CN108533700B

CN108533700B - Continuously variable transmission

Info

Publication number: CN108533700B
Application number: CN201710118090.8A
Authority: CN
Inventors: 蔡有建
Original assignee: Individual
Current assignee: Shanghai Jianlin Automotive Technology Co ltd
Priority date: 2017-03-01
Filing date: 2017-03-01
Publication date: 2024-05-03
Anticipated expiration: 2037-03-01
Also published as: WO2018157806A1; DE112018001076T5; DE112018001076B4; CN108533700A

Abstract

The present invention discloses a continuously variable transmission, comprising: a planetary power transmission mechanism, the planetary power transmission mechanism comprising at least: a power input member; the power output part comprises an output shaft and at least one planetary driven part which is connected with the output shaft and drives the output shaft to rotate, and the planetary driven part is arranged on the outer side of the power input part and can rotate around the power input part under the driving of the power input part; a shift ring circumferentially coupled to the planetary driven member, the shift ring being movable back and forth in a first direction; the speed changing unit at least comprises a pressing device, wherein the pressing device is arranged on the outer side of the speed changing ring and is fixedly connected with the speed changing ring, and the speed changing ring is driven to move back and forth in the first direction to adjust the rotating speed of the power output part of the planetary power transmission mechanism.

Description

Continuously variable transmission

Technical Field

The invention relates to a stepless speed changer which can be applied to automobiles and other mechanical devices for transmitting power.

Background

The automatic transmission is used as a core component of automobiles and other mechanical transmission devices, and currently mainly comprises four main types of an electric control mechanical automatic transmission (AMT), a hydraulic Automatic Transmission (AT), a double clutch automatic transmission (DCT) and a mechanical stepless automatic transmission (CVT). The mechanical stepless automatic transmission (CVT) has the characteristics of continuous speed change, sustainable power output in the speed change process and the like, so that the rotating speed of an engine can be kept in the most economical working area, and the effects of lowest oil consumption, most gentle running and the like in an automobile or a mechanical device of the same type under the same condition are realized. In addition, the mechanical stepless automatic transmission (CVT) has the advantages of simple structure, less parts, smaller volume, lighter weight and the like compared with the traditional transmission.

Mechanical continuously variable automatic transmissions (CVT) exist in various forms other than the mainstream belt and chain type, such as cone ring type, roller type, etc., in which power is transmitted between an active cone pulley, a passive cone pulley, or a cone disc through a metal ring or a metal disc. However, these types of mechanical stepless automatic transmissions are limited in maximum torque transmission and speed change stability due to the small contact area at the power transmission position and the relatively concentrated stress, and are only applied to small vehicle types at present.

Disclosure of Invention

In view of the drawbacks of the prior art, an object of the present invention is to provide a continuously variable transmission.

According to an aspect of the present invention, there is provided a continuously variable transmission including: a planetary power transmission mechanism, the planetary power transmission mechanism comprising at least: a power input member; the power output part comprises an output shaft and at least one planetary driven part which is connected with the output shaft and drives the output shaft to rotate, and the planetary driven part is arranged on the outer side of the power input part and can rotate around the power input part under the driving of the power input part; a shift ring circumferentially coupled to the planetary driven member, the shift ring being movable back and forth in a first direction; the speed changing unit at least comprises a pressing device, wherein the pressing device is arranged on the outer side of the speed changing ring and is fixedly connected with the speed changing ring, and the speed changing ring is driven to move back and forth in the first direction to adjust the rotating speed of the power output part of the planetary power transmission mechanism.

Preferably, the power input part comprises an input shaft and a central sun gear sleeved on the input shaft; the power output part further comprises a planet carrier with the output shaft, wherein the central sun gear is arranged in the planet carrier; the planetary driven part is arranged on the outer side of the central sun gear, connected with the planet carrier and the central sun gear and the speed changing ring, and can rotate around the center of the speed changing ring under the rotation driving of the central sun gear so as to drive the output shaft to rotate.

Preferably, the planetary driven member includes: a driven planetary gear meshed with the sun-center gear, the driven planetary gear being disposed within the carrier; the planetary cone pulley is coaxial with the driven planetary gear and is mutually fixed, and the planetary cone pulley is connected with the speed changing ring; the planet gear shaft is fixedly connected with the driven planet gear and the planet cone pulley, and the planet gear shaft also penetrates through the driven planet gear and the planet cone pulley to be connected with the planet carrier.

Preferably, the input shaft is coaxially arranged with the output shaft.

Preferably, the power output member includes a plurality of the planetary driven members, wherein the plurality of planetary driven members are circumferentially disposed outside the power input member.

Preferably, the shift ring includes: an annular central shaft; the conical elastic pieces are arranged on the annular central shaft, and each conical elastic piece can rotate around the annular central shaft; the pressing device controls at least one conical spring piece to roll on the surface of the planetary driven part while rotating around the annular central shaft so as to drive the speed changing ring to move along the first direction.

Preferably, the speed change unit further includes: the variable speed screw rod mechanism is arranged outside the pressing device, and comprises: a lead screw extending in the first direction; the screw rod nut is sleeved on the screw rod and can move back and forth along the screw rod in a first direction; the compressing device is connected with the screw nut and can synchronously move along with the screw nut in the first direction so as to drive the speed changing ring to move in the first direction; and the speed change control mechanism is connected with the screw rod and drives the screw rod to rotate so as to control the screw rod nut to move along the screw rod in a first direction.

Preferably, the speed changing unit comprises a plurality of speed changing screw rod mechanisms, the plurality of speed changing screw rod mechanisms are arranged on the outer side of the pressing device in a surrounding mode, and screw rods of the plurality of speed changing screw rod mechanisms are connected with the speed changing control mechanism.

Preferably, each variable speed screw mechanism further comprises a synchronous sprocket, and the synchronous sprockets are arranged at the same end of the variable speed screw mechanism; the speed changing unit further comprises a toothed chain connected with each synchronous sprocket.

Preferably, a clamping groove extending along the first direction is formed in a surface of one side, facing the speed changing ring, of the pressing device, and the conical spring piece of the speed changing ring is clamped in the clamping groove.

Preferably, the pressing device is sleeve-shaped and surrounds the speed-changing ring.

Preferably, the continuously variable transmission further includes a housing, and the planetary power transmission mechanism and the speed change unit are disposed in the housing.

Compared with the prior art, the continuously variable transmission provided by the embodiment of the invention has the advantages that the planetary driven part of the power output part is driven by the power input part to rotate around the power output part, so that the output shaft of the power output part is driven to rotate, the power transmission can be effectively increased by the transmission mode of the transmission torque, and the requirement of a large-torque working condition is met.

In addition, the continuously variable transmission also realizes the speed change of the continuously variable transmission by controlling the speed change ring to move along the first direction by the speed change unit so as to adjust the rotation speed of the power output part of the power transmission mechanism, wherein in the speed change process, the speed change ring moves on the surface of the planetary cone in a rolling mode in the moving process of the first direction because the speed change comprises a plurality of conical spring plates which can rotate around the annular central shaft as the center, and compared with the sliding mode adopted by the steel belt of the prior mechanical continuously variable automatic transmission (CVT) in the speed change process, the continuously variable transmission has the advantages of small friction resistance, realization of rapid speed change and the like. And after the structure of the planetary cone pulley is combined, the speed changing ring deforms under the co-extrusion of the pressing device and the planetary cone pulley, and the contact area with the planetary cone pulley is increased, so that the planetary cone pulley has the advantages of large contact area, small running abrasion, long service life and the like. The structure of the continuously variable transmission also avoids the adoption of a complex hydraulic pressing device in the existing continuously variable transmission, thereby having the advantages of simpler manufacture, lower cost, higher reliability and the like.

Drawings

Other features, objects and advantages of the present invention will become more apparent upon reading of the detailed description of non-limiting embodiments, given with reference to the accompanying drawings in which:

fig. 1 is a schematic cross-sectional structure of a continuously variable transmission of a first embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view of the structure A-A of FIG. 1;

FIG. 3 is a partial enlarged view at B in FIG. 2;

fig. 4 is a schematic diagram of a motion trace of a conical spring of a shift ring on a planetary cone of the continuously variable transmission in the shifting process.

Reference numerals

1. Power input part

11. Input shaft

13. Sun gear

2. Power output part

21. Output shaft

23. Planet carrier

25. Planetary driven member

251. Driven planetary gear

252. Planetary cone pulley

253. Planetary gear shaft

3. Gear ring

31. Conical spring plate

32. Annular center shaft

4. Variable speed screw rod mechanism

41. Screw rod

42. Screw nut

43. Synchronous sprocket

5. Compacting device

53. Axial clamping groove

6. Shell body

Detailed Description

Existing mechanical continuously variable automatic transmissions (CVT) suffer from at least two problems that limit the maximum transmission torque of the transmission:

1. The working contact surface is limited, if the positive pressure for generating friction force is too large, the mechanism is easy to be excessively stressed to cause failure;

2. The friction force for transmitting power and the friction resistance to be overcome by speed change are on the same contact surface and are both sliding friction, and if the friction force for transmitting power is improved at one time, the speed change can not be smoothly carried out.

Therefore, if the existing mechanical continuously variable automatic transmission is applied to a vehicle or an apparatus having high torque and high motion performance requirements, there are at least the following problems:

1) The transmission belt is easy to damage, so that the requirement on the material of the transmission belt is high;

2) The transmission cannot withstand a large load;

3) The transmission belt cannot be moved quickly, so that the use requirement of quick speed change of the vehicle cannot be met;

4) The manufacturing process of the transmission is complicated.

In view of the above, the present invention provides a continuously variable transmission. According to the gist of the present invention, the continuously variable transmission includes a planetary power transmission mechanism including at least: a power input member; the power output part comprises an output shaft and at least one planetary driven part which is connected with the output shaft and drives the output shaft to rotate, and the planetary driven part is arranged on the outer side of the power input part and can rotate around the power input part under the driving of the power input part; a shift ring circumferentially coupled to the planetary driven member, the shift ring being movable back and forth in a first direction; the speed changing unit at least comprises a pressing device, wherein the pressing device is arranged on the outer side of the speed changing ring and is fixedly connected with the speed changing ring, and the speed changing ring is driven to move back and forth in the first direction to adjust the rotating speed of the power output part of the planetary power transmission mechanism.

The technical contents of the present invention will be further described with reference to the accompanying drawings and examples.

Fig. 1 to fig. 4 are schematic cross-sectional structures of a continuously variable transmission, schematic structures of a shift ring and a pressing device, and schematic motion trajectories of conical spring plates of the shift ring during shifting according to an embodiment of the invention. Wherein FIG. 2 is a schematic cross-sectional view of the structure at A-A in FIG. 1; fig. 3 is a partial enlarged view at B in fig. 2. In a preferred embodiment of the present invention, the continuously variable transmission mainly includes a planetary power transmission mechanism, a shift ring, and a shift unit.

The planetary power transmission mechanism includes at least a power input member and a power output member. The power output part comprises an output shaft and at least one planetary driven part which is connected with the output shaft and drives the output shaft to rotate, and the planetary driven part is arranged on the outer side of the power input part and can rotate around the power input part under the driving of the power input part.

Specifically, in the embodiment shown in fig. 1 and 2, the power input member 1 includes an input shaft 11 and a sun gear 13 disposed around the input shaft 11. The sun gear 13 and the input shaft 11 are fixed to each other and are rotatable in synchronization with the input shaft 11 (rotation here means rotation of the input shaft 11 by driving an engine or the like).

The power take-off 2 comprises a planet carrier 23 having an output shaft 21 and a driven member 25. In the embodiment shown in fig. 1, the output shaft 21 is located at the left end of the planet carrier 23, and preferably the output shaft 21 is arranged coaxially with the input shaft 11. The sun gear 13 is disposed within the planet carrier 23.

The planetary driven member 25 is provided outside the sun gear 13. The planetary driven member 25 is connected with the carrier 23, the sun gear 13, and the shift ring 3. In a preferred embodiment of the present invention, the power take-off member 2 may comprise a plurality of planetary driven members 25. Wherein a plurality of planetary driven members 25 are disposed circumferentially outside the power input member 1. In the embodiment shown in fig. 1 and 2, the power take-off member 2 comprises two driven members 25, the two planetary driven members 25 being symmetrical to each other with respect to the annular center axis of the planet carrier 23. Although the power output member 2 having two driven members 25 symmetrical to each other with respect to the annular center axis of the carrier 23 is illustrated in the embodiment shown in fig. 1 and 2, the present invention is not limited thereto, and in other embodiments of the present invention, the number of the planetary driven members may be adjusted according to the actual torque, for example, three or four planetary driven members may be used to simultaneously transmit torque, thereby effectively increasing the power transmission. The plurality of planetary driven members are not necessarily arranged symmetrically in pairs, and will not be described here again.

Specifically, the planetary driven member 25 includes a driven planetary gear 251, a planetary cone 252, and a planetary gear shaft 253. Wherein driven pinion 251 is disposed within carrier 23 and in meshing engagement with sun pinion 13. The planetary cone gear 252 and the driven planetary gear 251 are coaxially arranged and fixedly connected with each other, and can be integrally formed. Preferably, the surface of the planetary cone 252 has grooves to reduce slip of the shift ring. The planetary gear shaft 253 is coaxially and fixedly connected with the driven planetary gear 251 and the planetary cone 252, passes through the driven planetary gear 251 and the planetary cone 252, is connected with the planet carrier 23, and can rotate on the planet carrier 23.

The shift ring 3 surrounds the planetary driven member, and the shift ring 3 is movable back and forth in a first direction (X-axis direction in fig. 1). As shown in fig. 2 and 3, the speed-changing ring 3 may be a steel ring formed by a plurality of conical spring plates. Specifically, the gear ring 3 includes an annular central shaft 32 and a plurality of conical spring plates 31. The conical spring plates 31 are disposed on the annular central shaft 32. Each conical spring piece 31 can rotate around the annular central shaft 32 as a center and roll on the surface of the planetary cone pulley 252, so that the speed-changing ring 3 can roll in the process of moving along the first direction to realize the speed change of the continuously variable transmission.

In the embodiment shown in fig. 1 and 2, the shift ring 3 is connected to the planetary cone 252. Here, the connection between the planetary cone 252 and the shift ring 3 may refer to the mutual engagement between the planetary cone 252 and the shift ring 3, or may refer to only the mutual engagement between the planetary cone 252 and the shift ring 3. Further, when the driven planetary gear 251 is rotated by the sun gear 13, the planetary driven member 25 is rotated around the center of the shift ring 3, thereby driving the planet carrier 23 and the output shaft 21 thereof to rotate, and outputting power. In addition, although the embodiment of the present invention shown in fig. 1 to 4 is illustrated by taking the gear shifting ring including the annular central shaft 32 and the plurality of conical spring plates 31 as an example, the present invention is not limited thereto, and any gear shifting ring may be used in the prior art to achieve the gear shifting function of the continuously variable transmission, and will not be described herein.

The shift unit controls movement of the shift ring in a first direction to adjust a rotational speed of the power output member. The speed changing unit comprises a speed changing screw rod mechanism 4, a pressing device 5 and a speed changing control mechanism. In the embodiment shown in fig. 1 and 2, the gear change unit comprises two gear change screw mechanisms 4. Wherein, two speed change screw rod mechanisms 4 are respectively arranged at two sides of the speed change ring 3 (in fig. 1 and 2, are arranged at the upper side and the lower side of the speed change ring 3), and each speed change screw rod mechanism 4 is connected with one speed change control mechanism. It should be noted that, although the embodiment shown in fig. 1 and 2 is illustrated by taking the gear shifting unit having two gear shifting screw mechanisms 4 as an example, the present invention is not limited thereto, and in other embodiments of the present invention, the number of the gear shifting screw mechanisms may be adjusted according to actual needs, for example, three or four gear shifting screw mechanisms are provided, which is not described herein.

Since the two shift screw mechanisms 4 are identical in structure in this embodiment, the shift screw mechanism 4 disposed above the shift ring 3 in fig. 1 will be described as an example. Specifically, the shift screw mechanism 4 is provided outside the shift ring 3, and the shift screw mechanism 4 includes a screw 41 and a screw nut 42. As shown in fig. 1, the screw 41 extends in a first direction (X-axis direction in fig. 1). The screw nut 42 is sleeved on the screw 41 and can move back and forth along the screw 41 in the first direction. The movement of the screw nut 42 along the screw 41 means movement along the thread on the surface of the screw 41 during the rotation of the screw 41.

The pressing device 5 is arranged outside the speed changing ring 3 and is connected with the screw nut 42 and the speed changing ring 3. The pressing device 5 can synchronously move along with the screw nut 42 in the first direction so as to drive the speed changing ring to move in the first direction and adjust the rotating speed of the power output part of the planetary power transmission mechanism. In addition, the compressing device 5 can also have the function of extrusion deformation on the conical spring piece 31 of the speed changing ring 3, so that the speed changing ring 3 is attached to the planetary cone 252 in an elliptic mode, the contact area between the speed changing ring 3 and the planetary cone 252 is increased, the stress concentration and the slipping are avoided, and further, the effective power transmission is realized. Specifically, in the embodiment shown in fig. 1 to 3, the pressing device 5 is arranged outside the shift ring 3 in a sleeve shape. Also, in this embodiment, the pressing device 5 is integrally formed with the lead screw nuts 42 of the two variable speed lead screw mechanisms 4, and thus can move in synchronization with the lead screw nuts 42. The pressing device 5 controls (e.g., pushes or the like) at least one conical spring of the shift ring 3 to rotate about the annular center shaft 32 and roll on the surface of the planetary cone 252 to drive the shift ring 3 to move back and forth in the first direction, and in the embodiment shown in fig. 2 and 3, a clamping groove 53 extending in the first direction (X-axis direction in fig. 1) is provided on a side surface of the pressing device 5 facing the shift ring 3, and the conical spring 31 of the shift ring 3 is clamped in the clamping groove 53. Preferably, the number of the clamping grooves 53 is the same as the number of the conical spring pieces 31 of the shift ring 3. The engagement groove 53 can prevent the shift ring 3 from rotating (spinning), and further, the planetary cone 252 is enabled to rotate (revolve around the center of the shift ring 3) within the shift ring 3.

The shift control mechanism (not shown in fig. 1 and 2) is connected to the screw 41 to drive the screw 41 to rotate, thereby controlling the movement of the screw nut 42 along the screw 41 in the first direction.

Further, in the embodiment shown in fig. 1 and2, each variable speed screw mechanism 4 further comprises a synchronizing sprocket 43. Both synchronizing sprockets 43 are provided at the same end of the variable speed screw mechanism 4. The gear unit further comprises a toothed chain (not shown in fig. 1 and 2) surrounding the two synchronizing sprockets 43. The toothed chain is connected with the two synchronous chain wheels 43, so that the rotation speeds of the two screw rods 41 can be kept consistent, and the pressing device 5 can be linearly moved along the axial direction under the condition that the rotation speeds of the two screw rods 41 are consistent, thereby ensuring the stability of the shifting ring 3 in the moving process. It should be noted that, in some embodiments of the present invention, the pressing device may be a straight cylinder or a cone cylinder with a certain taper, for example, on the side of the input shaft 11, the diameter is reduced on the right side in the drawing, so as to achieve that the deformation of the gear ring 3 is greater when the gear ring moves to the area, so that the contact area between the gear ring 3 and the small end (i.e. the smaller end) of the planetary cone 252 is greater, so as to reduce the slip of the gear ring 3, which is not described herein.

Further, as shown in fig. 1 to 3, in the continuously variable transmission of the present invention, the sun gear 13 rotates (rotates) synchronously with the input shaft 11 and then drives the driven planetary gear 251 to rotate (rotates) so that the planetary cone 252 also rotates synchronously. Since the planetary cone 252 is connected to the shift ring 3 and the shift ring 3 is not rotated (fixed by the pressing device 5), the planetary cone 252 rotates (revolves) around the center of the shift ring 3 in the shift ring 3 during rotation (autorotation) of the planetary cone 252, and the planetary gear shaft 253 passes through the carrier 23, so that the carrier 23 and the output shaft 21 on the carrier 23 can be driven to rotate (autorotate), thereby realizing power transmission.

Further, in the case where the continuously variable transmission is required to perform a speed change in combination with the embodiment shown in fig. 1 and 2, the screw 41 of the speed change screw mechanism 4 is driven to axially rotate (i.e., spin) by the speed change control mechanism, and the screw nut 42 can be moved in the first direction after the screw 41 rotates. Since the hold-down device 5 is integrally formed with the lead screw nut 42, the hold-down device 5 also moves with the lead screw nut 42 in the first direction (X-axis direction in fig. 1). Further, the pressing device 5 pushes the shift ring 3 to roll the conical spring piece 31 of the shift ring 3 on the surface of the planetary cone 252 in the first direction. For clearly explaining the movement track of the conical spring of the speed changing ring, fig. 4 shows a schematic diagram of the movement track of the conical spring of the speed changing ring on the planetary cone gear in the speed changing process of the continuously variable transmission. Fig. 4 schematically illustrates a conical spring 31 on the shift ring 3. Specifically, as shown in fig. 4, when the pressing device 5 pushes the shift ring 3 in the first direction (X-axis direction in fig. 4), the conical spring 31 of the shift ring 3 rotates around the annular central shaft 32 (arrow in fig. 4) and rolls along the surface of the planetary cone 252, so that the shift ring 3 moves in the first direction (X-axis direction in fig. 4), and therefore, the continuously variable transmission adopts a rolling form as the shift ring during shifting, and compared with a sliding form adopted by a steel belt of a conventional mechanical continuously variable automatic transmission (CVT) during shifting, the continuously variable transmission has the advantages of small friction resistance, rapid shifting and the like.

Further, since the planetary cone pulley 252 has a different diameter along the path along which the variator 3 rolls in the first direction, it is possible to achieve deceleration or acceleration of the continuously variable transmission. In the embodiment shown in fig. 1, since the diameters of the planetary cone 252 are gradually increased in the direction along the X-axis and the angular velocities of the two planetary cone 252 are constant, the linear velocity of the meshing position of the planetary cone 252 with the speed change ring 3 is increased due to the increase in the diameters thereof, and thus the speed of rotation (revolution) of the planetary cone 252 in the speed change ring 3 is increased, the carrier 23 is pushed to rotate by the planetary gear shaft 253, and the output speed of the output shaft 21 is further increased. Conversely, the speed change ring 3 can be rolled in the direction opposite to the X-axis to slow the rotation speed of the output shaft 21.

Further, in the embodiment shown in fig. 1 and 2, the continuously variable transmission further comprises a housing 6. Wherein the planetary power transmission mechanism, the shift ring and the shift unit are all disposed in the housing 6.

In summary, in combination with the embodiments shown in fig. 1 to 4, in the continuously variable transmission provided by the embodiment of the invention, the planetary driven member of the power output member is driven by the power input member to rotate around the power output member, so as to drive the output shaft of the power output member to rotate.

In addition, the continuously variable transmission also realizes the speed change of the continuously variable transmission by controlling the speed change ring to move along the first direction by the speed change unit so as to adjust the rotation speed of the power output part of the power transmission mechanism, wherein in the speed change process, the speed change ring moves on the surface of the planetary cone in a rolling mode in the moving process of the first direction because the speed change comprises a plurality of conical spring plates which can rotate around the annular central shaft as the center, and compared with the sliding mode adopted by the steel belt of the prior mechanical continuously variable automatic transmission (CVT) in the speed change process, the continuously variable transmission has the advantages of small friction resistance, realization of rapid speed change and the like. And after the structure of the planetary cone pulley is combined, not only can a plurality of planetary cone pulleys simultaneously transmit torque, but also the speed changing ring deforms under the coextrusion of the pressing device and the planetary cone pulley, and the contact area with the planetary cone pulley is increased, so that the planetary cone pulley has the advantages of large contact area, small running abrasion, long service life and the like. The structure of the continuously variable transmission also avoids the adoption of a complex hydraulic pressing device in the existing continuously variable transmission, thereby having the advantages of simpler manufacture, lower cost, higher reliability and the like.

While the invention has been described above in terms of preferred embodiments, it is not intended to limit the invention thereto. Those skilled in the art to which the present invention pertains will appreciate that numerous changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is therefore defined by the appended claims.

Claims

1. A continuously variable transmission, characterized by comprising:

a planetary power transmission mechanism, the planetary power transmission mechanism comprising at least:

a power input member; and

The power output part comprises an output shaft and at least one planetary driven part which is connected with the output shaft and drives the output shaft to rotate, and the planetary driven part is arranged on the outer side of the power input part and can rotate around the power input part under the driving of the power input part;

a shift ring circumferentially coupled to the planetary driven member, the shift ring being movable back and forth in a first direction;

the speed changing unit at least comprises a pressing device, wherein the pressing device is arranged on the outer side of the speed changing ring and is fixedly connected with the speed changing ring, and drives the speed changing ring to move back and forth in the first direction to adjust the rotating speed of a power output part of the planetary power transmission mechanism;

Wherein, the shift ring includes: an annular central shaft; the conical elastic pieces are arranged on the annular central shaft, and each conical elastic piece can rotate around the annular central shaft; the compressing device controls at least one conical spring sheet to roll on the surface of the planetary driven part while rotating around the annular central shaft to drive the speed changing ring to move along the first direction, a clamping groove extending along the first direction is formed in one side surface of the compressing device, facing the speed changing ring, of the speed changing ring, and the conical spring sheet of the speed changing ring is clamped in the clamping groove.

2. The variable transmission of claim 1, wherein the power input member comprises an input shaft and a sun gear disposed over the input shaft;

The power output part further comprises a planet carrier with the output shaft, and the central sun gear is arranged in the planet carrier;

the planetary driven part is arranged on the outer side of the central sun gear, connected with the planet carrier and the central sun gear and the speed changing ring, and can rotate around the center of the speed changing ring under the rotation driving of the central sun gear so as to drive the output shaft to rotate.

3. The variable transmission of claim 2, wherein the planetary driven member comprises:

a driven planetary gear meshed with the sun-center gear, the driven planetary gear being disposed within the carrier;

The planetary cone pulley is coaxial with the driven planetary gear and is mutually fixed, and the planetary cone pulley is connected with the speed changing ring;

The planet gear shaft is fixedly connected with the driven planet gear and the planet cone pulley, and the planet gear shaft also penetrates through the driven planet gear and the planet cone pulley to be connected with the planet carrier.

4. The variable transmission of claim 2, wherein the input shaft is coaxially disposed with the output shaft.

5. The variable transmission of claim 1, wherein the power take-off member comprises a plurality of the planetary driven members, wherein the plurality of planetary driven members are circumferentially disposed outside the power input member.

6. The variable transmission of claim 1, wherein the shifting unit further comprises:

the variable speed screw rod mechanism is arranged outside the pressing device, and comprises:

A lead screw extending in the first direction; and

The screw rod nut is sleeved on the screw rod and can move back and forth along the screw rod in a first direction;

The compressing device is connected with the screw nut and can synchronously move along with the screw nut in the first direction so as to drive the speed changing ring to move in the first direction; and the speed change control mechanism is connected with the screw rod and drives the screw rod to rotate so as to control the screw rod nut to move along the screw rod in a first direction.

7. The continuously variable transmission according to claim 6, wherein the speed change unit includes a plurality of the speed change screw mechanisms, the plurality of speed change screw mechanisms being circumferentially disposed outside the pressing device, and screws of the plurality of speed change screw mechanisms being connected to the speed change control mechanism.

8. The variable transmission of claim 7, wherein each of the shift screw mechanisms further comprises a synchronizing sprocket disposed at a same end of the shift screw mechanism; the speed changing unit further comprises a toothed chain connected with each synchronous sprocket.

9. The variable transmission of claim 1, wherein the hold down device is sleeve-like around the shift ring.

10. The variable transmission according to any one of claims 1 to 9, further comprising a housing, wherein the planetary power transmission mechanism and the speed change unit are disposed inside the housing.