Claims:WE CLAIM:
1. A gear select-and-shift mechanism (20) for a transmission mechanism (14), said gear select-and-shift mechanism (20) configured to facilitate selection of and shifting to/from gear positions associated with gear pairs in said transmission mechanism (14), said select-and-shift mechanism (20) comprising:
a. a shifter rod (21) configured to be displaced linearly along a longitudinal axis thereof as well as angularly about the longitudinal axis thereof;
b. an integrated gear shifting block (22) fixedly mounted on said shifter rod (21), said integrated gear shifting block (22) having:
i. a bearing surface (23) configured to receive said shifter rod (21);
ii. a guiding track (24) defining a path corresponding to movements associated with selection and shifting and positions corresponding to said gear positions, said guiding track (24) configured to be in engagement with a guiding element (243), said shifter rod (21) configured to be displaced relative to said guiding element (243), wherein the engagement between said guiding track (24) and said guiding element (243) allows said shifter rod (21) to be displaced only along said path and to said positions; and
iii. at least one shifting finger (25) extending externally from said bearing surface (23), said shifting finger (25) configured to engage with a shifting element (30) to cause displacement of said shifting element (30), resulting in shifting from one gear pair transmitting power through said transmission mechanism (14) to another.
2. The gear select-and-shift mechanism (20) as claimed in claim 1, wherein said integrated gear shifting block (22) has a detent profile (26), said detent profile (26) configured to engage with a detenting element (263), wherein said shifter rod (21) is configured to be displaced relative to said detenting element (263), and the engagement between said detent profile (26) and said detenting element (263) facilitates holding said shifter rod (21) at one of the gear positions to which said shifter rod (21) is shifted.
3. The gear select-and-shift mechanism (20) as claimed in claim 2, wherein said integrated gear shifting block (22) has a neutral detection formation (27), wherein said neutral detection formation (27) is configured to be detected by a sensor (28) when said shifter rod (21) is in a neutral gear position.
4. The gear select-and-shift mechanism (20) as claimed in claim 3, wherein said guiding profile (24) and said detent profile (26) are formed on sectoral extensions extending from said bearing surface (23).
5. The gear select-and-shift mechanism (20) as claimed in claim 1, wherein said shifting finger (25) is formed as a radial extension from said bearing surface (23).
6. The gear select-and-shift mechanism (20) as claimed in claim 1, wherein said neutral detection formation (27) is defined by a chasm (271) between two radially valleys (272) extending from said bearing surface (23).
7. The gear select-and-shift mechanism as claimed in claim 1, wherein said neutral detection formation is formed as a radial extension from said bearing surface.
8. The gear select-and-shift mechanism (20) as claimed in claim 3, wherein said integrated gear shifting block (22) is a casted component of metal.
9. The gear select-and-shift mechanism (20) as claimed in claim 3, wherein said integrated gear shifting block (22) is a non-metallic component produced by an additive manufacturing method.
10. The gear select-and-shift mechanism (20) as claimed in claim 3, wherein said integrated gear shifting block (22) is produced by fixing together sub-blocks associated with said guiding track (24), said shifting finger (25), said detent profile (26) and said neutral detection formation (27), on a bearing element having said bearing surface (23) formed thereon.
, Description:FIELD
The present disclosure relates to gear shifting systems for vehicle transmission.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
A gear shifting system of an automobile having a manual transmission is actuated by a hand-held shifting stick provided with a knob at the upper end. The stick is generally displaceable along a predefined pattern, wherein the vehicle transmission mechanism is shifted from one gear ratio to another due to the displacement of the shifting stick from one ‘gear position’ to another. The pattern usually has a plurality of rows of gear positions, with each row usually has a pair of gear positions. For example, a typical 5-speed transmission has a first row comprising a first gear position and a second gear position, a second row comprising a third gear position and a fourth gear position and a third row comprising a fifth gear position and a reverse gear position. The ‘neutral position’, or rather, a ‘neutral line’ is defined between two gear positions in a row, wherein the transmission mechanism isolates power from being transmitted from the engine to the wheels of the vehicle. The shifting movement of the stick involves a ‘selection’ of one of the rows of gear positions along the ‘neutral line’, followed by a ‘shift’ of the stick into either of the gear positions in the row.
The transmission mechanism generally comprises a gearbox having a plurality of gears, wherein various combinations of gears define a fixed gear ratio. Shifter forks are displaceable along shafts to enable engagement and disengagement of gears for changing the effective gear ratio of the gearbox.
The shifter forks typically are displaced by a gear select-and-shift mechanism. The select-and-shift mechanism in turn is displaced by the shifting stick through a connecting assembly. A hitherto known select-and-shift mechanism, also sometimes referred to as the ‘shift tower subassembly’, comprises a guiding element, a shifting finger, a detent mechanism. A neutral detection system is being incorporated recently to comply with safety norms. The guiding element provides a track or a guiding path during selection and shifting. The shifting finger enables shifting to one of the gear positions in a selected gear pair. The detent mechanism ensures that the shifted position is maintained. The neutral detection system indicates on the dashboard of the vehicle whether the transmission mechanism is in neutral state or not.
Conventionally, the guiding element, the shifting finger, the detent mechanism and the neutral detection system are separate components. The more the number of components in a subassembly, the more is the assembly time and complexity in assembling during mass production. Separate tolerances for each part accumulates into a ‘tolerance stack-up’, which increases the likelihood of issues related to shift quality. Inevitably, the total weight of the subassembly also increases. Fine blanking and rolling is required for producing sheet metal components such as the neutral plate and the ‘H-gate’ of the guiding element subassembly. Servicing of the select-and-shift mechanism becomes highly tedious, and is often not possible. The weight of the complete subassembly necessitates significant shifting effort. Other issues related to the conventional select-and-shift mechanism can be noted, such as welding mismatch, packaging constraints, higher tooling, handling and overall part cost.
There is, therefore, felt a need of a gear select-and-shift mechanism, which alleviates the aforementioned issues.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to provide a gear select-and-shift mechanism that alleviates limitations of prior art.
Another object of the present disclosure is to provide a gear select-and-shift mechanism which has less number of components.
Yet another object of the present disclosure is to provide a gear select-and-shift mechanism which is easy to assemble.
Still another object of the present disclosure is to provide a gear select-and-shift mechanism which has weight lower than the conventional mechanism.
Yet another object of the present disclosure is to provide a gear select-and-shift mechanism that makes shifting gear easier.
Still another object of the present disclosure is to provide a gear select-and-shift mechanism which has low tolerance stack-up.
Yet another object of the present disclosure is to provide a gear select-and-shift mechanism which provides ease of servicing.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure envisages a gear select-and-shift mechanism for a transmission mechanism. The select-and-shift mechanism is configured to facilitate selection of and shifting to/from gear positions associated with gear pairs in the transmission mechanism. The select-and-shift mechanism comprises a shifter rod and an integrated gear shifting block. The shifter rod is configured to be displaced linearly along a longitudinal axis thereof as well as angularly about the longitudinal axis thereof. The integrated gear shifting block is fixedly mounted on the shifter rod.
The integrated gear shifting block of the present disclosure has a bearing surface, a guiding track and at least one shifting finger. The bearing surface is configured to receive the shifter rod. The guiding track defines a path corresponding to movements associated with selection and shifting and positions corresponding to the gear positions. The guiding track is configured to be in engagement with a guiding element. The shifter rod configured to be displaced relative to said guiding element. The engagement between the guiding track and the guiding element allows the shifter rod to be displaced only along the aforementioned path and to the aforementioned positions. The shifting finger extends externally from the bearing surface. The shifting finger is configured to engage with a shifting element to cause displacement of the shifting element resulting in shifting from one gear pair transmitting power through the transmission mechanism to another.
In an embodiment, the integrated gear shifting block has a detent profile. The detent profile is configured to engage with a detenting element. The shifter rod is configured to be displaced relative to the detenting element. The engagement between the detent profile and the detenting element facilitates holding the shifter rod at one of the gear positions to which the shifter rod is shifted. Further, in an embodiment, the integrated gear shifting block has a neutral detection formation, wherein the neutral detection formation is configured to be detected by a sensor when the shifter rod is in a neutral gear position.
In a preferred embodiment, the guiding profile and the detent profile are formed on sectoral extensions extending from the bearing surface. The shifting finger is formed as a radial extension from the bearing surface. In an embodiment, the neutral detection formation is defined by a chasm between two radially valleys extending from the bearing surface. Alternatively, the neutral detection formation is formed as a radial extension from the bearing surface.
In an embodiment, the integrated gear shifting block is a casted component of metal. In another embodiment, the integrated gear shifting block is a non-metallic component produced by an additive manufacturing method. In yet another embodiment, the integrated gear shifting block is produced by fixing together sub-blocks associated with the guiding track, the shifting finger, the detent profile and the neutral detection formation, on a bearing element having the bearing surface formed thereon.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The gear select-and-shift mechanism of the present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a gear select-and-shift mechanism of prior art;
Figure 2 illustrates a plot of shifting effort versus the various shifting operations using a gear select-and-shift mechanism of prior art;
Figure 3 is an isometric view of an integrated gear shifting block according to an embodiment of the present disclosure;
Figure 4a is an isometric view of an integrated gear shifting block according to another embodiment of the present disclosure;
Figure 4b is another isometric view of the integrated gear shifting block of Figure 4a;
Figure 5 illustrates a shifting stick of a typical gear shifting system of an automobile;
Figure 6 illustrates an isometric arrangement illustrating the connection between the transmission mechanism and the shifting stick;
Figure 7 illustrates an isometric view illustrating the internal view of the transmission mechanism of Figure 6;
Figure 8 illustrates details of the connecting assembly of Figure 6;
Figure 9 is a zoomed in view of the integrated gear shifting block of Figure 7 assembled in the gear shifting system;
Figure 10 is a side view of the integrated gear shifting block of Figure 4a assembled in the gear shifting system;
Figure 11 is an isometric view of the gear shifting system with an integrated gear shifting block of the present disclosure; and
Figure 12 is an isometric superimposed view of selected positions of the gear shifting system with the integrated gear shifting block of the present disclosure; and
Figure 13 illustrates a plot of shifting effort versus the various shifting operations using a gear select-and-shift mechanism of the present disclosure.
LIST OF REFERENCE NUMERALS
10 gear shifting system
11 knob
12 shifting stick
13 mount
14 transmission mechanism
141 transmission casing
15 connecting assembly
151 stick-side connector
152 transmission-side connector
153 selection cable
154 shifting cable
20’ select-and-shift mechanism of prior art
21’ shifter rod
24a’ H-gate
24b’ neutral plate
25’ shifting finger
26’ detent plate
20 select-and-shift mechanism of the present disclosure
201 mounting plate
21 shifter rod
22 integrated gear shift block
23 bearing surface
24 guiding track
241 slot
242 protrusion
243 guiding pin
25 shifting finger
26 detent profile
261 ridge
262 valley
263 detent pin
27 neutral detection formation
271 chasm
272 ramp
28 sensor
291 selection link
292 selection shaft
293 shifting link
30 fork
31 fork-holding shaft
32 socket
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms “comprises”, “comprising”, “including” and “having” are open-ended transitional phrases and therefore specify the presence of stated features, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
When an element is referred to as being “mounted on”, “engaged to”, “connected to” or “coupled to” another element, it may be directly on, engaged, connected or coupled to the other element. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed elements.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
Terms such as “inner”, “outer”, “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used in the present disclosure to describe relationships between different elements as depicted from the figures.
A gear select-and-shift mechanism 20’ of a prior art is shown in Figure 1. Disposed on a shifter rod 21’ is an H-gate 24a’, a neutral plate 24b’, a pair of shifting fingers 25’ and a detent plate 26’ of a detent mechanism. Each separate component adds to the complexity of assembly of the gear select-and-shift mechanism 20’. Each component has to separately pass quality standards. The high number of tolerances increases likelihood of a bad shift quality. The part count contributes to high weight, higher manufacturing, handling and packaging costs, amongst other issues. Therefore, there is a need of a gear select-and-shift mechanism, which alleviates the aforementioned issues.
The present disclosure envisages an integrated gear shifting block 22 of a gear select-and-shift mechanism 20 for a transmission system of a vehicle. According to an embodiment as shown in Figure 3, the integrated gear shifting block 22 comprises a bearing surface 23, a guiding track 24, a shifting finger 25 and a detent profile 26. The bearing surface 23 is configured to receive a shifter rod 21 therewithin. Preferably, a key hole is provided in the block 22 for rotatably locking the shifter rod 21 with the block 22. The guiding track 24 comprises a plurality of protrusions 242 defining a plurality of slots 241, wherein the slots 241 define a selection and shifting pattern. A guiding element in the form of a guiding pin 243, as shown in Figure 9 and Figure 10, is configured to engage with the guiding track 24 and to facilitate guiding of the gear select-and-shift mechanism 20 as the guiding track 24 gets angularly displaced to be guided along the pattern defined by the guiding track 24. The guiding track 24 defines a path corresponding to movements associated with selection and shifting and positions corresponding to the gear positions. The shifting finger 25 is configured to engage with a socket 32 fixedly attached on a fork-holding shaft 31. Each pair of selectable gear positions has an associated shifting element, typically a shifting fork 30, and an associated fork-holding shaft 31. The fork-holding shafts are placed parallel to each other and the shifter rod 21 is placed in a plane perpendicular to a plane parallel to the fork-holding shafts (31), as shown in Figure 11. The detent profile 26 engages with a detenting element such as a spring-loaded detent pin 263 of the detent mechanism. The detent profile 26 has four ridges 261 separated by three valleys 262, wherein the central valley corresponds to the neutral position and the outer valleys correspond to gear positions to be shifted to.
In an embodiment, the guiding profile 24 and the detent profile 26 are formed on sectoral extensions extending from the bearing surface 23. The shifting finger 25 is formed as a radial extension from the bearing surface 23.
The shifter rod 21 is supported by a mounting plate 201 on a casing 141 of the transmission mechanism 14. Similarly, the guiding pin 243 and the detent pin 263 are held stationary relative to the casing 141 of the transmission mechanism 14.
According to an embodiment of the present disclosure, the gear shifting system 10 has a shifting stick 12, that is manually operable by a shifting knob 11, is located in the vicinity of the vehicle operator’s seat, and is supported by a mount 13, as shown in Figure 5. The act of displacement of the shifting stick (12), which generally involves sliding with pulling backward or pushing forward, causes a connecting assembly 15 of Figure 6 to be displaced as per the direction of displacement of the shifting stick 12. An exemplary connecting assembly comprises a shifting cable 154 connecting a stick-side connector 151 with a transmission-side connector 152, as shown in Figure 8. As shown in Figure 8, the stick-side connector 151 is configured to have two degrees of freedom of movement – one being a lateral movement corresponding to the displacement for selection and the other being an angular movement corresponding to the displacement for shifting. Separate cables – a selection cable 153 for actuating the selection and a shifting cable 154 for actuating the shifting – are provided. The selection cable 153 pulls a selection link 291 configured to actuate movement for selection in the select-and-shift mechanism, and the shifting cable 154 pulls a shifting link 293 configured to actuate movement for shifting in the select-and-shift mechanism. The selection link 291 and the shifting link 293 are provided with an ‘eye’ for attaching the selection cable 153 and the shifting cable 154 respectively. A selection shaft 292 is coupled to the shifter rod 21 to cause linear axial displacement of the shifter rod 21 on rotation of the selection shaft 292, wherein, on being pulled by the selection cable 153, the selection shaft 292 is configured to rotate about its longitudinal axis. On being pulled by the shifting cable 154, the shifting link 293 is configured to generate rotational movement in the shifter rod 21 about its longitudinal axis. Linear axial displacement of the shifter rod 21 results in selection of the pair of gear positions from the predefined pattern, and rotational movement of the shifter rod 21 results in selection of a gear position between the selected pair of gear positions, as shown in Figure 12.
According to another embodiment as shown in Figures 4a and Figure 4b, the integrated gear shifting block 22 further comprises a neutral detection formation 27. In an embodiment, the neutral detection formation 27 consists of a chasm 271 separated by two ramps 272, wherein, a sensor is positioned to detect the chasm 271 when the block 22 is in a neutral state. The guiding pin 243 and the detent pin 263 are held stationary relative to the casing 141 of the transmission mechanism 14. In another embodiment, the neutral detection formation is formed as a radial extension from the bearing surface.
In an embodiment, the sensor 28 is a proximity sensor. The sensor 28 is configured to generate a signal corresponding to the neutral position of the integrated gear shifting block 22 and thereby of the transmission mechanism 14 of Figure 6 and Figure 7, and to communicate the generated signal to a neutral detection module of a control unit of the vehicle. The neutral detection module activates a visual indication, e.g., a green light indicator, located on the dashboard of the vehicle, to indicate that the transmission mechanism 14 is in a neutral state.
In an embodiment, the integrated gear shifting block 22 of the present disclosure is a casted component of metal, which is machined and microfinished, if required. In another embodiment, the integrated gear shifting block 22 is produced from a metallic block by machining alone. In yet another embodiment, the integrated gear shifting block 22 is a non-metallic component produced by an additive manufacturing method. In another embodiment, the integrated gear shifting block 22 is produced by fixing together, preferably by welding or by any other suitable means, sub-blocks associated with the guiding track 24, the shifting finger 25, the detent profile 26 and the neutral detection formation 27 on a bearing element having the bearing surface 23 configured thereon.
Thus, the integrated gear shifting block 22 of the present disclosure combines the functions of the pair of shifting fingers 25’, an H-gate 22a’, a neutral plate 22b’ and a detent plate 26’ of prior art, thereby reducing part count and overall weight of the gear select-and-shift mechanism 20. The subassembly of the gear select-and-shift mechanism 20 is highly simplified, which also increases ease of servicing. The number of tolerances associated with more number of components of prior art is reduced, thereby making the gear select-and-shift mechanism 20 less likely to generate quality issues. Costs associated with manufacturing, packaging and handling are significantly reduced.
Measurements were taken of the shifting effort for all possible gear position shifts in a six-speed transmission gearbox with a gear select-and-shift mechanism of prior art and with a gear select-and-shift mechanism of the present disclosure. The plot of Figure 2 shows the maximum value, the minimum value and the average value of force measurements on Y-axis against individual gear position shifts on the X-axis for the gear select-and-shift mechanism of prior art. The plot of Figure 13 shows the maximum value, the minimum value and the average value of force measurements on Y-axis against individual gear position shifts on the X-axis for the gear select-and-shift mechanism of the present disclosure. Comparison between the corresponding forces for individual gear position shifts reveals that the overall effort required during gear shifting has been noticeably reduced due to implementation of the select-and-shift mechanism of the present disclosure. Observing the plots further reveals that the values of force for gear position shifting with the gear select-and-shift mechanism of prior art were brought down by large values when the gear select-and-shift mechanism of the present disclosure was used. For instance, for the shift between 1st and 2nd gear positions, the average value of force was reduced from 37.3 units to 15.1 units.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a gear select-and-shift mechanism which:
• has less number of components;
• is easy to assemble;
• has low weight;
• makes shifting easier;
• has low tolerance stack-up; and
• provides ease of servicing.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments 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.
The foregoing description of the specific embodiments 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.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.