TECHNICAL FIELD

The subject mailer described herein, in general, relates to a drive train of a vehicle and, in particular, relates to an axle assembly of a vehicle.

BACKGROUND

Heavy vehicles, particularly four-wheel drive tractors, are preferred where high traction is required like for haulage over steep slope or during a wet land operation. Four-wheel drive tractors have the advantage of providing high traction by utilizing the overall weight of the tractor. They possess the ability to ascend an upward slope and uneven surfaces with ease, l-or the purpose, the axle assembly of a four-wheel drive tractor is assembled in such a way that it allows the axle to move in a vertical direction, thus allowing the tractor lo move over uneven surfaces without turning over, the degree of vertical movement of the axle is known as articulation angle, which is limited to a predetermined value during the assembling of the axle.

In conventional tractors, the axle articulation angle is set at 8.5 degrees, which is very low. and thus the ability of the tractors to move over uneven surfaces is restricted. For a tractor working in adverse conditions, it is desirable to have a higher articulation angle than what is usually assigned. However, the load acting on the front axle assembly during such conditions is also severe, and therefore an increase in the articulation angle may cause damage to the front axle assembly or even lead to the failure of the front axle assembly.

SUMMARY
The subject matter described herein is directed towards an axle assembly of a vehicle. According to one embodiment, the axle assembly of the present subject matter is a front axle of 'a tractor. The axle assembly includes an axle housing, a drive head assembly, and a pair of wheel end assemblies, the axle housing is provided with a pair of stoppers to limit an articulation angle of the axle assembly of the tractor hereinafter referred to as an axle articulation angle. The stoppers are formed such that the stoppers have a surface contact with slots provided on a frame part of the tractor. for example, at a front engine support bracket, when the tractor travels over an irregular surface, For the purpose, the frame part of the tractor is provided with slots for securing the stoppers.

In said embodiment, the stoppers arc formed such that the stoppers define higher axle articulation angles, for example of up to 11 degrees, on each side and remain in surface contact with the face of the slots on the frame part of the tractor during maximum tilting of the axle assembly. Further, the sections of the axle housing at various positions are sized in such a manner that the strength of the axle housing is enhanced thereby increasing the load bearing capacity of the axle housing.

These and other features, aspects, and advantages of the present subject matter will better understood with reference; to the following description and appended claims, This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

The above and other features, aspects, and advantages of the subject matter will become better understood with regard to the following description, appended claims, and accompanying drawings where:

Fig. la illustrates a perspective view of an axle assembly connected to a frame part of a vehicle.

Fig, lb illustrates another perspective view of the axle assembly.

Fig. 2 illustrates an exploded view of an axle housing of the axle assembly.

Fig. 3 illustrates a magnified view of the axle assembly pivoted to the frame part of the vehicle.

Fig. 4a illustrates a schematic representation of the axle housing in accordance with one embodiment of the present subject matter.

Fig. 4b depicts a cross-sectional view of the axle housing along an axis AA.

Fig. 4c depicts a cross-sectional view of the axle housing along an axis BIJ.

Fig. 4d depicts a cross-sectional view of the axle housing along an axis CC.

Fig. 5 illustrates an exploded view of a drive head assembly of the axle assembly in accordance with one embodiment of the present subject matter.

Fig, 6 illustrates a sectional view of a wheel-end assembly of the axle assembly in accordance with one embodiment of the present subject matter,

DETAILED DESCRIPTION

The subject matter described herein is directed to an axle assembly for a vehicle. According to one embodiment of the present subject matter, the axle assembly is a front axle of a tractor. the axle assembly as described herein includes an axle housing, a drive head assembly, and a pair of wheel-end assemblies.

The drive head assembly is mounted on one side of the axle housing to align with a propeller shaft of the tractor. The propeller shaft transmits torque from the engine to the drive head assembly, which in turn provides a torque multiplication and passes on the resultant to the pair of wheel-end assemblies through a pair of drive shafts. The two wheel-end assemblies are provided to support a left and a right front wheel of the tractor, respectively. 1 he wheel-end assemblies work in tandem with the drive head assembly to transfer the torque to the left and the right front wheel, thus providing a rotational motion to the wheels.

The axle assembly further includes a pair of stoppers to limit an articulation angle of the axle assembly of the tractor hereinafter referred to as an axle articulation angle. For a safe and efficient working of the tractor on an uneven surface, the axle articulation angle is set to a fixed maximum possible value at the time of assembling of the axle assembly, The maximum possible value of articulation angle is selected based on various factors, such as the load-bearing capacity of the axle, load-bearing capacity of the stoppers, and the limit beyond which the tractor, if allowed to tilt, would topple over, The stoppers govern this maximum limit of the axle articulation angle during operation on an uneven surface. In one embodiment, the stoppers come in contact with a front engine support bracket of the tractor when the maximum possible value of the articulation angle is reached. This prevents the axle assembly from moving further up and prevents the tractor from turning over. For the purpose, the frame part is provided with a pair of slots such that the stoppers can rest at a surface of the slots when the maximum articulation angle is reached,

Fig.1a illustrates a perspective view of an axle assembly 100 connected to a frame part 102 of a vehicle. For example, and by no way limiting the scope of the subject matter, the axle assembly 100 pertains to a front axle of a four wheel drive tractor (not shown in Fig, 1). In one embodiment, the frame part 102 is a front engine support bracket Fixed to a chassis of the tractor. The axle assembly 100 is pivoted to the frame part 102 through a pivoting member 104, which is located substantially at The center of the axle assembly 100, and is capable of tilting relative to the frame part 102.

Fig. 1b illustrates another perspective view of the axle assembly 100 of the tractor in accordance with one embodiment o{ the present subject matter. In said embodiment, the axle assembly 100 includes an axle housing 106, a drive head assembly 108, and a pair of wheel end assemblies 110-1 and 110-2. The axle assembly 100 gets drive from a propeller shaft (not shown in Figs, la and lb) connected to a power output divider (POD) assembly (not shown in Figs, la and lb). I he POD assembly includes multiple gears and a mechanism to control engagement and disengagement of the axle assembly 100. The axle housing 106 is the basic structural member on which various other assemblies can be mounted,

Further. the drive head assembly 108 is mounted on one side of the axle housing 106 to align with the propeller shaft. The propeller shaft provides a torque to drive the drive head assembly 108. The drive head assembly 108 multiplies the received torque and provides the multiplied torque to the wheel end assemblies 110-l and 110-2 through a pair of drive shafts (not shown m the Figs, la and lb). The wheel end assemblies 110-1 and 110-2 are provided to support a left and a right front wheel (not shown in Figs, la and lb) of the tractor, respectively. The wheel end assemblies 110-1 and 110-2 work in tandem with the drive head assembly 108 to transfer the torque to the wheels, thus providing them with the required rotational motion.

The axle assembly 100 further includes a pair of stoppers 112-1 and 112-2 mounted on lop of the axle housing 106 to limit the axle articulation angle of the tractor. The axle articulation angle is the degree of freedom to which the axle can move in a vertical direction. Hence, the extent of the vertical movement of the axle assembly 100 is. in a way. limited by the stoppers 112-1 and 112-2,

It will be understood by a person skilled in the art that the invention as described herein With reference to a front axle assembly may also be applied to rear or intermediate axles of a vehicle with similar effectiveness. Such application is contemplated within the scope of the present invention. The description is provided with reference to a front axle for clarity.

Fig. 2 illustrates an exploded view of the axle assembly 100 of the tractor, The axle housing 106 houses a pair of drive shafts 200-1 and 200-2, hereinafter collectively referred to as drive shafts 200, a pair of tie rods 202-1 and 202-2, and a steering cylinder 204 for steering the wheel end assemblies ll0-I and 110-2 of the tractor. The drive shafts 200 are connected on either side of the drive head assembly 108. 'The drive shafts 200 are further connected to the wheel-end assemblies 110-1 and 110-2, thus connecting the wheel end assemblies lI0-l and 110-2 to the drive head assembly 108. In one implementation, the drive head assembly 108 uses a castle nut for preloading the pinion bearings and uses a split pin For preventing loosening of the castle nut. This reduces the service cost. The wheel end assemblies 110-1 and 110-2 are also connected to the tie rods 202-1 and 202-2. The tie rods 202-1 and 202-2 are further connected to cither side of the steering cylinder 204 such that the wheel end assemblies 110-1 and 110-2, the tic rods 202-1 and 202-2. and the steering cylinder 204 are interconnected with each other.

Fig. 3 illustrates a magnified view of the axle assembly 100 pivoted onto the frame part 102 of the tractor. The figure depicts a condition when the front left wheel of the tractor passes over a bump or an elevated surface, i.e.. the left front wheel is on a higher level in relation to The right front wheel, in such a case, the axle assembly 100 tilts in a direction to let the left wheel move over the bump without making the right front wheel leave contact with the ground. The maximum degree of the tilt is controlled by the articulation angle of the tractor, which is set to a predetermined maximum value at the time of assembling of the axle assembly 100.

In an implementation of the above embodiment, the maximum degree of articulation angle can be 11 degrees, This maximum limit of the articulation angle allows the tractor lo till at one side without turning over. As said earlier, the stoppers 112-1 and 112-2 are provided to define the limit of the axle articulation angle. The stoppers 112-1 and 112-2 come in contact with the surface of the frame part 102, when the maximum possible value of 'the articulation angle is reached, and thus prevent the axle assembly 100 from moving further up.

In one embodiment, the heights of the top-most ends of both the stoppers 112-1 and 112-2 from an axis 300 of the axle assembly 100 are substantially equal. The topmost ends of the stoppers 112-1, 112-2 of the present subject matter are machined to be tapered so as to enter slots 302-1 and 302-2 of the frame part 102. respectively. The top-most surfaces of the stoppers 112-1 and 112-2 arc further formed such that the surfaces arc able to match with a mating surface of the slots 302-1 and 302-2 in a surface contact position. In one implementation, the top-most surfaces of the stoppers 112 may be tapered to match with mating surfaces of the slots 302.

In normal operating conditions, when the tractor is moving on an even surface, the axle articulation angle is zero degrees, and hence the stoppers 112-1 and 112-2 are not in contact with the frame part 102. During operation, when the tractor travels over a bump or an uneven surface, the surface of the stoppers U2-I and 112-2 comes in contact with the slots 302-1 and 302-2 if the axle tills by an angle equal to the maximum articulation angle. Surface contact of the stoppers 112-1 and 112-2 with the slots 302-1 and 302-2 on the frame part 102 ensures that the effective maximum upward movement of the axle is restricted. In addition, the possibility of damage occurring to the stoppers 112-1 and 112-2 during operation is also substantially minimized. This is because the load gels distributed over the surface of the stopper rather than being concentrated at a contact point or on a contact line. Such a configuration of the stoppers II2-I and 112-2 ensures an optimum axle articulation angle, for example up to 11 degrees.

Fig. 4a illustrates a schematic representation of an axle housing 106 in accordance with one embodiment of the present subject matter. The axle housing 106 is a stationary structure on which various assemblies can be mounted. In one implementation, the axle housing 106 is connected to the wheels of the tractor through the wheel-end assemblies 110-1 and UO-2. 1 he sections of the axle housing 106 at various positions are sliced in such a manner that the strength of the axle housing 106 is enhanced thereby increasing the load bearing capacity of the axle housing 106. As a result, the axle housing is able to bear a predetermined maximum load that is applied on the axle when the axle is at the predetermined maximum articulation angle.

Figs. 4b, 4c. and 4d depict cross sectional views 400, 402. and 404 of the axle housing 106 along axes AA, BB, and CC, respectively as shown in Fig. 4a. The cross sections 400. 402, and 404 having length (L) and a breadth (B) are formed such that the axle housing 106 can carry heavy loads. In an example, the dimensions of the cross sections 400, 402. and 404 of the axle housing 106 can be 130 mm by 105 mm, 135 mm by 98 mm, and 116 mm by 91 mm. respectively. In such a ease, the inertia of the cross section at the maximum stress locations is improved by 14 to 42% in comparison with conventional axle assemblies. Thus, the axle assembly 100 can be configured to resist severe loads acting upon it. such as due to an increase in the axle articulation angle. In addition, the axle housing 106 ably supports the stoppers 112-1 and 112-2 when the axle reaches the maximum possible articulation angle value, where the stoppers 112-1 and 112-2 come in surface contact with the frame part 102. At this instance, despite the load on the stoppers being the maximum, the cross sections provide a strong base for the stoppers 112-1 and 112-2. Ii will be understood that the axle cross section with similar load bearing capacity can be suitably designed using other methods known in the art. Additionally, the modified axle assembly can transfer greater power than conventional axle assemblies. For example, in one implementation, the axle assembly can transfer power in the range of 45 lo 55 hp.

Fig. 5 illustrates an exploded view of the drive head assembly 108 of the axle assembly 100 in accordance with one embodiment of the present subject matter. The drive head assembly 108 is provided on one side of the axle assembly 100 so that the drive head assembly 108 aligns with the propeller shaft (not shown in Fig. 5) and gets driven by the same. The drive head assembly 108 of the present subject matter includes a differential casing 500, which is a stationary member, and houses a crown wheel 502 and a pair of differential carriers 504-1 and 504-2, collectively referred to as differential carriers 504. The pair of differential carriers 504 forms a housing to accommodate thrust washers 506-1 and 506-2, differential gears 508-1 and 508-2. collectively referred to as differential gears 508. differential pinions 510-1. 510-2, 510-3, and 5J0-4. collectively referred lo as differentia! pinions 510. and the cross pins 512-1 and 512-2. A two 'piece construction of the cross pins 512-1 and 512-2 enables the usage of available steel bars that can be machined by turning operation, rather than manufacturing a single piece integral cross pin component using forging operation. This further reduces the cost of the drive head assembly.

When the vehicle moves on a straight path, the propeller shaft drives the wheels through the crown wheel 502. the differential gears 508, and the drive shafts 200. When a wheel experiences resistance relative to another wheel, differential action commences as drive is transmitted to the drive shafts 200 through the crown wheel 502. the differential gears 508, and the differential pinions 510. The differential action thus helps in keeping the wheels of the tractor in motion.

Further, the crown wheel 502 is fastened to a flange of the differential carriers 504. A pair of ring nuts 514-1 and 514-2, collectively referred lo as 514, can be used to adjust the position of the crown wheel 502 and other components to achieve any specified backlash and gear tooth contact pattern, 'the ring nuts 514 arc provided on either side of the drive head assembly 108 so that preloading of bearings 516-1 and 516-2 can be done in a fast and effective manner. I his enables easy assembly of the drive head assembly 108 as compared to conventional drive head assemblies that use a shim on one side and a ring locking nut on the other, since the use of the shim reduces serviceability and increases production time. The bearings 516-1 and 516-2 provide a friction free rotational movement to the drive shafts 200. In one embodiment, the crown wheel 502, the differential gears 508, and the differential pinions 510 can be spiral bevel gears.

Fig. 6 illustrates a sectional view of the wheel end assembly 110-1 in accordance with one embodiment of the present subject matter. The wheel end assembly 110-1 includes a swivel housing 600. a wheel hub 602. a planetary assembly 604, and the driveshaft 200-1 having two yoke shafts 606-1 and 606-2. The swivel housing 600 connects the axle housing 202 with the wheel hub 602 of the (racier. The swivel housing 600 facilitates steering of (he wheels as it provides a swinging motion required for the wheels while turning. The swivel housing 600 can swing up to. for example, 52 degrees on each side. The yoke shafts 606-1 and 606-2, collectively referred to as 606. are connected by a double cardon joint 608. The double cardon joint 608 includes two universal joints 610-1 and 610-2, which are induction hardened for enhanced strength and wear resistance.

The yoke shaft 606-1 provides motion to the wheel hub 602 through the planetary gear assembly 604. The yoke shaft 606-1 is connected to a sun gear 612 of the planetary gear assembly 604 and provides motion to the sun gear 612, The sun gear 612 in turn rotates planetary gears 614-1 and 614-2 fastened to the wheel hub 602. The annular ring gear 616 of the planetary gear assembly 604 is a fixed element and is connected to the swivel housing 600. In one empodiment the annular ring gear 616 is made integral with the swivel housing 600. This, thus, reduces the number of components in the cross section of the wheel end assembly 110-1, thereby reducing the cost and production time,

Further, a pair of taper roller bearings 618-1 and 618-2 is provided in the wheel hub 602 to bear the load acting on the wheel hub 602, In addition, a thrust washer 620 is provided at an end of the drive shaft 200-1. The thrust washer 620 controls the float of the drive shaft 200-1. thereby maintaining the center position of the double cardon joint 608.

While certain features of the claimed subject matter have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the claimed subject matter.

We Claim:

1. An axle assembly (100) for a vehicle, said axle assembly (100) comprising:

an axle housing (106) pivoted to a frame part (102) of said vehicle; and a pair of stoppers (112-1 and 112-2) provided on said axle housing (106): characterized in that,

said pair of stoppers (112-1 and 112-2) are tapered such that said frame part (102) and said pair of stoppers (112-1 and 112-2) are in surface contact when said axle assembly (100) is at a predetermined maximum articulation angle.

2. The axle assembly (100) as claimed in claim 2. wherein said pair of stoppers (112-1 and 112-2) enter a pair of slots (302-1 and 302-2) provided in said frame part (102).

3. The axle assembly (100) as claimed in claim 1. wherein said articulation angle is II degrees.

4. The axle assembly (100) as claimed in claim 1. wherein a cross section of said axle housing (106) is formed such that said axle housing (106) sustains a predetermined maximum load applied when said axle assembly (100) is at said predetermined maximum articulation angle.

5. A vehicle comprising:

a frame part (102) attached to a chassis of said vehicle;

an axle assembly (100) pivoted to said frame part (102), wherein said axle assembly (100) comprises an axle housing (106): and

at least two stoppers (112-1 and 112-2) provided on said axle housing (106); characterized in that,

said frame part (102) and said stoppers (112-1 and 112-2) are in surface contact when said axle assembly (100) is at a predetermined maximum articulation angle.

6. The vehicle as claimed in claim 5, wherein said stoppers (112-1 and 112-2) are tapered such that said Frame part (102) and said pair of stoppers (112-1 and 112-2) have a surface contact.

7. The vehicle as claimed in claim 5. wherein said frame part (102) comprises at least two slots (302-1 and 302-2).

8. The vehicle as claimed m claim 7. wherein said stoppers (112-1 and 112-2) enter said slots (302-1 and 302-2).

9. The vehicle as claimed in claim 5, wherein said vehicle is a tractor,

10. The vehicle as claimed claim 5, wherein said articulation angle is ] 1 degrees.