DESC:Field of the invention
The present invention relates to devices for reduction of noise, vibration and harshness (NVH) levels of the engines and more particularly to a mechanism for reduction of NVH levels of the IC engines.
Background of the invention
Automobile driving systems include internal combustion (IC) engines that are generally divided into categories such as two stroke, four stroke and six stroke and the like. IC engines are also categorized on the basis of fuels such as diesel, petrol, CNG and the like. The powertrain of the IC engines comprises a piston cylinder that is connected to a crank shaft by a piston rod. A flywheel is attached to one end of the crankshaft. The powertrain comprises stationary and transmission components. The transmission components of the powertrain rotate in the same direction which results into rotating inertia. The rotating inertia gets accelerated during compression stage of IC engines. However, the stationary structure of the powertrain produces vibrations in opposition to said inertial torque. These vibrations may be passed to the vehicle chassis that results into unnecessarily increased noise, vibration and harshness levels (NVH levels, hereinafter). Moreover, meeting the NVH level targets in a vehicle with a three cylinder engine is a very challenging task.
The most common way to reduce NVH levels in the engines is by use of a balancer shaft.
For example, the Chinese patent no. CN203822940 U discloses the balancer shaft for an engine. The balancer shaft is fastened to the engine body by connecting members such as bolts and baffles. The balancer shaft is used for balancing inertial forces in order to reduce vibration and noise levels. In addition, it additionally creates a challenge wherein little or no change in crank train parameters are allowed for reducing the mount vibrations if the engine is carry over. A user may appreciate a device that reduces vibrations without changing much of the crank train design thereby additionally reducing unbalanced forces/moments at the CG location.
Accordingly, there is a need of a balancing weight mechanism for engines that reduces NVH levels in the power train as a result of opposite forces to rotation inertia without adding frictional losses or cost.
Summary of the invention
The present invention provides a power train having a crank shaft, a plurality of pistons, a plurality of cylinders, a piston rod and a flywheel, the power train positioned with a weight balancing mechanism. The weight balancing mechanism of the present invention is adapted to reduce noise, vibration and harshness levels in the engines. The weight balancing mechanism comprises a first balancing weight and a second balancing weight that are attached at predefined positions on the power train. The first and second balancing weights respectively have a predefined weight. The predefined weight of the first and second balancing weights is preferably 1 kg. However, it is understood that the first and second balancing weights can be tuned for the different ranges of refinement and cost.
The first and second balancing weights are selectively attached at predefined locations on the crankshaft of a three cylinder diesel engine. The first balancing weight is positioned at a first distance from a center of the cylinder. The second balancing weight positioned at a second distance from the center of the cylinder. The first and second balancing weights suspend at a third distance from a center of the crankshaft.
In an embodiment, the first balancing weight may be optionally connected to a Torsional Vibration Damper attached to the crankshaft. The second balancing weight is optionally connected to a crankshaft pulley attached to the crankshaft. In second embodiment, the first balancing weight is optionally connected to a clutch assembly attached to the crankshaft, and the second balancing weight is connected to the Front of the Crankshaft.
The weight balancing mechanism of the present invention eliminates the need of additional balancer shaft from the powertrain. The balancing weights reduce frictional losses by eliminating use of balancing shafts or other fastening components from the powertrain. The balancing weights compensate for inherent unbalanced moments for three cylinder engine. The balancing weights reduce the moment or unbalanced forces by at least 20% to 30 %.
Brief Description of the drawings
FIG. 1 is a perspective view of a powertrain mounted with a balancing weight mechanism constructed in accordance with the present invention;
FIG. 2 is a schematic representation of the balancing weight mechanism of the present invention;
FIG. 3A is a perspective view of an embodiment of the balancing weight mechanism attached to a crankshaft pulley and TVD of the powertrain;
FIG. 3B is a cross sectional side view showing the balancing weight mechanism of FIG. 3A;
FIG. 4A is a perspective view showing an embodiment of the balancing weight mechanism attached to a front of crankshaft and a clutch assembly of the powertrain;
FIG. 4B is a cross sectional side view showing the balancing weight mechanism of FIG. 4A;
FIG. 5A is a perspective view showing an embodiment of the balancing weight mechanism attached to crankshaft and a flywheel assembly of the powertrain;
FIG. 5B is a cross sectional side view showing the balancing weight mechanism of FIG. 5A; and
FIG. 6 is a graphical representation showing changes in moment after application of the balancing weight mechanism.
Detailed Description of the invention
Although specific terms are used in the following description for sake of clarity, these terms are intended to refer only to particular structure of the invention selected for illustration in the drawings, and are not intended to define or limit the scope of the invention.
The present invention discloses a mechanism for balancing unbalanced inertia forces thereby attaching balancing weights at predefined locations in the powertrain which results into reduction of vibration, noise and harshness levels in the diesel engines. The mechanism of the present invention is adapted preferably for diesel engines, however may be optionally used with petrol and CNC engines in other alternative embodiments of the present invention.
Referring to FIG. 1, a power train 100 in accordance with the present invention is shown. The power train 100 includes a crank shaft 102, a plurality of pistons, a plurality of cylinders, a piston rod and a flywheel 103. The power train 100 includes a balancing weight mechanism having a plurality of balancing weights 104, 106. In this one embodiment, the balancing weights 104, 106 are attached at predefined positions on the power train 100. Each of the balancing weights 104, 106 has a predefined weight. Preferably, the predefined weight is 1 kg in accordance with the present invention. However, it is understood that the number and weight of the balancing weights may vary per intended application of the power train 100 in other alternative embodiments of the present invention. The balancing weights 104, 106 reduce vibration and noise levels in the diesel engines thereby balancing unbalanced inertial forces in the cylinders.
Referring to FIG. 2, a schematic arrangement 200 for a three cylinder diesel engine is shown wherein a balancing weight mechanism is attached at predefined locations on a crankshaft of the powertrain thereby maintaining predefined distances therein. The three cylinder diesel engine comprises a first cylinder 1, a second cylinder 2 and a third cylinder 3. In this one embodiment, the balancing weight mechanism includes a first balancing weight 204 and a second balancing weight 202. The first balancing weight 204 is attached at a first location 208 as illustrated. The second balancing weight 202 is attached at a second location 206 as illustrated. The first balancing weight 204 is attached at a first distance “a” from a center of the first cylinder 1 as illustrated. The second balancing weight 202 is attached at a second distance “b” from the center of the first cylinder 1 as shown. The first and second balancing weights 204, 202 suspend at a third distance “c” from central axis of the crankshaft as shown. In this one embodiment, the first distance “a” is about 135 mm. The second distance “b” is about 283 mm. The third distance “c” is about 100 mm.
Referring to FIGS. 3A and 3B, a power train 300 is shown that includes a crankshaft 302. The crankshaft 302 has a first end that is attached to a tuned vibration, preferably Torsional Vibration Damper (TVD, hereinafter) 305. The crankshaft 302 has a second end that is attached to a crank shaft pulley 303. The power train 300 includes a balancing weight mechanism that is attached at predefined locations as illustrated. In this one embodiment, the balancing weight mechanism includes a first balancing weight 304 and a second balancing weight 306. The first balancing weight 306 is attached to the TVD 305 as illustrated. The second balancing weight 306 is attached to the crankshaft pulley 303 as illustrated.
Referring to FIGS. 4A and 4B, a powertrain 400 is shown that includes a crankshaft 402. The crankshaft 402 has a first end that is attached to a clutch assembly 403. The crankshaft 402 has a second end 405.The power train 400 includes a balancing weight mechanism that is attached at predefined locations as illustrated. In this one embodiment, the balancing weight mechanism includes a first balancing weight 404 and a second balancing weight 406. The first balancing weight 404 is attached to the clutch assembly 403 at a predefined position as shown. The second balancing weight 406 is attached to the second end 405 at a predefined position as illustrated.
Referring to FIGS. 5A and 5B, a power train 500 is shown that includes a crankshaft 502. The crankshaft 502 has a first end that is attached to a flywheel 503. The crankshaft 502 has a second end 505. The power train 500 includes a balancing weight mechanism that is attached at predefined locations as illustrated. In this one embodiment, the balancing weight mechanism includes a first balancing weight 504 and a second balancing weight 506.The first balancing weight 504 is attached to a predefined location on the flywheel 503. The second balancing weight 506 is attached to the second end 505 at a predefined location as illustrated.
Referring to FIGS. 1-5B, in operation, reciprocation of the piston generates first order inertia forces. The force exerted by the first order inertia forces on the crankshaft set vibrations which may be passed to the chassis of the vehicle and create unnecessary noises. In order to balance these first order inertia forces, the crankshaft whose phase is 120° is to be rotated at a constant speed. The unbalanced inertia forces are balanced by attaching balancing weights at predefined positions which may vary according to the need. The resultant forces ?F=0 and moment of inertia forces ?M?0 are derived from the first principle for the IC engines.
As shown in FIG. 6, a graphical representation of reduction forces (moment forces) as a result of application of balancing weights at predefined locations on the power train assembly is shown. In said graph, speed of the engine in RPM is plotted on X axis and moment in Nmm is plotted on Y axis. The graphical representation shows moment of Z axis, X axis and Y axis by continuous lines of black, blue and red color at increasing speed of IC engines in RPM. The graphical representation shows reduced moments of Z axis and X axis respectively shown by dotted lines of black and blue color at said speed of IC engine. The graphical representation shows that application of balancing weights to the powertrain at various positions, as shown in FIG. 2, results in the reduction in moments by around 20% to 30% that eventually leads to reduction of vibrations, noise and harshness (NVH) levels of the IC engines.
Referring again to FIGS. 1-6, the balancing weight mechanism 100 of the present invention reduces NVH levels in the IC engines thereby adopting existing powertrains with least changes in design thereof. The balancing weight mechanism of the present invention is configured to be advantageously applied to the new powertrains. The balancing weight mechanism of the present invention eliminates use of additional balancer shaft in the powertrains. The balancing weight mechanism of the present invention advantageously reduces frictional losses by eliminating use of balancing shafts or other fastening components.
The balancing weight mechanism of the present invention automatically compensates for inherent unbalanced moments for three cylinder engine. The balancing weight mechanism of the present invention advantageously improves fuel economy of the vehicle. The balancing weight mechanism of the present invention advantageously makes the size of the engine compact. The balancing weight mechanism of the present invention advantageously reduces unbalanced forces or moment forces by 20 % to 30 %.
The embodiments of the invention shown and discussed herein are merely illustrative of modes of application of the present invention. Reference to details in this discussion is not intended to limit the scope of the claims to these details, or to the figures used to illustrate the invention.
,CLAIMS:
1. A power train having a crank shaft, a plurality of pistons, a plurality of cylinders, a piston rod and a flywheel, the power train mounted with a weight balancing mechanism for reducing noise, vibration and harshness levels in the engines,
characterized in that, the weight balancing mechanism comprising:
a first balancing weight and a second balancing weight attached at locations on the crankshaft, the first balancing weight positioned at a first distance from a center of the cylinder, the second balancing weight positioned at a second distance from the center of the cylinder, the first and second balancing weights suspending at a third distance from a center of the crankshaft.
2. The power train as claimed in claim 1, wherein the first and second balancing weights respectively have a predefined weight of 1 kg that can be tuned for the different ranges of refinement and cost.
3. The power train as claimed in claim 1, wherein the first distance is 135 mm.
4. The power train as claimed in claim 1, wherein the second distance is 283 mm.
5. The power train as claimed in claim 1, wherein the third distance is 100 mm.
6. The power train as claimed in claim 1, wherein the first balancing weight is connected to the crankshaft through a torsional vibration damper.
7. The power train as claimed in claim 1, wherein the second balancing weight is connected to the crankshaft through a crankshaft pulley.
8. The power train as claimed in claim 1, wherein the second balancing weight is connected to the crankshaft through a clutch assembly.
9. The power train as claimed in claim 1, wherein the second balancing weight is connected to the crankshaft through a flywheel assembly.
10. The power train as claimed in claim 1, wherein the first balancing weight is connected to the front of crankshaft assembly.
11. The power train as claimed in claim 1, wherein the balancing weights reduce the moment or unbalanced forces in the engines by at least 20% to 30 %.