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Rocker arm for valve control apparatus

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Rocker arm for valve control apparatus


To provide a rocker arm for a valve control apparatus of an automobile engine, which enables downsizing of the valve control apparatus and provides improved fuel economy of the engine. The rocker arm is provided with: a top plate; at least one upright wall section; a cam slide section, formed on top of the top plate, in contact with a cam mounted on a camshaft; a supporting member for rockably supporting the rocker arm about the rocking center of the supporting member; and a pad face, formed at the other end of the rocker arm, in contact with a valve system. Said at least one upright wall section has a smaller width than the top plate, and extends from the top plate at a substantially right angle.
Related Terms: Downsizing

Browse recent Nittan Valve Co., Ltd. patents - Kanagawa, JP
USPTO Applicaton #: #20140007832 - Class: 123 9039 (USPTO) -
Internal-combustion Engines > Poppet Valve Operating Mechanism >Rocker

Inventors: Ken-ya Sugawara, Mamoru Kato

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The Patent Description & Claims data below is from USPTO Patent Application 20140007832, Rocker arm for valve control apparatus.

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FIELD OF THE INVENTION

This invention relates to a rocker arm for use with a valve control apparatus for controlling the valve open/close operation of an automobile engine via a rocker arm rocked by the cam of a camshaft, the rocker arm providing an improved the fuel economy of the engine and enabling down sizing of the valve control apparatus

BACKGROUND ART

OF THE INVENTION

A rocker arm rocked by a cam driven by a camshaft of the engine for lifting and lowering an engine valve is disclosed in a patent document listed below. The rocker lever (rocker arm) 1 of Patent Document 1 has a semi-spherical recess 2 engaged with the semi-spherical end 4 of a support member 3 for rockably supporting the rocker lever 1 in contact with the base section (or valve stem) of a gas exchange valve (engine valve) urged by a valve spring for closing the valve (not shown). Provided at the center of the rocker lever (rocker arm) 1 is a roller 6 in contact with a camshaft (not shown). The rocker lever 1 opens the engine valve by pushing down the roller 6 (not shown) and allows the engine valve to be closed by means of a valve spring (not shown) urging the valve.

PRIOR ART DOCUMENT

PATENT DOCUMENT: JPA Laid Open H10-37719

SUMMARY

OF THE INVENTION Objects to be Achieved by the Invention

In general a camshaft is subjected to a force of a valve spring urging the valve stem to close the valve and a frictional torque generated between the rocker arm and the cam pushing down the rocker arm in opposition to the force of the valve spring during a valve opening period. This frictional torque impedes the rotation of the camshaft. Since this frictional torque lowers the fuel economy of the engine, the valve control apparatus of Patent Document 1 utilizes a rocker lever 1 having a roller 6 in contact with the cam so as to reduce the friction between the cam and the rocker arm, and hence the frictional torque acting on the camshaft.

However, although the roller 6 can reduce the friction between the cam and rocker lever 1, such roller 6 greatly increase the weight of the rocker lever 1, since the roller 6 requires needle bearings for example. An increase in weight of the rocker lever 1 entails an increase in the inertial moment of the rocker lever 1, which implies that a stronger valve spring is required to close the valve. However, a stronger valve spring will cause the roller 6 to exert a stronger force on the cam, thereby increasing the frictional torque acting on the camshaft.

As a consequence, in spite the roller 6 can reduce the frictional torque, the rocker lever 1 having such roller 6 suffers from an increment of the frictional torque due to the increased spring force of the valve spring. Hence, reduction of the frictional torque by the use of cam in rolling contact with the roller 6 is overwhelmed by an increment of the frictional torque due to an increment of the valve force of the valve spring. This is a serious problem from the point of the fuel economy of the engine. The use of a roller poses a further problem that it increases the dimensions of the rocker lever 1, making it difficult to downsize the valve control apparatus.

In view of the problems mentioned above, the present invention is directed to an improved rocker arm operably coupled to the camshaft, which enables not only reduction of the disadvantageous frictional torque that impedes the rotation of the camshaft but also enables downsizing of the valve control apparatus, thereby facilitating improvement of the fuel economy of the engine.

Means for Achieving the Objects

An inventive rocker arm for a valve control apparatus in accordance with claim 1 has a top plate and at least one upright wall section, wherein the top plate is: provided on top thereof with a cam slide section in contact with a cam of a camshaft; supported at one end thereof by a supporting member rockably about the rocking center of the supporting member; and is provided at the other end thereof a pad face in contact with a valve system, and said at least one upright wall section has a smaller width than the top plate, and extends from the top plate at a substantially right angle.

In the rocker arm of claim 1, in order to reinforce the top plate subjected to the reactive force of the valve spring acting on the pad face and the cam force acting on the cam slide section, said at least one upright wall section is integrated with the top plate.

(Function) In the rocker arm of the valve control apparatus of claim 1, the top plate has a minimum possible thickness, yet it is reinforced by the upright wall having a thickness less than that of the top plate, so that the weight and inertial moment of the rocker arm are significantly reduced. As a consequence, the valve control apparatus equipped with the rocker arm of claim 1 can use an extremely light-weight valve spring, which in turn permits great reduction of the frictional torque arising from the force of the valve spring and applied to the camshaft. That is, a torque that would otherwise impede the rotation of the camshaft is greatly reduced.

As a result, in the rocker arm of claim 1, reduction of the frictional torque due to the elimination of a roller and reduction of the weight (or the urging force) of the valve spring outweighs generation of a minor frictional torque that takes place between the rocker arm and the cam sliding on the rocker arm.

In the rocker arm of the valve control apparatus of claim 1, at least one of the cam slide section and pad face of the rocker arm may be surface treated to reduce its frictional coefficient, as recited in claim 2.

(Function) In the rocker arm of claim 2, the frictional coefficient of the surface treated section is reduced, thereby reducing the friction generated between the cam and the cam slide section or between the valve stem and pad face, which in turn further reduces the frictional torque acting on the camshaft.

In the rocker arm for a valve control apparatus of claim 1 or 2, the top plate may have at least one hole in a region except for the cam slide section, as recited in claim 3.

(Function) In the rocker arm of claim 3, the weight of the rocker arm is further reduced by the formation of the hole. As a consequence the force of the valve spring transmitted to the cam, and hence the frictional torque applied to the camshaft, is further reduced.

In the rocker arm a valve control apparatus in accordance with any one of claims 1 through 3 may have at least one hole formed in the upright wall section, as recited in claim 4.

(Function) In the rocker arm of claim 4, the weight of the rocker arm is reduced still further that the frictional torque applied to the camshaft is reduced still further.

In the rocker arm for a valve control apparatus in accordance with claim 4, the hole formed in the upright wall section may be formed on the rocking trajectory of the cam slide section rocking about its rocking center, as recited in claim 5.

(Function) In the rocker arm of claim 5, the hole thus formed on the rocking trajectory of the cam slide section reduces the weight of that portion of the rocker arm in contact with the cam. Accordingly, the inertial moment of the cam pushing the rocker arm of claim 5 is reduced.

In the rocker arm for a valve control apparatus in accordance with any one of claims 1 through 5, the cam slide section may be provided with oil grooves, as recited in claim 6.

(Function) In the rocker arm of claim 6, oil fed to the cam slide section in contact with the cam stays in the oil grooves and forms an oil film between the cam and cam slide section. As a result, the friction between the cam and cam slide section is reduced, which improves the wear resistances of the cam and cam sliding section.

In the rocker arm for use with a valve control apparatus in accordance with any one of claims 1 through 6, at least one of the cam slide section and the pad face can be configured to have a convex transverse cross section, as recited in claim 7.

If both of the cam slide section and pad face have flat transverse cross sections, the pad face is likely to be inclined relative to the valve spring in the event that the cam slide section is inclined relative to the cam due to a backlash of the rocker arm. In this case, a corner of the cam slide section may come into contact with the cam and cause an unexpected frictional force, while the pad face may come into contact with a corner of the valve stem and cause an unexpected frictional force. Such frictional forces will impede the rotation of the camshaft.

(Function) If, on the other hand, at least one of the cam slide section and pad face has a convex transverse cross section, the corner of either the cam slide section or the valve stem is less likely to come into contact with the cam or pad face. As a consequence no corner-plane contact is less likely to take place between the cam and cam slide section or between the pad face and the valve stem. Thus, in the rocker arm of claim 7, the cam can push down the cam slide section of the rocker arm downward with a reduced inertial moment, thereby facilitating the stability of open/close operations of the engine valve.

The rocker arm for use with a valve control apparatus in accordance with any one of claims 1 through 7, wherein the upright wall section has a pair of inner walls each spaced apart from the periphery of the valve stem by a distance in the range from 0.1 mm to 1 mm.

(Function) Since in this case there is provided an adequate allowance between the valve stem and the upright walls, disadvantageous friction will not take place between them, thereby facilitating the stability of the open/close operations of the engine valve.

RESULTS OF THE INVENTION

The rocker arm of claim 1 has a greatly reduced weight and hence gives rise to much less frictional torques, and hence it has greatly improved the fuel economy of an engine as compared with conventional rocker arms. Further, since the rocker arm has no rollers, it can be downsized with less components. It is not troubled with abnormal wear of needle bearings and/or shaft.

In the rocker arm according to any one of claims 2 through 4 a frictional torque acting on the camshaft is further reduced, thereby improving the fuel economy of the engine.

In the rocker arm of claim 5, the cam can push down the cam slide section of the rocker arm with a reduced torque, thereby reducing the frictional torque acting on the camshaft still further and improving the fuel economy of the engine still further.

In the rocker arm of claim 6, the frictional force that takes place between the cam and cam slide section is reduced, thereby further reducing the frictional torque acting on the camshaft and improving the fuel economy of the engine still further.

In the rocker arm of claim 7, at least one of the frictional force that takes place between the cam and cam slide section and the frictional force that takes place between the pad face and the valve stem is reduced, thereby reducing the frictional torque acting on the camshaft still further and hence improving the fuel economy of the engine.

With the rocker arm of claim 8, stability of the valve movement is facilitated by the fact that the friction between the valve and the upright walls is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS



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stats Patent Info
Application #
US 20140007832 A1
Publish Date
01/09/2014
Document #
14006883
File Date
10/04/2011
USPTO Class
123 9039
Other USPTO Classes
International Class
01L1/18
Drawings
8


Downsizing


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