FIELD OF THE INVENTION
The present invention relates in general to a center bearing assembly for supporting rotating shaft, and in particular to an improved rubber housing for center bearing assembly for rotatably supporting an intermediate portion of a vehicle drives line assembly.
BACKGROUND OF THE INVENTION
Housing for centre bearing assembly with solid profiled shape is a known art. Different locking mechanism such as slotted bracket, positive locking by a protruding profile is currently in practice.
In typical rear wheel drive vehicles, the source of power/engine is located towards the front of the vehicle. The engine is connected by means of a drive line to rotate multiple driven wheels, which are located at the rear of the vehicle. The driveline typically extends between the transmission unit connected with the engine and a differential unit connected to the driven wheels via an axle. The main function of the drive line is to transmit power/torque at different rotation speeds compensating the difference in angle of operation. In some vehicles the distance separating the transmission and the differential is relatively short. In these vehicles the driveline is relatively simpler in construction.
In other vehicles, the distance separating the transmission and the differential is relatively long, making the use of a one-piece drive shaft impractical. In these vehicles, the drive line is composed of a drive shaft and one or more coupling shafts. The coupling shafts are connected to the drive shaft (and to each other) by universal joints. The drive shaft is also equipped with sliding mechanism to

adjust the operating length in action to compensate the variation caused due to flexibility of suspension system. Such complex drive shaft assembly needs to be supported intermittently with resilient support structures, typically referred to as center bearing assemblies.
Due to the running load in a vehicle drive shaft, dynamic forces act upon the shaft and on the center bearing support member, when used and tend to transmit vibration and/or noise through the bearing to the vehicle body via the supports. The dynamic force may comprise secondary couple loads which results from transmitting rotary power at an angle, as well as forces resulting from slight unbalance or misalignment of the connected part. These vibrations are best isolated by use of a radially soft mount for supporting the drive shaft center bearing to the vehicle frame.
Besides responding to the excitations produced by the driveline, the support bearing can also be sensitive to other vehicle vibrations. Throughout the low, medium and high speed range of the vehicle, the driveshaft may act as a transmitter. Considering these dynamic loading on the support bearings, the rubber housing is configured such that the bracket shall be isolated from this vibration response of the vehicle.
A typical center bearing assembly includes an annular ball bearing, within which the coupling shaft is rotatably supported. The ball bearing is itself placed within a generally annular resilient support member. The resilient support member is, in turn placed within a generally U-shaped bracket which is secured to the lower surface of a cross member extending between the side rails of the vehicle frame. The resilient support member is provided to reduce vibrations of the drive line in the vicinity of the center bearing assembly and to prevent any such vibrations

from being transmitted to the vehicle frame. Many center bearing assembly structures of this general type using solid rubber are known in the art.
In context of the above, it is evident that the performance of the resilient member plays a crucial role in damping driveline disturbances due to the dynamic forces to a satisfactory level. In addition to this supports the self weight of the driveline assembly and resisting the forces resulting from the maximum applied torque. In real life under dynamic field operating conditions the line of action of forces changes dramatically, resulting complex resultant forces on the center bearing assembly based on application. So this necessitate an improve rubber housing to cater satisfactorily the varying operating conditions.
The use of solid rubber type of design is one of the known arts; shown in figure 1. The main housing is having metal bush inside to which the rotary bearing is fitted (Arrangement shown in figure 2). The stiffness of the solid rubber increases as the dynamic load increase. This will increase the dynamic force on the supporting bracket. Thus the bracket undergoes fatigue load of high amplitude during service. Such solid constructions are having higher natural frequency which is not desirable. Moreover the varying stiffness requirement is also difficult to attain in such design.
However, the known housing can be improved to address the complex loading conditions that occur in the field during application. There is a scope of improvement in life of the product along with performance. There also exists a scope for improvement of frequency response characteristics.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved rubber housing device for center bearing assembly in a vehicle driveline.
Another object of the invention is to propose an improved rubber housing device for center bearing assembly in a vehicle driveline, which reduces dynamic forces from front propeller shaft to housing bracket by efficient damping during transmission.
A still another object of the invention is to propose an improved rubber housing device for center bearing assembly in a vehicle driveline, which increases the dynamic fatigue life of the supporting members.
A further object of the invention is to propose an improved rubber housing device for center bearing assembly in a vehicle driveline, which allows isolating the driveline disturbances by preventing transmission of the disturbances to the super structure and passenger compartment.
SUMMARY OF THE INVENTION
According to the invention, the shape and geometry of the rubber housing is optimized considering the loading conditions in the field application. Slots of calculated dimensions are introduced at different pitch circle diameter, so that the required stiffness in different direction is achieved. Based on requirement a multiple series of slots can be considered. The gap and angle between the slots

are such that compression of one of the slots protruding into the other. The depth of the slot can be same or varying depending on requirement but are controlled. With this configuration, the natural frequency is also lowered. To provide a predominant effect of better cushioning after the initial compression, curved sliced cuts are also introduced at the outer periphery of the rubber housing at the bottom corners. The effect of these cut slices come in working under higher dynamic forces. These maintain the response of the rubber same as lower dynamic forces.
During running of the heavy vehicles, the drive shaft experiences axial play. The majority of such play is compensated by the splined joint in the connected shafts. The front shaft is generally fixed in nature, so that the axial thrusttends to displace the position of the center bearing assembly. So the outer profile of the housing is locked with the metal support by providing positive from lock. (Convex shape in the housing and concave shape in the metal bracket). This ensures an accurate seating in the assembly as well as an effective contact area and proper support ensures vibration isolation. The top bracket helps in positive locking of the assembly.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 :Isometric view showing the prior art housing formed of solid rubber. Figure 2: Isometric view showing the general arrangement of prior art center
bearing assembly. Figure 3:Isometric view showing the rubber housing of the present invention. Figure 4:Isometric view showing the rubber housing of figure 3 in different
orientation. Figure 5: Isometric view showing the bracket for the new housing.

Detail Description of the Preferred Embodiment
General arrangement for fitment of a bracket 1 and a rubber housing 5 is shown in figure 5. A bearing 6 is fitted on a front end piece 3. The bearing 6 is press fitted in a metallic bush 9. The Metallic bush 9 and the rubber housing 5 are bonded with each other. Two oil seals 10 are provided in the metallic bush 9 to prevent the bearing 6 from dust. A coupling flange 2 is put on the front end piece 3 and locked with a nut 4. A dust cover 9 is tack welded to the front end piece 3 as an additional safety measure against dust.
The bearing 6 is press fitted in the metallic bush 9. The Rubber housing 5 is fitted in the bracket 1. A top bracket 1, a clamp 7 is put to compress the rubber in top side. Also, this clamp 7 is bent to rigidly attach with the bracket 1.
As shown in figure 1, the solid rubber housing 10 is used in prior art design. This design has some limitation on vibration damping and has high force transmissibility to the bracket. To overcome these issues, a new rubber is housing 5 is developed according to the invention.
Figure 4 shows the modified rubber design. The Rubber housing 5 has slots at inner side 11, and at outer side 18. There are total eight number of slots in each row. Distance 13 between these slots (11, 18) are decided to get adequate mechanical strength along with vibration damping. Wall thickness 19 between the inner slot 11, and the outer slot 18, defines the damping at high rotational speed. All slots are oblong in shape, having a radius 12, equal to half of the slot thickness 20.

A slot 21 within the outer row slot's 18 has more width as compared to other slots to transfer the force at 45° with proper cushioning. Overlap rubber thickness 17 of the rubber housing is chosen to avoid solidification of rubber at high rotational speed. Solid lump of mass 16 is kept at bottom to support the propeller shaft weight.
The orientation, location and radius of a slice cut 14 work as a cushioning and provide an additional stiffness at higher speed. The Slice cut 14 is placed in between the slots on the outer row 18 at bottom. Wall thickness 22 of the rubber housing in the slice cut 14 is proposed on strength point of view also.
The rubber housing 5 has a convex profile 15 which is fitting on a concave profile 23 of the bracket 1. This arrangement will give the smooth sliding of the rubber housing 5 in the bracket 1, and further ensure the self location of the rubber housing after displacing from its original position.
Two oblong slots 25 are provided in the bracket to fit the total assembly with the propeller shaft on vehicle chassis. The Bracket has an additional rib to increase the fatigue life, and interalia provides smooth variation of section changes.
The improved rubber housing was tested in the laboratory against the prior art solid rubber design for stiffness, strength and endurance with calculated values and it is observed that:
• The stiffness in the axial direction was found to be 20% higher, but the 20-30% lower in the operating direction, which is desirable.
• The strength in both the designs was found satisfactory.

• Up to 40% improves life noted in the resonance testing.
To inhibit the transmitted vibrations produced by the driveline, rubber housing with relatively low natural frequency and spring rates are desired and the improved design is in line to satisfy these requirement.
According to the invention, the rubber housing is improved with addition of suitable slots and cut-out at desired postions, so that the rubber housing can perform under variable loading patterns imposed during the field application. These additional slots and cuts outs also provide better vibration isolation of the bracket from the propeller shaft excitation. The slot geometry varies the damping ratio of the rubber material under loaded conditions, which is desired.
Apart from that an additional effective way of locking is proposed to prevent the axial shift of the housing from the bracket during application.

WE CLAIM :
1. An improved rubber housing for center bearing assembly for rotatably supporting an intermediate portion of a vehicle drives line assembly; the improvement is characterized in that :-
two row of slots configured in the rubber housing are so oriented that
variable stiffness can be achieved;
length and width of the slots and wall thickness between two slots are
constructed for vibration isolation;
overlap distance of the two row slots is selected to maintain cushioning;
a convex profile on the rubber housing and a concave profile in the
bracket provided to control the axial movement of the rubber in a bracket,
which allows flexibility in self alignment of the rubber housing with in said
bracket;
slice cut is oriented at the bottom of the rubber housing to create a gap
between the bracket and the rubber housing;
the slice cuts are oriented between the outer raw of slots at a specified
distance from the bottom to avoid the solidification of rubber; and
depth of this slice cut inside the rubber housing is controlled to maintain
the cushioning effect.

2. An improved rubber housing for center bearing assembly for rotatably supporting an intermediate portion of a vehicle drives line assembly as substantially described and illustrated herein with reference to the accompanying drawings.