TECHNICAL FIELD
Embodiments of the disclosure relate to a gear shift mechanism in automotive vehicles. More particularly, embodiments relate to shifter shaft, dog and fork assembly in transmission.

BACKGROUND OF THE DISCLOSURE AND PRIOR ARTS
In automotive transmission, driver interacts with manual transaxle through gearshift lever. Driver interactions are transferred through gearshift lever / linkage to selector / shifter shaft in transmission. Primary function of selector / shifter shaft is to further transmit interactions of driver to transaxle internal gearshift mechanism (shifter shaft, forks, shifter sleeve and synchronizers) to actually shift or select the particular gear or gate.. Shift finger is connected to the selector / shifter shaft. Further gear shifting occurs in transmission through shift finger which transmit motion / force to gearshift dog. The gearshift dog is mechanically locked to the shifter shaft through a dowel or other means and moves shifter shaft axially. Axial motion of the shifter shaft is transferred to the shifter fork because of the shifter fork is mechanically locked to the shifter shaft. The shifter fork in turn transmits motion to the shifter sleeve which leads to actual gear shifting in transmission.

For five forward and one reverse speed transmission, there are at least three shifter shaft, dog and shifter fork assemblies in the transmission. One for 1st and 2nd gear shifting, second for 3rd and 4th gear shifting and third for 5th and reverse gear. Increase or decrease in number of shifter shaft depends on increase or decrease in number of gear speed available. In conventional transmission system, the shifter shafts are generally supported in the transmission housing.

The conventional mechanism suffer from a drawback that each shifter shaft, dog and fork assembly requires separate space in transmission to get supported on either side. Hence this leads to increase in overall size of the transmission. Thus, increase in size of transmission further impose requirement of increase in transmission oil quantity due to increase volume inside transmission. Due to increase in transmission oil quantity, drag torque of the transmission also increases leading to reduction in transmission efficiency and further increases CO2 emission marginally.

OBJECTS OF THE DISCLOSURE
The object of the present disclosure is to provide co-axial shifter shaft, dog and fork assembly.

The object of the present disclosure is to provide a compact shifter shaft, dog and fork assembly and to assemble to the transmission with ease.

STATEMENT OF THE DISCLOSURE
Accordingly, the present disclosure relates to a shifter shaft assembly for automotive transmission comprising a plurality of shifter shafts placed concentrically one inside the other; plurality of slots disposed on outer and intermediate shafts of said concentric shafts; at least one dog, at least one shifter fork and at least one stopper connected to said outer shifter shaft; at least one dog, at least one shifter fork and at least one stopper connected to each intermediate shafts or inner shifter shaft through the slots on the outer and/or intermediate concentric shafts; the outer shifter shaft is supported on transmission housing through bearings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The novel features and characteristic of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

Figure 1 shows a cross sectional diagram of assembly of shifter shaft and dog in accordance with one embodiment of the present disclosure.
Figure 2 shows a cross sectional diagram of assembly of shifter shaft, dog and shifter fork in accordance with one embodiment of the present disclosure.
Figure 3 shows front view of shifter shaft assembly in accordance with one embodiment of the present disclosure.
Figure 4 shows back view of shifter shaft assembly in accordance with one embodiment of the present disclosure.
Figure 5 shows side view of shifter shaft assembly in accordance with one embodiment of the present disclosure.
Figure 6 shows front view and side view of stopper plate in accordance with one embodiment of the present disclosure.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION
In the following detailed description, reference is made to the accompanying figures, which form a part hereof. In the figures, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, and figures are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

This disclosure is drawn, inter-alia, to a shifter shaft assembly for automotive transmission, a method of shifting gear and a method of assembling.

Referral numerals:
1: 5th/reverse shifter fork
2: 3rd/4th shifter fork
3: 1st/2nd shifter fork
4: 3rd/4th shifter shaft
5: 1st/2nd shifter shaft
6: 5th/reverse shifter shaft
7: 5th/reverse dog
8: 3rd/4th dog
9: 1st/2nd dog
10, 11: Transmission housing
12: Shift finger
13: Slot on 3rd/4th shifter shaft for connecting 1st/2nd dog
14: Slot on 1st/2nd and 3rd/4th shifter shaft for connecting 5th/Reverse dog
15: Slot on 1st/2nd and 3rd/4th shifter shaft for connecting 5th/Reverse fork
16: Slot on 3rd/4th shifter shaft for connecting 1st/2nd fork
17: Stopper on 1st/2nd shifter shaft
18: Stopper on 3rd/4th shifter shaft
19: Stopper on 5th/Reverse shifter shaft
20: Stopper plate mounting bolts
21: Transmission housing
22: Detent ball between stopper plate on 1st/2nd and 3rd/4th shifter shaft
23: Detent ball between stopper plate on 3rd/4th and 5th/Reverse shifter shaft
24: Slot on 1st/2nd and 3rd/4th shifter shaft to connect 5th/Reverse stopper
25: Slot on 3rd/4th shifter shaft to connect 1st/2nd stopper
26: Stopper Plate
27: Bore in stopper plate for detent balls

With reference to Figures 1-6, the present disclosure provides a co-axial shifter shaft, dog and shifter fork assembly for automotive transmission. The shifter shaft assembly comprises a 5th/reverse shifter shaft (6) assembled in hollow 1st/2nd shifter shaft (5) which in turn is held in hollow 3rd/4th shifter shaft (4). A 1st/2nd dog (9) and a 1st/2nd shifter fork (3) are connected to a 1st/2nd shifter shaft (5). A 3rd/4th dog (8) and a 3rd/4th shifter fork (2) are connected to a 3rd/4th shifter shaft (4). A 5th/Reverse dog (7) and a 5th/Reverse shifter fork (1) is connected to a 5th/Reverse shifter shaft (6). A 3rd/4th shifter shaft (4) is supported in bore provided in transmission housings (10, 11). The bore in the transmission housings (10, 11) supports the shifter shaft assembly and also guides the 3rd/4th shifter shaft (4) during gear change operation. 1st/2nd stopper (17) is connected to 1st/2nd shifter shaft (5), a 3rd/4th stopper (18) is connected to the 3rd/4th shifter shaft (4) and 5th/Reverse stopper (19) is connected to the 5th/Reverse shifter shaft (6). Detent balls (22, 23) are assembled in bore (27) slides and provide motion to desired shaft and lock remaining two shafts. A Stopper plate (26) is connected to transmission housing (21) through mounting bolts (20).

The concentric shafts can be more than three to accommodate more than 5 +1 gear ratios. The connection of dog, fork and stopper to the shafts can be in any order as per the layout of the transmission gear.

During shifting to 1st gear, a shift finger (12) transmits motion to 1st/2nd dog (9) downwards. The 1st/2nd dog (9) slides during this downward motion in the slot (13) provided on the 3rd/4th shifter shaft (4). Downward motion of the 1st/2nd shifter shaft (5) and the 1st/2nd dog (9) assembly further leads to downward motion of the 1st/2nd shifter fork (3) in the slot (16). The 1st/2nd shifter fork (3) slides in the slot provided on the 3rd/4th shifter shaft (4). During gear change operation the 1st/2nd shifter shaft (5) is supported and guided at both ends or throughout by the 3rd/4th shifter shaft (4) and the 5th/Reverse shifter shaft (6).

While shifting to 2nd gear, shift finger (12) transmits motion to the 1st/2nd dog (9) upwards. The 1st/2nd dog (9) slides during this upwards motion in the slot (13) provided on the 3rd/4th shifter shaft (4). Upwards motion of the 1st/2nd shifter shaft (5) and the 1st/2nd dog (9) assembly further leads to upwards motion of the 1st/2nd shifter fork (3) in the slot (16). The 1st/2nd shifter fork (3) slides in the slot provided on the 3rd/4th shifter shaft (4). During gear change operation the 1st/2nd shifter shaft (5) is supported and guided at both ends or throughout its length by the 3rd/4th shifter shaft (4) and the 5th/reverse shifter shaft (6).

During shifting to 3rd gear, shift finger (12) transmits motion to the 3rd/4th dog (8) downwards. The 3rd/4th dog (8) being directly welded to the 3rd/4th shifter shaft (4) moves downwardly. The downward motion of the 3rd/4th shifter shaft (4) and the 3rd/4th dog (8) assembly further leads to downward motion of the 3rd/4th shifter fork (2), since it is directly welded onto the 3rd/4th shifter shaft (4). During gear change operation the 3rd/4th shifter shaft (4) is supported and guided at both ends through bore provided in transmission housings (10, 11).

While shifting to 4th gear, shift finger (12) transmits motion to the 3rd/4th dog (8) upwards. The 3rd/4th dog (8) being directly welded to the 3rd/4th shifter shaft (4) moves upwards. The upward motion of the 3rd/4th shifter shaft (4) and the 3rd/4th dog (8) assembly further leads to upward motion of the 3rd/4th shifter fork (2) since it is directly welded onto the 3rd/4th shifter shaft (4). During gear change operation, the 3rd/4th shifter shaft (4) is supported and guided at both ends through bore provided in transmission housings (10, 11).

During shifting to 5th gear, shift finger (12) transmits motion to the 5th/Reverse dog (7) downwards. The 5th/Reverse dog (7) slides during this downward motion in the slot (14) provided on the 1st/2nd shifter shaft (5) and the 3rd/4th shifter shaft (4). The downward motion of 5th/Reverse shifter shaft (6) and the 5th/Reverse dog (7) assembly further leads to downward motion of the 5th/Reverse shifter fork (1) in the slot (15). The 5th/Reverse shifter fork (1) slides in the slot provided on the 1st/2nd shifter shaft (5) and the 3rd/4th shifter shaft (4). During gear change operation, the 5th/Reverse shifter shaft (6) is supported and guided at both ends or throughout its length by the 3rd/4th shifter shaft (4).

While shifting to reverse gear, shift finger (12) transmits motion to 5th/Reverse dog (9) upwards. The 5th/Reverse dog (7) slides during this upward motion in the slot (14) provided on the 1st/2nd shifter shaft (5) and the 4th shifter shaft (4). The upward motion of the 5th/Reverse shifter shaft (6) and the 5th/Reverse dog (7) assembly further leads to upward motion of the 5th/Reverse shifter fork (1) in the slot (15). The5th/Reverse shifter fork (1) slides in the slot provided on the 1st/2nd shifter shaft (5) and the 3rd/4th shifter shaft (4). During gear change operation, the 5th/Reverse shifter shaft (6) is supported and guided at both ends or throughout its length by the 3rd/4th shifter shaft (4).

During 1st/2nd gear shifting, shift finger (12) transmits motion to the 1st/2nd dog (9) upwards / downwards. This leads to upwards / downwards motion of the 1st/2nd shifter shaft (5) and the 1st/2nd dog (9) assembly further leads to upwards / downward motion of the 1st/2nd stopper (17). This motion of stopper (17) will push detent balls (22, 23) towards 3rd/4th stopper (18) and lock axial motion of 5th/Reverse shifter shaft (6) and 3rd/4th shifter shaft (4) against stopper plate (26). Since, stopper plate is held against transmission housing (21), shifter shaft (4, 6 ) indirectly get lock against transmission housing (21) and only one 1st/2nd shifter shaft (5) will have translational motion.

During 3rd/4th gear shifting, shift finger (12) transmits motion to the 3rd/4th dog (8) upwards / downwards. This leads to upwards / downwards motion of the 3rd/4th shifter shaft (4) and the 3rd/4th dog (8) assembly further leads to upwards / downward motion of the 3rd/4th stopper (18). This motion of stopper (18) will push detent balls (22, 23) on either side and lock axial motion of 5th/Reverse shifter shaft (6) and 1st/2nd shifter shaft (5) against stopper plate (26). Since, stopper plate is held against transmission housing (21), shifter shaft (5, 6) indirectly get lock against transmission housing (21) and only one 3rd/4th shifter shaft (5) will have translational motion.

During 5th/Reverse gear shifting, shift finger (12) transmits motion to the 5th/Reverse dog (7) upwards / downwards. This leads to upwards / downwards motion of the 5th/Reverse shifter shaft (6) and the 5th/Reverse dog (7) assembly further leads to upwards / downward motion of the 5th/Reverse stopper (19). This motion of stopper (19) will push detent balls (22, 23) towards 3rd/4th stopper (18) and lock axial motion of 3rd/4th shifter shaft (4) and 1st/2nd shifter shaft (5) against stopper plate (26). Since, stopper plate is held against transmission housing (21), shifter shaft (4, 5) indirectly get lock against transmission housing (21) and only one 5th/Reverse shifter shaft (6) will have translational motion.

Advantages:
In one embodiment, the shifter shaft assembly as disclosed herein is compact in size.
In one embodiment, the shifter shaft assembly as disclosed herein is an integrated design and easy to handle during servicing and assembling.
In one embodiment, the shifter shaft assembly as disclosed herein requires less space in transmission and hence less transmission oil.
In one embodiment, the shifter shaft assembly as disclosed herein ensures low drag torque and high efficiency, and low CO2 emission by optimum use of the transmission oil.
In one embodiment, the shifter shaft assembly as disclosed herein is low cost.
In one embodiment, the shifter shaft assembly as disclosed herein is simple in construction and robust in functioning.

Equivalents
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

We claim:
1. A shifter shaft assembly for automotive transmission comprising:
a) a plurality of shifter shafts placed concentrically one inside the other;
b) plurality of slots disposed on outer and intermediate shafts of said concentric shafts
c) at least one dog, at least one shifter fork and at least one stopper connected to said outer shifter shaft;
d) at least one dog, at least one shifter fork and at least one stopper connected to each intermediate shafts or inner shifter shaft through the slots on the outer and/or intermediate concentric shafts;
e) the outer shifter shaft is supported on transmission housing through bearings.

2. The shifter shaft assembly as claimed in claim 1, wherein three shifter shafts, an inner shaft, an intermediate shaft and an outer shaft are concentrically mounted.

3. The shifter shaft assembly as claimed in any one of the preceding claims, wherein the said intermediate shaft (5) is assembled in hollow outer shifter shaft (4) and supported on said hollow outer shifter shaft (4) and inner shifter shaft (6) at both ends or throughout its length.

4. The shifter shaft assembly as claimed in any one of the preceding claims, wherein a 3rd/4th dog, a 3rd/4th fork and 3rd/4th stopper are connected to said outer shaft.

5. The shifter shaft assembly as claimed in any one of the preceding claims, wherein a 1st/2nd dog, a 1st/2nd fork and 1st/2nd stopper are connected to said intermediate shaft.

6. The shifter shaft assembly as claimed in any one of the preceding claims, wherein a 5th /reverse dog, a 5th /reverse fork and a 5th /reverse stopper are connected to said inner shaft.

7. The shifter shaft assembly as claimed in any one of the preceding claims, wherein said pair of dog, fork and stopper are connected to each shaft in any order.

8. The shifter shaft assembly as claimed in claim 1, wherein slots are provided in longitudinal direction of said shafts.

9. The shifter shaft assembly as claimed in claim 8, wherein slots are sufficiently extended to guide the dogs, forks and stopper during shifting.

10. The shifter shaft assembly as claimed in any one of the preceding claims, wherein said dog, fork and stopper connected to the inner shaft through the slots on said intermediate and outer shaft.

11. The shifter shaft assembly as claimed in any one of the preceding claims wherein said dog, fork and stopper connected to the intermediate shaft through the slots on said outer shaft.

12. The shifter shaft assembly as claimed in any one of the preceding claims wherein said dog, fork and stopper are directly connected to the outer shafts.

13. The shifter shaft assembly as claimed in claim 1 wherein said stopper connected to a stopper plate mounted on the transmission housing with detent balls to controlling the movement of shifter shafts.

14. A shifter shaft assembly substantially as herein above described and as illustrated in accompanying drawings.