DESC:Field of Invention:
[001] The present invention relates to a transmission system and in particular relates to automatic manual transmission (AMT) system used in a vehicle.
Background of Invention:
[002] The transmission is one of the essential and important component of an automotive vehicle. The motive force produced by a prime mover is transferred to the driving wheels of the vehicle through the transmission system. The power produced needs to be transferred in a controlled manner to wheels which is done by the transmission using specific combinations of gear arrangements. The gear ratio may be changed or selected through a gear shifting mechanism based on vehicle operating conditions. Typically transmission is a bulky component. Transmissions may be classified as automatic, semi-automatic, automated manual transmission (AMT) or manual based on how gear shifting is accomplished.

[003] In case of automatic transmission there is no manual intervention for shifting the gears and the power is transmitted through a pulley and belt system. This system generally suffers loss of efficiency due to belt and pulley arrangement. Whereas, in case of AMT gears are also changed automatically; however it does not utilize the belt and pulley mechanism rather the power is transmitted through conventional gear system which has higher transmission efficiency as compared to belt and pulley. Hence transmission efficiency of AMT is higher as compared to automatic transmission. The AMT system comprises a gear shift motor for actuating gears and a clutch actuation motor for actuating the clutch during shifting of gears while rest of the system remains similar as in conventional manual transmission. The motors are operated based on pre-determined control logic which is pre-stored in a processor or vehicle control unit (VCU) of the vehicle.

[004] The conventional transmission is bulky and requires considerable space in any automotive vehicle, especially in case of two wheeled or three wheeled or small four wheeled vehicle (for example Quadricycle) where vehicle space constraint is a major challenge. With AMT system the existing transmission may become more bulky as it requires space to install gear shifting motor and clutch actuation motor. With compact vehicles where there is a space constraint it may become challenging to accommodate the gear shifting and clutch actuation motors. Generally in any compact vehicle there is a space constraint in a vertical direction for example, in a particular type of vehicle lay out ,in order to provide vertical mounting of motors the complete layout of existing vehicle may need to be changed which is a costly and time consuming task.

[005] In case of two wheeled vehicles the motors may be visible from outside and can hamper the overall aesthetics of the vehicle. Hence the motors need to be placed such that the aesthetics of the vehicle is not compromised. Also, another challenge is an external impact on the motors such as stone hitting or environmental impact which may damage the motors completely. Therefore, the motors needs to be packaged such that there is minimum external impact on motors and remains protected.

[006] In AMT system motors provide essential actuating force for actuating both gears and clutch. The motor output may not be used as it is and needs to be reduced to a suitable level using a reduction mechanism. The reduction mechanism comprises a number of gear pairs which reduces output torque and speed. The number of reduction gear pairs may vary based on requirement such as output torque, speed required for actuating the clutch and gears. There is a transmission loss with use of such a reduction mechanism. As per prior art systems, the motor output shaft and the gear shift mechanism are placed at a distance from each other which requires longer and complex mechanisms to transmit the power of motor to the gear shift mechanism. Due to this, there is a higher transmission loss, also the cost of the system is higher due to complex mechanism. Hence it is desirable that the motor and gear shift mechanism are placed close to each other such that there is minimum transmission loss.

[007] Hence an object of the present invention is to provide an automatic manual transmission (AMT) system in a compact space with minimum changes in the existing vehicle layout.
[008] Another object of the present invention is to provide an automatic manual transmission (AMT) which is less complex at lower cost.

Summary of Invention:
[009] With such objects in view, the present invention provides a transmission system for a vehicle comprising:
at least two gear pairs with a gear shifting mechanism configured to transmit power produced by an engine and enclosed by a crankcase on one side of the engine and a clutch cover mounted on the other side of the engine and the crankcase; and
at least a gear shift motor for shifting gear and a clutch actuation motor for actuating a clutch wherein; the gear shift motor is mounted substantially horizontal on a crankcase and the clutch actuation motor is mounted substantially horizontal on a clutch cover.

[010] The gear shift motor is motor is mounted along the width direction of transmission when viewed from front side and the clutch actuation motor is mounted on the opposite side of the gear shift motor and mounted along the longitudinal direction of the transmission system.

[011] Both the gear shift and clutch actuation motor are mounted horizontally, they may appear substantially perpendicular to each other in a top view.

[012] The motors are mounted such that no part of said motors is beyond the width and longitudinal dimensions of the transmission system. This allows a compact arrangement for the transmission system.

[013] The clutch actuation motor is mounted at an angle to the axis of the gear shift motor when viewed from side. Further, the clutch actuation motor makes an acute or obtuse angle with horizontal plane when viewed from side thereby further assisting in compact arrangement.

[014] The gear shift motor is mounted on the crankcase such that the motor is placed close to the gear shift mechanism. The motor output shaft is connected to a reduction mechanism which is further connected to the gear shifting mechanism. According to a preferred embodiment, the gear shift mechanism comprises a gear shift drum and at least one lever which is used to select or change the gear pair.

[015] The gear shift drum comprises slots on its peripheral surface and engages with at least a lever for selecting gears as used in conventional drum type gear shifting. The working and design of gear shift drum system is explained in applicant’s another patent application 4942/MUM/2015 filed on 30/12/2015 the reference of which is brought herein.

[016] According to one of the embodiments, the reduction mechanism is a two-step reduction mechanism wherein, the motor output shaft is connected to a first reduction gear mounted on an intermediate shaft which is further connected to the second reduction gear. The output from the second reduction gear is used to rotate the gear shift drum during change of gear pair.

[017] Additionally, a clash relieving mechanism may be provided between motor output and the gear shift drum in order to minimize gear clash condition. The clash relieving mechanism, construction and working is explained in applicant’s another patent application 3470/CHE/2011 dated 07/10/2011 the reference of which is brought herein. The clash relieving mechanism provides sufficient time to shift the gear in clash condition and helps in avoiding or overcoming the gear clash condition.

[018] The location of gear shift motor and the gear shift drum along with reduction mechanism is designed to be minimum in order to have compact arrangement with minimum transmission loss.

[019] Similar to the gear shift motor, the clutch actuation motor is connected to a clutch through a reduction mechanism for the clutch motor. The output torque of the motor is utilized to actuate the clutch. The rotational motion of the clutch actuation motor needs to be converted into linear motion which may be done using suitable means such as worm and worm wheel or nut and screw arrangement. The clutch actuation motor is mounted on the clutch cover which is most convenient location for operating the clutch as it minimizes the distance between clutch and clutch actuation motor which allows use of a less complex mechanism and compact arrangement. The axis of the clutch actuation motor is at an angle, preferably an obtuse angle with the horizontal plane, though an acute angle is also possible. The clutch actuation motor is mounted along the longitudinal direction of transmission such that it does not protrude beyond the width of the transmission.

[020] Hence according to a particularly preferred embodiment of the present invention, the transmission system is provided with a gear shift motor and the clutch actuation motor mounted substantially horizontally on the crankcase and clutch cover respectively, opposite to each other and within the width of the transmission system. The Clutch actuation and gear shifting motors are mounted substantially horizontal such that both the motors are not protruding from the transmission and located well within the dimensions of the transmission. This helps in achieving a compact arrangement as well as improving the aesthetics and protecting the gear shift and clutch actuation motors from any external impact. This results in a compact and most convenient arrangement which helps in saving space and cost.

Brief Description of Drawings:
[021] The transmission system of the present invention may be more fully understood from the following description of preferred embodiments thereof, made with reference to the accompanying drawings in which

[022] Figure 1 illustrates an isometric view of AMT system along with an engine according to an embodiment of the present invention
[023] Figure 2 illustrates a front isometric view of the AMT system shown in Figure 1.

[024] Figure 3 illustrates a side isometric view of the AMT system shown in Figures 1 and 2.
[025] Figure 4 illustrates a top view of the AMT system shown in Figures 1 to 3.
[026] Figure 5 illustrates the gear actuation mechanism for the AMT system shown in Figures 1 to 4.
[027] Figures 6a and 6b illustrate isometric views of AMT systems along with an associated engine according to a second embodiment of the present invention.
[028] Figures 7a and 7b illustrates a side view of the AMT system from right and left side respectively according to the second embodiment of the present invention.
[029] Figure 8 illustrates a front view of the AMT system shown in Figures 6a to 7b.
[030] Figure 9 illustrates a rear view of the AMT system shown in Figures 6a to 8.
[031] Figure 10 illustrates a top view of the AMT system shown in Figures 6a to 9.
[032] Figure 11 illustrates a bottom view of the AMT system shown in Figures 6a to 10.

Detail Description of Invention:
[033] The AMT system developed according to the present invention is explained with the help of Figures 1 to 11. The figures 1 to 4 illustrates the compact arrangement of an AMT system according to the one of the embodiment of the present invention and figures 6a to 11 represents AMT system according to another embodiment of the present invention.

[034] The figure 1 illustrates the isometric view of transmission with AMT system (100) mounted on an engine (110). The AMT System (100) comprises a gear shift motor (120) and a clutch actuation motor (140). The AMT system (100) is provided with a clutch cover (135) on one side of engine (110) and a crankcase (145) on other side. Both the gear shifting motor (120) and Clutch actuation motor (140) are mounted substantially horizontally to have a compact packaging. The power produced by the engine (110) is transferred to the transmission system of AMT comprising gear arrangement. The gear shift motor (120) is configured to operate the said gear arrangement whereas the clutch actuation motor (140) actuates the clutch for example during shifting of gears. Both the gear shift motor (120) and the clutch actuation motor (140) operates according to a predetermined control strategy as per typical AMT system. The control strategy is pre-stored in an ECU (not shown) of the vehicle. A starter motor (150) may also be mounted on the crankcase (145) of engine (110). This arrangement is irrespective of engine type, capacity etc. and may be applicable for any sort of engines.

[035] The arrangement of both gear shift motor (120) and the clutch actuation motor (140) is further explained with respect to different views as illustrated in figure 2 to figure 4. The gear shift motor (120) is mounted on a crankcase (145) substantially horizontally such that the axis of the motor (120) is substantially parallel to the horizontal plane. The clutch actuation motor (140) is mounted on a clutch cover (135) such that its axis is at an angle with the horizontal plane i.e. the clutch actuation motor (140) is mounted substantially horizontal within the dimensions of the transmission. The angle of inclination may be acute or obtuse decided based on the available space in the vehicle. Preferably, the axis of clutch actuation motor (140) is also at an angle to the axis of gear shift motor. This angle may also be acute or obtuse based on the vehicle and transmission layout.

[036] According to the illustrated embodiments, the gear shift motor (120) and the clutch actuation motor (140) may appear substantially perpendicular when viewed from the top. Both the motors (120,140) are installed well within the overall dimensions of the transmission. This arrangement helps to achieve a compact layout with minimum interference to the other associated components in the vehicle.

[037] The gear shift motor (120) is mounted as close as possible to its reduction gear arrangement such that there is minimum transmission loss as well as any complex mechanism to transfer motor torque to gear shift arrangement may be avoided. According to one of the embodiment the transmission system (100) comprises a drum type gear shifting arrangement (500) as illustrated in figure 5. The gear shifting arrangement (500) comprises a drum (505) and at a lever (510) used to shift the gears (515). The number of gears may vary based on the vehicle specification and requirements. The drum (505) rotates which moves the lever (510) and engages the required gear. In case of AMT system the drum (505) is rotated using a gear shift motor (120). The output shaft (180) of the motor (120) is connected to the drum (505) such that the rotational motion of the output shaft of motor forces the drum (505) to rotate by pre-determined amount which further engages the desired gear. The output shaft (180) of the motor is connected to the drum through a clash relieving mechanism (130), details of which are described in applicant’s another patent application having application number 3470/CHE/2011 dated 07/10/2011 the reference of which is brought herein. As the gear shift motor (120) is mounted horizontally on the crankcase such that the output shaft of the motor is close to the drum type gear shift arrangement (500). The horizontal arrangement helps in having a simple mechanism to transmit the force to the drum as against the vertical mounting of motor which requires a complex mechanism.

[038] The clutch actuation motor (140) is mounted such that there is a minimum of complex mechanisms for transmitting torque produced by the motor (140) to actuate the clutch. The rotational motion of the output shaft of the motor (140) needs to be converted into a linear motion of clutch actuation shaft which actuates the clutch. The rotational motion of the output shaft may be converted into linear motion by various known mechanisms such as rack and pinion, screw and thread mechanism etc. According to a particularly preferred embodiment of the present invention, the screw and thread type mechanism (not shown) is used wherein, the clutch actuation shaft is partly provided with threaded or toothed surfaces which engages inside a nut having internal threads. The nut is rotated using a clutch actuation motor (140) which forces the clutch actuation shaft to move linearly preferably in forward direction for actuating the clutch. The horizontal mounting of clutch motor (140) on the clutch cover assist in having a simple mechanism for operating clutch with higher transmission efficiency.

[039] Figures 6 to 11 represents AMT system according to a second embodiment of the present invention which is useful in a vehicle with inclined or substantially horizontal mounting of engines such as in case of compact four wheeled vehicle including quadricycle and three wheeled vehicle. In such type of vehicle layout vertical mounting of engine is not possible due to space constraints in vertical direction hence the engine is mounted inclined or substantially horizontal. The horizontal mounting of actuation motors is advantageous in these type of engine as it allows compact packaging and does not require any vertical space. This helps in minimum modification in existing layout of the vehicle.

[040] As illustrated in the figure 6 to 11, the engine (610) is mounted substantially horizontal and provided with a transmission (600) equipped with AMT system and comprising plurality of gears. The transmission is provided with a clutch cover (635) on one side and a crankcase (645) on other side of engine (610). A clutch actuation motor (640) is mounted on the clutch cover (635) substantially horizontally and a gear actuation motor (620) is mounted on the crankcase on the opposite side of clutch actuation motor (640). The gear actuation motor (620) is also mounted substantially horizontally.

[041] Figures 7a and 7b respectively provide views of each side of the transmission (600). The clutch actuation motor (640) is mounted inclined to the horizontal plane. The angle of inclination may be acute or obtuse decided based on the available space and vehicle layout. However, motor (640) may also be mounted perfectly horizontal. The motor (640) is mounted within the longitudinal dimension of the transmission (600) and also within width. Therefore, no part of clutch actuation motor (640) is protruding out from the transmission system. This arrangement helps in compact arrangement.

[042] Similar to the clutch actuation motor (640), the gear actuation motor (620) is mounted on the crankcase (645) opposite side of the clutch actuation motor (620). The gear actuation motor (620) is also mounted substantially horizontally on the crankcase (645) such that the motor (620) is within width of the transmission system (600). The transmission system (600) comprises a complete assembly of the components mounted to the crankcase (645) including flywheel, magneto etc. Hence, both the gear actuation motor (620) and the clutch actuation motor (640) are mounted well within dimensions of the transmission system (600). The horizontal mounting of actuators (620, 640) helps in compact arrangement without need of any modifications in vehicle layout.

[043] Similar to the first embodiment of present invention, the gear and clutch actuation system remains same. The gear actuation motor (620) is mounted closer to the gear arrangement within transmission system in order to improve the efficiency and reduce transmission loss. The clutch actuation motor (640) is mounted near to the clutch actuation mechanism which gives similar benefits.

[044] The size of the transmission may vary based on the specification such as number of gear pairs, type of gear shift mechanism, Clutch and related mechanism. However, according to the present system both the actuators/ motors are accommodated well with the dimensions of the transmission irrespective of size of transmission and may be applicable to any type of vehicle including two-wheeled, three wheeled and four wheeled vehicle such as quadricycle. In addition, the present system is applicable to the transmission of both two stroke and four stroke engines irrespective of capacity of engine.

[045] Modifications and variations to the AMT system described in the present specification may be apparent to skilled readers of this disclosure. Such modifications and variations are deemed within the scope of the present invention. ,CLAIMS:We Claim:
1. A transmission system for a vehicle comprising:
at least two gear pairs with a gear shifting mechanism configured to transmit power produced by an engine and enclosed by a crankcase on one side of the engine and a clutch cover mounted on the other side of the engine and the crankcase; and
a gear shift motor for shifting the gear pair and a clutch actuation motor for actuating a clutch wherein; the gear shift motor is mounted substantially horizontal on a crankcase and the clutch actuation motor is mounted substantially horizontal on a clutch cover.

2. A transmission system for a vehicle as claimed in claim 1 wherein; the gear shift motor is mounted along the width direction of transmission when viewed from front side and the clutch actuation motor is mounted on the opposite side of the gear shift motor and mounted along the longitudinal direction of the transmission system.

3. A transmission system for a vehicle as claimed in claim 1 wherein; the gear shift and clutch actuation motor are mounted horizontally and are substantially perpendicular to each other in a top view.

4. A transmission system for a vehicle as claimed in claim 1 wherein; the gear shift motor and clutch actuation motor are mounted such that no part of said motors is beyond the width and longitudinal dimensions of the transmission system.

5. A transmission system for a vehicle as claimed in claim 1 wherein; the clutch actuation motor is mounted inclined at an angle to the axis of the gear shift motor when viewed from side.

6. A transmission system for a vehicle as claimed in claim 1 wherein; the gear shift motor is mounted on the crankcase such that the motor is placed proximate to the gear shift mechanism wherein; the gear shift mechanism is in connection with the output shaft of gear shift motor and comprises a reduction mechanism connected to a gear shift drum and at least one lever used to select or change the gear pair.

7. A transmission system for a vehicle as claimed in claim 6 wherein; the reduction mechanism is a two-step reduction mechanism wherein, the output shaft of the gear shift motor is connected to an intermediate shaft through a first reduction gear which is further connected to a second reduction gear wherein; the second reduction gear is further connected to the gear shift drum.

8. A transmission system for a vehicle as claimed in claim 6 wherein; the gear shift mechanism comprises a clash relieving mechanism in order to minimize gear clash condition.

9. A transmission system for a vehicle as claimed in claim 1 wherein; the clutch actuation motor is connected to a clutch through a reduction mechanism wherein; the reduction mechanism comprises at least one gear pair used to connect an output shaft of the clutch actuation motor to the clutch.

10. A transmission system for a vehicle as claimed in claim 1 wherein; the clutch actuation motor is connected to the clutch such that the rotational motion of the clutch actuation motor is converted into a linear motion to actuate the clutch using suitable means including a worm and worm wheel or a nut and screw type arrangement.

11. A transmission system for a vehicle as claimed in any of the claim above wherein; the transmission system is applicable to any type of vehicle including two-wheeled, three wheeled and four wheeled vehicle such as quadricycle and both two stroke and four stroke engines irrespective of capacity of engine.