JPH0730887Y2 - 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.
A desmodromic valve opening / closing device is known 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) By the way, in such a valve opening / closing device, the adhesion force between the valve and the valve seat when the valve is closed is low in the low speed range of the engine.
A spring is provided to apply a predetermined valve closing force to the valve.

However, since the torsion spring 20 attached to the rocker shaft 4 in the structure shown in FIG. 3 has a problem that the spring 20 is easily damaged and lacks in durability.

Further, in the structure shown in FIG. 4, the coil spring 21 is interposed between the retainer 15 screwed to the valve shaft 14 and the cylinder head. In this case, the engaging portion between the retainer 15 and the rocker arm 13 has a variation in size. If so, it is difficult to adjust the position of the retainer 15, and for example, the valve closing force of the coil spring 21 may not be transmitted to the valve 16. Also, if there are variations in the dimensions, the lower flange of the retainer 15 will cause the coil spring 21
There is a problem in that it may hit the rocker arm 13 and generate noise.

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

(Means for Solving the Problems) According to the present invention, a cam for opening and closing an exhaust valve, which opens and closes an exhaust valve, and a cam for closing and closing an exhaust valve, which is sucked through at least a rocker arm, are formed. In a valve forced opening / closing device of an internal combustion engine, a retainer is attached to a valve shaft of an intake / exhaust valve, and an engaging portion of the rocker arm is brought into contact with a lower surface of the retainer. Is formed between the spring seat and the cylinder head that are loosely fitted to the valve shaft so as to come into contact with the engaging portion from the lower surface,
The exhaust valve is provided with a coil spring that applies a predetermined valve closing force.

(Effect) Therefore, even if there are variations in the dimensions of the rocker arm and retainer, the intake and exhaust valves have good seating characteristics when the valve is closed, and because the rocker arm is always in close contact with the retainer due to the coil spring, valve opening or No abnormal noise is generated when the valve is closed, and since the upper and lower surfaces of the engaging portion of the rocker arm are formed into convex curved surfaces, the operation of the contact surface with the retainer or the spring seat is smooth, and noise can be prevented.

(Embodiment) FIGS. 1 and 2 show an embodiment of the present invention, in which 30 is a camshaft rotationally driven by an engine, 31 is an intake valve or an exhaust valve (hereinafter referred to as valve), and 32, 33. Is camshaft 3
The rocker shaft is arranged between 0 and the valve 31 in parallel with the cam shaft 30.

A valve opening cam 34 and a valve closing cam 35 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 34 from above. On the rocker arm 33, a substantially V-shaped valve closing rocker arm 37 is provided, one end of which is in sliding contact with the valve closing cam 35 from below.

The valve-opening cam 34 is formed in a profile having a high position 34a at one position in the circumferential direction and the valve-closing cam 35 is formed in a profile having a low position 35a at one position in the circumferential direction. It is set by the cycle and the sliding contact position of the rocker arms 36, 37.

The valve opening rocker arm 36 and the valve closing rocker arm 27 are swingably supported by the rocker shafts 32, 33 via the boss portions 36a, 37a, and the rocker shafts 32, 33 are arranged on both sides of the boss portions 36a, 37a. Supported by brackets 38, 39. In addition,
The rocker arm 36 is also formed in a substantially V shape, and both rocker arms 3
The 6,37 may be supported on one rocker shaft.

On the other hand, the valve 31 is slidably supported in the valve axis direction via a valve guide 40, a collet 42 is fitted in a groove 41 a formed in an upper portion of the valve shaft 41, and a retainer 43 is provided via the collet 42. Is installed.

Then, the valve shaft end 44 of the valve 31 is connected to the rocker arm for opening the valve.
The tip portion 36b of the 36 is abutted from above via an adjusting screw 46 fixed by a nut 45, and the retainer
An engaging portion 37b at the tip of the valve closing rocker arm 37 is brought into contact with the lower surface 43a of 43 from below.

In this case, the engagement portion 37b of the valve closing rocker arm 37 is connected to the valve shaft 41
Is formed in a U shape so as to come into contact with the lower surface 43a of the retainer 43 while holding the upper surface 37c of the engaging portion 37b (retainer 43
And a lower surface 37d (spring seat 47 described later)
And contact surfaces) are formed into smooth convex curved surfaces.

A coil spring 48 for urging the valve 31 in the valve closing direction via the engaging portion 37b of the valve closing rocker arm 37 is formed in the spring seat 47 and the cylinder head 49 that are in contact with the lower surface 37d of the engaging portion 37b. It is interposed between the spring seat 50.

The coil spring 48 is a valve when the valve is closed in the low engine speed range.
For obtaining a predetermined adhesion between 31 and the valve seat 51,
You don't need a strong spring.

With this configuration, when the valve 31 is open, the valve opening cam
34, the tip end side of the valve opening rocker arm 36 and the valve closing rocker arm 37 follows the valve closing cam 35, and the valve 31 is opened via the adjusting screw 46 of the valve opening rocker arm 36, while the valve 31 When closing, the same cam 34 for opening the valve,
Following the valve closing cam 35, the tip ends of the valve opening rocker arm 36 and the valve closing rocker arm 37 move upward, and the valve closing rocker arm
The valve 31 is inserted through the retainer 43 that abuts the engaging portion 37b of the valve 37.
Is closed.

Then, when the valve 31 is opened, the coil spring 48 is compressed via the retainer 43 and the engaging portion 37b of the valve closing rocker arm 37, and when the valve 31 is closed, the coil spring 48 is passed through the engaging portion 37b and the retainer 43. The spring force of 48 is transmitted to the valve 31.

That is, since the coil spring 48 is interposed between the retainer 43 and the retainer 43 so as to hold the engaging portion 37b of the rocker arm 37 for closing the valve, even if the dimensions of the retainer 43 and the rocker arm 37 vary, A predetermined valve closing force can be accurately applied to the valve 31 when the valve is closed by the spring force, and a sufficient adhesion between the valve 31 and the valve seat 51 can be obtained.

Also, the contact surfaces 37c, 3c of the engaging portion 37b of the valve closing rocker arm 37 are
Since 7d is formed into a smooth convex curved surface, smooth operation is obtained, and the spring force of the coil spring 48 causes the retainer 43, the rocker arm 37, and the spring seat.
47 etc. will not hit each other and will not make noise. Since the coil spring 48 is used, high durability can be obtained.

(Effect of the Invention) As described above, according to the present invention, the cam opening and closing valve for opening and closing the exhaust valve and the closing cam for opening and closing the exhaust valve through at least the rocker arm are formed. In a valve forced opening / closing device of an internal combustion engine, a retainer is attached to a valve shaft of an intake / exhaust valve, and an engaging portion of the rocker arm is brought into contact with a lower surface of the retainer. Since a coil spring is provided between the spring seat and the cylinder head, which is loosely fitted to the valve shaft so as to come into contact with the engaging portion from the lower surface, and which gives a predetermined valve closing force to the exhaust valve. Even if there are variations in the dimensions of the rocker arm and retainer, the seating properties of the intake and exhaust valves when the valve is closed are good, and because the rocker arm is always in close contact with the retainer due to the coil spring, it can be opened or closed. No abnormal noise is generated, and since the upper and lower surfaces of the engaging portion of the rocker arm are formed into convex curved surfaces, there is an effect that the operation of the contact surface with the retainer and the spring seat is smooth and the generation of noise can be prevented. .

[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, 34 ... Valve opening cam, 35 ...
Valve closing cam, 36 ... Valve opening rocker arm, 37 ... Valve closing rocker arm, 37b ... Engaging portion, 41 ... Valve shaft, 43 ... Retainer, 47
… Spring seats, 48… Coil springs.

Claims (1)

[Scope of utility model registration request] 1. A valve forced opening / closing apparatus for an internal combustion engine, comprising a cam opening cam for opening and closing an exhaust valve on a cam shaft and a cam closing valve for closing and opening an exhaust valve through at least a rocker arm. A retainer is attached to the valve shafts of the intake and exhaust valves, and the lower surface of the retainer is brought into contact with the engagement portion of the rocker arm. The engagement portion has upper and lower surfaces formed into smooth convex curved surfaces, and this engagement is performed. Sucked between the spring seat and the cylinder head, which were loosely fitted to the valve shaft so as to come into contact with the lower part
A valve forced opening / closing device for an internal combustion engine, wherein a coil spring that applies a predetermined valve closing force to the exhaust valve is interposed.