Claims:We claim:
1. A shift rod assembly (400) to introduce delay in gearshifts in a transmission (108) of a vehicle, said shift rod (114) is connected to a gearshift lever through at least one mechanical linkages,
characterized in that:
a split sleeve (202) comprising an opening between a first end (2022)
and a second end (2024), said sleeve (202) is co-axially coupled to said shift rod (114) and in such a manner that on movement of said gear shift lever, said sleeve (202) first rotates relative to said shift rod (114), and then rotates said shift rod (114) to shift gear.

2. The shift rod assembly (400) as claimed in claim 1, further comprises
a stopper (402), radially protruding out from said shift rod (114), said stopper (402) is arranged in an opening between said first end (2022) and said second end (2024) of said sleeve (202), and
at least one spring (404, 406) provided in said opening and is associated with said shift rod (114) and said sleeve (202), to assist relative movement between said shift rod (114) and said sleeve (202) when said gearshift lever is actuated.

3. The shift rod assembly (400) as claimed in claim 2, wherein a first spring (404) connects said first end (2022) of said sleeve (202) to a first end (502) of said stopper (402), and a second spring (406) connects said second end (2024) of said sleeve (202) to a second end (504) of said stopper (402).

4. The shift rod assembly (400) as claimed in claim 3, wherein said first spring (404) and said second spring (406) undergoes tension and compression due to relative motion between said sleeve (202) and said shift rod (114).

5. The shift rod assembly (400) as claimed in claim 2, wherein said shift rod (114) comprises a detent (602) on its side surface and said sleeve (202) comprises a cavity (604) opposite to said detent (602), a spring-loaded ball (606) is located inside said detent (602) and said cavity (604).

6. The shift rod assembly (400) as claimed in claim 5, wherein profile of said detent (602) is designed in a manner that on actuation of said gearshift lever, said sleeve (202) rotates relative to said shift rod (114) causing said profile to engage with said ball (606) thereby compressing said spring (404) inside said cavity (604).

7. The shift rod assembly (400) as claimed in claim 6, wherein said spring (404) expands and pushes said ball (606) against said profile of said detent (602) when said gearshift lever is released, causing said sleeve (202) to move to a default position.

8. The shift rod assembly (400) as claimed in claim 2, wherein a torsional spring is located in an annular space between said shift rod (114) and said sleeve (202).

9. The shift rod assembly (400) as claimed in claim 8, wherein said torsional spring is under tension when said sleeve (202) rotates relative to said shift rod (114).

10. The shift rod assembly (400) as claimed in claim 8, wherein said torsional spring brings said sleeve (202) and said shift rod (114) to a default position when said gearshift lever is released. , Description:Field of the invention:
[0001] The present disclosure relates to a shift rod in a transmission, and particularly relates to an assembly of the shift rod to introduce intentional delay in gearshifts in a semi-automatic or manual transmission.

Background of the invention:
[0002] In an e-clutch system, when the gear is upshifted or downshifted, the clutch should be opened before the gear gets changed. The clutch actuator requires certain time (~140ms) to open the clutch. If the existing push pull cable is used in an e-clutch system, the actuator gets less time to respond. So, there is a resistive force at the gear lever for the driver to change gear which leads to improper disengagement of gears. There is a loss of comfort for the driver while shifting. Further, this also lead to wear in the gear shifting mechanism especially near the shift fork and the collar of the shifting mechanism.
[0003] Thus, there is a need of having a delay in the shifting mechanism itself without affecting the drivability.

Brief description of the accompanying drawings:
[0004] An embodiment of the disclosure is described with reference to the following accompanying drawings,
[0005] Fig. 1 illustrates schematic of a conventional transmission of a vehicle;
[0006] Fig. 2 illustrates a conventional shift rod in a transmission of a vehicle;
[0007] Fig. 3 illustrates a graphical response curves of gearshift lever for two types of transmissions, according to an embodiment of the present disclosure;
[0008] Fig. 4 illustrates a schematic of a first shift rod assembly, according to an embodiment of the present disclosure;
[0009] Fig. 5 illustrates a top view of the first shift rod assembly, according to an embodiment of the present disclosure, and
[0010] Fig. 6 illustrates a top view of a second shift rod assembly, according to an embodiment of the present disclosure.

Detailed description of the embodiments:
[0011] Fig. 1 illustrates schematic of a conventional transmission of a vehicle. A general gear shifting mechanism is explained. An engine 102 is coupled to a gearbox/ transmission 108 through a clutch 104 and an input shaft 106. In a typical manual or semi-automatic transmission, the gears is engaged or disengaged by a driver by shifting the gearshift lever (not shown). For the manual transmission the clutch 104 is operated manually, whereas for the semi-automatic transmission the clutch 104 is operated by a clutch actuator. After overcoming the tolerances and backlashes, the movement of the gearshift lever, transmits the force of the driver through at least one shift cable 116 and at least one mechanical linkages to the shift rod 114 which is mounted in the gearbox/ transmission 108. A shift fork 112 is shifted or rotated to move a collar (also known as sliding sleeve) 1082 from the engaged gear to the next gear to be engaged. The shift fork 112 basically has a detent mechanism to ensure the gear remains in engaged position unless and until the driver applies the force to disengage a particular gear. An output shaft 110 then transmits the torque to the rear wheels with additional reduction/differential gears or other relevant attachments/ couplings. The shift rod 114 is also referred to as shift tower or selector rod or shift/selector shaft and must not be understood in limiting sense.
[0012] Fig. 2 illustrates a conventional shift rod in a transmission of a vehicle. The shift cable 116 is connected to a gearshift lever (not shown). A linear motion of the shift cable 116, shown by bi-directional arrow 208, is converted into rotational motion of a sleeve 202. The sleeve 202 is rigidly attached to the shift rod 114. Generally, whenever the sleeve 202 is rotated, the shift rod 114 also starts rotating without any delay due to the rigid interconnection. A corresponding attachment 204 is connected to the shift rod 114, which interacts with the shift fork 112, collar 1082 and the synchronizers (not shown) to engage the gears upon rotation of the shift rod 114. The sleeve 202 is shown for simplicity of understanding, and usually the shift cable 116 is directly connected to the shift rod 114 without any sleeve 202. A curved bi-directional arrow 210 represents the rotation of the shift rod 114 about the axis 214. The vertical bi-directional arrow 212 represents the up and down or axial movement of the shift rod 114 to select the specific gear lane or gate. The axial movement of the shift rod 114 is performed to select a gear lane, and the rotational movement of the shift rod 114 is performed to engage to a specific gear. For example: Left or right movement in an H-shaped gear layout is to select the gear lane and the forward and the reverse movement is to shift to a specific gear. A balancing weight 206 is attached to the sleeve 202 to reduce vibrations towards the gearshift lever and alignment of the sleeve 202 and shift rod 114.
[0013] Fig. 3 illustrates a graphical response curves of gearshift lever for two types of transmissions, according to an embodiment of the present disclosure. A first graph 314 represents a response curve for a three pedal manual transmission and a second graph 316 represents a response curve for a two pedal semi-automatic transmission. The X-axis 302 represents time and Y-axis 304 represents position in respective suitable units. The first graph 314 comprises a first curve 306 representing the opening of the clutch 104. A second curve 308 represents movement of gearshift lever while changing from one gear to another gear. The response time after opening the clutch 104 of the changing gear is more as shown by reference numeral 312. The gear must change as soon as the clutch 104 is opened.
[0014] With respect to second graph 316, the semi-automatic transmission though eliminates the large response time found in the manual transmission (explained for the first graph 314) but the driver feels a notch or resistance while moving the gearshift lever. A third curve 310 represents the movement of the gearshift lever by the driver. The third curve 310 is shown to be moving while the clutch 104 is still opening, hence causing a resistance in changing the gear. The Fig. 3 explains the problems associated with the vehicle transmissions 108 to bring out the need of an improvement.
[0015] Fig. 4 illustrates a schematic of a first shift rod assembly, according to an embodiment of the present disclosure. The present disclosure provides a solution to create/introduce delay in the gearshifts in the transmission 108 without affecting the stability of the transmission 108. The solution comprises a shift rod assembly 400 to introduce delay in gearshifts in a transmission 108, and particularly in a semi-automatic transmission. However, the same shift rod assembly 400 is possible to be implemented for a manual transmission. The semi-automatic transmission is also referred to as automated manual transmission. The shift rod 114 is connected to a gearshift lever through at least one mechanical linkage (not shown). The assembly 400 is characterized by a split sleeve 202 comprising an opening between a first end 2022 and a second end 2024. The split sleeve 202 is co-axially coupled to the shift rod 114 and in such a manner that on movement of the gearshift lever, the split sleeve 202 first rotates relative to the shift rod 114, and then rotates the shift rod 114 to shift the gear. The shift rod 114 is axially movable to select a specific gear lane. After the shift rod 114 is moved, the shift rod 114 is rotated to engage the attachment 204 with shift fork 112. The shift fork 112 then moves the collar 1082 to shift the gear. The split sleeve 202 is replaceable when required.
[0016] The split sleeve 202 is not rigidly connected to the shift rod 114, rather movably coupled to the shift rod 114. The shift rod assembly 400 further comprises a stopper 402, radially protruding out from the shift rod 114. The stopper 402 is arranged in an opening between a first end 2022 and a second end 2024 of the split sleeve 202. The shift rod assembly 400 still further comprises at least one spring 404, 406 provided in the opening. The springs 404, 406 are associated with the shift rod 114 and the split sleeve 202, to assist relative movement between the shift rod 114 and the split sleeve 202 when the gearshift lever is actuated/moved.
[0017] Fig. 5 illustrates a top view of the first shift rod assembly, according to an embodiment of the present disclosure. The first spring 404 is positioned between the first end 2022 of the split sleeve 202 and a first end 502 of the stopper 402. In other words, the first spring 404 connects the first end 2022 of the split sleeve 202 to a first end 502 of the stopper 402. Similarly, a second spring 406 is positioned between the second end 2024 of the split sleeve 202 and a second end 504 of the stopper 402. The first spring 404 and/or the second spring 406 are either arranged inside a recess of the first end 2022, 502 and second end 2024, 504 or directly connected to the respective ends. The gap between the first ends 2022, 502, and the second ends 2024, 504 of the split sleeve 202 and the stopper 402 respectively, provides the required or necessary delay in gear shift.
[0018] A method of operating the first shift rod assembly 400 is explained as below. When the driver shifts or moves the gearshift lever, the shift cable 116 is pulled or pushed based on the movement. The shift cable 116 is connected to the split sleeve 202 through at least one mechanical linkages. The gear selection and shifting operation is performed through the mechanical linkages, which imparts the movement to the shift rod 114 in axial and rotary manner. The mechanical linkages are not shown for simplicity and the same must not be understood in limiting sense. The shift cable 116 is also the part of the mechanical linkages, but addressed separately for explanation.
[0019] A pull action on the shift cable 116 rotates the split sleeve 202 in anti-clock direction. Thus, the first end 2022 of the split sleeve 202 moves towards the first end 502 of the stopper 402. While moving, the first spring 404 is compressed. Simultaneously, the second end 2024 of the split sleeve 202 moves away from the second end 504 of the stopper 402. The second spring 406 expands and is held in tension. The split sleeve 202 rotates relative to the shift rod 114 until the first end 2022 touches the first end 502 of the stopper 402, or is unable to move forward towards the first end 502 of the stopper 402 due to the stiffness or properties of the first spring 404 or the second spring 406.
[0020] At this moment, the shift rod 114 starts rotating along with the split sleeve 202 until the respective gear is engaged. When the desired gear is engaged, the driver releases the gearshift lever, the first spring 404 and the second spring 406 comes back to respective default state, and while doing so, the split sleeve 202 is rotated in clockwise direction. The shift rod assembly 400 comes back to default position where a gap exists between the first end 2022 of the split sleeve 202 and the first end 502 of the stopper 402. Similarly, a gap exists between the respective second ends.
[0021] The shift rod assembly 400 works in very much the similar way when the shift cable 116 is pushed, rotating the split sleeve 202 in clockwise direction. The first spring 404 and the second spring 406 undergoes tension and compression due to relative motion between the split sleeve 202 and the shift rod 114.
[0022] Fig. 6 illustrates a top view of a second shift rod assembly, according to an embodiment of the present disclosure. The second shift rod assembly 400 works similar to the first shift rod assembly 400 with a different construction. The shift rod 114 comprises a detent 602 on its side surface and the split sleeve 202 comprises a cavity 604 opposite to the detent 602. Further, a spring 404 loaded with ball 606 is located inside the detent 602 and the cavity 604. The stiffness of the spring 404 is predetermined along with the profile of the detent 602. According to another embodiment, the cavity 604 is provided on the shift rod 114 and the detent 602 is provided on the internal surface of the split sleeve 202.
[0023] The profile of the detent 602 is designed in such a manner that on actuation of the gearshift lever, the split sleeve 202 rotates relative to the shift rod 114 causing the ball 606 to engage with the profile of the detent 602. The split sleeve 202 rotates till one end touches or abuts the one end of the stopper 402. The ball 606 is then pushed inside the cavity 604 thereby compressing the spring 404 inside said cavity 604. When one end of the split sleeve 202 abuts the one end of the stopper 402, the ball 606 moves but remains in contact with the profile. The ball 606 moves and is in contact with an edge or corner of the profile. The ball 606 is partially pushed inside the cavity 604. The spring 404 loaded with the ball 606 together with the gap creates the necessary delay. After compression, the spring 404 is in a state where it urges the ball 606 to move out of the cavity 604, i.e. the spring 404 forces the ball 606 against the profile of the detent 602. Not to mention, the mechanical linkages are not shown and not explained for the simplicity of understanding.
[0024] During a pull action on the shift cable 116, the split sleeve 202 rotates in anti-clock direction until the first end 2022 of the split sleeve 202 touches/ abuts the first end 502 of the stopper 402. Once touched, the split sleeve 202 starts rotating the shift rod 114 and engages the gear. The time taken during the relative motion between the split sleeve 202 and the shift rod 114 creates the required delay. During the delay the shift intention of the driver is detected and provides the clutch actuator with enough and sufficient time to open the clutch 104 and engage the gear. The spring 404 is in compressed state whereas the ball 606 is held against an end part of the profile of the detent 602.
[0025] When the driver releases the gearshift lever, the spring 404 expands and pushes the ball 606 against the profile of the detent 602. Since the ball 606 is in contact with the profile, the spring 404 is able to push the ball 606 against the profile and comes to normal state. The expansion of the spring 404 causes the split sleeve 202 to move to a default position. Now, the shift rod assembly 400 is ready to introduce delay for the next gear shift operation. The detent 602 ensures that the delay is achieved between motions of the split sleeve 202 and the shift rod 114. The profile of the detent 602 and the characteristics of the spring 404 are achieved based on required delay in the gear shifting mechanism.
[0026] According to an embodiment of the present disclosure, a third shift rod assembly comprising a torsional spring is provided. The third shift rod assembly also works based on the relative motion between the sleeve 202 and the shift rod 114. A torsional spring is located in an annular space between the shift rod 114 and the sleeve 202. The annular space is created by profiling the side surface of the shift rod 114 or the internal surface of the sleeve 202 or both.
[0027] When the gearshift lever is moved, the shift cable 116 is pulled, rotating the sleeve 202 relative to the shift rod 114 in anti-clock direction. The torsional spring is under tension when the sleeve 202 rotates relative to the shift rod 114. The torsional spring imparts forces on the opposite direction of the rotation. When the first end 2022 of the sleeve 202 touches the first end 502 of the stopper 402 or when the sleeve 202 is unable to rotate further due to the stiffness of the torsional spring, then the shift rod 114 starts rotating with the sleeve 202, followed by engaging the gear.
[0028] When the driver releases the gearshift lever, the sleeve 202 is rotated in clockwise direction by due to retraction of the torsional spring to the normal state. Now, the shift rod assembly is ready for the next gear shift operation. The torsional spring brings the sleeve 202 and the shift rod 114 to a default position when the gearshift lever is released.
[0029] In general, whenever the driver tries to shift gears (example from 1st gear to 2nd gear) then the shift cable 116 is pulled and the sleeve 202 starts rotating clockwise or anticlockwise. Because of the rotation of the sleeve 202 the force transferred by the shift cable 116 is used for compressing the at least one spring 404, 406 between the stopper 402 or the shift rod 114 and the sleeve 202. Once the spring is compressed the contact is established between the sleeve 202 and the stopper 402 and hence the shift rod 114 starts rotating. The spring stiffness is selected such that the overall vibration inside the gearbox/ transmission 108 remain similar to what it was in the conventional design. The balancing weight 206 and the detent mechanism stiffness is changeable to adapt the overall stiffness.
[0030] The present disclosure creates/ introduces a mechanism comprising at least two rotating members i.e. the shift rod 114 and the split sleeve 202, and at least one spring to produce an inherent delay in the gear shifting process. The rest position and the amount of delay (Tdelay) is designed as a function of the torsional stiffness of the spring (Kt), the relative motion between the rotating members (Xre), and stroke of the shift rod 114 from engaged odd gear to engaged even gear (Xstroke). A similar delay is achieved in the detent mechanism between the split sleeve 202 and the shift rod 114 along with a relative motion between them.
[0031] According to an embodiment of the present disclosure, at least one assembly 400 to create delay in gear shifts is provided in the at least one mechanical linkages instead of the shift rod 114. The present disclosure, provides sufficient time to open the clutch 104. Due to time delay, the gear change is completely notch free. The gearshift lever is more stable and provides better user experience. There is smooth flow of power from engine 102 to the transmission 108 due to proper actuation of clutch 104. The delay introduced is referred to as time delay or mechanical delay.
[0032] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.