Transmission device for electric bicycle

Abstract

A transmission device for an electric bicycle, comprising a driving motor (1), a first worm (2), a first worm gear (3), a second worm (4), a second worm gear (5), and a crankshaft (6), wherein the driving motor (1) is provided with a transmission shaft (11); the first worm (2) is coaxially connected to the transmission shaft (11); the first worm gear (3) and the first worm (2) mesh with each other; the second worm (4) is coaxially connected to the first worm gear (3); the second worm gear (5) and the second worm (4) mesh with each other; the crankshaft (6) is connected to the second worm gear (5). The transmission device does not have a complex and bulky multi-stage gear mechanism, so that the overall size can be reduced, and the transmission device can be mounted in a limited internal space of the electric bicycle.

Description

Transmission of electric bicycle TECHNICAL FIELD

[0001] The present invention relates to a transmission, in particular to a transmission of electric bicycle. BACKGROUND

[0002] The transmission system of electric bicycle generally requires high transmission ratio. In order to obtain a larger transmission ratio, the gear mechanism of the transmission system is designed as a fixed shaft gear train, which requires multi-stage gear (i.e. multiple reduction gears) transmission, so the structure of the transmission device is complex and large, and the installation precision between multiple gears is also high. However, the internal space of electric bicycle is limited, which limits the size of the mechanism of the transmission system. If the transmission ratio cannot be improved, the output torque of the electric bicycle will be too low.

[0003] Therefore, how to overcome the above-mentioned defects through structural design improvement has become one of the important problems to be solved in the field.

[0004] SUMMARY

[0005] The technical problem to be solved by the present invention is to provide a transmission of electric bicycle to overcome the shortcomings of the prior art.

[0006] In order to solve the above-mentioned technical problems, one of the technical solutions adopted by the present invention is to provide a transmission of electric bicycle, which comprises a driving motor, a first worm, a first worm wheel, a second worm, a second worm wheel and a crankshaft. The driving motor has a transmission shaft. The first worm is connected to the transmission shaft. The first worm wheel is engaged with the first worm. The second worm is coaxially connected to the first worm wheel. The second worm wheel is engaged with the second worm. The crankshaft is connected to the second worm wheel.

[0007] In order to solve the above-mentioned technical problems, another technical solution adopted by the present invention is to provide a transmission of electric bicycle, which comprises a driving motor, a first worm, a first worm wheel, a second worm, a bevel gear, a crankshaft and at least one one-way clutch. The driving motor has a transmission shaft. The first worm is coaxially connected to the transmission shaft. The first worm wheel is engaged with the first worm. The second worm is coaxially connected to the first worm wheel. The bevel gear is engaged with the second worm. The crankshaft is connected to the bevel gear. The at least one one-way clutch is arranged inside at least one of the first worm wheel and the bevel gear.

[0008] One of the beneficial effects of the present invention is that the transmission of electric bicycle provided by the present invention can output high torque and high transmission ratio only through the structure of two sets of worm / worm wheel. Compared with the existing transmission device, the transmission device of the present invention does not have a complex and large multi-stage gear mechanism, so the overall size can be reduced, which is beneficial to installation in the limited internal space of electric bicycle.

[0009] For further understanding of the features and technical contents of the present application, please refer to the following detailed description of the present application and the attached drawings. However, the drawings provided are only for reference and illustration, and are not intended to limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0010] Fig. 1 is a schematic diagram of the system architecture of the transmission device of the electric bicycle according to the first embodiment of the present application.

[0011] Fig. 2 is a schematic diagram of the transmission device of the electric bicycle according to the first embodiment of the present application.

[0012] Fig. 3 is a schematic diagram of the internal structure of the transmission device of the electric bicycle according to the first embodiment of the present application.

[0013] Fig. 4 is a schematic diagram of the cross section of the first worm gear and the second worm according to the first embodiment of the present application.

[0014] Fig. 5 is a schematic diagram of the cross section of the second worm gear and the crankshaft according to the first embodiment of the present application.

[0015] Fig. 6 is a schematic diagram of the transmission device of the electric bicycle according to the second embodiment of the present application.

[0016] Fig. 7 is a schematic diagram of the transmission device of the electric bicycle according to the third embodiment of the present application. DETAILED DESCRIPTION

[0017] The following is a description of the embodiments of the present application, which discloses the transmission device of the electric bicycle. Those skilled in the art can understand the advantages and effects of the present application from the disclosure. The present application can be implemented or applied by other different embodiments, and the details in the description can be modified and changed based on different views and applications without departing from the concept of the present application. In addition, the drawings of the present application are only simple schematic illustrations, and are not intended to depict the actual size. The following embodiments will further illustrate the technical contents of the present application, but the disclosure is not intended to limit the scope of protection of the present application.

[0018] It should be understood that although the terms "first", "second", "third" and the like can be used herein to describe various elements, these elements should not be limited by these terms. These terms are mainly used to distinguish one element from another. In addition, the term "or" used herein can include any one or a combination of the associated listed items.

[0019] First Embodiment

[0020] Referring to FIG. 1 to FIG. 3, FIG. 1 is a schematic diagram of a system architecture of a transmission device of an electric bicycle according to a first embodiment of the present application, FIG. 2 is a schematic diagram of the transmission device of the electric bicycle according to the first embodiment of the present application, and FIG. 3 is a schematic diagram of an internal structure of the transmission device of the electric bicycle according to the first embodiment of the present application. The first embodiment of the present application provides a transmission device D of an electric bicycle, which includes a driving motor 1, a first worm 2, a first worm wheel 3, a second worm 4, a second worm wheel 5, and a crankshaft 6. The first worm 2, the first worm wheel 3, the second worm 4, the second worm wheel 5, and the crankshaft 6 are disposed in a housing S, and the driving motor 1 is disposed on one side of the housing S.

[0021] As shown in FIG. 1 and FIG. 3, the driving motor 1 has a transmission shaft 11. It is noted that, for the sake of clarity, the driving motor 1 in the figures only shows the transmission shaft 11, and does not further show the specific appearance of other parts of the driving motor 1. The first worm 2 is coaxially connected to the transmission shaft 11, the second worm 4 is coaxially connected to the first worm wheel 3, and the crankshaft 6 is coaxially connected to the second worm wheel 5. Further, in the first embodiment, the second worm wheel 5 is directly disposed on the crankshaft 6, and the second worm wheel 5 and the crankshaft 6 are coaxially disposed.

[0022] Continuing to refer to FIG. 3, the first worm wheel 3 and the first worm 2 are in meshing engagement with each other, and the second worm wheel 5 and the second worm 4 are in meshing engagement with each other. A plurality of ball bearings B are further provided on the transmission shaft 11, the second worm 4, and the crankshaft 6. In the first embodiment, the first worm 2 and the second worm 4 have a thread number greater than or equal to 2, that is, the first worm 2 and the second worm 4 are double-threaded or more than double-threaded worms. Through this design, the lead angle of the worms (the first worm 2 and the second worm 4) can be increased. Alternatively, the lead angle of the first worm 2 and the second worm 4 can be designed to be greater than 4 degrees (without self-locking function).

[0023] As shown in FIG. 2 and FIG. 3, the crankshaft 6 has a first end 61 and a second end 62, and the first end 61 and the second end 62 extend out of the housing S. Further referring to FIG. 1, the crankshaft 6 can be connected to a pedal member E at each of the first end 61 and the second end 62. The driving motor 1 can output power, which is transmitted to the crankshaft 6 through the transmission shaft 11, the first worm 2, the first worm wheel 3, the second worm 4, and the second worm wheel 5, thereby driving the pedal member E to rotate. Further, the driving motor 1 can provide an auxiliary power to reduce the user's effort when the user rides the electric bicycle.

[0024] Referring to FIG. 4 and FIG. 5, FIG. 4 is a cross-sectional view of the first worm gear and the second worm, and FIG. 5 is a cross-sectional view of the second worm gear and the crankshaft. The transmission D further comprises a first one-way clutch 71 and a second one-way clutch 72. The first one-way clutch 71 is disposed in the first worm gear 3 and connected to the second worm 4. The second one-way clutch 72 is disposed in the second worm gear 5 and connected to the crankshaft 6. A one-way clutch can also be called a one-way bearing, which can only transmit power in one direction (e.g., only in the clockwise direction or the counterclockwise direction).

[0025] In addition, as shown in FIG. 1, the transmission D further comprises a torque sensor 8, which is disposed on the crankshaft 6 and electrically connected to the drive motor 1. The torque sensor 8 can detect the torque applied to the crankshaft 6.

[0026] Referring to FIG. 1, and FIG. 3 to FIG. 5, the operation sequence of the transmission D of the present application is described as follows. When the user steps on the pedal E to drive the crankshaft 6, the torque sensor 8 detects the torque applied to the crankshaft 6 and outputs a signal to the drive motor 1. The drive motor 1 outputs power according to the preset assist ratio (i.e., the ratio of the power output by the drive motor 1 to the user's effort), which is combined with the force of the user stepping on the pedal E to drive the electric bicycle forward.

[0027] When the rotation speed of the pedal E is higher than the rotation speed of the drive motor 1, the first one-way clutch 71 can disengage the first worm gear 3 from the second worm 4, so that the first worm gear 3 cannot drive the second worm 4 (i.e., power cannot be transmitted from the first worm gear 3 to the second worm 4). In this way, it can prevent the user's pedaling speed from being too fast to interfere with the operation of the drive motor 1.

[0028] On the other hand, when the user pedals the pedal E in the reverse direction to rotate the pedal E in the reverse direction, the second one-way clutch 72 can disengage the second worm gear 5 from the crankshaft 6, so that the second worm gear 5 cannot drive the crankshaft 6 (i.e., power cannot be transmitted from the second worm gear 5 to the crankshaft 6). In this way, it can prevent the user from pedaling the pedal E in the reverse direction to interfere with the operation of the drive motor 1.

[0029] Second embodiment

[0030] Referring to FIG. 6, which is a schematic diagram of a transmission of an electric bicycle according to a second embodiment of the present application. The second embodiment provides another transmission D' of an electric bicycle, which is substantially the same as the first embodiment. The main difference is that the transmission D' of the second embodiment replaces one set of worm / gear (the second worm 4 and the second gear 5 in FIG. 3) with a worm and a bevel gear (the second worm 4 and the bevel gear 5' in FIG. 6). In detail, the transmission D' comprises a driving motor 1 (see FIG. 1), a first worm 2, a first gear 3, a second worm 4, a bevel gear 5', and a crankshaft 6. The first worm 2 is coaxially connected to a transmission shaft 11 of the driving motor 1, the second worm 4 is coaxially connected to the first gear 3, and the crankshaft 6 is coaxially connected to the bevel gear 5'. Further, the bevel gear 5' is coaxially arranged with the crankshaft 6. The first gear 3 is engaged with the first worm 2, and the bevel gear 5' is engaged with the second worm 4.

[0031] The driving motor 1 can output power, which is transmitted to the crankshaft 6 through the transmission shaft 11, the first worm 2, the first gear 3, the second worm 4, and the bevel gear 5', to drive the pedal member E to rotate. Further, the driving motor 1 can provide an auxiliary power to reduce the effort of the user when the user rides the electric bicycle.

[0032] In addition, the interior of at least one of the first gear 3 and the bevel gear 5' is provided with a one-way clutch. Alternatively, the interior of each of the first gear 3 and the bevel gear 5' is provided with a one-way clutch. The one-way clutches are not shown in FIG. 6, and their positions can be referred to FIG. 4 and FIG. 5. When the rotation speed of the pedal member E is higher than the rotation speed of the driving motor 1, the one-way clutch in the interior of the first gear 3 can disengage the first gear 3 from the second worm 4, so that power cannot be transmitted from the first gear 3 to the second worm 4, thereby preventing the user's pedaling speed from interfering with the operation of the driving motor 1. On the other hand, when the user pedals the pedal member E in the reverse direction to make the pedal member E rotate in the reverse direction, the one-way clutch in the interior of the bevel gear 5' can disengage the bevel gear 5' from the crankshaft 6, so that power cannot be transmitted from the bevel gear 5' to the crankshaft 6, thereby preventing the user's pedaling the pedal member E in the reverse direction from interfering with the operation of the driving motor 1.

[0033] Third Embodiment

[0034] Referring to FIG. 7, which is a schematic diagram of a transmission of an electric bicycle according to a third embodiment of the present application. The third embodiment provides a transmission D" of an electric bicycle, which comprises a driving motor 1 (see FIG. 1), a first worm 2, a first worm wheel 3, a second worm 4, a second worm wheel 5, and a crankshaft 6. Further, compared with the first embodiment, the transmission D" of the third embodiment further comprises a gear set 9. The gear set 9 comprises a first helical gear 91 and a second helical gear 92, which are coaxially connected to the second worm wheel 5 and the crankshaft 6, respectively. Further, the second helical gear 92 is directly arranged on the crankshaft 6, and the second helical gear 92 is coaxial with the crankshaft 6. In addition, the diameter (pitch diameter) of the second helical gear 92 is greater than that (pitch diameter) of the first helical gear 91.

[0035] Due to the design of the transmission D" of the third embodiment, the arrangement positions of the first one-way clutch 71 and the second one-way clutch 72 are different from those of the first embodiment. In the third embodiment, the first one-way clutch 71 is arranged in the second worm wheel 5, and the second one-way clutch 72 is arranged in one gear of the gear set 9, for example, the second helical gear 92. The functions of the first one-way clutch 71 and the second one-way clutch 72 are the same as those of the first embodiment, and thus are not repeated here.

[0036] Due to the design of the gear set 9 (the first helical gear 91 and the second helical gear 92), the third embodiment does not need to limit the number of threads of the worms (the first worm 2 and the second worm 4) to be greater than or equal to 2, in other words, the first worm 2 and the second worm 4 can be single-threaded worms. In addition, in the third embodiment, the lead angle of the worms (the first worm 2 and the second worm 4) can not be limited to be greater than 4 degrees (with self-locking function).

[0037] Advantages of the embodiments

[0038] The transmission D, D', D" of the electric bicycle provided by the present application can output high torque and high transmission ratio only through the architecture of two sets of worm gears. Compared with the existing transmission, the transmission of the present application does not have a complex and large multi-stage gear mechanism, so the overall size can be reduced, which is beneficial for installation in the limited space inside the electric bicycle.

[0039] The above disclosure is only the preferred and feasible embodiments of the present application, and does not limit the protection scope of the claims of the present application, so any equivalent technical changes made according to the content of the specification and drawings of the present application are included in the protection scope of the claims of the present application.

Claims

1. A transmission for an electrically powered bicycle, characterized in that, The transmission of the electric bicycle comprises: a driving motor having a driving shaft; a first worm coaxially connected to the driving shaft; a first worm gear intermeshing with the first worm; a second worm coaxially connected to the first worm gear; a second worm gear intermeshing with the second worm; and a crankshaft connected to the second worm gear.

2. The transmission of an electrically driven bicycle according to claim 1, characterized in that, The second worm gear is coaxially connected to the crankshaft.

3. A transmission for an electrically driven cycle as claimed in claim 2, characterised in that, The first worm and the second worm have a thread number greater than or equal to 2.

4. The transmission of an electrically driven bicycle according to claim 2, characterized in that, The first worm and the second worm have a lead angle greater than or equal to 4 degrees.

5. The transmission of an electrically driven bicycle according to claim 2, characterized in that, The transmission of the electric bicycle further comprises a first one-way clutch and a second one-way clutch, the first one-way clutch is arranged in the first worm gear, and the second one-way clutch is arranged in the second worm gear.

6. The transmission of an electrically driven bicycle according to claim 1, characterized in that, The transmission of the electric bicycle further comprises a gear set for connecting the crankshaft and the second worm gear.

7. A transmission for an electrically powered cycle as claimed in claim 6, characterised in that, The gear set comprises a first helical gear and a second helical gear intermeshing with each other, the first helical gear is coaxially connected to the second worm gear, and the second helical gear is coaxially connected to the crankshaft.

8. The transmission of an electrically driven bicycle according to claim 7, characterized in that, The transmission of the electric bicycle further comprises a first one-way clutch and a second one-way clutch, the first one-way clutch is arranged in the second worm gear, and the second one-way clutch is arranged in the second helical gear.

9. The transmission of an electrically driven bicycle according to claim 1, characterized in that, The transmission of the electric bicycle further comprises a torque sensor arranged in the crankshaft, and the torque sensor is electrically connected to the driving motor.

10. A transmission for an electrically powered bicycle, characterised in that, The transmission of the electric bicycle comprises: a driving motor having a driving shaft; a first worm coaxially connected to the driving shaft; a first worm gear intermeshing with the first worm; a second worm coaxially connected to the first worm gear; a helical gear intermeshing with the second worm; a crankshaft connected to the helical gear; and at least one one-way clutch arranged in the interior of at least one of the first worm gear and the helical gear.

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