CLIAMS:We claim:
1. A shifter assembly (500) for a gearbox of a vehicle, the assembly (500) comprising:
a selector member (103a) pivoted in a gearbox housing (501), wherein the selector member (103a) is adapted to rotate in the gearbox housing (501) when a gear shift lever is actuated;
a shifter element (103b) provisioned on the selector member (103a), wherein the shifter element (103b) is configured to engage with at least one shifter fork (102a) in the gearbox housing (501) when the selector member (103a) is rotated; and
a mechanism (300) configured in the gearbox housing (501) to control reverse gear engagement, the mechanism (300) comprising:
at least one detent (200) slidably disposed in at least one bore (100) of the gearbox housing (501), wherein the at least one detent (200) is adapted to selectively contact the selector member (103a), the at least one detent (200) comprises:
a housing (201) having a first bore (201a) and a second bore (201b);
a first resilient member (203) with a first predetermined stiffness axially disposed in a first bore (201a) of the housing (201), wherein one end of the first resilient member (203) is configured to contact an end of the first bore (201a) and the other end of the first resilient member (203) is loaded on a guide member (202);
a second resilient member (204) with a second predetermined stiffness axially disposed in the second bore (201b) of the housing (201), wherein one end of the second resilient member (204) is configured to contact an end of the second bore (201b) and the other end of the second resilient member (204) is adapted to contact gearbox housing (501);
wherein, the first predetermined stiffness is greater than the second predetermined stiffness; and
at least one actuator (205) configured in between the at least one detent (200) and the gearbox housing (501), wherein the at least one actuator (205) is adapted to move between a first position and a second position to control reverse gear engagement.

2. The assembly (500) as claimed in claim 1, wherein the at least one shifter fork (102a) is connected to at least one shaft (101a).

3. The assembly (500) as claimed in claim 2, wherein the at least one shifter fork (102a) is configured to engage a gear in the gearbox.

4. The assembly (500) as claimed in claim 1, wherein the at least one actuator (205) is interfaced with a control unit (206) of the vehicle.

5. The assembly (500) as claimed in claim 1, wherein the at least one actuator (205) is configured to move to at least one of the first position (FP) and the second position (SP) depending on a predefined vehicle speed.

6. The assembly (500) as claimed in claim 5, wherein the predefined speed of the vehicle ranges from 5 kilometre per hour to about 10 kilometre per hour.

7. The assembly (500) as claimed in claim 5, wherein the actuator (205) moves to the first position (FP) when the vehicle is moving at a speed higher than the predefined speed.

8. The assembly (500) as claimed in claim 7, wherein the movement of the actuator (205) to the first position (FP) prevents compression of the second resilient member (204) to prevent engagement of the reverse gear.

9. The assembly (500) as claimed in claim 5, wherein the actuator (205) is adapted to move to the second position (SP) when the vehicle is moving at a speed lesser than the predefined speed.

10. The assembly (500) as claimed in claim 9, wherein the movement of the actuator (205) to the second position (SP) facilitates engagement of the reverse gear by compressing the second resilient member (204).

11. The assembly (500) as claimed in claim 1, wherein the actuator (205) in first position (FP) facilitates engagement of reverse gear by compressing the first resilient member (203).

12. The assembly (500) as claimed in claim 11, wherein a force is applied on the at least one detent (200) to overcome first predetermined stiffness of the first resilient member (203), thereby facilitating engagement of the reverse gear.

13. A mechanism (300) to control reverse gear engagement in a gearbox of a vehicle, the mechanism (300) comprising:
at least one detent (200) configurable in a gearbox housing (501), wherein the at least one detent (200) is adapted to regulate movement of a selector member (103a) in the gearbox housing (501), the at least one detent (200) comprises:
a housing (201) having a first bore (201a) and a second bore (201b);
a first resilient member (203) with a first predetermined stiffness axially disposed in a first bore (201a) of the housing (201), wherein one end of the first resilient member (203) is configured to contact an end of the first bore (201a) and the other end of the first resilient member (203) is loaded on a guide member (202);
a second resilient member (204) with a second predetermined stiffness axially disposed in the second bore (201b) of the housing (201), wherein one end of the second resilient member (203) is configured to contact an end of the second bore (201b) and the other end of the second resilient member (204) is adapted to contact gearbox housing (501);
wherein, the first predetermined stiffness is higher than the second predetermined stiffness; and
at least one actuator (205) configurable in between the at least one detent (200) and the gearbox housing (501), wherein the at least one actuator (205) is adapted to move between a first position and a second position to control reverse gear engagement.

14. The mechanism (300) as claimed in claim 13, wherein the at least one actuator (205) in the first position (FP) contacts the guide member (202) to prevent contact of the at least one detent (200) with the gearbox housing (501).

15. The mechanism (300) as claimed in claim 13, wherein the at least one actuator (205) in the second position (SP) moves away from the guide member (202) to allow the contact between the at least one detent (200) with the gearbox housing (501).

16. The mechanism (300) as claimed in claim 14, wherein the at least one actuator (205) is at least one of solenoid, pneumatic actuator and a hydraulic actuator.

17. The mechanism (300) as claimed in claim 14, wherein the at least one actuator (205) comprises of a plunger (205a) configured to be moved between the first position (FP) and the second position (SP).

18. A vehicle comprising a shifter assembly (500) for a gearbox as claimed in claim 1.
,TagSPECI:TECHNICAL FIELD
The present disclosure generally relates to Automobile engineering. Particularly but not exclusively, the present disclosure relates to transmission system of a vehicle. Further, embodiments of the present disclosure disclose a mechanism to control reverse gear shifting in the vehicle.

BACKGROUND
Transmission system of vehicles generally includes a drive train between the engine and drive wheels to provide plurality of gear ratios, which propel the vehicle in forward direction, and reverse direction. The transmission system is a necessary part of any vehicle through which the engine delivers power (i.e. torque as well as required speed) to the drive wheels. In addition, the transmission system allows the speed of the engine to be maintained within its optimum operating range for the delivery of maximum torque or power, as the vehicle accelerates from a “stationary” or “stopped” position to desired speed. The speed reduction between the engine and the resulting rotation of the drive wheels provided by the transmission system results in a controlled application of the torque, by which the drive wheels are rotated. In other words, magnitude of torque applied on drive gears varies depending on the speed of the engine. The forward gear and reverse gear engagement is effected by moving (more specifically by pushing or pulling) the gear selector lever, which accordingly engages the desired gear on the output shaft with that of the input shaft, through an intermediate shaft called counter-shaft. When a forward gear ratio, commonly designated as "first", “second” and so on is selected, the transmission system imparts an appropriate speed to the drive wheels, and at the same time imparts a torque corresponding to that particular speed from the engine to rotate the drive wheels. This is necessary to overcome static inertia of the vehicle. If vehicle is to be moved in reverse direction, the gear shifting lever is moved in a predetermined direction, so that reverse gear is engaged. Reverse gear engagement is usually achieved through an auxiliary gear called idler gear.

A common problem encountered while shifting between different forward gears, and more particularly while shifting between high speed gears, is the inadvertent/undesirable shift to reverse gear. In other words, there is always a possibility that the control lever is shifted to reverse gear when the vehicle is moving in forward gear, which is not desirable. This occurs when the force applied on the gear shift lever is inappropriate. This sudden shift from a forward gear to reverse gear results in serious problems such as complete failure of the transmission system, over-stresses in the gears constituting the transmission system, excessive torsional stresses in speed shafts, and so on. The over-stresses typically result from a large mismatch between vehicle inertia and vehicle speed. These over-stresses are undesirable since they subsequently lead to deformation of associated components in the transmission system, which makes the transmission system unreliable. There are also possibilities that the associated components may fail due to these over-stresses.

To overcome the problems associated with the inadvertent shift to reverse gear, number of mechanical and electro-mechanical reverse gear detent mechanisms for both manual and automatic transmission vehicles have been designed and developed in recent past. One such system incorporates a mechanical reverse detent member loaded with a high stiffness spring. The stiffness of the spring herein above and below is defined as the magnitude of force required to produce unit deformation in the spring. Hence, to deform a spring with high stiffness, considerably large force is required. While driving at forward speeds (i.e. when forward gears are engaged), the spring loaded detent prevents accidental shift to reverse gear under resisting force of the high stiffness spring. However, this detent mechanism has a limitation that when reverse gear engagement is desired, the driver has to apply considerably larger force on the shift lever, so as to overcome forces of high stiffness spring. This causes discomfort to the driver when movement of the vehicle in reverse direction is desired.

One such reverse gear detent mechanism is disclosed in U.S. Patent number 3,894,443, which is of electro-mechanical type, comprising two locking mechanisms – a first locking mechanism and a second locking mechanism. The first locking mechanism prevents continuous displacement of the speed control lever in a down-shifting direction as well as to completely prevent down-shift if engine speed is excessive. The second locking mechanism holds the directional control lever in a neutral position and prevents its displacement to a reverse position if vehicle speed is excessive. This is accomplished by a pawl which is actuated by an electric solenoid based on vehicle speed. However, this mechanism involves a number of electro-mechanical components which makes the entire system complex, making it difficult to be incorporated in the transmission system. In addition, electrical systems have very low preload capability than mechanical actuators, and there is inherent friction between the armature of solenoid and pawl. As a result, the solenoid may not be able to unlock the locking pawl. To overcome this problem, the electric solenoid must be sufficiently sized to provide a relatively large force, which is not desirable owing to the increased size of the solenoid.

In addition to above mentioned reverse gear detent mechanisms, many other mechanical detents such as spring loaded bullet shaped detents, spring loaded spherical detents, and the like have been used to inhibit undesirable shift to reverse gear. This detent mechanism increases the resistance to shifting movement of the shifter rod by the vehicle operator from either a neutral position or a forward driving position to the reverse position. Thus the vehicle operator must exert an increased shifting effort upon the control lever in order to condition the mechanism for reverse drive operation. This increases the effort to be applied by the operator when reverse gear is to be engaged, which causes discomfort. Another major drawback associated with mechanical reverse gear detents is friction and subsequently the wear of contact surfaces, which makes the entire detent mechanism inoperative over a period of time.

In light of foregoing discussion, it is necessary to develop an improved mechanism to control shifting of reverse gear, to overcome one or more limitations stated above.

SUMMARY
One or more drawbacks of conventional mechanisms as described in the prior art are overcome and additional advantages are provided through the mechanism as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be a part of the claimed disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

In a non-limiting embodiment of the present disclosure, there is provided a shifter assembly for a gearbox of a vehicle. The assembly comprises of a selector member pivoted in a gearbox housing, wherein the selector member is adapted to rotate in the gearbox housing when a gear shift lever is actuated. A shifter element is provisioned on the selector member, wherein the shifter element is configured to engage with at least one shifter fork in the gearbox housing when the selector member is rotated. The assembly further comprises of a mechanism configured in the gearbox housing to control reverse gear engagement. The mechanism comprises of at least one detent slidably disposed in at least one bore of the gearbox housing, wherein the at least one detent is adapted to selectively contact the selector member. Further, the at least one detent comprises a housing having a first bore and a second bore, wherein a first resilient member with a first predetermined stiffness is axially disposed in the first bore of the housing. One end of the first resilient member is configured to contact an end of the first bore and the other end of the first resilient member is loaded on a guide member. Further, a second resilient member with a second predetermined stiffness is axially disposed in the second bore of the housing, wherein one end of the second resilient member is configured to contact an end of the second bore and the other end of the second resilient member is adapted to contact gearbox housing. The first predetermined stiffness is greater than the second predetermined stiffness. At least one actuator is configured in between the at least one detent and the gearbox housing, wherein the at least one actuator is adapted to move between a first position and a second position to control reverse gear engagement.

In an embodiment of the present disclosure, the at least one shifter fork is connected to at least one shaft and is configured to engage a gear in the gearbox.

In an embodiment of the present disclosure, the at least one actuator is interfaced with a control unit of the vehicle, wherein the at least one actuator is configured to move to at least one of the first position and the second position depending on a predefined vehicle speed. The predefined speed of the vehicle ranges from 5 kilometre per hour to about 10 kilometre per hour.

In an embodiment of the present disclosure, the actuator moves to the first position when the vehicle is moving at a speed higher than the predefined speed. The movement of the actuator to the first position prevents compression of the second resilient member to prevent engagement of the reverse gear.

In an embodiment of the present disclosure, the actuator is adapted to move to the second position when the vehicle is moving at a speed lesser than the predefined speed. The movement of the actuator to the second position facilitates engagement of the reverse gear by compressing the second resilient member.

In an embodiment of the present disclosure, the actuator in first position facilitates engagement of reverse gear by compressing the first resilient member by applying higher force on the at least one detent to overcome first predetermined stiffness of the first resilient member.

In another non-limiting embodiment of the present disclosure, there is provided a mechanism to control reverse gear engagement in a gearbox of a vehicle. The mechanism comprises at least one detent configurable in a gearbox housing, wherein the at least one detent is adapted to regulate movement of a selector member in the gearbox housing. The at least one detent further comprises of a housing having a first bore and a second bore, wherein a first resilient member with a first predetermined stiffness axially is disposed in a first bore of the housing. One end of the first resilient member is configured to contact an end of the first bore and the other end of the first resilient member is loaded on a guide member. A second resilient member with a second predetermined stiffness is axially disposed in the second bore of the housing, wherein one end of the second resilient member is configured to contact an end of the second bore and the other end of the second resilient member is adapted to contact gearbox housing. The first predetermined stiffness is higher than the second predetermined stiffness. At least one actuator is configured in between the at least one detent and the gearbox housing, wherein the at least one actuator is adapted to move between a first position and a second position to control reverse gear engagement.

In an embodiment of the present disclosure, the at least one actuator is at least one of solenoid, pneumatic actuator and a hydraulic actuator.

In an embodiment of the present disclosure, the at least one actuator comprises of a plunger configured to be moved between the first position and the second position.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
The novel features and characteristics of the disclosure are set forth in the appended description. 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:

FIG. 1 illustrates the sectional front view of the shifter assembly provided with the mechanism to control reverse gear engagement in a vehicle, according to an embodiment of the present disclosure.

FIG. 2 illustrates perspective view of a detent used to control reverse gear engagement in a vehicle.

FIGS. 3a and 3b illustrate sectional front view and right side view respectively of the mechanism with actuator in first position, which inhibits reverse gear engagement in the vehicle, according to one embodiment of the present disclosure.

FIGS. 4a, 4b and 4c illustrate sectional front views and right side view respectively of the mechanism with actuator in second position, which allows reverse gear engagement in the vehicle, according to another embodiment of the present disclosure.

FIG. 5 illustrates sectional front view of the mechanism to facilitate reverse gear engagement in a vehicle, during non-operative condition of the actuator, according to an exemplary embodiment of the present disclosure.

FIG. 6 illustrates a flowchart depicting control logic of the control unit to regulate reverse gear engagement in the vehicle, according to an exemplary 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
The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the scope of the disclosure as set forth in the appended claims. The novel features which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

To overcome one or more limitations stated in the background, the present disclosure provides a shifter assembly in a gearbox of a vehicle comprising a mechanism to control reverse gear engagement in the vehicle.

The gearbox of an automobile is necessarily a drive train which transmits power (torque and angular velocity) from the engine shaft (hereinafter referred to as input shaft) to the transmission shaft (hereinafter referred to as output shaft) which is commonly known as propeller shaft. The gearbox essentially comprises of a shifter assembly to control transmission of power from input shaft to the output shaft, so that the vehicle can be propelled at required speed. The gearbox is provided with a gear shifter lever to enable transmission between different gears, so that selected gears on input shaft mesh with that on the output shaft, thereby achieving required gear ratio. This is achieved by manipulating the gear shift lever to a specified position in the gearbox by applying appropriate force on it. For example, if the gear shift lever is manipulated to a position corresponding to first gear in the gearbox, the first gear engages with the driving gear on the input shaft, thereby transmitting power from input shaft to output shaft. If second gear is to be engaged, the shifter lever is manipulated so as to axially slide the second gear on the output shaft, so that the second gear meshes the with driving gear on the input shaft, thereby transmitting power from the input shaft and output shaft. An intermediate shaft called counter-balance shaft is provided in between the input shaft and the output shaft through which the power transmission takes place from input shaft. Conventionally, the gearbox is assembled in the vehicle with various configurations including but not limiting to constant mesh configuration and synchromesh configuration. The gear shift lever is generally pivoted on a shaft, wherein the shaft is mounted with a selector member which selects and engages required gear in the gearbox. The selection is achieved through a plurality of selector forks engageable with the selector member for meshing desired gear on the output shaft with driving gear on the input shaft. The plurality of selector forks are capable of sliding in axial direction to axially move the desired gear for meshing with the driving gear on the input shaft. This shifting of gear shift lever is generally done when clutch is in disengaged condition. When vehicle is to be moved in reverse direction, the gear shift lever is manipulated such that selector member is engaged with the selector fork which appropriately meshes reverse gear with driving gear on the input shaft. This is effected through an auxiliary gear drive called idler gear.

The gearbox further comprises of a mechanism to inhibit engagement of reverse when vehicle is moving in forward direction. This is required since when the vehicle is moving in forward direction (i.e. forward gears are engaged), there is a possibility that the reverse gear is inadvertently engaged, which tends to move the vehicle in reverse direction. This results in large magnitude of forces resulting in over-stresses in gear drives, which may be attributed to sudden change in direction of vehicle inertia. To overcome this, the mechanism is appropriately designed to inhibit reverse gear engagement during forward gear ratios. In addition to this, the shifter assembly should be capable of providing improved shift feel (during both forward and reverse gear engagements) so that operator can easily shift between gears, resulting in hassle free transmission, and consequently, mobility of the vehicle. The mechanism to inhibit reverse gear engagement is explained in a greater detail in forthcoming paragraphs of the detailed description with reference to figures and referral numerals.

Use of terms such as “comprises”, “comprising”, or any other variations thereof in the description, are intended to cover a non-exclusive inclusion, such that a setup system, device, mechanism, assembly or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a mechanism proceeded by “comprising… a” does not, without more constraints, preclude the existence of other elements or additional elements in the mechanism.

Reference will now be made to a shifter assembly for a gearbox of a vehicle for transmission of power from input shaft to output shaft, and thereafter to a mechanism for controlling reverse gear engagement in the vehicle, and is explained with the help of figures. The figures are for the purpose of illustration only and should not be construed as limitations on the shift assembly as well as on the mechanism. Wherever possible, referral numerals will be used to refer to the same or like parts.

FIG. 1 illustrates sectional front view of the shifter assembly (500) in gearbox provided with a mechanism (300) to control reverse gear engagement in a vehicle, according to an embodiment of the present disclosure. The shifter assembly (500) is a fundamental part of the gearbox through which the vehicle speed is controlled, so that the vehicle can be propelled within safe driving limits. The shifter assembly (500) essentially comprises of a gear shift lever (not shown) and is generally operated manually to shift to various gear ratios. All the other sub-assemblies and/or components of the gearbox are enclosed within the gearbox housing (501). The gear shift lever is pivotally disposed on a shaft (502) so that the lever can be pivotally manipulated by the operator for engagement of an appropriate gear. Further, the gear shift lever is configured to move in transverse directions (forward-backward direction and side-wards) about the shaft (502). The shaft (502) is further mounted with a selector member (103a) which is configured to have a rocking motion when the gear shift lever is manipulated. In other words, the selector member (103a) is adapted to rotate during manipulation of gear shift lever. The selector member (103a) further comprises of a radial recess cut on its underside into which a selector element (103b) is inserted. The selector element (103b) comprises of a projection to engage in each of the plurality of slots of a plurality of selector forks (102a, 102b). In an embodiment of the present disclosure, the selector element includes but not limiting to a finger shaped element. The plurality of selector forks (102a, 102b) are placed parallel to each other below the selector member (103a), each of which is configured to axially slide to selectively engage specific gear on the output shaft (not shown) with driving gear of the input shaft (not shown).

Further, the shifter assembly (500) comprises a mechanism (300) to inhibit reverse gear engagement when the vehicle is moving in forward direction, above a predetermined speed. The mechanism essentially comprises of a detent (200) positioned in a bore (100) of the gearbox housing (501) in such a way that the one end of the detent (200) is in contact with the selector member (103a). This contact assists in restraining the selector member (103a) depending on whether or not the reverse gear is engagement is required. In other words, the detent (200) which contacts with the selector member (103a) restricts the rotation of selector member (103a) when reverse gear engagement is undesired, and conversely, allows the selector member (103a) to rotate freely when reverse gear engagement is desired. This can be explained in detail as follows: When reverse gear engagement is undesired (i.e. when vehicle is moving in forward direction above a predetermined speed), the detent (200) comes in contact with selector member (103a). The presence of actuator (205) in between rear end of the detent (200) and gearbox housing (501) obstructs the movement of the detent (200) to extreme end position inside the bore (100) of gearbox housing (501). This prevents rotation of selector member (103a) by the gear shift lever, when an attempt is made to engage reverse gear. If reverse gear is to be engaged, the actuator (205) is retracted so that it moves away from the detent (200), allowing the detent (200) to be moved to extreme end in the bore (100) of the gearbox housing (501). When the gear shift lever is manipulated to engage the reverse gear, the selector member (103a) pushes the detent (200) inside the bore (100) so as to freely rotate and then engage the reverse gear shifter fork (102b).

FIG. 2 is an exemplary embodiment of the disclosure which illustrates perspective view of the detent (200) used in mechanism (300) to control reverse engagement in a vehicle. The detent (200) essentially comprises of housing (201) which encloses all the components within it. One end of the housing (201) maintains contact with selector member (103a) as clearly explained in previous paragraphs. The other end of the housing (201) has an enlarged stepped portion, whose end surface comes in contact with the extreme end of the bore (100) of the gearbox housing (501), when reverse gear is engaged. In an embodiment of the present disclosure, the shape of the detent (200) is frusto-conical with arcuate front end. The housing (201) further comprises of a first bore (201a) and a second bore (201b) provisioned up to a predetermined axial depth. A first resilient member (203) is axially inserted in a first bore (201a) such that one end of the first resilient member (203) contacts an end portion of the first bore (201a), and other end of the first resilient member (203) is loaded on a guide member (202). In an embodiment of the present disclosure, the guide member (202) includes but not limiting to a closed pipe, plate and cap shaped member. Further, the first resilient member (203) has a first predetermined stiffness. The stiffness of a resilient member herein above and below can be defined as the magnitude of force required to cause unit deformation or deflection in it. Further a second resilient member (204) is provisioned in the second bore (201b) such that one end of the second resilient member (204) is configured to contact an end of the second bore (201b) and the other of the second resilient member (204) is adapted to contact gearbox housing (501). The second resilient member (204) has a second predetermined stiffness. In an embodiment of the present disclosure, the first resilient member (203) and the second resilient member (204) includes but not limiting to a spring, such as but not limiting to a helical spring. In another embodiment of the present disclosure, the first predetermined stiffness of the first resilient member (203) is greater than the second predetermined stiffness of the second resilient member (204). This can be ascribed as follows: The first resilient member (203) having first predetermined stiffness of a higher value requires large magnitude of force to cause unit deflection. For example, a helical compression spring with a high stiffness requires large magnitude compressive forces to compress it by a unit value. Similarly, the second resilient member (204) with considerably lesser stiffness can be deformed by a small magnitude force. In an alternate embodiment of the present disclosure, the second bore (102b) is provided in the guide member (202) into which the second resilient member (204) is inserted. The above quoted example is for the purpose of illustration only and is not in any way limiting the scope of the disclosure

FIGS. 3a and 3b illustrate sectional front view and right side view respectively of the mechanism (300) with actuator (205) in first position (FP), to prevent reverse gear engagement in the vehicle, according to one embodiment of the present disclosure. The mechanism (300) comprises of detent (200) whose constructional features are clearly outlined in previous paragraphs of the detailed description. The mechanism (300), in addition to the detent (200), comprises of at least one actuator (205) configured to extend and retract in the gap between the detent (200) and gearbox housing (501). The actuator (205) is adapted to be interfaced with the control unit (206) (not shown) of the vehicle. The control unit (206) controls extension-retraction movement of the actuator (205) based on various conditions such as vehicle speed and clutch engagement/disengagement. In an exemplary embodiment of the present disclosure, the actuator (205) includes but not limiting to electrical solenoid, pneumatic and hydraulic actuator. In another exemplary embodiment of the present disclosure, the actuator (205) comprises of a plunger configured to move between the first position (FP) and the second position (SP). The control unit (206) regulates the movement of the actuator (205) between first position (FP) and second position (SP). In an embodiment of the present disclosure, the control unit (206) provided in the vehicle includes but not limiting to Electronic Control Unit (ECU) of a vehicle, a microprocessor and a microcontroller. The logic signals are transmitted based on a predetermined speed of the vehicle moving in forward direction, as well as on whether or not the clutch is engaged. In an embodiment of the present disclosure, the predetermined speed of the vehicle ranges from 5 kilometre per hour to 10 kilometre per hour.

As clearly depicted in FIGS. 3a and 3b, when the vehicle moves in forward direction with a speed greater than lower limit of predefined speed range (i.e. greater than 5 kilometre per hour), the actuator (205) is moved to the first position (FP) so as to obstruct the movement of the detent (201) axially inside the bore (100) of the gearbox housing (501), and thereby prevents contact between the detent (201) with the gearbox housing (501). This is accomplished by the guide member (202) of the detent (200) which is configured to selectively contact the actuator (205). When an attempt is made to engage reverse gear by applying force on the detent (200), the actuator (205) in First position (FP) contacts the guide member (202), preventing its movement towards gearbox housing (501), and thereby tries to compress the first resilient member (203). However, the first resilient member (203) which is inserted in a pre-compressed state in first bore (201a) resists further compression, owing to its high stiffness. The second resilient member (204), however, remains in free-state (i.e. uncompressed state) in this condition. Further, stopping (or obstruction) of the detent (200) by the actuator (205) prevents rotation of the selector member (103a) (shown in FIG. 3) when an attempt is made to engage the shifter fork (102b) corresponding to reverse gear. Even if an attempt is made to engage reverse gear by applying more force on the gear shift lever, the first predetermined stiffness of the first resilient member (203) offers very large resistance to detent (200) movement in the bore (100). In this way, the engagement of reverse gear is inhibited when vehicle moves in forward direction.

FIGS. 4a, 4b and 4c illustrate sectional front views, and right side view respectively of the mechanism (300) with actuator (205) in second position (SP), which allows reverse gear engagement in the vehicle, according to another embodiment of the present disclosure. The mechanism (300) not only allows the operator to shift to reverse gear when vehicle is to be moved in reverse direction, but also improves the shift feel so that the operator can engage reverse gear with reduced effort. When speed of the vehicle comes below the lower limit of the predetermined speed (i.e. below 5 kilometre per hour), the actuator (205) is activated by the control unit (206) (not shown) so that the actuator (205) is moved to second position (SP) (shown in FIG. 4a). This movement of the actuator (205) to second position (SP) evacuates the space (or gap) between the detent (200) and the gearbox housing (501). This facilitates the movement of the detent (200) axially in the bore (100) of the gearbox housing (501) to its extreme end. When gear shift lever is manipulated to engage reverse gear shifter fork (102b), the selector member (103a) pushes the detent (200) in the bore of the gearbox housing (501), compressing the second resilient member (204). This is because, the second resilient member (204) being a low stiffness member can be deformed (compressed) easily by application of small magnitude force. This allows the detent (200) to come in contact with the gearbox housing (501) as clearly shown in FIG. 4b. In this way, the mechanism (300) facilitates engagement of the reverse gear when desired.

FIG. 5 illustrates sectional front view of the mechanism (300) to facilitate reverse gear engagement in a vehicle during emergency conditions, according to an exemplary embodiment of the present disclosure. During emergency conditions like failure of actuator (205), non-operation of control unit (206), and the like, there should be an appropriate arrangement in the mechanism (300) to allow engagement of reverse gear, when it is desired. The above mentioned emergency conditions are for the purpose of understanding only and should not be construed as factors limiting the scope of the disclosure. During emergency conditions, the actuator (205) remains in the gap between the detent (200) and the gearbox housing (501), preventing the contact between the detent (200) and gearbox housing (501). When the gear shift lever is manipulated to engage reverse gear shifter fork (102b), the selector member (103a) pushes the detent (200) towards the extreme end of the bore (100) in gearbox housing (501), which is prevented by the actuator (205). However, if operator applies a large force on the gear shift lever which sufficiently overcomes the first predetermined stiffness of the first resilient member (203), the detent (200) can be moved to extreme end of the bore (100) in gearbox housing (501). This causes deformation (or deflection) in the first resilient member (203) by a small magnitude. The movement of the detent (200) is attributed to the presence of a rectangular recess (201c) provisioned axially to a small depth at the bottom of the detent housing (201), so that the plunger of the actuator (205) fills the rectangular recess (201c). But the guide member (202) is obstructed by the actuator (205) during this movement of detent housing (201) towards gearbox housing (501). In other words, when the detent (200) is pushed by the selector member (103a), only the detent housing (201) makes a contact with the gearbox hosing (501), while the guide member (202) is obstructed by the actuator (205). This causes the guide member (202) to be pushed axially inward relative to the direction of movement of the detent housing (201).
In an exemplary embodiment of the present disclosure, the actuator (205) is an electric solenoid with a plunger. During reverse gear inhibition, plunger of the solenoid fills the gap between the detent housing (201) and gearbox housing (501), so that the detent (200) is not allowed to come in contact with gearbox housing (501). When reverse gear engagement is desired, the solenoid is energized by electric power so as to retract the plunger away from the detent (200), thereby evacuating the gap between the detent (200) and gearbox housing (501). This allows the movement of detent (200) to come in contact with gearbox housing (501).

FIG. 6 is an exemplary embodiment of the disclosure which illustrates a flowchart depicting control logic of the control unit (206) to regulate reverse gear engagement in the vehicle. The operation of actuator (205) is dependent on the control signals transmitted by the control unit (206) of the vehicle. The operation of control unit (206) in turn is dependent on speed of the vehicle as well as on the clutch position. As shown in FIG. 6, the control unit (206) collects data such as vehicle speed and clutch position by appropriate input devices. In an embodiment of the present disclosure, the input device to provide vehicle speed data includes but not limiting to speed sensors, and input device to provide clutch position data includes but not limiting to position sensors, such as but not limiting to proximity sensors. Then, the control unit (206) makes a decision based on open and close positions of the clutch, and based on whether vehicle is moving at a speed of 5 kilometre per hour or not. The working of control logic is as follows: Based on data received from respective input devices, the control unit (206) checks whether clutch is engaged. If clutch is in engaged condition, then no signal will be sent to the actuator (205) and actuator (205) will not operate (i.e. the actuator (205) will remain in first position (FP)). If clutch is disengaged, then the control unit (206) checks whether vehicle is moving at a speed greater than 5 kilometre per hour or not. If speed is above 5 kilometre per hour, no signal will be transmitted to actuator (205) and the actuator (205) remains in first position (FP). If clutch is in disengaged condition and vehicle is moving at a speed lesser than 5 kilometre per hour, signal will be transmitted to the actuator (205) so that the actuator (205) moves from First position (FP) to second position (SP), allowing the reverse gear engagement.

Advantages:
The present disclosure provides a mechanism to inhibit reverse gear engagement when vehicle is moving in forward direction. The mechanism is of electro-mechanical type which has high degree of precision and control when compared to mechanical counterparts.

The present disclosure provides a mechanism to control reverse gear engagement/disengagement based on vehicle speed and clutch position, resulting in smooth and hassle free transmission between gears.

The present disclosure provides a mechanism to control reverse engagement, which allows easy shift to reverse gear by facilitating compression of a low stiffness resilient member, thereby improves shift feel of the operator.

The present disclosure provides a mechanism to control reverse engagement, which facilitates reverse gear engagement during unanticipated circumstances such as failure of control unit, failure of actuator and transmission lines, and the like. This makes the mechanism reliable.

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.

TABLE OF REFERRAL NUMERALS

Referral Numerals Description
500 Shifter assembly
501 Gearbox housing
100 Bore in gearbox
101a Shafts
102a Forward gear shifter forks
102b Reverse gear shifter fork
103a Selector member
103b Shifter element
300 Mechanism to control reverse gear
200 Detent
201 Housing
201a First bore
201b Second bore
201c Rectangular recess
202 Guide member
203 First resilient member
204 Second resilient member
205 Actuator