CROSS REFERENCE TO RELATED APPLICATION

This Application is based on and derives the benefit of Indian Provisional Application 202211031700 filed on 2 ^nd June 2022, the contents of which are incorporated herein by reference

TECHNICAL FIELD

[001] The embodiments herein generally relate to drivetrains in vehicles and more particularly, to the drivetrain which can be operated in a reduction drive mode and an overdrive mode in the vehicle such as an agricultural vehicle.

BACKGROUND

[002] Generally, a drivetrain is used to transfer power from a power source (engine/ electric motor) to the wheels of a vehicle. Commonly, the drivetrain of an agricultural vehicle such as a tractor mainly includes a speed transmission unit, a range transmission unit, and a differential unit. The range transmission unit of the tractor’s drivetrain enables an operator to choose between different gear ranges such as a low range and a high range, and in some tractors, a middle range is provided.

[003] Each gear within the range transmission unit offers a specific set of gear ratios and these ratios determine the relationship between the input speed from the engine and the output speed to the wheels. To enable the operator to switch between the gear ranges, a shifting mechanism comprising a lever is provided in the vehicle. To achieve the different gear ranges and speeds, the transmission units in agricultural vehicles require a greater number of gears of overdrive and reduction drive ratios and also require additional components such as shifting sleeves, shifting forks, rails, and levers for selecting the required gear for achieving overdrive and reduction drive mode.

[004] The overdrive mode refers to a gear range in which the gear ratio is higher than 1:1 of direct drive, i.e., the output speed of the transmission is higher than the input speed from the engine. This mode is typically used for achieving higher speeds during transportation or when operating in lighter-duty tasks. Tractors equipped with overdrive gears allow the engine to run at a lower speed while maintaining a higher ground speed. In some types of agricultural vehicles, the overdrive mode is achieved by incorporating an extra gear with more teeth on the input shaft compared to the corresponding gear on the output shaft. When the overdrive gear is engaged, the power from the engine is transmitted through this gear arrangement, resulting in a higher output speed. Alternatively, in some agricultural vehicles, an auxiliary transmission, also known as a splitter or a range multiplier, is incorporated to achieve the overdrive mode. The auxiliary transmission is a separate gearbox that is mounted in line with the main transmission and generally consists of additional gears that provide extra gear ratios, including an overdrive ratio. By engaging the overdrive gear in the auxiliary transmission, the output speed of the main transmission is increased, allowing for higher ground speeds.

[005] The reduction mode refers to a gear range in which the gear ratio is lower than the 1:1 ratio of direct drive. In this mode, the output speed of the transmission is lower than the input speed from the engine. This mode is typically used to increase torque and power output for tasks that require more pulling force. By engaging the reduction gears the torque generated by the engine is multiplied, allowing the vehicle to handle heavy loads, or overcome obstacles more effectively. The reduction ratio is achieved by pairing gears with a smaller number of teeth on the input shaft relative to the output shaft. In some agricultural vehicles, particularly those used in specialized applications, an additional set of creeper gears is incorporated to achieve a lower gear ratio.

[006] The arrangement of gears and shifting components in the drivetrain of the agricultural vehicle for achieving the overdrive mode and reduction mode for different gear ranges consumes more packaging space and incurs high cost as well as increases an overall length of the vehicle resulting in longer wheelbase of the vehicle.

[007] Therefore, there exists a need for a drivetrain for a vehicle, which obviates the aforementioned drawbacks.

OBJECTS

[008] The principal object of embodiments herein is to provide a compact drivetrain for a vehicle, which can be operated in a reduction drive mode and an override drive mode.

[009] Another object of embodiments herein is to provide the drivetrain with six forward speeds and three reverse speeds. [0010] Another object of embodiments herein is to provide an integrated first sliding gear for selecting one of a first speed gear, a second speed gear and a third speed gear thereby eliminating usage of a greater number of shift forks, shifting sleeve and speed gear pairs.

[0011] Another object of embodiments herein is to provide an integrated second sliding gear for selecting a low range gear, a high range gear and a reverse speed gear thereby eliminating usage of a greater number of shift forks, shifting sleeve and gear pairs.

[0012] Another object of embodiments herein is to provide a third speed gear pair in the drive train as reduction ratio for 1 ^st low range, 2 ^nd low range, 1 ^st reverse speed and 2 ^nd reverse speed, and conversely as overdrive ratio in 3 ^rd high range for higher ground speed.

[0013] Another object of embodiments herein is to provide the compact drivetrain which achieves a reduced (shorter) wheelbase of the vehicle.

[0014] These and other objects of embodiments herein will be better appreciated and understood when considered in conjunction with following description and 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

[0015] The embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

[0016] Fig. 1 illustrates a drivetrain operated in an overdrive mode, according to embodiments as disclosed herein;

[0017] Fig. 2 illustrates the drivetrain operated in a reduction drive mode, according to embodiments as disclosed herein.

DETAILED DESCRIPTION [0018] 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.

[0019] The embodiments herein achieve a compact drivetrain for a vehicle. Referring now to Figs. 1 and fig. 2, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.

[0020] Fig. 1 illustrates a drivetrain (10) operated in an overdrive mode, according to embodiments as disclosed herein. In an embodiment, the drivetrain (10) includes a speed input shaft (102), a constant mesh driving gear (104), a constant mesh driven gear (106), a speed countershaft (108), integrated first sliding gear (110, 112, 114), a third speed driving gear (116), a first speed driven gear (118), a second speed driven gear (120), a third speed driven gear (122), a speed output shaft (124), a high range member (125), a range input shaft (126), a low range driving gear (128), a reverse speed driving gear (130), an integrated second sliding gear (132, 134, 136) an a range output shaft (138). For the purpose of this description and ease of understanding, the drivetrain (10) is explained herein with below reference to be provided in an agricultural vehicle such as a tractor. However, it is also within the scope of the invention to use/practice the components of the drivetrain (10) in any other agricultural machines or any other off-road vehicles or any other vehicles without otherwise deterring the intended function of the drivetrain (10) as can be deduced from the description and corresponding drawings.

[0021] The speed input shaft (102) is rotatably supported to a transmission housing (not shown) through a pair of first bearings (101), as shown in fig. 1). The constant mesh driving gear (104) is rotatably mounted onto the speed input shaft (102). The constant mesh driven gear (106) is rotatably mounted onto the speed countershaft (108) and is in constant mesh with the constant mesh driving gear (104). A front end of the speed countershaft (108) is rotatably supported to the transmission housing through a third bearing (105), as shown in fig. 1), and a rear end of the speed countershaft (108) is freely mounted onto a front end of the range input shaft (126) through a first needle roller bearing (not shown). [0022] The integrated first sliding gear (110, 112, 114) is slidably mounted onto the speed countershaft (108). In an embodiment, the integrated first sliding gear (110, 112, 114) includes a first speed driving gear (110), a second speed driving gear (112) and a first shifting member (114). The second speed driving gear (112) is integrated to the first speed driving gear (110). The first shifting member (114) is integrated to the second speed driving gear (112). A first shift fork (not shown) is connected to the first shifting member (114). The integrated first sliding gear (110, 112, 114) is adapted to be moved between one of a first speed gear position or a second speed gear position or a third speed gear position or a neutral position. In the first speed gear position, the first speed driving gear (110) is engaged with the first speed driven gear (118). In the second speed gear position, the second speed driving gear (112) is engaged with the second speed driven gear (120). In the third speed gear position, the first shifting member (114) is engaged with the third speed driving gear (116). For example, the first shifting member (114) defines a plurality of internal splines (not shown) corresponding to plurality of external splines (not shown) on the third speed driving gear (116). In the third speed gear position, the internal splines of the first shifting member (114) are engaged with external splines of the third speed driving gear (116). In the neutral position, the first speed driving gear (110), the second speed driving gear (112) and the first shifting member (114) are dis-engaged from the first speed driven gear (118), the second speed driving gear (112) and the third speed driving gear (116) respectively.

[0023] The third speed driving gear (116) is rotatably mounted onto the range input shaft (126). For example, the third speed driving gear (116) is spline fitted onto the range input shaft (126). The first speed driven gear (118), the second speed driven gear (120), the third speed driven gear (122) and the high range member (125) are defined on the speed output shaft (124). The third speed driven gear (122) is in constant mesh with the third speed driving gear (118). The first speed driven gear (118) and the second speed driven gear (120) are separate parts which are mounted on the speed output shaft (124). The third speed driven gear (122) and the high range member (125) are integral parts of the speed output shaft (124). For the purpose of the description and ease of understanding, the high range member (125) is considered to be external splines defined on the speed output shaft (124). A front end of the speed output shaft (124) is freely mounted to a rear end of the speed input shaft (102), and a rear end of the speed output shaft (124) is rotatably supported to the transmission housing through a second bearing (103), as shown in fig. 1). [0024] The low range driving gear (128) and the reverse speed driving gear (130) are defined on the range input shaft (126). The low range driving gear (128) and the reverse speed driving gear (130) are separate parts which are mounted onto the range input shaft (126). A front end of the range input shaft (126) is rotatably supported to the transmission housing through a fourth bearing (107), as shown in fig. 1), and a rear end of the range input shaft (126) is rotatably supported to the transmission housing through a fifth bearing (109), as shown in fig. 1). A front end of the range output shaft (138) is freely mounted onto the rear end of the speed output shaft (124) through a second needle roller bearing (not shown), and a rear end of the range output shaft (138) is rotatably supported to transmission housing through a sixth bearing (111), as shown in fig. 1).

[0025] The integrated second sliding gear (132, 134, 136) is slidably mounted onto the range output shaft (138). In an embodiment, the integrated second sliding gear (132, 134, 136) includes a low range driven gear (132), a reverse speed driven gear (134) and the second shifting member (136). The reverse speed driven gear (134) is integrated to the low range driven gear (132) at a corresponding side. The second shifting member (136) is integrated to the low range driven gear (132) at a corresponding another side. A second shift fork (not shown) is connected to the second shifting member (136). The drivetrain (10) includes a reverse idler gear (not shown) rotatably connected to the reverse speed driving gear (130). The integrated second sliding gear (132, 134, 136) is adapted to be moved between one of a low range gear position or a high range gear position or a reverse speed gear position or a neutral range position. In the low range gear position, the low range driven gear (132) is engaged with the low range driving gear (128). In the high range gear position, the second shifting member (136) is engaged with the high range member (125). For example, the second shifting member (136) defines a plurality of internal splines (not shown) corresponding to high range member (125, external splines). In the high range position, the internal splines of the second shifting member (136) are engaged with high range member (125, external splines). In the reverse speed gear position, the reverse speed driven gear (134) is engaged with the reverse idler gear (not shown) thereby rotatably connecting reverse speed driving gear (130) with the reverse speed driven gear (134) through the reverse idler gear. In the neutral range position, the low range driven gear (132), the second shifting member (136) and the reverse speed driven gear (134) are disengaged from the low range driving gear (128), the high range member (125) and the reverse idler gear (not shown) respectively. [0026] In an embodiment, the drivetrain (10) is configured to be operated in a reduction drive mode (as shown in fig. 2) in which the integrated first sliding gear (110, 1121, 114) is moved to the first speed gear position, and the integrated second sliding gear (132, 134, 136) is moved to the low range gear position.

[0027] When the drivetrain (10) is operated in the reduction drive mode, the constant mesh driving gear (104) is adapted to drive the speed countershaft (108) through the constant mesh driven gear (106), and the first speed driving gear (110) is adapted to drive the speed output shaft (124) through the first speed driven gear (118), and the third speed driven gear (122) is adapted to drive the range input shaft (126) through the third speed driving gear (116), and the low range driving gear (128) is adapted to drive the range output shaft (138) through the low range driven gear (132).

[0028] In an embodiment, the drivetrain (10) is configured to be operated in an overdrive mode (as shown in fig. 1) in which the integrated first sliding gear (110, 1121, 114) is moved to the third speed gear position, and the integrated second sliding gear (132, 134, 136) is moved to the high range gear position.

[0029] When the drivetrain (10) is operated in overdrive mode, the constant mesh driving gear (104) is adapted to drive the speed countershaft (108) through the constant mesh driven gear (106), and the third speed driving gear (116) is adapted to drive the speed output shaft (124) through the third speed driven gear (112), and the high range member (125) is adapted to drive the range output shaft (138).

[0030] The technical advantages of drivetrain (10) are as follows. The drivetrain is provided with six forward speeds and three reverse speeds. The third speed gear pair is provided in the drive train as reduction ratio for 1 ^st low range, 2 ^nd low range, 1 ^st reverse speed and 2 ^nd reverse speed, and conversely as overdrive ratio in 3 ^rd high range for higher ground speed. The drivetrain is compact and eliminates usage of a greater number of shift forks, shifting sleeve and speed gear pairs.

[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 embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications within the spirit and scope of the embodiments as described herein.