by loosening the lock nut 38 of the pivot 37 supporting the rocker arm 39, setting the pivot 37 to a predetermined height, and fixing the pivot 37 again with the lock nut 38. Can be adjusted.

Therefore, even if the rocker arms 35 and 39, the retainer 43, and both valves 31 have dimensional variations and wear, the clearances can be set to appropriate values, and as a result, noise and vibration can be prevented when the valve 31 is opened and closed, and the valve 31 can be closed. At times, incomplete adhesion of the valve 3 to the valve seat can be prevented, and good operation is always ensured.

Note that the pivot 37 allows the valve closing rocker arm 39 and the retainer 43 to be cleared at the same time as the valve closing rocker arm 39.
The clearance between the valve closing cam 34 and the valve closing cam 34 is adjusted. In this case, the valve closing cam 34 and the valve closing cam 34 are closed at a position N on a line symmetrical to the center line M of the valve 31 with respect to the center line L of the pivot 37. Since the slide contact position of the valve rocker arm 39 is set so that adjustment of these clearances is extremely easy,
Moreover, in this case, even when the pivot 37 is moved up and down, the valve closing rocker arm 39 maintains the initial lever ratio (arm ratio),
The cam and valve clearance can be adjusted in a state close to the design value of the valve characteristic.

Further, the above-mentioned embodiment is applied to an engine having two intake valves and two exhaust valves in one cylinder, but of course it can be applied to an engine having one intake and exhaust valves.

(Effects of the Invention) As described above, the present invention allows the camshaft to intake and exhaust the valve through the rocker arm for opening the valve and the cam for opening the valve to close and close the exhaust valve. In a valve forced opening / closing device of an internal combustion engine having a cam for closing the valve, the rocker arm for closing the valve is sucked and engaged with a retainer fixed to the valve shaft of the exhaust valve, and the rocker arm for closing the valve is located at the central portion thereof. The pivot is pivotally supported so that one end abuts on the cam and the other abuts on the retainer, and the pivot is mounted on the cylinder head via a screw so that the height position can be adjusted, and the screw With respect to the center line of the section, the center of the cam shaft is set to be on a line that is approximately symmetrical to the center line of the intake and exhaust valves.Therefore, by raising or lowering the height of the pivot, cam,
The valve clearance can be easily adjusted and the proper clearance can be maintained even if there are variations in the size of the rocker arm for closing the valve or the retainer, and wear can be prevented, while noise and vibration can be prevented. Since it is located at the geometrically symmetrical center of the camshaft, the initial rocker ratio (arm ratio) of the valve closing rocker arm is maintained regardless of whether the pivot is up or down, and the cam and valve clearance can be adjusted by designing valve characteristics. The effect is that it can be performed in a state close to.

[Brief description of drawings]

1 and 2 are a side view and a plan view showing an embodiment of the present invention, and FIGS. 3 and 4 are side views of a conventional example. 30 ... Cam shaft, 31 ... Valve, 33 ... Cam for opening valve, 34 ...
Cam for closing valve, 35 ... Rocker arm for opening valve, 37 ... Pivot,
38 ... Lock nut, 39 ... Valve closing rocker arm, 41 ... Valve shaft, 43 ... Retainer.

Front page continuation (72) Inventor Kugo Hamai, 2 Takara-cho, Kanagawa-ku, Yokohama, Kanagawa Pref., Nissan Motor Co., Ltd. (56) Reference JP 61-11408 (JP, A) US Patent 3430614 (US, A)

Claims (1)

[Scope of utility model registration request] Claim: What is claimed is: 1. A camshaft has a valve-opening cam that sucks air through a valve-opening rocker arm and opens an exhaust valve, and a valve-closing cam that sucks air through a valve-closing rocker arm and closes an exhaust valve. In the forced valve opening and closing device for an internal combustion engine, the valve closing rocker arm is sucked and engaged with the retainer fixed to the valve shaft of the exhaust valve, and the pivot for positioning the valve closing rocker arm at its center is used as a fulcrum. The pivot part is swingably supported so that the other end abuts on the retainer and the other end abuts on the retainer. A valve forced opening / closing device for an internal combustion engine, wherein the cam shaft center is set on a line that is substantially symmetrical to the center line of the exhaust valve.