FORM 2
THE PATENT ACT, 1970,
(39 OF 1970)
&
THE PATENTS RULE, 2003
Complete Specification
"BALANCER SHAFT FOR INTERNAL COMBUSTION COMMON RAIL
ENGINE"


Mahindra & Mahindra Limited An Indian Company, R&D Center, Automotive Sector, 89, M.I.D.C., Satpur, Nashik-422 007, Maharashtra, India.

The following specification particularly describes the invention and the manner in which it is to be performed


FILED OF INVENTION:
The present invention is related to balancer shaft in internal combustion engine. More particularly the present invention is related to balancer shaft used in internal combustion common rail engine for balancing the reciprocating unbalanced mass of an engine and for driving fuel injection pump.
BACKGROUND OF THE PRESENT INVENTION:
Generally in internal combustion engine of an automotive vehicle a balancer shaft is used to balance the reciprocating unbalance mass. To drive the fuel injection pump separate drives are used. For automotive applications, in two cylinder internal combustion common rail diesel engine, multifold requirement from the different components such as functional requirement, technical requirement, rigidity and compactness are necessary in order to make the system less complex.
Patent No. US6405702 and European patent No. EP1136721 describes the balancer shaft that has a drive member that is interposed in the timing drive and a torsional vibration damper that is interposed between this drive member and the balancer masses on the balancer shaft to avoid transmission of crankshaft vibrations to the balancer shaft without affecting the valve timing. Balancer shaft has at least offset balance masses formed thereon and is also formed with integral bearings mounted directly on opposite sides of each of the balance masses. Above said arrangement have been provided for improving smoothness in engine operation by having a balancer shaft that is driven from the crank shaft and a pair of counter weights provided to balance certain vibration forces of the engine. This prior art teaches only balancing of unbalance mass.
PCT application No. WO 2005093286 discloses balancer shaft for a multi-cylinder engine. The invention relates to a balancer shaft, for a multi-cylinder in-line engine, comprising at least two balance weight sections and at least one bearing point, whereby the balance weight sections are symmetrically-arranged
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with relation to the bearing point and at least one of the balance weight sections is connected to a further shaft section at an end away from the bearing point. According to the invention, a flexible coupling element is provided between the end of the at least one balance weight section, away from the bearing point and the further shaft section, which permits a deflection of the end of the connected balance weight section in the direction of the resultant centrifugal forces on a rotation of the balancer shaft.
Japanese Patent application No. JP 2001012224 describes balancer device for an IC engine to reduce a friction loss from a collision of lubricating oil with a weight member by smoothing discharge of lubricating oil. Housing consists of housing upper and a housing lower and a pair of shaft housing chambers are formed independently each other inside of the housing. A balancer shaft having a weight member with a semicircular section is housed in each shaft housing chamber. The inner circumference surface of a first weight housing surrounding the weight member does not have a true circular form but has a form close to an involute curve so that a clearance from the outer circumference surface of the weight member increase gradually along the rotation direction of the balancer shaft. An oil discharging port is opened in tangential direction at a bottom step where the clearance becomes the maximum. A smaller diameter side portion above the step forms a thin partition wall to smoothly divide lubricating oil flow.
None of the prior art concepts on balancer shaft talk about provision of cam lobe to drive the fuel injection pump. Also none of the prior art concepts describe the provision of reinforcement rib on the balancer shaft to protect the balancer shaft from deflection due to torsional vibrations.
OBJECTIVES OF THE PRESENT INVENTION:
The main object of the present invention is to provide a novel balancer shaft for two cylinder internal combustion common rail diesel engine with masses thereon to balance the vibrations.
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Further object of the present invention is to provide a novel balancer shaft with a reinforcement rib at the center to avoid deflection of the shaft.
Another object of the present invention is to provide a novel balancer shaft with a cam lobe thereon at its one end.
Another object of the present invention is to provide a novel balancer shaft for two cylinder internal combustion common rail diesel engine to drive fuel injection pump.
Still another object of the present invention is to provide a novel balancer shaft which is simple in construction and cost effective.
STATEMENT OF INVENTION:
A balancer shaft for internal combustion common rail engine comprising of a shaft having cylindrical shape with flattened portion, integrated with at least two mass balances to dampen the torsional vibrations; at least a reinforcement rib opposite to the said mass balances to protect the shaft from deflection; and at least an integrated cam lobe provided at front end to drive the fuel injection pump.
According to another embodiment the invention provides a balancer shaft assembly for internal combustion common rail engine comprises the balancer shaft , having semi cylindrical shape with flattened portion, integrated with at least two mass balances to dampen the torsional vibrations; at least a reinforcement rib opposite to the said mass balances to protect the shaft from deflection; and at least an integrated cam lobe provided at front end to drive the fuel injection pump, mounted on the crankcase parallel to the crank shaft at distant with the extreme ends of said shaft supported in the two bearing housings on which the roller bearings are completely pressed in; and the said balancer shaft parallel to the crank shaft but not in the same horizontal plane, coupled to a spur gear with 1:1 ratio in the front end which is driven directly by the crankshaft in such a way that no vibration of the engine resulted.
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DESCRIPTION OF THE FIGURES:
Further objectives and advantages of the present invention will become apparent from the following description and claims taken in conjunction with the accompanying drawings wherein,
Figure 1 shows the balancer shaft with integrated masses and cam lobe thereon in accordance with the present invention,
Figure 2 shows the balancer shaft with its fitment components in accordance with the present invention.
Figure 3 shows the balancer shaft fitted in mesh with the crank shaft of an engine.
DESCRIPTION OF THE PRESENT INVENTION:
Referring to figure 1, balancer shaft assembly (11) comprises of a shaft (12), mass balances (13), reinforcement rib (5) and cam lobe (16). The shaft (12) is semi-cylindrical in shape with two integrated semi-cylindrical counter weights (13) with its edges flattened (14) to take care of unbalanced primary inertia forces. A conic profiled reinforcement rib (5) is provided on the flat side of the shaft (12) to avoid the deflection of the shaft (12) due to torsional vibrations at high speeds. The provision of conic profiled rib (5) eliminates the need for one more support bearing at the center. An integrated cam lobe (16) is provided on the shaft (12) at the front end closer to the extreme end support. A cam lobe (16) drives a fuel injection pump and its placement closer to the front end support avoid bending and torsional deflection of the shaft (12).
Referring to figure 2, a balancer shaft (12) is supported on two cylindrical roller bearings (4 & 6) which are lubricated by oil mist. The roller bearings (4 & 6) are positioned at two extreme ends of the shaft (12) having very low friction compared to the conventional journal bearings lubricated by pressurized oil supply. The provision of two roller bearings (4 & 6) at two extreme ends of the
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shaft (12) reduces the friction and overall weight of the balancer shaft assembly (11).
The balancer shaft (12) is mounted on the crankcase with the help of two bearing housings {3 & 7) on which the roller bearings (4 & 6) are completely pressed in. The balancer shaft (12) is coupled to a spur gear (2) in the front end which is driven directly by the crankshaft as shown in figure 3. It rotates in the opposite direction of the crankshaft with the drive ratio 1:1. The balancer shaft is parallel to the crank shaft but not in the same horizontal plane. The horizontal planes of balancer shaft and crank shaft are away from each other by 46.5 mm and the balancer shaft is adjusted with reference to the crank shaft before coupling to the crank shaft by spur gear with 1:1 ratio such that the vibration of engine is reduced to zero.
The engine provided with balancer shaft is run on diesel or petrol or gasoline or LPG and like fuels.
It should be understood that the present invention is not to be limited by the exact details of the illustrated embodiment. However, it is to be taken as the preferred example of the invention and that various changes may be resorted to by a person skilled in the art without departing from the spirit of the invention or the scope of below mentioned claims. Also, the terminologies used herein are for the purpose of description and should not be regarded as limiting.
ADVANTAGES OF THE PRESENT INVENTION:
• Low friction and low cost.
• Reduction in weight of balancer shaft assembly due to elimination of central support.
• No additional oil gallery is required for the mass balancer bearings, thus elimination of complex oil galleries.
• Ease of assembly and dismantling.
• Compact packing of the mass balancer assembly.
• Feasibility of replacing complete mass balancer system in case of failure, reduced repair cost.
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Claim:
1. A balancer shaft (11) for internal combustion common rail engine comprising of a shaft (12), having cylindrical shape with flattened portion, integrated with at least two mass balances (13) to dampen the torsional vibrations; at least a reinforcement rib (5) opposite to the said mass balances to protect the shaft from deflection; and at least an integrated cam lobe (16) provided at front end to drive the fuel injection pump.
2. A balancer shaft for internal combustion common rail engine as claimed in claim 1 wherein, the said shaft (12) is semi-cylindrical in shape with a flatten edge, and the said reinforcement rib is a having conical profile provided on the flat side of the said shaft (12) to avoid the deflection due to torsional vibrations at high speeds.
3. A balancer shaft for internal combustion common rail engine as claimed in claim 2 wherein, the said cam lobe (16) on the shaft (12) is at the front end closer to an extreme end support,
4. A balancer shaft assembly for internal combustion common rail engine comprises the balancer shaft (12), having semi cylindrical shape with flattened portion, integrated with at least two mass balances (13) to dampen the torsional vibrations; at least a reinforcement rib (5) opposite to the said mass balances to protect the shaft from deflection; and at least an integrated cam lobe (16) provided at front end to drive the fuel injection pump, mounted on the crankcase parallel to the crank shaft at distant with the extreme ends of said shaft supported in the two bearing housings (3 & 7) on which the roller bearings (4 & 6) are completely pressed in; and the said balancer shaft (12), the plane of balancer shaft adjusted with reference to the plane of crank shaft , coupled to a spur gear (2) with 1:1 ratio in the front end which is driven directly by the crankshaft in such a way that no vibration of the engine resulted.
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5. An internal combustion common rail engine fitted with the balancer shaft as claimed in claims 1 to 4.
6. The internal combustion common rail engine fitted with the balancer shaft as claimed in claim 5 wherein, said the engine is run on diesel or petrol or gasoline or LPG and like fuels.
7. A balancer shaft assembly for internal combustion common rail engine substantially as herein described with reference to accompanying drawings.
Dated this 1st Day of July, 2009

M.S.Khadilkar (Agent for the applicant)