DESC:FIELD
The present disclosure relates to the field of mechanical engineering. More specifically, the present disclosure relates to the field of a valve train system.
BACKGROUND
A valve train is an assembly of components which controls the operation of valves, particularly, intake and exhaust valves of an internal combustion (i.c) engine. In an internal combustion engine, the intake valve controls the ingress of air and fuel mixture into the combustion chamber and the exhaust valve controls expulsion of combustion gases from the combustion chamber for facilitating combustion. The opening and closing of the valves is governed by a valve train system in which components thereof arranged in sequence transmits motion to a valve stem to facilitate actuation of the intake and exhaust valves. The valves are usually of the poppet type and are actuated by the valve train system. The poppet valves typically require small coil springs, to keep them closed when not actuated by the camshaft of the valve train system.
The valve train system controls the amount of air and fuel mixture entering the combustion chamber at any given point in time. Particularly, the conventional valve train system includes valves, rocker arm, and camshaft(s). The camshaft receives driving power from the crankshaft and rotates, more specifically, the camshaft is synchronized to the crankshaft by a chain, belt, or gear. The cams located on the camshaft rotate with the rotating camshaft and interact with one end of the rocker arm to cause swiveling of the rocker arm about a pivot. The other end of the rocker arm in turn actuates a valve stem connected to the valve via a tappet, thereby establishing a sliding contact between the tappet and the valve stem for causing actuation of valve.
As the price of crude oil is soaring high, there is a need for modern engines that exhibits improved fuel economy and energy efficiency by reducing frictional losses arising at various contacting surfaces. Out of total frictional losses in an engine, 20% of friction losses occur in the valve train system. Accordingly, there is a need for a valve train system that eliminates sliding contact during transmission of actuating forces required for actuation of the intake and exhaust valves and that eliminates other drawbacks associated with sliding contact between interacting elements of the valve train system. Further, there is a need for a valve train system that reduces frictional losses. Further, there is need for a valve train system that reduces wear and tear of the interacting elements of the valve train system and enhances service life of the valve train system. Further, there is a need for the valve train system that reduces service requirements associated therewith and enhances reliability thereof. The valve is maintained in a closed configuration by a small coil spring that urges the valve against the valve seat in order to keep it closed when not actuated by the camshaft of the valve train system. The valves are actuated by the valve train system, particularly, the tappet disposed on the end of the rocker arm in sliding contact with the valve stem so as to transmit the actuating forces. Further, in case of inaccurate valve timing, i.e. if the opening and closing of the intake and exhaust valves is not accurate, the proportion of air and fuel mixture drawn into the combustion chamber and the extent of combustion falls outside the standard operating range, which if continued, might become detrimental to the service life of the engine. Also, the fuel efficiency of the internal combustion engine will be severely compromised. Accordingly, there is a need for a valve train system that ensures accurate valve timing.
Attempts have been made in the past to reduce the friction arising between the contacting surfaces of the rocker arm tappet and the valve stem. A known solution is to provide a convex surface with a specific radius of curvature at the end of the tappet so as to establish a point contact between the contacting surfaces of the tappet and the valve stem. Although this solution to some extent reduces the amount of friction, the structural failures that arises in the course of its functioning makes it an unviable solution especially in case of a valve train system. Another known solution is to provide a drum that rolls freely about an axis on the tappet of the rocker arm. As the axis is fixed, the rolling of the drum is confined to a single plane. During an event of actuation, the tangential force acting on the surface of the drum tends to shift the contacting surface continuously thereby reducing the amount of friction. Further, in case of drum provided at the end of the tappet, there is line contact and more wear.
Taking in to account the frequency of actuation, time available for recovery from strain and the limited degrees of freedom to roll, the contacting surface of the drum is subjected to heavy loads resulting in fatigue and structural failures.
To address the aforementioned drawbacks associated with the prior art, there is a need for an effective solution which reduces the frictional losses in the valve train system.
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 eliminates sliding contact between interacting elements of the valve train system and drawbacks associated with the sliding contact.
Still another object of the present disclosure is to provide a valve train system with a spherical rolling contact for reducing the frictional losses due to sliding friction between tappet and valve head.
Yet another object of the present disclosure is to provide a valve train system with spherical rolling contact 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 for opening and closing a valve of an internal combustion engine of a vehicle. The system includes a pivotal arm and a valve stem. The system also includes a spherical roller interfaced between the pivotal arm and the valve stem to provide point contact during the opening and closing of a valve associated with the valve stem. The system is also provided with a holder for receiving the roller.
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 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 section view of the tappet assembly of valve train system of Figure 1, wherein the roller is held in a holder configured on the tappet assembly;
Figure 3 illustrates an isometric view of the tappet assembly of Figure 2 with the roller held in the holder;
Figure 4 illustrates an exploded view of the tappet assembly of Figure 2;
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 a roller for transmitting actuating forces to the valve stem; 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 roller for transmitting actuating forces to the valve stem.
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 illustrates a valve train system 100 in accordance with an embodiment of the present disclosure. The valve train system 100 opens and closes a valve 145 of an internal combustion engine (not illustrated in Figures) of a vehicle (not illustrated in Figures). The system 100 includes a pivotal arm 130 (also known as rocker arm) and a valve stem 147 connected to the valve 145.
The pivotal arm 130 is actuated by a valve actuating mechanism 120. In accordance with one embodiment, the valve actuating mechanism 120 is a cam assembly that includes a cam 126 mounted on a camshaft 127. The cam has a cam lobe 125. The cam lobe 125 when in contact with one end 130a of the pivotal arm 130 pushes the pivotal arm 130 to open the valve 145. In one embodiment a rolling element 135 is connected to the pivotal arm 130 that is in contact with the valve actuating mechanism 120. The camshaft 127 is connected to the crankshaft (not illustrated in Figures) of the vehicle and is actuated by the crankshaft. Typically, the camshaft 127 is connected to the crankshaft by a chain arrangement or a belt arrangement or a gear arrangement.
The pivotal arm 130 has a second end 130b that has an opening 150 in which a tappet assembly 110 is fitted. Figure 2 illustrates the cross-sectional view of the tappet assembly 110. Figure 3 illustrates a perspective view of the tappet assembly 110. Figure 4 illustrates an exploded view of the tappet assembly 110. The tappet assembly 110 has a holder 106 within which a roller 107 is fitted. In an operative configuration, the roller 107 rotate freely along the three axes within the holder 106 upon application of a tangential force when the roller 107 comes in contact with the valve stem 147. In one embodiment, the roller 107 is spherical in shape. The roller 107 is interfaced between the pivotal arm 130 and the valve stem 147 to provide a point contact during the opening and closing of the valve 145 associated with the valve stem 147. In one embodiment, the tappet assembly 110 includes a second stem 105 to which the holder 106 is fitted at one end.
In accordance with one embodiment, the holder 106 is press-fitted with the second stem 105. In accordance with another embodiment, the holder 106 is threadably fitted with the second stem 105.
As the roller 107 is in rolling contact with the valve stem 147, the drawbacks associated with the sliding contact between a roller (not illustrated in Figures) and a valve stem (not illustrated in Figures) of a conventional valve train mechanism are eliminated.
Further, the provision made inside the tappet assembly 110 allows the roller 107 to rotationally shift its surface offers a multitude of benefits as described hereafter. As there is a continuous shift in the point of contact of the roller 107 after an event of actuation due to the rotary degrees of freedom provided in the tappet assembly 110, the surface of the roller 107 will have sufficient recovery time before the same point of contact again receives the impact. Further, as the roller 107 can rotate about more axis of rotation more surface area is available for bearing collision events when the valve stem 147 contacts the roller 107. As there is a rolling contact, the frictional force generated between the contacting surfaces is also minimal. Therefore, the tappet assembly 110 makes the valve train system 100 more resilient and efficient. The valve train system 100 thus leads to better acceleration, faster pick – up, improvements in fuel economy and a pleasant user experience for the rider.

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 roller 107. 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 A represents the curve generated by use of conventional valve train without use of roller and curve B represents the curve generated by use of the valve train system 100 of the present disclosure with roller 107. 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 A has more Torque (Nm) at a predetermined engine speed (RPM), curve B has less 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 eliminates sliding contact between interacting elements of the valve train system and drawbacks associated with the sliding contact;
? a valve train system with a spherical rolling contact for reducing the frictional losses due to sliding friction between tappet and valve head; and
? a valve train system with spherical rolling contact that improves the fuel efficiency and noise characteristics of the engine. ,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 comprises a spherical roller adapted to rotate freely about an axes in a three dimensional plane, interfaced between the pivotal arm and the valve stem to provide point contact 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 roller .
3) 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.
4) The valve train system as claimed in claim 3, wherein said holder is press-fitted or welded or fastened with said second stem.
5) The valve train system as claimed in claim 3, wherein said holder is threadably fitted with said second stem.