OF A VEHICLE TRANSMISSION SYSTEM”

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and derives the benefit of Indian Provisional Application 202111051621 filed on 10/11/2021, the contents of which are incorporated herein by reference.

FIELD OF INVENTION

[001] The embodiments herein generally relate to transmission system for vehicles such as a tractor or other agricultural or construction vehicle, more particularly to a universal coupling for connecting gear trains in a final drive system of the vehicle transmission system having a variable (or adjustable) wheelbase.

BACKGROUND OF INVENTION

[002] Agricultural vehicles such as tractors and other similar vehicles are primarily used in agricultural field operations. Further, agriculture has a tremendous need for tractors having various characteristics. This need has been met primarily by building a wide variety of tractors, including wheeled and tracked, of various wheelbase, heights and configurations. To achieve this, conventionally there are a number of wheel supporting structures for the vehicles which are adapted for level adjustment. This supporting structure includes a pair of link rods, parallel with each other and different in the length from each other, for the interconnection between a ground wheel and a vehicle body, and a hydraulic power cylinder for adjusting the working position of the parallel linkage, to thereby adjust the vertical position of the ground wheel relative to the vehicle body, thereby permitting the vehicle level to be adjusted. The variable wheelbase is a result of changing of the ground clearance of the agricultural tractor. Change of ground clearance results in shifting of center of gravity (CG) of the tractor. Hence, two variants of vehicle are made viz Low CG and High CG are achieved. The Low CG corresponds to low ground clearance whereas the High CG corresponds to high ground clearance.

[003] Further, various transmission systems having a speed reduction gear-set at each driven wheel of a motor vehicle have been employed for different purposes. For example, a conventional art describes a driveline for a tractor, in which the rear wheels are supported on a U-shaped frame having legs extending rearward. Power developed by an engine is transferred through a differential mechanism located forward of the axle shafts from a differential mechanism through right-hand and left-hand chain drive mechanisms rearward to the vicinity of the driven wheels. The chain drive mechanisms each drive a simple speed reduction gear-set whose output is driveably connected to the corresponding axle shaft. This arrangement of the power flow provides a free space between the legs of the U-shaped frame between the rear wheels so that auxiliary units can be readily coupled to the frame of the tractor.

[004] Currently, speed reduction rotating power devices are generally classified into worm speed reducers and differential planetary gear speed reducers. With a simple structure, a worm speed reducer is easy to manufacture. But it has problems such as friction-induced wearing and heating, low efficiency, and less durability, which limits the scope of its use. A differential planetary speed reducer uses a profile shifted gear of which an amount of addendum modification (or addendum modification coefficient) is adjusted, which causes problems associated with noise, wear, and durability and it is difficult to manufacture the differential planetary speed reducer. Further, providing a simple connection between an input shaft and an output shaft for power flow in the transmission system of the agricultural vehicle with varying wheelbase is a challenging task. [005] Therefore, there exists a need for a universal coupling for connecting gear trains in a final drive system of the vehicle transmission system having a variable (or adjustable) wheelbase, which eliminates the aforementioned drawbacks.

OBJECT OF THE INVENTION

[006] The principal object of an embodiment of this invention is to provide a universal coupling for connecting gear trains in a final drive system of a vehicle transmission system having a variable (or adjustable) wheelbase.

[007] Another object of an embodiment of this invention is to provide the universal coupling which is adapted to avoid misalignment of an output gear shaft with an input gear shaft of a final drive reduction unit.

[008] Yet another object of an embodiment of this invention is to provide the universal coupling which avoids force transfer from a bottom bevel pinion shaft to a top bevel gear shaft, thereby increasing life of top bevel housing and a differential housing.

[009] Still another object of an embodiment of this invention is to provide the universal coupling which aids in necessary positive power transfer without any slippage in a lesser space.

[0010] Yet another object of an embodiment of this invention is to provide the universal coupling which facilitates easy assembly and serviceability of the vehicle transmission system.

[0011] These and other objects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF DRAWINGS

[0012] The embodiments herein are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

[0013] Fig. 1 depicts an exploded view showing a wheel and an engine components of an agricultural vehicle with a low wheel base (i.e. low center of gravity), according to an embodiment of the invention as disclosed herein;

[0014] Fig. 2 depicts another exploded view showing the wheel and the engine components of the agricultural vehicle with high wheel base (i.e. high center of gravity), according to an embodiment of the invention as disclosed herein;

[0015] Fig. 3 depicts exploded view of a final drive reduction unit of an agricultural vehicle, according to embodiments as disclosed herein;

[0016] Fig. 4 depicts a cross sectional view of the final drive reduction unit, according to embodiments as disclosed herein;

[0017] Fig. 5 depicts perspective view of the final drive reduction unit, according to embodiments as disclosed herein; and

[0018] Fig. 6 depicts a superimposed view of final drive reduction unit at lower position of wheelbase and at higher position of wheelbase, according to the embodiments as disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0019] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[0020] The embodiments herein achieve a universal coupling for connecting gear trains in a final drive system of a vehicle transmission system having a variable (or adjustable) wheelbase. Further, the embodiments herein achieve the universal coupling which is adapted to avoid misalignment of an output gear shaft with an input gear shaft of a final drive reduction unit. Furthermore, the embodiments herein achieve the universal coupling which avoids force transfer from a bottom bevel pinion shaft to a top bevel gear shaft, thereby increasing life of top bevel housing and a differential housing. Additionally, the embodiments herein achieve the universal coupling which aids in necessary positive power transfer without any slippage in a lesser space. Moreover, the embodiments herein achieve the universal coupling which facilitates easy assembly and serviceability of the vehicle transmission system. Referring now to the drawings, and more particularly to FIGS. 1 through 6, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.

[0021] Fig. 1 depicts an exploded view showing a wheel and an engine components of an agricultural vehicle with a low wheel base (i.e. low center of gravity), according to an embodiment of the invention as disclosed herein. Fig. 2 depicts another exploded view showing the wheel and the engine components of the agricultural vehicle with high wheel base (i.e. high center of gravity), according to an embodiment of the invention as disclosed herein. For the purpose of this description and ease of understanding, the transmission system (200) is explained herein with below reference to a tractor (agricultural vehicle). However, it is also within the scope of the invention to practice and/or use the transmission system (200) in any other type of vehicles, without otherwise deterring the intended function of the transmission system (200) as can be deduced from the description and corresponding drawings.

[0022] In an embodiment, the transmission system (200) is used in the agricultural vehicle in which the wheelbase can be adjusted in accordance to working conditions. For example, the wheelbase for the agricultural vehicle may be held at a low position (i.e. low wheelbase position or low center of gravity) and a high position (i.e. high wheelbase position or high center of gravity). The transmission system (200) is fabricated such that the transmission system (200) may be used for both the low wheelbase position and the high wheelbase position. The transmission system (200) derives power from a power supply means which is communicated to a brake shaft (i.e. an input shaft) (102) through engine components. Further, the power is transmitted to a rear axle shaft (i.e. an output shaft (104) though a final drive reduction unit (300). The power transmitted to the output shaft (104) through the final drive reduction unit (300) is utilized for driving the wheels of the vehicle.

[0023] Fig. 3 depicts exploded view of a final drive reduction unit of an agricultural vehicle, according to embodiments as disclosed herein. The transmission system (200) includes the final drive reduction unit (300) which is disposed between the input shaft (102) and the output shaft (104). The final drive reduction unit (300) is provided in the transmission system (200) to reduce power flow (or speed) transferred from the power supply means i.e. engine of the vehicle to the wheels of the vehicle. The final drive reduction unit (300) includes a first gear-set (108), a second gear-set (112), and the universal coupling (100).

[0024] Fig. 4 depicts a cross sectional view of the final drive reduction unit, according to embodiments as disclosed herein. The final drive reduction unit (300) includes the first gear-set (108) which is engaged to the input shaft (102) which derives power from the power supply means. In an embodiment, the first gear-set (108) is at least a pair of bevel gears. The first gear-set (108) includes a first bevel pinion (108a) having a first predetermined splines defined therein. The splines on the first bevel pinion (108a) is adapted to mesh with a plurality of splines (102s) defined in the input shaft (102). Further, the first gear-set (108) includes a first bevel gear shaft (108b) which is adapted to engage with the first bevel pinion (108a) at one end. Further, the first bevel gear shaft (108b) is coupled to a joint (114) at other end. The first bevel gear shaft (108b) is engaged transversely with the first bevel pinion (108a) i.e., the first bevel pinion (108a) and the first bevel gear shaft (108b) are located perpendicular to each other. Furthermore, the first bevel gear shaft defines an opening which is adapted to receive a spring dowel pin (118). The first bevel gear shaft (108b) further defines plurality of bottom splines (108sl) which are configured to engage with splines in the joint (114).

[0025] Fig. 5 depicts perspective view of the final drive reduction unit, according to embodiments as disclosed herein. The final drive reduction unit (300) includes the second gear-set (112) which is connected to the output shaft (104) which transmits power to wheels of the vehicle. In an embodiment, the second gear-set (112) is at least a pair of bevel gears. The second gear-set (112) includes a second bevel pinion (112a) having a second predetermined splines defined therein. The splines on the second bevel pinion (112a) is adapted to mesh with a plurality of splines (104s) defined in the output shaft (104). Further, the second gear-set (112) includes a second bevel gear shaft (112b) which is adapted to engage with the second bevel pinion (112a) at one end. Further, the second bevel gear shaft

(112b) is coupled to the joint (114) at other end. The second bevel gear shaft (112b) is engaged transversely with the second bevel pinion (112a) i.e., the second bevel pinion (112a) and the second bevel gear shaft (108b) are located perpendicular to each other. The second bevel gear shaft (112b) further defines plurality of top splines (112s 1) which are configured to engage with the joint (114).

[0026] The final drive reduction unit (300) further includes the universal coupling (100) which is connected between the first gear-set (108) and the second gear-set (112). The universal coupling (100) includes the joint (114) which is fabricated such that a motion of first bevel gear shaft (108b) is transferred to the second bevel gear shaft (108b). Further, the joint (114) includes a first end (114a) adapted to engage with the first bevel gear shaft (108b) and a second end (114b) adapted to engage with the second bevel gear shaft (112b). The joint (114) includes a first yoke member (114a) and a first shaft (114b) extending away from the first yoke member (114a). Further, the joint (114) includes a second yoke member (114c) and a second shaft (114d) extending away from the second yoke member (114c) in a direction opposite to the first shaft (114b). The first end (114f) of the joint (114) includes a first hollow shaft having a plurality of third splines which are adapted to engage with the bottom splines (108s 1) of the first bevel gear shaft (108b) there within. Similarly, the second end (114s) of the joint (114) includes a second hollow shaft having a plurality of fourth splines which are adapted to engage with top splines (112sl) of the second bevel gear shaft (112b) there within. The joint (114) further includes a cross-piece which pivotally connects the first yoke member (114a) with the second yoke member (114c). Furthermore, the first shaft (114b) of the joint (114) defines at least one aperture at a predetermined location. The aperture is defined such that the aperture is aligned with the opening defined in the first bevel gear shaft (108b). The spring dowel pin (118) is configured to be inserted in the aperture and the opening to limit an axial movement between the first shaft (114b) of the joint (114) and the first bevel gear shaft

(108b). The joint (114) is adapted to transfer a predetermined torque from the first gear-set (108) to the second gear-set (112) and thereby transfer a predetermined power from the input shaft (102) to the output shaft (104). Further, the joint (114) is fabricated such that the joint (114) maintains the connection between the first gear-set (108) and the second gear-set (112) in low eg position and at high eg position. Furthermore, the joint (114) is adapted to provide additional rotational movement of a predetermined angle towards the second end (114s) of the joint (114) i.e., the joint (114) facilitates in providing additional freedom to the second yoke member (114c) and a second shaft (114d) about an axis of the joint (114). Also, the joint (114) is fabricated such that any offset between the first shaft (114b) and the second shaft (114d) is compensated (or nullified) by the joint (114).

[0027] Further, the final drive reduction unit (300) includes a first housing (106), a second housing (110) and a third housing (116). The first housing (106) is adapted to receive the input shaft (102) there within at one side i.e. one end of the input shaft (102) is disposed within the first housing (106). Further, the second housing (110) of the final drive reduction unit (300) is disposed parallel and in a spaced relation to the first housing (106). The second housing (110) is adapted to receive the output shaft (104) there within in a direction opposite to the input shaft (102) i.e. one end of the output shaft (104) is disposed within the second housing (110). Furthermore, the final drive reduction unit (300) includes the third housing (116) which is connected between the first housing (106) and the second housing (110). The third housing (116) is configured to cover the joint (114).

[0028] Furthermore, the transmission system (200) includes a spigot guide (120) defined adjacent to said first housing (106). The spigot guide (120) is adapted to facilitate shifting of the final drive reduction unit (300) from a lower wheelbase position (low center of gravity) to a higher wheelbase position (high center of gravity) and vice-versa. [0029] Fig. 6 depicts a superimposed view of final drive reduction unit at lower position of wheelbase and at higher position of wheelbase, according to the embodiments as disclosed herein. The final drive reduction unit (300) along with the output shaft (104) is rotated in one of first direction and second direction about an axis of the input shaft (102) to shift the final drive reduction unit (300) from the lower wheelbase position (low center of gravity) to the higher wheelbase position (high center of gravity) and from the higher wheelbase position to the lower wheelbase position, respectively. The aforementioned spigot guide (120) facilitates in shifting the final drive reduction unit easily.

[0030] The technical advantages achieved by the embodiments disclosed herein includes light weight transmission system, facilitate easy assembly and serviceability, necessary final reduction of tractor in lesser space, and facilitates easy assembly while switching variants from low CG to high CG and vice-versa.

[0031] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.