Claims:1) A valve train system for opening and closing a valve of an internal combustion engine of a vehicle, said system including a pivotal arm and a valve stem, wherein the system comprising a primary roller and a plurality of auxiliary rollers surrounding and in point contacts with said primary roller, such that said auxiliary rollers facilitates said primary roller to rotate freely about an axes in a three dimensional plane, said primary roller interfaced between the pivotal arm and the valve stem to provide point contacts during the opening and closing of a valve associated with the valve stem.

2) The valve train system as claimed in claim 1, wherein said pivotal arm is actuated by a valve actuating mechanism and said arm includes a tappet assembly having a holder adapted to receive said primary roller and said auxiliary rollers.

3) The valve train system as claimed in claim 2, wherein said holder has a plurality of blind slots for accomodating auxiliary rollers.

4) The valve train system as claimed in claim 2, wherein said tappet assembly includes a second stem to which said holder is fitted at one end and said pivot arm includes an opening in which said second stem is fitted.

5) The valve train system as claimed in claim 4, wherein said second stem has a blind slot for accomdating one auxiliary roller from said auxiliary rollers.

6) The valve train system as claimed in claim 4, wherein said holder is press-fitted or welded or fastened with said second stem.

7) The valve train system as claimed in claim 4, wherein said holder is threadably fitted with said second stem. , Description:This application is a patent of addition to Indian Patent Application No. 3231/MUM/2014 filed on 11th October 2014, the entire contents of which are specifically incorporated herein by reference.
FIELD
The present disclosure relates to the field of mechanical engineering. More specifically, the present disclosure relates to the field of vehicles.
BACKGROUND
A vehicle has a valve train system that controls the operation of valves, particularly, intake and exhaust valves of an internal combustion (i.c) engine. Generally, the valve train system includes a valve actuating mechanism, such as a cam, a pivotal/rocker arm and a tappert assembly that is selectively connected to and actuates a valve stem of a valve of an engine. The tappet assembly includes a a holder fitted to a stem. A roller is disposed between the holder and the stem. A portion of the roller is seated in the stem and a portion of the roller is seated in a hole configured in the holder such that the portion of the roller projects out from the holder through the hole to selectively engage with the valve stem. The roller rotates within the holder. The rotation of the roller causes friction between the roller and the holder and the roller and the stem, resulting in wear and tear of the roller, the stem and/or the holder. The wear and tear results in reduction of the life of the valve train system.
Hence, there is a need of a valve train system, the components of which, will experience less wear and tear which will, in turn increase the overall life of the valve train.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a valve train system for reducing the frictional losses in the valve train system.
Another object of the present disclosure is to provide a valve train system that has comparatively more life.
Yet another object of the present disclosure is to provide a valve train system with spherical rolling contacts that improves the fuel efficiency of the engine.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure discloses a valve train system. The valve train system opens and closes a valve of an internal combustion engine of a vehicle. The system includes a pivotal arm and a valve stem, wherein the system comprises a primary roller and a plurality of auxiliary rollers surrounding and in point contacts with the primary roller such that the auxiliary rollers facilitates the primary roller to rotate freely about an axes in a three dimensional plane. The primary roller is interfaced between the pivotal arm and the valve stem to provide a point contact therebetween during the opening and closing of a valve associated with the valve stem.
In one embodiment, the pivotal arm is actuated by a valve actuating mechanism and the pivotal arm includes a tappet assembly having a holder that receives the primary roller and the auxiliary rollers.
Typically, the holder has a plurality of blind slots for accomodating auxiliary rollers.
In one embodiment, the tappet assembly includes a second stem to which the holder is fitted at one end and the pivot arm includes an opening in which the second stem is fitted.
Typically, the second stem has a blind slot for accomodating an auxiliary roller.
In one embodiment, the holder is press-fitted or welded or fastened with the second stem.
Typically, the holder is threadably fitted with the second stem.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
A valve train system of the present disclosure will now be described with the help of accompanying drawings, in which:
Figure 1 illustrates a schematic representation of a valve train system with a primary roller configured on a tappet assembly for transmitting actuation force to a valve stem for actuation of the valve in accordance with an embodiment of the present disclosure;
Figure 2 illustrates a cross sectional view of a tappet assembly of Figure 1 having the primary roller and auxiliary rollers;
Figure 3a and 3b illustrate different views of the tappet assembly of Figure 1;
Figure 4 illustrates an exploded view of the tappet assembly of Figure 1;
Figure 5 illustrates a graphical representation depicting comparison of the variation of friction losses with respect engine speed in case of valve train having conventional tappet and the valve train of Figure 1 having the tappet assembly with the primary roller and the auxiliary rollers; and
Figure 6 illustrates a graphical representation depicting comparison of variation of torque with respect engine speed in case of valve train having conventional tappet and the valve train of Figure 1 having tappet assembly with a primary roller and the auxiliary rollers.
DETAILED DESCRIPTION
The disclosure will now be described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Figure 1 and 2 illustrate a valve train system 100 in accordance with an embodiment of the present disclosure. The valve train system 100 opens and closes a valve (not illustrated in Figures) of an internal combustion engine (not illustrated in Figures) of a vehicle (not illustrated in Figures). The system 100 includes a pivotal arm 102 (also known as rocker arm) and a valve stem 104 connected to the valve.
The pivotal arm 102 is actuated by a valve actuating mechanism 106. In accordance with one embodiment, the valve actuating mechanism 106 is a cam assembly that includes a cam 106a mounted on a camshaft (not illustrated in Figures). The cam 106a has a cam lobe 106b. The cam lobe 106b when in contact with one end 102a of the pivotal arm 102 pushes the pivotal arm 102 to open the valve. In one embodiment a rolling element 108 is connected to the pivotal arm 102 that is in contact with the valve actuating mechanism 106. The camshaft is connected to the crankshaft (not illustrated in Figures) of the vehicle and is actuated by the crankshaft. Typically, the camshaft is connected to the crankshaft by a chain arrangement or a belt arrangement or a gear arrangement.
The pivotal arm 102 has a second end 102b that has an opening 102bi in which a tappet assembly 110 is fitted. Figure 3a and 3b illustrates different views of the tappet assembly 110. Figure 4 illustrates an exploded view of the tappet assembly 110. The tappet assembly 110 comprises a holder 114 fitted to a second stem 112. The holder 114 accomodates a primary roller 116 and a plurality of auxiliary rollers 118 and 120. The auxiliary rollers 118 and 120 are disposed at a pre-determined distance from each other. The primary roller 116 has a portion projecting out of the holder 114. In an operative configuration of the valve train system 100, the projected portion of the primary roller 116 touches the valve stem 112. The projected portion of the primary roller 116 projects outside the holder 114 such that, in an operative configuration, the projected portion of the primary roller 116 has a point contact witht the valve stem 104. At least a portion of the auxiliary roller 118 is seated in the second stem 112 and the remaining portion of the auxiliary roller 118 is projects out from the second stem 112. The projected portion has a point contact with the primary roller 116. The auxiliary rollers 120 are configured to be seated in blind slots 114a provided in the holder 114. The primary roller 116 has a point contact with each of the auxiliary rollers 120. In an operative configuration, the primary roller 116 rotate freely along the three axes with the four point contact with the auxiliary rollers 118 and 120 within the holder 114 upon application of a tangential force when the primary roller 116 comes in contact with the valve stem 104. As the primary roller 116 has four point contact with the auxiliary roller 118 and 120, the contact area between the primary roller 116 and the holder 114 and between the primary roller 116 the second stem 112 is avoided substantially by auxiliary rollers 118, thereby there is less friction between the primary roller 116 and the holder 114 and the primary roller 116 and the second stem 112. In one embodiment, the primary roller 116 and the auxiliary rollers 118 and 120 are spherical in shape. The primary roller 116 is interfaced between the pivotal arm 102 and the valve stem 104 to provide a point contact therebetween during the opening and closing of the valve associated with the valve stem 104.
In accordance with one embodiment, the holder 114 is press-fitted with the second stem 112. In accordance with another embodiment, the holder 114 is threadably fitted with the second stem 112. In one embodiment, the holder is configured with at least one hole 114b for introducing a lubricant in the holder 114. The introduction of lubricant reduces friction at the contact point between the primary roller 116 and the auxiliary rollers 118 and 120.
Although the present disclosure is described by having single auxiliary roller 118 and three auxiliary rollers 120. However, the present disclosure is not limited to the number of auxiliary rollers 118 and the number of the auxiliary rollers 120 and any number of the auxiliary rollers can be provided.
As the primary roller 116 is in rolling contact with the valve stem 104, the drawbacks associated with the sliding contact between a tappet (not illustrated in Figures) and a valve stem (not illustrated in Figures) of a conventional valve train mechanism are eliminated.
Figure 5 illustrates a graphical representation of Frictional Power (hp) v/s Engine speed (RPM), wherein curve A represents the curve generated by use of the conventional valve train without roller and curve B represents the curve generated by use of the valve train system 100 of the present disclosure with the primary roller 116 and the auxiliary rollers 118 and 120. The conventional valve train system is installed in a two wheeler vehicle. The engine of the two wheeler vehicle has capacity of 110 cubic centimeter displacement volume and the valve train system 100 of the present disclosure is installed in another two wheeler vehicle which has the engine capacity of 110 cubic centimeter displacement volume. Figure 5 shows that the curve A has more frictional power (hp) at a predetermined engine speed (RPM) and curve B has less frictional power (hp) at a predetermined engine speed (RPM) .

Figure 6 illustrates a graphical representation of Torque (Nm) v/s Engine (RPM), wherein curve C represents the curve generated by use of conventional valve train without use of roller and curve D represents the curve generated by use of the valve train system 100 of the present disclosure with primary roller 116 and the auxiliary rollers 118 and 120. The conventional valve train system is installed in a two wheeler. The engine of the two wheeler has capacity of 110 cubic centimeter displacement volume and the valve train system 100 of the present disclosure is installed in another two wheeler which has the engine capacity of 110 cubic centimeter displacement volume. Figure 6 shows that the curve C has less Torque (Nm) at a predetermined engine speed (RPM), curve D has more Torque (Nm) at a predetermined engine speed (RPM) .
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The valve train system of the present disclosure described herein above has several technical advantages including but not limited to the realization of:
? a valve train system for reducing the frictional losses in the valve train system;
? a valve train system that has comparatively more life; and
? a valve train system with spherical rolling contacts that improves the fuel efficiency of the engine.