Description:FIELD OF THE INVENTION
[001] The present invention relates to a vehicle. More specifically, it relates to an endless transmission assembly for a vehicle.

BACKGROUND OF THE INVENTION
[002] An endless transmission assembly, also referred as a drive chain assembly, is an integral part of a vehicle. Typically, the endless transmission assembly being configured to transmit power from a power mover to one or more wheels. A conventional endless transmission assembly primarily includes one or more sprockets and a drive chain. The drive chain includes interconnected parts such as pins, bushes, plates, and rollers, which are conventionally composed of steel as base material. These parts engage with the sprocket, wherein the sprocket being attached to the power source. More specifically, the power generated by the power source is transmitted through the drive chain, thereby causing the wheels to rotate and propel the vehicle.
[003] It is observed that the drive chain assembly is exposed to environmental elements like dirt, mud or water. The ingression of mud or water can affect the durability of the chain. Therefore, designers tend to cover a portion of the sprocket and chain to reduce the exposure to abovementioned environmental factors. In addition to the above, the prolonged use of vehicle leads to more wear and tear, friction, tension, which can further lead to chain degradation, reduced efficiency, unwanted noise. This requires frequent maintenance and replacement. However, to address the abovementioned problems, OEMs tend to recommend using various lubricants which necessitate chain adjustments at predetermined intervals. Owing to the complex nature of the job involved, lubricating and tensioning requires a rider to frequently visit workshops, thereby resulting in loss of free time and an increased cost of operating the vehicle.
[004] One of the most widely used methods for lubricating involves applying grease to the drive chain. The effectiveness of grease is mostly impaired by exposure to dirt, thereby resulting in an increased wear. This, in turn, requires lubricating the drive chain at even more frequent intervals.
[005] Hard carbide layer coating on the pin and bush of the drive chain followed by another coating of a diamond like carbon material, an amorphous carbon material, has also been suggested in the state-of-the-art. However, this results in an increased surface roughness of the drive chain or parts thereof, which in turn results in increased noise and vibration, and might require more frequent maintenance. Further, due to the limited lubrication of assembly components (only bush and pin), the overall efficiency is likely to be reduced.
[006] The use of carbon material, particularly 100% amorphous carbon material alone, as a lubricant is also of concern. Due to the increased operating temperature of the drive chain assembly owing to its vicinity to the power source, the amorphous carbon material is likely to deteriorate and form an aqueous layer. This requires replacing the lubricant at frequent intervals and hence, increasing the cost of maintenance and loss of free time.
[007] To summarize, the challenges associated with the existing state-of-the-art include, such as but not limited to, increased friction in the drive chain components resulting in high energy consumption and power loss, increased noise and vibration, exposure to corrosion due to environmental moisture and contaminants, loss of free time, and increased likelihood of accidents and injuries due to machinery failure.
[008] Thus, there is a need in the art for a drive chain assembly which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION
[009] In one aspect, the present invention is directed to a drive chain assembly. The drive chain assembly comprises at least one sprocket and a drive chain wound on at least one sprocket. The drive chain comprises a plurality of inner plates, a plurality of outer plates, a plurality of bushes, a plurality of pins and a plurality of rollers. Each of the bushes are disposed between a pair of the inner plates. Each of the pins are inserted inside each of the bushes and disposed between a pair of the outer plates thereby connecting each of the outer plates with the inner plate. Each of the rollers are disposed on each of the bushes. The drive chain is at least partially coated with a carbon material having a crystalline phase and a non-crystalline phase in a ratio ranging between 40:60 to 60:40.
[010] In an embodiment of the invention, the coating has a thickness ranging between 4.0 µm to 7.0 µm.
[011] In another embodiment of the invention, the the coating has a surface roughness range: Ra from 0.15 µm to 0.40 µm, and Rz from 1.20 µm to 3.50 µm.
[012] In another aspect, the present invention is directed to a process for manufacturing the above drive chain assembly. The process includes coating the drive chain at least partially with the carbon material.
[013] In an embodiment of the invention, the coating is carried out on one or more of: the plurality of inner plates, the plurality of outer plates, the plurality of bushes, the plurality of pins, and the roller.
[014] In another embodiment of the invention, maximum elongation in length of the drive chain is less than 2.5%, determined in accordance with chain measurement rig method.
[015] In yet another aspect, the present invention is directed to a process for lubricating the above drive chain assembly. The process includes coating the drive chain at least partially with the carbon material.

BRIEF DESCRIPTION OF THE DRAWINGS
[016] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figures 1A and 1B illustrate a top view and a side view, respectively, of an endless transmission assembly having a drive chain in accordance with an embodiment of the present invention.
Figure 2 illustrates a segment of the top view of the drive chain illustrated in Figure 1A in accordance with an embodiment of the present invention.
Figure 3 shows an exploded view of the drive chain illustrated in Figure 2 in accordance with an embodiment of the present invention.
Figure 4 shows a graphical representation comparing a predetermined service-related parameter of the endless transmission assembly with conventional assemblies in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
[017] Various features and embodiments of the present invention here will be discernible from the following further description thereof, set out hereunder. In the ensuing exemplary embodiments, the vehicle is a two wheeled vehicle. However, it is contemplated that the disclosure in the present invention may be applied to any automobile capable of accommodating the present subject matter without defeating the spirit of the present invention.
[018] In one aspect, the present invention relates to a drive chain assembly.
[019] In an embodiment, the drive chain assembly may be interchangeably also referred to as an endless transmission assembly.
[020] The drive chain assembly 100 comprises at least one sprocket (not shown in Figures) and a drive chain 110. The drive chain 110 is wound on the at least one sprocket. In an embodiment, the drive chain assembly 100 is fitted in a vehicle.
[021] As is known to a person skilled in the art, the sprocket is designed to engage and transmit motive force from one component to another in the vehicle. The sprocket embodies a circular or polygonal disc-like structure, distinguished by a series of precisely engineered, evenly spaced, and toothed projections or teeth, extending radially from its perimeter. These teeth are strategically profiled to intermesh with corresponding links or elements of the drive chain 110, thereby wounding on the sprocket. Moreover, the sprockets may be positioned at various locations, including an input end and an output end of the drive chain 110. For instance, the input end of the drive chain 110 may be connected to a power unit of the vehicle, whereas the output end of the drive chain 110 may be connected to a rear wheel of the vehicle.
[022] As shown in Figures 1A-1B, and 2, the drive chain 110 comprises a plurality of inner plates 120, a plurality of outer plates 130, a plurality of bushes 122, a plurality of pins 132, and a plurality of rollers 140.
[023] A segment of the drive chain 110 is shown in Figure 3. A continuous connection of multiple segments to a desired chain length forms the drive chain 110.
[024] In every segment of the drive chain 110, each of the bushes 122 are disposed between the pair of inner plates 120. Further, each of the pins 132 are inserted inside each of the bushes 122 and disposed between the pair of outer plates 130. Thereby, each of the outer plate 130 gets connected with the inner plate 120. In this regard, Figure 1B shows the side view of the drive chain assembly 100, particularly showing the plurality of the outer plates 130 and the plurality of inner plates 120 connected with each other in the drive chain 110. Furthermore, each of the rollers 140 are disposed on each of the bushes 122.
[025] The person skilled in the art is aware of suitable techniques for combining multiple segments, as shown in Figure 3, to the desired chain length for obtaining the drive chain 110.
[026] In an embodiment, the drive chain 110 having multiple segments, as described above, is at least partially coated with a carbon material. The present invention carbon material has a mix of a crystalline phase as well as a non-crystalline phase (or amorphous phase), thereby providing a duplex form of the carbon material having characteristics from both the phases. Herein, the term "phase" as applied to the carbon material signifies a distinctive state or condition within the carbon material, characterized by the arrangement and organization of the constituent carbon atoms.
[027] The duplex form imparts a mix of characteristics from both the phases. The crystalline phase being generally hard, contributes to wear resistance properties, thereby maintaining the longevity of the coating. The non-crystalline or amorphous phase being a soft structure helps in improving the lubrication property due to its inherent nature of solid lubrication as well as reduces the coefficient of friction.
[028] In an embodiment, the crystalline phase and the non-crystalline phase in the carbon material is in a ratio ranging between 40:60 to 60:40. In another embodiment, the crystalline phase and the non-crystalline phase is in the ratio 50:50. Said otherwise, the carbon material contains both the crystalline phase and the non-crystalline phase in equal ratios.
[029] In another embodiment, the carbon material is coated onto the drive chain 110. Particularly, the coating is carried out on one or more of: the plurality of inner plates 120, the plurality of outer plates 130, the plurality of bushes 122, the plurality of pins 132, and the plurality of rollers 140. Unlike the existing drive chains wherein the coating is carried out on the pins and/or the bushes alone and a majority of the components of the drive chain are left uncoated, the present invention requires, in an embodiment, that all the aforementioned components of the drive chain 110 are at least partially coated with the carbon material. In another embodiment, the drive chain 110 is fully coated with the carbon material, thereby resulting in each of the aforementioned components of the drive chain 110 being covered with the carbon material, as described above.
[030] Although, suitable methods for coating in general are known to the person skilled in the art. In an embodiment, the drive chain 110 is coated with the carbon material, as described above, using vapor deposition technique. Vapor deposition techniques are classified as physical vapor deposition (PVD) and chemical vapor deposition (CVD).
[031] PVD represents a specialized coating technique employed for the application of thin films or coatings (of the carbon material) upon solid substrates, such as the components of the drive chain 110. PVD encompasses a range of methodologies wherein a source material, typically in solid form (such as a target or cathode), undergoes a phase transition into a vaporized state within a controlled vacuum environment. The process commences with the generation of a high-energy plasma or vapor phase, facilitated by methods such as resistive heating, electron beam evaporation, or sputtering. In PVD, the vaporized material is propelled toward the substrate surface, where it condenses and adheres, thereby forming a thin, adherent layer with properties determined by the material source, deposition parameters, and substrate characteristics. PVD processes encompass various subcategories, including but not limited to sputter deposition, evaporation deposition, and cathodic arc deposition. These methods permit precise control over coating properties, facilitating advancements in material performance, corrosion resistance, wear resistance, and aesthetics across a spectrum of industrial domains.
[032] CVD involves the chemical reaction of gaseous precursor compounds within a controlled environment to yield a condensed solid-phase coating material (the carbon material) on the substrate surface, such as the components of the drive chain 110. In CVD, precursor compounds are introduced into a reaction chamber at controlled pressures and temperatures. These precursors react either thermally or chemically, yielding the desired coating material. Deposition parameters, including temperature, pressure, gas flow rates, and precursor composition, are meticulously regulated to achieve precise control over the coating's properties, such as thickness, composition, microstructure, and uniformity. CVD encompasses variations such as chemical vapor deposition, atomic layer deposition (ALD), and plasma-enhanced chemical vapor deposition (PECVD), each tailored to specific requirements and material systems.
[033] In an embodiment, arc physical vapor deposition or arc PVD method is employed for coating the drive chain 110. As known to the person skilled in the art, arc PVD involves creating a high-energy plasma by initiating an electric arc between a cathode (target material) and an anode within a vacuum chamber. Several parameters can be controlled and adjusted during arc PVD to tailor the properties of the deposited coatings. Such parameters include, but are not limited to, choice of target material, arc current and voltage, gas atmosphere, deposition rate, target to substrate distance, pulse frequency, and the likes.
[034] In an embodiment, the coating on the drive chain 110, as described above, has a thickness ranging between 4.0 µm to 7.0 µm. It has been observed that the thickness beyond the prescribed range results in the sprocket being chipped out as well as the cost of the coating increasing substantially. Moreover, owing to the size constraints in the sprocket, particularly the tooth, the thickness beyond the prescribed range has not been found to be suitable for long term performance of the drive chain assembly 100. Furthermore, the prescribed thickness range of the coating results in durable and improved adhesion properties between the drive chain 110 and the sprocket.
[035] In another embodiment, the coating has a surface roughness range: Ra from 0.15 µm to 0.40 µm, and Rz from 1.20 µm to 3.50 µm. Herein ‘Ra’ or average roughness is a measure of average deviation of surface heights from a reference plane (measured in microns). In fact, Ra provides a single numerical value that characterizes the roughness on the components of the drive chain 110. Lower Ra values indicate smoother surfaces, while higher values suggest rougher surfaces.
[036] Furthermore, ‘Rz’ or average maximum height measures the average of five highest peaks and five deepest valleys within a specified sampling length along the surface profile. It represents the average of these maximum and minimum deviations from the reference plane. Smaller Rz values indicate surfaces with less variation in height, while larger values indicate more significant variations or roughness.
[037] In an embodiment, both Ra and Rz values are determined using suitable surface profilometers. For instance, an optical profiler may be used for determining both Ra and Rz values.
[038] Coating of the drive chain 110 with the carbon material, as described above, results in acceptable performance of the drive chain assembly 100 in accordance with various industry standards. In comparison to regular greases, which require coating of the drive chain at frequent intervals, say 2000 kms of driving the vehicle, the carbon material coated drive chain 110 results in acceptable or even improved lubrication with reduced maintenance and frequency, thereby resulting in increased availability of free time of a rider. In fact, the drive chain 110 coated with the carbon material does not require replenishment of the coating at frequent intervals and is only applied once.
[039] In another aspect, the present invention relates to a process for lubricating the above drive chain assembly 100.
[040] In an embodiment, the drive chain assembly 100 is at least partially coated the carbon material, as described above. Accordingly, the embodiments pertaining to the drive chain assembly 100, as described above, are applicable here as well.
[041] Advantageously, the coating of the drive chain 110 with the duplex form of the carbon material results in improved lubrication in the drive chain assembly 100. Moreover, coating all the components of the drive chain 110 results in reduced noise generation due to liquid phase characteristic of the non-crystalline phase, and reduced wear due to crystalline phase. Further, the durability in terms of the maintenance requirement of the drive chain assembly 100 is also improved over grease due to enhanced adhesion of the carbon material on the drive chain 110. Hence, the vehicle can be driven considerably more in comparison to grease. Also the life of the drive chain 100 has been found to be enhanced due to the carbon material coating.
[042] Furthermore, maximum elongation in length of the drive chain 110 coated with the carbon material, as described above, is less than 2.5% as determined in accordance with chain measurement rig method. Coating the drive chain 110 with the carbon material further results in reduced power losses due to friction and wear and tear of the components of the drive chain 110, reduced noise and vibration in the components, reduced exposure to corrosion due to environmental moisture and contaminants, availability of more free time as the rider does not requires to make frequent visits to workshops, and reduced likelihood of accidents and injuries due to machinery failure.
EXAMPLES
[043] The following experimental examples are illustrative of the invention but not limitative of the scope thereof:
[044] Several drive chain assemblies were coated with different lubricants, such as grease (refer Comp. Ex. 1-2), and compared with the carbon material (refer Inv. Ex. 1) having crystalline phase and non-crystalline phase in the ratio 50:50.
[045] For chain measurement rig method, tensile load was applied on the drive chain ends till the time of failure. Subsequently, the chain was tested at a rig where the chain slackness was measured at a point located at the centre of drive and driven sprockets, i.e., the input end and the output end of the drive chain. The rig was subjected to mud, water, and dust with the help of simulation studies. The temperature of the drive chain was maintained between 35?C to 45?C for the measurement.
[046] Table 1: Comparative and Inventive examples
Examples Kilometers No. of services required Permissible elongation limit Whether chains within limit
Comp. 1 0 to 25016 13 2.50% Yes
Comp. 2 0 to 24531 12 2.50% Yes
Inv. 1 0 to 20116 0 2.50% Yes

[047] It is evident from the above shared table; the conventional drive chains require frequent greasing. The drive chain when lubricated with grease (refer Comp. 2) and driven up to 24531 kms, required a total number of 12 services to maintain the permissible elongation in the drive chain. Another sample lubricated with grease (refer Comp 1) and driven up to 25016 kms, required a total number of 13 services to maintain the permissible elongation in the drive chain. Both the samples required frequent replenishment with grease coating on the drive chain. In fact, the drive chain was coated with fresh grease after approx. every 2000 kms. Certainly, this results in increased service cost and maintenance time for the rider.
[048] As shown in Figure 4 and Table 1 above, the drive chain coated with the carbon material in accordance with the present invention did not require any service and/or replenishment of the coating even after driving the vehicle up to 20116 kms. Further, the elongation of length of the drive chain remained within the permissible limits of 2.5%.
[049] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.
, Claims:1. A drive chain assembly (100), the drive chain assembly (100) comprising:
at least one sprocket;
a drive chain (110) wound on the at least one sprocket, the drive chain (110) comprising:
a plurality of inner plates (120);
a plurality of outer plates (130);
a plurality of bushes (122), each of the bushes (122) being disposed between a pair of the inner plates (120);
a plurality of pins (132), each of the pins (132) being inserted inside each of the bushes (122) and disposed between a pair of the outer plates (130) thereby connecting each of the outer plate (130) with the inner plate (120); and
a plurality of rollers (140), each of the rollers (140) being disposed on each of the bushes (122);
wherein the drive chain (110) being at least partially coated with a carbon material having a crystalline phase and a non-crystalline phase in a ratio ranging between 40:60 to 60:40.

2. The assembly as claimed in claim 1, wherein the coating has a thickness ranging between 4.0 µm to 7.0 µm.

3. The assembly as claimed in claim 1, wherein the coating has a surface roughness range: Ra from 0.15 µm to 0.40 µm, and Rz from 1.20 µm to 3.50 µm.

4. A process for manufacturing the drive chain assembly (100) as claimed in claims 1 to 3, the process comprising: coating the drive chain (110) at least partially with the carbon material.

5. The process as claimed in claim 4, wherein the coating is carried out on one or more of: the plurality of inner plates (120), the plurality of outer plates (130), the plurality of bushes (122), the plurality of pins (132), and the roller (140).

6. The process as claimed in claim 4 or 5, wherein maximum elongation in length of the drive chain (110) is less than 2.5%, determined in accordance with chain measurement rig method.

7. A process for lubricating the drive chain assembly (100) as claimed in claims 1 to 3 or as obtained from the process as claimed in claims 4 to 6, said process comprising coating the drive chain (110) at least partially with the carbon material.