JPH02233813A - Valve forced on-off device for internal combustion engine - Google Patents

Abstract

PURPOSE:To hold a rocker arm stably even to thrust force without deflecting to both directions by supporting one side of the rocker arms connected to each other on a rocker shaft free of rocking motion. CONSTITUTION:A valve opening cam 2 and a valve closing cam 3 both are installed in a camshaft 1, and a valve opening rocker arm 5 responding in contact with this valve opening cam 2 is made contact with a valve stem of a valve 4 in the depressing direction. In addition, a valve closing rocker arm 15 responding in contact with the valve closing cam 3 is engaged with the valve stem of the valve 4 in the depressing direction likewise. Then, the rocker arm 5 is supported by a rocker shaft 6 set up in a cylinder head 9 in parallel with the camshaft 1. With this constitution, when thrust force works on these rocker arms 5, 15, these arms are in no case tilted in both directions so that they are always stably supported. Therefore a cam lift characteristic can be accurately transmitted to the valve 4 and vibration and noise can be prevented from occurring in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a forced valve opening/closing device for forcibly opening and closing intake and exhaust valves of an internal combustion engine. (Prior art) In order to stabilize the opening and closing characteristics of the intake and exhaust valves (valve) mainly in the high engine speed range, a cam shaft is provided with a valve opening cam and a valve closing cam, and the opening and closing of the valve is controlled by a valve spring. First, a device for forcibly opening and closing a valve (desmodromic) was developed, for example, in JP-A-60-341.
This method is disclosed in Publication No. 2, Japanese Patent Application Laid-Open No. 60-32910, etc. However, when one valve is driven by two cams, one for valve opening and one for valve closing, and two rocker arms that act in response to these cams, the space occupied by the rocker arm and rocker shaft increases, making the valve train larger. There was a problem. Therefore, the applicant proposed a solution to these problems in Japanese Patent Application No. 63-203521. In this system, a valve-opening rocker arm and a valve-closing rocker arm are swingably connected to each other, and one rocker arm is swingably supported relative to the cylinder head via a spherical pivot. There is no need to provide a rocker shaft, which reduces the space occupied.Also, by adjusting the center of swing up and down via the spherical pivot, it is possible to adjust the valve clearance between the valve opening cam and the valve closing cam. There is also the advantage that both can be done at the same time. (Problem to be Solved by the Invention) However, according to this valve train, since the spherical pivot supporting the valve opening and valve closing rocker arms is single, shaking and tilting occur when thrust force is applied to the rocker arms. It was easy to use, and the support stability of the rocker arm was lacking. Especially in the high rotation range, even the slightest vibration has a large effect on the overall vibration and noise, and also makes it difficult to accurately transmit cam lift to the valves. The present invention aims to solve such problems. (Means for Solving the Problem) The present invention provides a valve opening cam and a valve closing cam on a camshaft that rotates in synchronization with engine rotation, and a valve opening rocker arm that contacts and responds to the valve opening cam. is brought into contact with the valve shaft of the valve in the downward direction, and the valve-closing port arm, which contacts and responds to each of the valve-closing cams, is similarly engaged with the valve shaft in the upward direction, and one rocker arm is brought into contact with the other. One of the rocker arms was swingably supported in the middle of the rocker arm, and one of the rocker arms was swingably supported on a rocker shaft installed in the cylinder head parallel to the camshaft. (Function) Therefore, the valve (intake/exhaust valve) is driven in the valve opening direction by the valve opening rocker arm that responds to the valve opening cam, and is returned to the valve closing direction by the valve closing locking arm that responds to the valve closing cam. ．． One of the rocker arms, which are connected to each other so as to be able to swing, is supported so as to be able to swing freely on a rocker shaft that is arranged parallel to the camshaft. It provides stable support without shaking, allows cam lift to be accurately transmitted to the valves, and suppresses the occurrence of vibrations, improving stability and quietness in high-speed rotation ranges. (Examples) The present invention will be explained below based on some examples. In the first embodiment shown in FIGS. 1 and 2, reference numeral 1 in the figures is a camshaft, and this camshaft 1 has a camshaft 1 located above each whistle valve (intake or exhaust valve) 4. One valve opening cam 2, and two valve opening cams on both sides of this valve opening cam 2.
The two valve-closing cams 3 are each integrally formed. The valve-opening rocker arm 5, which contacts the valve-opening cam 2 via the cam follower portion 5a, has its swinging tip abutting portion 5b in contact with the end of the valve shaft 4a of the valve 4, and its base. The end 5C is swingably supported by a rocker shaft 6 attached to the cylinder head 9, and in response to the valve opening cam 2, the valve 4 is pushed down using the rocker shaft 6 as a fulcrum. The rocker shaft 6 is arranged parallel to the camshaft 1 and is attached to the cylinder head 9 by a support bolt 7. On the other hand, the valve-closing rocker arm 15, which is arranged with the valve-opening rocker arm 5 sandwiched between them,
Cam follower parts 15 that come into contact with the two valve-closing cams 3 at the tips of the bifurcated branch parts 12m and 12b, respectively.
a, 15b are formed, and the intermediate portions of the branching portions 12a and 12b are swingably supported via the support shaft 16 with respect to the valve opening rocker arm 5, while the locking portion 1 at the swinging tip thereof is formed.
5e is attached to the valve shaft 4a or contacts (locks) the retainer 17 from below, and uses the support shaft 16 as a fulcrum to pull up the valve 4 while responding to the valve-closing cam 3. Note that the valve-opening cam 2 Cam profiles are formed so that when the valve 4 is pushed down, the valve closing cam 3 does not obstruct this, and when the valve closing cam 3 pulls up the valve 4, the valve opening cam 2 is not obstructed. is,
As a result, both the vertical movement of the valve 4 is driven by the cam without the need for a valve spring. It is constructed as described above, and its operation will be explained next. When the rocker arm 5 corresponding to the valve-opening cam 2 swings about the rocker shaft 6 as the camshaft 1 rotates, the tip of the valve 4 is pushed down by the abutting portion 5b at the tip to open the valve. Thereafter, the rocker arm 15 that responds to the valve-closing cam 2 swings about the support shaft 16 as a fulcrum, pulling up the valve 4 via the locking portion 15e and closing the valve. 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 that surging does not occur even in the high rotation range.
Valve 4 can be opened and closed stably. Since the rocker arm 5 for opening the valve is supported by the rocker shaft 6 disposed in the cylinder head 9 parallel to the camshaft 1, even if a thrust force is applied to the rocker arms 5 and 15, they will not tilt to the left or right. , is always stably supported. Therefore, the cam lift characteristics can be accurately transmitted to the valve 4, and the generation of vibration and noise can also be prevented. Although there are two rocker arms 5.15 for opening and closing the valve, only one rocker shaft 6 is required, which makes the structure of the valve train compact and reduces the space it occupies. The rocker shaft 6 can be installed as a short shaft instead of a single long shaft. Next, the embodiment shown in FIG.
In order to drive two intake valves (or exhaust valves), the tips of the rocker arms 5 and 15 are bifurcated, and contact portions 5b and 5bz and locking portions 15c and 15c2 are formed in the bifurcation portions, respectively. By doing so, two valves 4 can be operated at the same time.
It is now possible to open and close the . In the embodiment shown in FIG. 4, a rocker shaft 6 which is the fulcrum of the rocker arm 5 is used to adjust the valve clearance.
The bolt 7 is screwed into the rocker shaft guide 8 that supports both ends of the rocker shaft 6, and the screwed position is fixed by a locking nut 7b. The tip of the bolt 7 is a non-threaded rod portion 7a, and the tip is a support hole 9 provided in the cylinder head 9.
Insert into a. The valve clearance is adjusted by adjusting the cam follower part 5a of the rocker arm 5 for opening the valve, the cam follower part 15m of the rocker arm 15 for closing the valve, in the cam base circle.
This is done by moving the rocker shaft 6 up and down via the bolt 7 so that the cam surfaces 15b and 15b come into close contact with the respective cam surfaces. In this way, since both valve clearances can be checked at the same time, for example, a thread is formed at the tip of the valve 4, and the contact position with the abutment part 5a of the valve opening rocker arm is set at the position of the cap screwed into the thread. Compared to those that require adjustment, the structure is simpler, and there is no need to worry about damaging the valve oil seal with screws when installing the valve 4. In the embodiment shown in FIG. 5, one valve opening cam 2 and one valve closing cam 3 are provided, and one valve 4 is driven to open and close. , which has the same structure but drives two valves 4 at the same time. Therefore, in these embodiments, one cam follower portion 5a and one cam follower portion 15a are formed in the rocker arms 5 and 15 for opening and closing the valve, respectively. Incidentally, in each of the above-mentioned embodiments, the structure in which the valve-closing rocker arm 15 is swingably supported in the middle of the valve-opening rocker arm 5 and the valve-opening opening lever arm 5 is further supported on the rocker shaft 6 has been illustrated. The present invention is also applicable to a structure in which the valve-closing rocker arm 15 is supported on the rocker shaft 6, and the valve-opening rocker arm 5 is swingably supported in the middle thereof. (Effects of the Invention) As described above, according to the present invention, one of the rocker arms connected to each other is swingably supported by the rocker shaft parallel to the camshaft, so that the rocker arm can withstand thrust force. It is possible to stably support the valve without shaking from side to side, accurately transmit cam lift to the valve, and suppress the occurrence of vibrations, improving stability and quietness in the high-speed rotation range.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the first embodiment of the present invention, Fig. 2 is a plan view thereof, Fig. 3 is a plan view of the second embodiment, and Fig. 4 is a rocker shaft of the third embodiment. 5 and 6 are plan views of the fourth and fifth embodiments, respectively. 1...Camshaft, 2...Valve opening cam, 3...
Valve closing cam, 4... Valve (intake, exhaust valve), 5...
Rocker arm, 5a... cam follower part, 6... rocker shaft, 7... bolt, 9... cylinder head, 15... rocker arm, 15a... cam follower part. 1st Figure 1--1 camshaft 2-11 question 4n shell cam sheath/interval valve cam 4-11 valve in use. Exhaust valve) 5-One bite deer arm 5a--η Muforoa Anko 6. Ichiron sword ifhihi 7-November Q Reto 9--Ichigo Soshita κtsuhi 15--Ichirotsu arm 15a--〃Muforoa bite vomit

Claims (1)

[Claims] A valve-opening cam and a valve-closing cam are provided on a camshaft that rotates in synchronization with engine rotation, and a valve-opening rocker arm that contacts and responds to the valve-opening cam comes into contact with the valve shaft of the valve in a downward direction. At the same time, the valve-closing rocker arms that contact and respond to each of the valve-closing cams are similarly locked to the valve shaft from the lifting direction, and one rocker arm is swingably supported in the middle of the other rocker arm. A valve forced opening/closing device for an internal combustion engine, characterized in that one rocker arm is swingably supported by a rocker shaft disposed in a cylinder head parallel to a camshaft.