Transmission for motor

A transmission for a motor is provided, which optimizes a transmission for outputting a rotational force only in one direction at different shifting ratios according to forward/reverse rotation directions of a rotational shaft of the motor while enabling a reverse input, accurately transmits the rotational force without slippage and has durability even upon use thereof for a long period of time, thereby improving reliability and shifting accuracy and maximizing marketability and market competitiveness.

TECHNICAL FIELD

The present invention relates to a transmission for a motor, and more particularly, to a transmission for a motor, which optimizes a transmission for outputting a rotational force only in one direction at different shifting ratios according to forward/reverse rotation directions of a rotational shaft of the motor while enabling a reverse input, accurately transmits the rotational force without slippage and has durability even upon use thereof for a long period of time, thereby improving reliability and shifting accuracy and maximizing marketability and market competitiveness.

BACKGROUND ART

Generally, a transmission is provided to improve the operating performance of overall industrial machinery or the driving performance of transportation equipment such as a bicycle, a wheelchair, an automobile, a scooter, a motorcycle, a ship or the like, which is provided with wheels and travels using various kinds of driving forces such as man power or an electromotive force.

Such a transmission performs shifting in response to manipulation of a rider or a user to obtain a torque or speed required under a driving condition.

Recently, a transmission in which a planet gear set consisting of a sun gear, planet gears, a ring gear and a carrier is provided in a hub shell to shift speeds at multiple ranges has been employed. However, there are technical problems in that this conventional transmission has a small number of shifting ranges in spite of its complicated structure, and particularly, a pawl that has been strongly restricted by a driving load when a shifting manipulation is being performed in a loaded driving travel state is not smoothly controlled, whereby the shifting is not smoothly performed.

A continuously variable transmission (CVT) has been developed as an alternative to a transmission using a planetary gear set having such a problem. Although the continuously variable transmission (CVT) can continuously and freely change shifting ratios without being bound by a predetermined shifting range, there are problems in that as compared with a conventional gear type transmission, the CVT is bulky and has a complicated structure, resulting in high manufacturing costs; in particular, durability is degraded when a large load is applied thereto since the rotational force should outputted through shifting based on a frictional force; and a power loss is likely to occur due to slippage between components, among other things.

Particularly, in recent years, as a bicycle, a scooter or the like that employs a motor as a drive source has been rapidly propagated, there is a need for a transmission having a compact and durable structure even if it has a small number of shifting ranges.

DISCLOSURE

Technical Problem

The present invention is conceived to solve the aforementioned problems and provides a transmission for a motor, which optimizes a transmission for outputting a rotational force only in one direction at different shifting ratios according to forward/reverse rotation directions of a rotational shaft of the motor while enabling a reverse input, accurately transmits the rotational force without slippage, thereby improving reliability and shifting accuracy for the transmission, and has durability even upon use thereof for a long period of time through symmetrically arranged helical gears, thereby maximizing marketability and market competitiveness of the transmission.

Technical Solution

The present invention is achieved by a transmission for a motor, wherein the transmission receives a rotational force from a rotational shaft of a motor to perform an output to an output shaft through shifting, and outputs the rotational force only in one direction at different shifting ratios according to forward/reverse rotation directions of the rotational shaft of the motor. The transmission includes a driving shaft having one or more one-way clutch contact surfaces formed on an outer periphery of a certain region of the driving shaft; a dual one-way clutch including a carrier for accommodating forward restrictors and reverse restrictors in both faces of the carrier, respectively, wherein the forward and reverse restrictors are radially equidistantly arranged with a predetermined phase angle difference, and a forward output ring and a reverse output ring disposed outside the forward restrictors and the reverse restrictors, respectively, to be selectively rotated according to a rotation direction of the driving shaft; and a low-speed rotational force transmitting means and a high-speed rotational force transmitting means including a plurality of gears engaged with one another, wherein the low-speed rotational force transmitting means and the high-speed rotational force transmitting means receive the rotational force independently from the forward output ring and the reverse output ring of the dual one-way clutch so as to rotate the output shaft with the shifting ratios though different paths. Accordingly, the dual one-way clutch allows a reverse input in a direction opposite to a rotation direction of an output of the output shaft.

Preferably, the carrier of the dual one-way clutch has a flange-shaped extension formed between the forward output ring and the reverse output ring, elastic bodies for elastically supporting balls toward the forward output ring and the reverse output ring are accommodated in the extension, and grooves are formed on the forward output ring and the reverse output ring, respectively, wherein each of the grooves corresponds to the ball and extends along an outer periphery of the corresponding output ring.

More preferably, the low-speed rotational force transmitting means and the high-speed rotational force transmitting means include a plurality of gear trains consist of helical gears arranged in opposite directions with respect to the dual one-way clutch, so that the helical gears are rotated while receiving symmetrical forces when the rotational forces are transmitted thereto.

Advantageous Effects

The transmission for a motor according to the present invention optimizes a transmission for outputting a rotational force only in one direction at different shifting ratios according to forward/reverse rotation directions of a rotational shaft of the motor while enabling a reverse input, accurately transmits the rotational force without slippage, thereby improving reliability and shifting accuracy for the transmission, and has durability even upon use thereof for a long period of time through symmetrically arranged helical gears, thereby maximizing marketability and market competitiveness of the transmission.

BEST MODE

FIG. 1is a front perspective view showing a transmission for a motor according to the present invention, andFIG. 2is a rear perspective view showing the transmission for the motor according to the present invention.

Further,FIG. 3is a front exploded perspective view of the transmission for the motor according to the present invention, in a state where the motor and a cover are disassembled;FIG. 4is a rear exploded perspective view of the transmission for the motor according to the present invention, in the state where the motor and the cover are disassembled; andFIG. 5is a front view of the transmission for the motor according to the present invention, in a state where the cover is removed.

Moreover,FIG. 6is a front exploded perspective view of the transmission for the motor according to the present invention, in a state where bearings are disassembled; andFIG. 7is a rear exploded perspective view of the transmission for the motor according to the present invention, in the state where the bearings are disassembled.

Next,FIG. 8is a front exploded perspective view of a dual one-way clutch in the transmission for the motor according to the present invention; andFIG. 9is a rear exploded perspective view of the dual one-way clutch in the transmission for the motor according to the present invention.

Finally,FIG. 10is a front view of the dual one-way clutch in the transmission for the motor according to the present invention; andFIG. 11is a plan view of the transmission for the motor according to the present invention, in the state where the motor and the cover are removed.

As shown inFIGS. 1 to 11, the transmission for the motor according to the present invention is basically characterized in that despite of a simple structure, an output shaft500is rotated only in one direction at different shifting ratios according to forward/reverse driving of a rotational shaft12of the motor10while enabling a reverse input, a malfunction caused by slippage is prevented in advance, and durability is improved to enable the transmission to be used for a long period of time.

As shown inFIGS. 1 to 4, the transmission for the motor according to the present invention receives a rotational force from a rotational shaft12of a motor10to perform an output to an output shaft500through shifting, and outputs the rotational force only in one direction at different shifting ratios according to forward/reverse rotation directions of the rotational shaft12of the motor10. The transmission includes a driving shaft100having one or more one-way clutch contact surfaces110formed on an outer periphery of a certain region of the driving shaft; a dual one-way clutch200including a carrier210for accommodating forward restrictors211and reverse restrictors212in both faces of the carrier, respectively, wherein the forward and reverse restrictors are radially equidistantly arranged with a predetermined phase angle difference, and a forward output ring220and a reverse output ring230disposed outside the forward restrictors211and the reverse restrictors212, respectively, to be selectively rotated according to a rotation direction of the driving shaft100; and a low-speed rotational force transmitting means300and a high-speed rotational force transmitting means400including a plurality of gears engaged with one another, wherein the low-speed rotational force transmitting means and the high-speed rotational force transmitting means receive the rotational force independently from the forward output ring220and the reverse output ring230of the dual one-way clutch200so as to rotate the output shaft500with the shifting ratios though different paths, whereby the dual one-way clutch200preferably allows a reverse input in a direction opposite to a rotation direction of an output of the output shaft500.

If the rotational shaft12of the motor10is rotated in the forward direction, the output shaft500is rotated at a predetermined shifting ratio in the transmission for the motor according to the present invention; and if the rotational shaft12of the motor10is rotated in the reverse direction which is opposite to the forward direction, the output shaft500is rotated at a different shifting ratio. Accordingly, two-range shifting of high speed and low speed is determined only by the rotation direction of the rotational shaft12of the motor10.

The transmission for the motor according to the present invention is roughly composed of the driving shaft100, the dual one-way clutch200, the low-speed rotational force transmitting means300, the high-speed rotational force transmitting means400, and the output shaft500.

In particular, the transmission for the motor according to the present invention is optimized for a two-wheel vehicle such as a bicycle, a scooter or a motorcycle which can employ a motor as a driving source, but is not limited thereto.

In order to apply the transmission for the motor according to the present invention to an actual vehicle, the motor10, a cover20, a frame30and the like may be involved as illustrated inFIGS. 1 and 2.

The motor10rotates the rotational shaft12in response to supply of power. The rotation direction of the rotational shaft12of the motor10can be switched to the forward direction or the reverse direction according to a user's manipulation.

The rotational force from the rotational shaft12of the above motor10is transmitted to the driving shaft100of the transmission for the motor according to the present invention.

The cover20protects the transmission for the motor according to the present invention against an external shock, while preventing the transmission from being exposed to an outside and blocking entrance of foreign substances. The cover is secured to the frame30by means of a plurality of fastening means21.

The frame30functions as a framework for the transmission for the motor according to the present invention and may be formed integrally with a framework of the two-wheel vehicle described above. In view of assemblability and the like, however, it is preferable to separately form the frame30and then to secure the frame30to the vehicle.

A plurality of fastening holes may be formed in this frame30so that the fastening holes may be used, for example, to secure the frame30to a vehicle body or to couple or install a shock absorbing device or a braking device to the frame30.

RegardingFIGS. 1 to 4, the aforementioned motor10is secured to a left side of the frame30, when viewed in the figures, by a plurality of fastening means11; and the cover20in which the transmission for the motor of the present invention has been housed is assembled to a right side of the frame30, when viewed in the figures.

In the present invention, the driving shaft100receives the rotational force from the rotational shaft12of the motor10and is rotated in the forward or reverse direction. The rotational shaft12of the motor10may extend to be also used as the driving shaft100. In view of compatibility or assemblability, however, the present invention is illustrated as an embodiment in which the rotational shaft12of the motor10passes through the frame30and is then inserted into a left side of the driving shaft100, when viewed in the figures, so as to be engaged with an inner gear.

InFIGS. 6 and 7, the driving shaft100is rotatably supported by the cover20via a right bearing101and by the frame30via a left bearing102.

Particularly, one or more one-way clutch contact surfaces110are formed on an outer periphery of a certain portion of the driving shaft100.FIG. 10illustrates that six (6) one-way clutch contact surfaces110are formed. It is preferable that one-way clutch contact surfaces110are formed such that corners of the one-way clutch contact surfaces110are connected to each other with gentle curves at radially equal intervals.

The dual one-way clutch200is located outside the one-way clutch contact surfaces110of the driving shaft100.

In the present invention, as shown inFIGS. 8 to 10, the dual one-way clutch200is composed of the carrier210for rotatably accommodating the forward restrictors211and the reverse restrictors212, the forward output ring220, and the reverse output ring230.

The carrier210is a ring-shaped member in which reception recesses211aon a front face of the carrier210shown inFIG. 8and reception recesses212aon a rear face of the carrier210shown inFIG. 9are formed to be asymmetric with respect to each other. Here, the forward restrictors211are placed in the reception recesses211aon the front face and the reverse restrictors212are placed in the reception recesses212aon the rear face, respectively.

The forward restrictors211and the reverse restrictors212have the same shape and size, and they are classified into the forward restrictors211and the reverse restrictors212only depending on their functions.

The forward restrictors211and the reverse restrictors212may be in the form of a generally cylindrical roller and may also have a complete spherical shape.

The reception recesses211aand212aformed on the carrier210are provided for accommodating the forward restrictors211and the reverse restrictors212, respectively, and are configured to limit circumferential movements of the restrictors211and212accommodated in the reception recesses211aand212aand to guide the restrictors211and212so as to allow only radial movements of the restrictors211and212in a state where there is no rotation of the carrier210.

The reception recesses211aformed on the front face of the carrier210and the reception recesses212aformed on the rear face have the same shape and size, although in view of formed positions of the reception recesses211aand212a, they are arranged with a predetermined phase angle difference as shown inFIG. 10.

Such a phase angle difference is determined such that one forward restrictor211and one reverse restrictor212are located between corners of one one-way clutch contact surface110of the driving shaft100disposed in the carrier210. Accordingly, the plurality of reception recesses211aand212aare formed on one carrier210, and the forward restrictors211or the reverse restrictors212are placed in the respective reception recesses211aand212a.

AlthoughFIG. 10illustrates the configuration in which six (6) forward restrictors211and six (6) reverse restrictors212are used by employing the driving shaft100formed with six (6) one-way clutch contact surfaces110, it will be apparent that the number of the restrictors211and212may be properly increased or decreased.

In addition, the forward output ring220and the reverse output ring230are provided on the front face and the rear surface of the carrier210, respectively.

Thus, the one-way clutch contact surfaces110of the driving shaft100are located inside the forward restrictors211and the reverse restrictors212of the carrier210, and the forward output ring220and the reverse output ring230are placed on the front and rear faces of the carrier210, respectively, and outside the restrictors211and restrictors212.

Accordingly, when the driving shaft100is rotated in the forward direction, i.e., in a clockwise direction inFIG. 10, the forward restrictors211are confined between the one-way clutch contact surfaces110and the forward output ring220so as to transmit the rotational force in the clockwise direction, while the reverse restrictors212are located at positions where the reverse restrictors212are not confined so that no rotational force is transmitted to the reverse output ring230.

On the contrary, when the driving shaft100is rotated in the reverse direction, i.e., in a counter-clockwise direction inFIG. 10, the reverse restrictors212are confined between the one-way clutch contact surfaces110and the reverse output ring230so as to transmit the rotational force in the counter-clockwise direction, while the forward restrictors211are located at positions where the forward restrictors211are not confined so that no rotational force is transmitted to the forward output ring220.

As a result, the dual one-way clutch200rotates only the forward output ring220in the forward direction when the driving shaft100is rotated in the forward direction, and rotates only the reverse output ring230in the reverse direction when the driving shaft100is rotated in the reverse direction.

InFIGS. 8 and 9, reference numerals221and231indicate gears formed integrally with the forward output ring220and the reverse output ring230, respectively. The output from the dual-one way clutch200will be obtained via the gears221and231.

Furthermore, reference numerals201and202indicate snap rings fastened to prevent the dual one-way clutch200from being separated from the driving shaft100after the dual one-way clutch200has been assembled to the driving shaft100.

Finally, the low-speed rotational force transmitting means300and the high-speed rotational force transmitting means400independently receive the rotational force from the forward output ring220and the reverse output ring230of the dual one-way clutch200so as to rotate the output shaft500at shifting ratios established along different paths, and are comprised of a plurality of gears rotatably engaged with each other.

There is no limitation on the arrangement and kinds of such gears, and it is also possible to independently implement the low-speed rotational force transmitting means300and the high-speed rotational force transmitting means400such that they do not share each other. As shown in the figures, the low-speed rotational force transmitting means300and the high-speed rotational force transmitting means400may share some configurations to perform the output.

In the present invention, as illustrated inFIGS. 3 to 7, the low-speed rotational force transmitting means300and the high-speed rotational force transmitting means400may be implemented with a first shaft310on which a first large gear320and a first small gear330are provided, a second shaft410on which a second large gear420and a second small gear430are provided, and a gear510provided on the output shaft500.

The first shaft310is rotatably supported by the cover20via a bearing301provided on the right side in the figures and by the frame30via a bearing302provided on the left side in the figures.

The first large gear320and the first small gear330are provided integrally with the first shaft310, wherein the first large gear320is engaged with the gear231of the aforementioned reverse output ring230and the first small gear330is engaged with the second large gear420to be described later.

Moreover, the second shaft410is also rotatably supported by the cover20via a bearing401provided on the right side in the figures and by the frame30via a bearing402provided on the left side in the figures.

The second large gear420and the second small gear430are provided integrally with the second shaft410, wherein the second large gear420is simultaneously engaged with the gear221of the aforementioned forward output ring220and the first small gear330and the second small gear430is engaged with a gear510provided on the output shaft500.

With this configuration, the low-speed rotational force transmitting means300is composed of the reverse output ring230of the dual one-way clutch200→the first large gear320→the first small gear330→the second large gear420→the second small gear430→the output shaft500.

The high-speed rotational force transmitting means400is composed of the forward output ring220of the dual one-way clutch200→the second large gear420→the second small gear430→the output shaft500.

In other words, the low-speed rotational force transmitting means300performs shifting with a gear ratio via the first large gear320and the first small gear330, so that low-speed shifting is performed when the reverse output is produced from the rotational shaft12of the motor10, and the high-speed rotational force transmitting means400performs high-speed shifting without undergoing such low-speed shifting when the forward output is produced from the rotational shaft12of the motor10.

Of course, the present invention is not limited thereto, and it is possible to obtain appropriate shifting ratios for two ranges as required.

As for the rotation direction, when the driving shaft100is rotated in the forward direction (in the clockwise direction inFIGS. 5 and 10), the rotational force does not pass through the first large gear320and the first small gear330, so that the output shaft500performs an output while being rotated in the same direction (in the clockwise direction inFIG. 5). When the driving shaft100is rotated in the reverse direction (in the counter-clockwise direction inFIGS. 5 and 10), the rotational force passes through the first large gear320and the first small gear330and thus the rotation direction is reversed, so that the output shaft500perform an output while being rotated in the opposite direction (in the clockwise direction inFIG. 5).

The forgoing illustrates the configuration in which the first shaft310and the second shaft410are included to allow the output shaft500always outputs the rotational force in the clockwise direction inFIG. 5irrespective of the forward rotation (in the clockwise direction inFIGS. 5 and 10) or the reverse rotation (in the counter-clockwise direction inFIGS. 5 and 10) of the rotational shaft12of the motor10. For example, however, if the second shaft410is set as an output shaft, this output shaft may always output the rotational force in the counter-clockwise direction inFIG. 5irrespective of the forward rotation (in the clockwise direction inFIGS. 5 and 10) or the reverse rotation (in the counter-clockwise direction inFIGS. 5 and 10) of the rotational shaft12of the motor10.

Herein, reference numerals501and502indicate the bearings for allowing the output shaft500to be rotatably supported by the cover20and the frame30. It is possible to form a separate outer gear520at an intermediate portion of the output shaft500to enable the output to be transmitted to wheels of a vehicle through the outer gear520.

As a result, the present invention can output the rotational force in one direction at different shifting ratios according to the forward rotation or the reverse rotation of the rotational shaft12of the motor10.

In the embodiment of the present invention described above, the output shaft500is directly coupled to the plurality of gears constructing the low-speed rotational force transmitting means300and the high-speed rotational force transmitting means400, so that the plurality of gears are rotated together with one another in response to the rotation of the output shaft500.

Therefore, for example, when a user directly pulls an electric bicycle equipped with the transmission for the motor of the present invention so as to move the bicycle in a backward direction, a force in a direction (counter-clockwise direction inFIG. 5) opposite to a rotation direction (clockwise direction inFIG. 5) of the output shaft500for a forward movement of the bicycle may be reversely input to the output shaft500.

However, the transmission for the motor according to the present invention has a great advantage in that even if a rotational force in a direction opposite to the rotation direction of the output shaft500is reversely input through the plurality of gears constructing the low-speed rotational force transmitting means300and the high-speed rotational force transmitting means400, the dual one-way clutch200can allow input of such a rotational force in the opposite direction, so that damage to the transmission caused by the reverse input may be prevented in advance.

Additionally, in the transmission for the motor according to the present invention described above, if the carrier210is rotated together with the driving shaft100when the driving shaft100is rotated in the forward direction or the reverse direction, there is concern that the forward restrictors211and the reverse restrictors212may not be confined between the one-way clutch contact surfaces110of the driving shaft100and the forward output ring220or the reverse output ring230, and in this case, the rotational force may not be appropriately output.

Therefore, in order to prevent the occurrence of this phenomenon, the present invention is preferably configured such that as shown inFIGS. 8 and 9, the carrier210of the dual one-way clutch200is formed with a flange-shaped extension213between the forward output ring220and the reverse output ring230, elastic bodies215for elastically supporting balls214toward the forward output ring220and the reverse output ring230are accommodated in the extension213, and grooves222and232are formed on the forward output ring220and the reverse output ring230, respectively, wherein each of the grooves222and232corresponds to the ball214and extends along an outer periphery of the corresponding output ring220and230.

The figures illustrates that a total of twelve (12) holes216are formed in front and rear surfaces of the extension213of the carrier210. Six (6) holes216are equidistantly formed on a side at which the forward output is performed and six (6) holes216are equidistantly formed on a side at which the reverse output is performed, wherein the six (6) holes216formed on one of the sides are arranged with a phase angle difference of 60 degrees with respect to those formed on the other side.

Furthermore, the grooves222and232are formed along the outer peripheries of the forward output ring220and the reverse output ring230, respectively, and have a size corresponding to that of each of the balls214.

Particularly, since the plurality of balls214provided in the extension213of the carrier210are guided within the grooves222and232of the forward output ring220and the reverse output ring230, the balls214help more stable rotation of the carrier210.

Accordingly, the balls214are elastically supported within the respective holes216by the elastic bodies215, so that the balls214are maintained in contact with the forward output ring220or the reverse output ring230. As a result, the balls214inhibit the carrier210from being rotated together with the driving shaft100, so that a malfunction such as slippage that may occur as the carrier210is rotated together with the driving shaft100may be prevented in advance.

Furthermore, in the present invention, it will be most preferable that as illustrated inFIG. 11, the low-speed rotational force transmitting means300and the high-speed rotational force transmitting means400including a plurality of gear trains consist of helical gears arranged in opposite directions with respect to the dual one-way clutch200, so that the helical gears are rotated while receiving symmetrical forces when the rotational forces are transmitted thereto.

This cancels out eccentricity occurred on the helical gears when the forward output is performed and eccentricity occurred on the helical gears when the reverse output is performed, so that damage to the transmission due to accumulation of lateral forces acting on the shaft may be prevented in advance even when the transmission is used for a long period of time.

Hereinafter, an operation of the transmission according to the present invention will be described with reference toFIGS. 1 to 11.

In the transmission for the motor configured as described above, when the rotational shaft12of the motor10is rotated in the forward direction, the forward restrictors211are confined between the one-way clutch contact surfaces110of the driving shaft100and the forward output ring220in the dual one-way clutch200.

At this time, the reverse restrictors212are not confined due to the phase angle difference that is maintained by the carrier210.

Therefore, shifting is performed with a gear ratio while the rotational force is transmitted from the gear221formed on the forward output ring220, through the high-speed rotational force transmitting means400composed of the plurality of gear trains, and the output shaft500is then rotated at a high speed.

When the rotational shaft12of the motor10is rotated in the reverse direction, the reverse restrictors212are confined between the one-way clutch contact surfaces110of the driving shaft100and the reverse output ring230in the dual one-way clutch200.

At this time, the forward restrictors211are not confined due to the phase angle difference maintained by the carrier210.

Accordingly, shifting is performed with a gear ratio while the rotational force is transmitted from the gear231formed on the reverse output ring230, through the low-speed rotational force transmitting means300composed of the plurality of gear trains, and the output shaft500is then rotated at a low speed.

Moreover, in the dual one-way clutch200, the balls214further provided in the extension213are in elastic contact with the forward output ring220and the reverse output ring230, respectively, so that the carrier210may be prevented from being rotated together with the driving shaft100, thereby preventing a malfunction of the transmission.

Particularly, the plurality of gears constructing the low-speed rotational force transmitting means300and the high-speed rotational force transmitting means400are implemented by the helical gears arranged symmetrically with one another, it is also possible to prevent damage to the transmission caused by eccentric loads when the transmission is used for a long period of time.

Therefore, the transmission for the motor according to the present invention has great advantages in that a rotational force can be output only in one direction at different shifting ratios according to the forward/reverse rotation directions of the rotational shaft12of the motor10while enabling a reverse input and accurate transmission of a rotational force can be achieved without any slippage in the dual one-way clutch200.

Additionally, the transmission for the motor according to the present invention has an advantage in that the symmetrically arranged helical gears are employed for the plurality of gear trains provided in the transmission, thereby preventing damage to the transmission due to eccentric loads even upon use thereof for a long period of time and thus increasing durability.

The embodiment is merely an example for more specifically describing the technical spirit of the present invention, and the scope of the present invention is not limited to the embodiment or figures.

DESCRIPTION OF REFERENCE NUMERALS