TECHNICAL FIELD

The present subject matter, in general, relates to a power transmission assembly of a vehicle and, in particular, relates to a gearshift assembly of the power transmission assembly of the vehicle.

BACKGROUND

In general, where power transmission in a vehicle is achieved through a gearbox, a clutch is used to facilitate shifting of gears. The clutch is normally a multi-plate clutch immersed in a lubricant, and is also called a wet multi-plate clutch. The clutch is mounted on a counter shaft and transmits power from the counter shaft to a drive shaft.

To shift a gear, both the clutch and the gearbox need to be operated. In operation, first the clutch is disengaged and then the gear is shifted. However, in conventional semi-automated manual transmission (SMT) two-wheeled vehicles, the clutch is not controlled by a rider. The clutch is disengaged automatically when the rider actuates a gearshift lever to operate a gearshift mechanism. The gearshift lever is disposed in proximity to a footrest of the vehicle, and the rider pushes an end of the gearshift lever to operate the gearshift mechanism. The actuation of the gearshift lever first disengages the clutch and then moves gear shifting forks to shift the gears and achieve a desired gear ratio. Thus, operation of the clutch as well as gear shifting is achieved through a single actuation mechanism.

However, due to the absence of a manual clutch lever the rider has to apply more force to operate the gearshift mechanism, as both the clutch disengagement and the gear shifting are performed by the gearshift mechanism. This can cause discomfort to the rider when the gears have to be changed frequently, for example, while driving in heavy traffic conditions.

SUMMARY

The subject matter described herein is directed to a gearshift assembly of a vehicle. The gearshift assembly includes a gearshift unit, a gearshift shaft, and an electromechanical actuator.

The electromechanical actuator is coupled to the gearshift shaft and the gearshift shaft is connected to the gearshift unit. The electromechanical actuator includes a motor and an actuator gearbox assembly. The actuator gearbox assembly is coupled to a motor shaft of the motor. Further, the electromechanical actuator is coupled to the gearshift shaft. The electromechanical actuator actuates the gearshift shaft, which in turn actuates the gearshift unit. The gearshift unit is provided to shift gears of the vehicle.

These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

The above and other features, aspects and advantages of the subject matter will be better understood with regard to the following description, appended claims, and accompanying drawings where:

Fig. 1 illustrates a sectional top view of a gearshift assembly of a conventional semi-automated manual transmission (SMT) vehicle.

Fig. 2 illustrates a block diagram of an exemplary gearshift assembly of an SMT vehicle, according to an embodiment of the present subject matter.

Fig. 3 shows a side view of an internal combustion (IC) engine of an SMT vehicle positioning an exemplary electromechanical actuator, according to an embodiment of the present subject matter.

Fig. 4 shows an exemplary actuator gearbox assembly of an exemplary electromechanical actuator, according to an embodiment of the present subject matter.

DETAILED DESCRIPTION

Although a gearshift assembly of the present subject matter has been explained in considerable details with respect to a two-wheeled vehicle, however, it will be understood that the gearshift assembly can be implemented in any two-wheeled or three-wheeled vehicle having a constant mesh gearbox.

Fig. 1 illustrates a sectional top view of a gearshift assembly 100 of a conventional semi-automated manual transmission (SMT) two-wheeled vehicle. The gearshift assembly 100 is part of a power transmission assembly of the vehicle and includes a gearshift unit (not shown in the figure), a clutch assembly 102, a gearshift lever 104, a gearshift shaft 106, a gearshift arm assembly (not shown in the figure), and a vehicle gearbox (not shown in the figure).

The clutch assembly 102 includes a clutch 108, a counter shaft 110, an auto clutch release arm 112, and a clutch release pin 114. The gearshift shaft 106 connects the gearshift lever 104 to the auto clutch release arm 112. The gearshift shaft 106 further connects the gearshift lever 104 to the gearshift unit through the gearshift arm assembly. On operation of the gearshift lever 104, the gearshift shaft 106 operates the clutch 108, i.e., the gearshift shaft disengages the clutch 108 and subsequently actuates the gearshift unit. The gearshift unit further shifts a gear in the vehicle gearbox.

In the conventional SMT vehicle, the clutch 108 is an automatic clutch and, hence, does not need to be operated manually. The clutch 108 is a wet multi-plate clutch mounted on the counter shaft 110. The clutch 108 is automatically disengaged when a rider riding the SMT vehicle operates the gearshift lever 104 to shift a gear. The rider has to use foot movements to operate the gearshift lever 104, which is generally positioned near a left footrest of the vehicle. A push at either ends of the gearshift lever 104 can actuate the gearshift shaft 106.

The gearshift shaft 106 disengages the clutch 108 and subsequently actuates the gearshift arm assembly. The gearshift shaft 106 reciprocates along an axis 116, as indicated by an arrow 118, and, in the process, rotates the clutch release arm 112 about a pivot 120, as indicated by an arrow 122. Further, the clutch release arm 112 actuates the clutch release pin 114 to disengage the clutch 108. Once the clutch 108 is disengaged, the gearshift arm assembly actuates the gearshift unit, which shifts the gear by moving the gear shifting forks (not shown in the figure).

Hence, in the conventional SMT vehicle, for shifting a gear, the rider always needs to push the gearshift lever 104 by using foot movements. Pushing the gearshift lever 104 can create discomfort for the rider when the gears have to be frequently changed, for example, while riding in city traffic conditions. Moreover, due to varying rider-specific patterns of operating a manually controlled gearshift mechanism in vehicles, up to 2-5% variation in fuel consumption is also noticed. For example, when the rider rests his or her foot on the gearshift lever 104 while riding the vehicle, slight disengagement of the clutch 108 may occur, causing the clutch 108 to slip. This is known as partial disengagement or half-clutch position. Even seemingly slight clutch slips can cause variation in fuel consumption.

The subject matter described herein is directed to a gearshift assembly for a semi-automated manual transmission (SMT) vehicle, hereinafter referred to as an SMT vehicle.

An electromechanical actuator replaces a gearshift lever of a conventional SMT vehicle. In an embodiment of the present subject matter, the gearshift assembly includes the electromechanical actuator, which further includes a motor, for example, a permanent magnet direct current motor, and an actuator gearbox assembly having a compound gear train. The actuator gearbox assembly is coupled to a motor shaft of the motor. An output shaft of the actuator gearbox assembly is connected to an output link, which is in turn connected to a gearshift shaft through a connecting link.

In operation, when a rider wants to shift a gear, the rider can operate a switch provided on a handlebar of the SMT vehicle. The switch may be electronically coupled to the motor, thereby activating the motor when the switch is operated. In one implementation, there may be two switches coupled to the motor to select a direction of rotation of the motor.

On actuation of the motor, the actuator gearbox assembly coupled to the motor transfers the rotational motion of the motor to the output shaft. The rotational motion of the output shaft imparts a reciprocating motion to the connecting link via the output link. The reciprocating motion of the connecting link is transmitted to the gearshift shaft via an input link. The electromechanical actuator thus actuates the gearshift shaft and, in turn, a gearshift arm assembly connected to the gearshift shaft. The gearshift shaft disengages the clutch, while the gearshift arm assembly further actuates a gearshift unit, which then shifts the gear(s).

Fig. 2 illustrates a block diagram of an exemplary gearshift assembly 200 as implemented in a semi-automated manual transmission (SMT) vehicle (not shown in the figure), according to an embodiment of the present subject matter. The figure illustrates mechanical coupling of various components of the gearshift assembly 200. The positioning of the components as depicted in the figure is for the purpose of explanation only and should not be construed as a limitation.

In said embodiment, a vehicle gearbox (not shown in the figure) is a constant mesh gearbox. In one implementation, the SMT vehicle, is a step-through type of two-wheeled vehicle, such as a moped. Further, the gearshift assembly 200 of the SMT vehicle includes an electromechanical actuator 202, the clutch assembly 102, a gearshift unit 204, the gearshift shaft 106, and a gearshift arm assembly 206. The gearshift shaft 106 connects the electromechanical actuator 202 to the gearshift arm assembly 206, which is further connected to the gearshift unit 204.

The electromechanical actuator 202 includes a motor (not shown in this figure) and an actuator gearbox assembly (not shown in this figure). In an implementation, the motor is a permanent magnet direct current (PMDC). The actuator gearbox assembly is coupled to the gearshift shaft 106 through an output link 208, a connecting link 210, and an input link 212. The output link 208 is mounted on an output shaft 214 of the electromechanical actuator 202, whereas the input link 212 is mounted on the gearshift shaft 106. In an embodiment, the output link 210 and the input link 212 are placed substantially parallel to each other, and their movements are oscillating in nature.

Fig. 3 shows a side view of an internal combustion (IC) engine 300 of the SMT vehicle depicting a positioning of the electromechanical actuator 202, according to an embodiment of the present subject matter. In one implementation, the electromechanical actuator 202 is mounted on the engine crankcase 302 such that the output shaft 214 of the electromechanical actuator 202 is parallel to an axis of an engine crankshaft 304.

As already explained in fig. 2, the electromechanical actuator 202 includes a motor 306 and an actuator gearbox assembly 308 coupled to a motor shaft (not shown in this figure) of the motor 306. In one embodiment, the actuator gearbox assembly 308 is a step-down gearbox assembly. The output shaft 214 of the actuator gearbox assembly 308 is connected to a first end of the output link 208. A second end of the output link 208 is connected to an end of the connecting link 210, while another end of the connecting link 210 is connected to the input link 212. The input link 212 is, in turn, connected to the gearshift shaft 106. The gearshift shaft 106 is thus coupled to the output shaft 214 through the output link 208, the connecting link 210, and the input link 212.

The gearshift shaft 106, as explained in previous figures, is connected to the clutch assembly 102 of the vehicle gearbox. In one embodiment, the connecting link 210 is the smallest possible link between the electromechanical actuator 202 and the constant mesh gearbox. In operation, when a user wants to shift a gear, the user can operate a switch (not shown in this figure) provided on a handlebar (not shown in this figure) of the SMT vehicle. The switch is electronically coupled to the motor 306 by using any known ways or means.

The motor 306 is actuated when the switch is operated and, in turn, the electromechanical actuator 202 gets actuated. In one implementation, the SMT vehicle is provided with two switches: a first switch meant for upshifting the gears and a second switch meant for downshifting of the gears.

On actuation, the motor 306 rotates in either clockwise or anticlockwise direction depending on the switch operated. The actuator gearbox assembly 308 of the electromechanical actuator 202 transfers the rotational motion of the motor 306 to the output shaft 214 of the electromechanical actuator 202. In one implementation, the motor 306 is of approximate 100W capacity and gets power from a battery (not shown in the figure) present in the SMT vehicle.

The rotational motion of the output shaft 214 imparts a reciprocating motion to the connecting link 210 via the output link 208. The reciprocating motion of the connecting link 210 is transmitted to the gearshift shaft 106 via the input link 212. As already mentioned, the output link 210 and the input link 212 are placed substantially parallel to each other and their movements are oscillating in nature.

The electromechanical actuator 202 thus actuates the gearshift shaft 106, which then disengages the clutch 108 and subsequently actuates the gearshift arm assembly 206. The gearshift arm assembly 206 further actuates the gearshift unit 204, which then moves the gear shifting forks to shift the gear(s). The gearshift arm assembly 206 and the gearshift unit 204 may be conventional components used in existing SMT vehicles and equivalents thereof.

Once the gear is shifted to a desired gear, the electromechanical actuator 202 gets deactivated and the gearshift unit 204 returns back to its original position, partially due to springs (not shown in the figure) present in the gearshift unit 204 and due to clutch springs (not shown in the figure).

Further, the rotational motion of the motor 306 can be reversed by changing polarity of the voltage supplied to the motor 306, which is achieved by operating the appropriate switch. For the purpose, the electromechanical actuator 202, in one embodiment, is provided with an electronic control unit (not shown in the figure). The electronic control unit (ECU) can be any ECU known in the art. The ECU may receive inputs form both the switches, and, based on the input, the ECU decides the direction of rotation of the motor 306.

For example, if the rider wants to shift from a low gear to a high gear, such as from neutral to first gear or from first to second gear, the rider can operate the first switch. In this case, the ECU receives an input signal from the first switch. Based on the input signal, the ECU adjusts the polarity of voltage supplied to the motor 306 such that the motor 306 rotates in the required direction. For example, in an implementation, the motor 306 rotates in the clockwise direction for upshifting the gears.

Similarly, to shift from a high gear to a low gear, for example, from second gear to first gear, or first to neutral, the rider can operate the second switch. For example, the motor 306, in this case, may rotate in the anti-clockwise direction.

These switches, for example, can be any electric push buttons known in the art. The switches can easily be operated using thumb pressure. The force required to operate the switches is relatively very low as compared to the force that is generally required to press the gearshift lever 104 in the conventional SMT two-wheeled vehicles.

Further, a centrifugal clutch (not shown in the figure) is mounted on the crankshaft 304 of the SMT vehicle of the present subject matter. As known in the art, the centrifiigal clutch normally remains in a disengaged position and gets engaged only when the engine attains a threshold angular speed. The centrifugal clutch disengages as soon as the engine speed is reduced to a speed less than the threshold angular speed, thus interrupting the transmission of power from the crankshaft 304 to the clutch 108. Thus, the centrifugal clutch makes sure that the engine 300 does not stall during a gear shift operation when the speed of the engine falls below the threshold angular speed at some instance.

Fig. 4 illustrates the actuator gearbox assembly 308 having a compound gear train 400, according to an embodiment of the present subject matter. In said embodiment, the actuator gearbox assembly 308 is a step-down gearbox assembly. In one implementation, the compound gear train 400 includes four gears: a first gear 402, a second gear 404, a third gear 406, and a fourth gear 408. The first gear 402 is mounted on a motor shaft 410 of the motor 306 and rotates at the speed of rotation of the motor 306. The second gear 404 meshes with the first gear 402 and rotates at a speed equal to or lesser than the speed of the first gear 402.

The second gear 404 and the third gear 406 are mounted on an intermediate shaft 412 and rotate at the same speed. The third gear 406 is smaller in size than the other gears and meshes with the fourth gear 408, which is mounted on the output shaft 214. Due to its small size, the third gear 406 takes less time than the fourth gear 408 to complete one rotation. As the speed of rotation of a gear is inversely proportional to its size, the speed of rotation of the fourth gear 408 is less than the speed of rotation of the motor 306. Due to this, the output shaft 214 rotates at a speed less than the speed at which the motor 306 rotates. In this way, the actuator gearbox assembly 308 transfers the rotational motion of the motor 306 to the output shaft 214, at a reduced speed. As will be appreciated to those skilled in the art, the torque transferred from the motor 306 to the output shaft 214 gets increased.

The gearshift assembly as described herein provides convenience in gear shifting as the rider does not have to apply much force nor make foot movements. Further, due to the absence of a foot operated gearshift lever, accidental incidents of partial disengagement of clutch leading to clutch slips are avoided. Hence, there would be no fuel wastage resulting due to clutch slips. This can provide 2-5% of fuel efficiency in city driving conditions as now there is uniformity in gear shifting. Moreover, the gearshift assembly is helpful for riders with disability of moving their left leg. The gearshift assembly is particularly advantageous as it does not require any change in body panels of a conventional SMT step-through two-wheeled vehicle, thus providing an easy upgrade option.

Although embodiments for a gearshift assembly of a vehicle have been described in language specific to structural features and/or methods, it is to be understood that the invention is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as exemplary implementations for the gearshift assembly of a vehicle.

I/We claim:

1. A vehicle comprising:

a gearshift unit (204) to shift gears of the vehicle; and

a gearshift shaft (106) connected to the gearshift unit (204), wherein the gearshift shaft
(106) actuates the gearshift unit (204);

characterized in that the vehicle comprises,

an electromechanical actuator (202) coupled to the gearshift shaft (106) to actuate the gearshift shaft (106), wherein the electromechanical actuator (202) comprises

a motor (306); and

an actuator gearbox assembly (308) coupled to a motor shaft (410) of the motor (306).

2. The vehicle as claimed in claim 1 further comprising at least one switch coupled to the electromechanical actuator (202) to actuate the electromechanical actuator (202).

3. The vehicle as claimed in claim 1, wherein the gearshift shaft (106) is connected to an auto clutch release arm (112) to operate a clutch (108) of the vehicle.

4. The vehicle as claimed in claim 1 further comprising an engine crankcase (302), wherein the electromechanical actuator (202) is mounted on the engine crankcase (302).

5. The vehicle as claimed in claim 1, wherein the motor (306) rotates in a first direction to upshift gears of the vehicle, and wherein the motor (306) rotates in a second direction to downshift gears of the vehicle.

6. The vehicle as claimed in claim 1, wherein the motor (306) is a permanent magnet direct current motor.

7. The vehicle as claimed in claim 1, wherein the actuator gearbox assembly (308) further comprises an output shaft (214) coupled to the gearshift shaft (106).

8. The vehicle as claimed in claim 7 further comprising:

an output link (208) mounted on the output shaft (214);

an input link (212) mounted on the gearshift shaft (106); and

a connecting link (210) connecting the output link (208) to the input link (212).

9. The vehicle as claimed in claim 7, wherein the output shaft (214) is parallel to an engine crankshaft (304).

10. The vehicle as claimed in claim 1, wherein the vehicle is a semi-automated manual transmission (SMT) vehicle.