DESC:TECHNICAL FIELD
[001] The embodiments herein generally relate to power transmission unit in vehicles and more particularly, but not exclusively to self adjusting shift forks in power transmission unit of vehicles.

BACKGROUND
[002] Generally, manual transmission (MT) unit and automated manual transmission (AMT) unit comprises shift forks, which facilitates selection of corresponding gears thereby obtaining various gear ratios which are required for different driving conditions of a vehicle. A conventional power transmission unit includes a gear shift lever, shift rails, shift forks, shift fork rail-end, a shift tower assembly, synchronizer units, gears and other standard components. The shift fork rail-end is connected to the shift fork. The shift fork is mounted to the shift rail and has sliding movement during engagement of a shift tower finger of the shift tower assembly to the shift fork rail-end. In operation, the gear shift lever is pushed or pulled by the driver to move the shift tower finger of the shift tower assembly to engage the shift fork rail-end to move the shift fork to move a synchronizer sleeve thereby moving a synchronizer ring of the synchronizer unit to engage or disengage the corresponding gear. As and when the shift tower finger of the shift tower assembly engages the shift fork rail-end, a shift tower sleeve of the shift tower assembly engages the shift fork rail-end which causes the shift fork to tilt thereby applying force on the synchronizer sleeve which results in increased wear rate of the synchronizer ring and the shift fork. Further, the shift fork is free to move linearly on the shift rail due to the clearance (gap) available between the shift fork rail-end and the shift tower sleeve of the shift tower assembly which causes an error in the shift fork neutral position.
[003] Therefore, there exists a need for a self adjusting shift fork assembly for a power transmission unit of a vehicle, which obviates the aforementioned drawbacks.

OBJECTS

[004] The principal object of an embodiment of this invention is to provide a shift fork assembly for a power transmission unit of a vehicle, which restricts a relative movement between a shift fork rail-end and a shift tower sleeve.
[005] Another object of an embodiment of this invention is to provide a shift fork assembly for a power transmission unit of a vehicle, which facilitates reduced wear rate of synchronizer ring and shift fork.
[006] Yet another object of an embodiment of this invention is to provide a shift fork assembly for a power transmission unit of a vehicle, which facilitates smooth engagement/disengagement of synchronizer ring with/from corresponding gear.
[007] A further object of an embodiment of this invention is to provide a shift fork assembly for a power transmission unit of a vehicle, which facilitates smooth/easier movement of gear shift lever in selector and shift gates during diagonal shifting.
[008] 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
[009] The embodiments of the invention 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:
[0010] FIG. 1 depicts a perspective view of a portion of a power transmission unit of a vehicle, according to an embodiment of the invention as disclosed herein;
[0011] FIG. 2 depicts a perspective view of a shift fork assembly for the power transmission unit, according to an embodiment of the invention as disclosed herein;
[0012] FIG. 3 depicts an exploded view of a portion of the shift fork assembly, according to an embodiment of the invention as disclosed herein; and
[0013] FIG. 4 depicts a perspective view of a shift fork rail-end of the shift fork assembly, according to an embodiment of the invention as disclosed herein.

DETAILED DESCRIPTION
[0014] 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.
[0015] The embodiments herein achieve a shift fork assembly for a power transmission unit of a vehicle, which restricts a relative movement between a shift fork rail-end and a shift tower sleeve. Further, embodiments herein achieve a shift fork assembly for a power transmission unit of a vehicle, which facilitates reduced wear rate of synchronizer ring and shift fork. Referring now to the drawings, and more particularly to FIGS. 1 through 4, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0016] FIG. 1 depicts a perspective view of a portion of a power transmission unit 10 of a vehicle, according to an embodiment of the invention as disclosed herein. In an embodiment, the power transmission unit 10 includes a plurality of shift fork assemblies 100, a shift tower assembly 200, a plurality of shift rails 300, a plurality of synchronizer units (not shown), a plurality of gears (not shown), a gear shift lever (not shown) and may include other standard components as present in standard manual transmission (MT) unit or standard automated manual transmission (AMT) unit. In an embodiment, the power transmission unit 10 is at least one of a manual transmission (MT) unit and an automated manual transmission (AMT) unit.
[0017] In an embodiment, each shift fork assembly 100 includes a shift fork 102 (as shown in fig. 2), a shift fork rail-end 104 (as shown in fig. 2, fig. 3 and fig. 4), a plurality of resilient means 106 (as shown in fig. 3), a plurality of pads 108 (as shown in fig. 2 and fig. 3) and a plurality of locking pins 110 (as shown in fig. 3).
[0018] The shift forks 102 is used to facilitate selection of corresponding gears (not shown) through movement of corresponding synchronizer sleeve S (as shown in fig. 1) thereby obtaining various gear ratios which are required for different driving conditions of the vehicle. Each shift fork 102 is movably connected to each shift rail 300. Each shift fork 102 engages each synchronizer sleeve S.
[0019] Each shift fork rail-end 104 is used to move each shift fork 102 on engagement of a shift tower finger 204 (as shown in fig. 1) of the shift tower assembly 200. Each shift fork rail-end 104 is connected to each shift fork 102. In an embodiment, each shift fork rail-end 104 defines a plurality of resilient member receiving portions 104a (as shown in fig. 4), a plurality of locking pin receiving portions 104b (as shown in fig. 4), a finger receiving portion 104c (as shown in fig. 3) and a plurality of pad seating portions 104d (as shown in fig 3 and fig. 4) . In an embodiment, the plurality of resilient member receiving portions 104a of each shift fork rail-end 104 is adapted to receive corresponding resilient means 106. In an embodiment, the plurality of locking pin receiving portions 104b of each shift fork rail-end 104 is adapted to receive corresponding locking pin 110. The finger receiving portion 104c of each shift fork rail-end 104 is adapted to engage the shift tower finger 204 of the shift tower assembly 200 during corresponding shifted condition of the gear shift lever (not shown). In an embodiment, the plurality of pad seating portion 104d of each shift fork rail-end 104 is adapted to provide seating for corresponding pads 108. Further, for the purpose of this description and ease of understanding, the plurality of resilient member receiving portions 104a is considered to be cavities, the plurality of locking pin receiving portions 104b is considered to be openings and the finger receiving portion 104c is considered to an opening.
[0020] In an embodiment, the plurality of resilient means 106 are adapted to restrict a relative movement between each shift fork rail-end 104 and a shift tower sleeve 202 (as shown in fig. 1) of the shift tower assembly 200 during at least one of an engagement of the shift tower finger 204 with at least one shift fork rail-end 104, and a non-engagement of the shift tower finger 204 with at least one shift fork rail-end 104, where at least one shift fork 102 is in a neutral position. In an embodiment, the plurality of resilient means 106 are disposed inside corresponding resilient member receiving portions 104a of each shift fork rail-end 104. Each resilient means 106 includes a first portion 106a (as shown in fig. 3) and a second portion 106b (as shown in fig. 3). The first portion 106a of each resilient means 106 is adapted to engage a resilient member receiving portion 108d of a first portion 108b (as shown in fig. 3) of each pad 108 i.e., the portion 106a of each resilient means 106 is in direct contact with the first portion 108b of each pad 108. The second portion 106b of each resilient means 106 is adapted to engage corresponding resilient member receiving portions 104a of each shift fork rail-end 104. In an embodiment, each resilient means 106 is at least a spring. It is also within the scope of the invention to provide the each shift fork rail-end 104 with elastomers or any other means to restrict the relative movement between each shift fork rail-end 104 and the shift tower sleeve 202 of the shift tower assembly 200.
[0021] In an embodiment, the plurality of pads 108 are adapted to restrict the relative movement between each shift fork rail-end 104 and the shift tower sleeve 202 of the shift tower assembly 200 during at least one of an engagement of the shift tower finger 204 with at least one shift fork rail-end 104, and a non-engagement of the shift tower finger 204 with at least one shift fork rail-end 104, where at least one shift fork 102 is in the neutral position. Each pad 108 is engaged to corresponding pad seating portion 104d of each shift fork rail-end 104. In an embodiment, each pad 108 includes a plurality of locking pin receiving portions 108a (as shown in fig. 3), a first portion 108b (as shown in fig. 3) and a second portion 108c (as shown in fig. 3). In an embodiment, the plurality of locking pin receiving portions 108a of each pad 108 are adapted to receive corresponding locking pins 110 therethrough thereby engaging each pad 108 to each shift fork rail-end 104. In an embodiment, the plurality of locking pin receiving portions 108a of each pad 108 is at least an oblong hole. However, it is also within the scope of the invention to provide each pad 108 with any other type of openings or slots or holes without otherwise deterring the intended function of the plurality of locking pin receiving portions 108a of each pad 108 as can be deduced from the description. In an embodiment, the first portion108b of each pad 108 is towards each resilient means 106 and substantially away from each shift fork rail-end 104, i.e., the first portion 108b of each pad 108 is not in contact with each shift fork rail-end 104. In an embodiment, first portion 108b of each pad 108 defines a resilient member receiving portion 108d (as shown in fig. 3) adapted to receive the first portion 106a of each resilient means 106. In an embodiment, the second portion 108c of each pad 108 is always in direct contact with the shift tower sleeve 202 of the shift tower assembly 200 i.e., the second portion 108c of each pad 108 is in direct contact with the shift tower sleeve 204 during at least one of an engagement of the shift tower finger 204 with at least one shift fork rail-end 104, and a non-engagement of the shift tower finger 204 with at least one shift fork rail-end 104, where at least one shift fork 102 is in a neutral position. In an embodiment, each pad 108 is made of steel. However, it is also within the scope of the invention to provide each pad 108 to be made of any other material without otherwise deterring the intended function of each pad as can be deduced from the description. The shift tower sleeve S exerts a force on the second portion 108c of at least one pad 108 of each shift fork assembly 100 and the first portion 108b of at least one pad of each shift fork assembly 100 moves corresponding resilient mean 106 to absorb the energy thereby restricting the movement between each shift fork rail-end 104 and the shift tower sleeve, during at least one of an engagement of the shift tower finger 204 with at least one shift fork rail-end 104, and a non-engagement of the shift tower finger 204 with at least one shift fork rail-end 104, where at least one shift fork 102 is in a neutral position.
[0022] In an embodiment, the plurality of locking pins 110 are adapted to engage each pad 108 to each shift fork rail-end 104. The plurality of locking pins 110 are received by corresponding locking pin receiving portions 108a of each pad 108 and the corresponding locking pin receiving portions 104b of each shift fork rail-end 104 thereby engaging each pad 108 to each shift fork rail-end 104.
[0023] The shift tower assembly 200 is controlled by the gear shift lever (not shown) and is used to facilitate shifting and selection of gears (not shown). The shift tower assembly 200 includes a shift tower sleeve 202, a shift tower finger 204 and may include other standard components as present in standard shift tower assembly.
[0024] Each synchronizer unit (not shown) includes a synchronizer sleeve S, at least one synchronizer ring R and may include other standard components as present in standard synchronizer assembly.
[0025] The configuration of shift fork assemblies 100 in the power transmission unit 10 restricts the relative movement between each shift fork rails-end 104 and the shift tower sleeve 202 of the shift tower assembly 200 thereby facilitating smooth engagement/disengagement of synchronizer ring R with/from corresponding gear (not shown). Further, the aforementioned configuration of shift fork assembly 100 in the power transmission unit 10 reduces the wear and tear of each shift fork 102 and each synchronizer ring R thereby increasing the life of each shift fork 102 and each synchronizer ring R and also facilitates smooth/easier movement of gear shift lever in selector and shift gates during diagonal shifting.
[0026] 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 modification within the spirit and scope of the embodiments as described herein.
,CLAIMS:CLAIMS
We claim,
1. A shift fork assembly 100 in a power transmission unit 10 of a vehicle, said shift fork assembly 100 comprising:
at least one resilient means 106;
a shift fork 102;
a shift fork rail-end 104 having at least one resilient member receiving portion 104a adapted to receive said resilient means 106; and
at least one pad 108 connected to said shift fork rail-end 104,
wherein
said resilient means 106 and said pad 108 are adapted to restrict a relative movement between said shift fork rail-end 104 and a shift tower sleeve 202 of a shift tower assembly 200 of the power transmission unit 10 during at least one of an engagement of a shift tower finger 204 of the shift tower assembly 200 with said shift fork rail-end 104, and a non-engagement of shift tower finger 204 with said shift fork rail-end 104, where said shift fork 102 is in a neutral position.
2. The shift fork assembly 100 as claimed in claim 1, further comprising at least one locking pin 110 adapted to engage said pad 108 to said shift fork rail-end 104.
3. The shift fork assembly 100 as claimed in claim 1, wherein said resilient means 106 is at least a spring.
4. A power transmission unit 10 for a vehicle, said power transmission unit 10 comprising:
a shift tower assembly 200 comprising a shift tower sleeve 202 and a shift tower finger 204; and
a plurality of shift fork assemblies 100, each of said shift fork assembly 100 comprising, at least one resilient means 106; a shift fork 102; a shift fork rail-end 104 having at least one resilient member receiving portion 104a adapted to receive said resilient means 106; and at least one pad 108 connected to said shift fork rail-end 104,
wherein
said resilient means 106 and said pad 108 are adapted to restrict a relative movement between each of said shift fork rail-end 104 and the shift tower sleeve 202 of said shift tower assembly 200 during at least one of an engagement of the shift tower finger 204 with said at least one shift fork rail-end 104, and a non-engagement of the shift tower finger 204 with said at least one shift fork rail end 104, where at least one shift fork 102 is in a neutral position.
5. The power transmission unit 10 as claimed in claim 4, wherein said resilient means 106 is at least a spring.