A continuously variable transmission

Abstract

The present invention discloses a continuously variable transmission, comprising an active part and a driven part and a flexible element arranged between the active part and the driven part, wherein the active part comprises an active shaft and a pair of active cone discs which are arranged on the active shaft and used to clamp the flexible element, and the driven part comprises a driven shaft and a pair of driven cone discs which are arranged on the driven shaft and used to clamp the flexible element; an elastic member is arranged between the back of the active driving cone disc and an axially fixed limiting member, and an elastic speed regulating mechanism which can axially push the driven fixed cone disc is arranged on the back of the driven fixed cone disc, wherein the stiffness coefficient of the elastic member is K1, and the stiffness coefficient of the elastic speed regulating mechanism is K2, and K1≥K2. The present invention simplifies the speed regulating method of the continuously variable transmission, improves the speed regulating rate, and reduces the cost.

Description

Technical Field

[0001] The invention relates to a speed changing mechanism, in particular to a continuously variable transmission. Background Art

[0002] Chinese patent CN201110193407.7 discloses a continuously variable transmission, and specifically discloses two parallel transmission shafts, each of which has at least one pair of cone disks with conical surfaces arranged opposite to each other, at least one flexible transmission element is sandwiched between the cone disks, one cone disk in each pair of cone disks can move axially on the transmission shaft, and the other cone disk cannot move axially on the transmission shaft but can rotate with the transmission shaft; the back of the cone disk on one transmission shaft that can move axially between the shaft is connected to a spiral mechanism (motor-driven speed regulating mechanism), the spiral mechanism consists of a hollow screw and a nut matched with the hollow screw, and the transmission shaft is arranged in the hollow screw; one of the hollow screw and the nut of the spiral mechanism is connected to the transmission shaft to which it belongs through an axis that can simultaneously withstand axial loads and radial loads. The two axially movable cone disks respectively located on the two transmission shafts are respectively pressed against the flexible transmission element and the fixed cone disk by at least one spring or spring group directly or indirectly connected to the cone disk at one end and directly or indirectly connected to the transmission shaft to which the cone disk belongs; the stiffness coefficient or the total stiffness coefficient of the spring or spring group on the transmission shaft and the cone disk connected with the speed regulating screw mechanism is greater than the stiffness coefficient or the total stiffness coefficient of the spring or spring group on the other transmission shaft.

[0003] The above patent further provides one of the embodiments, in which a driven shaft compression spring is provided on the back of the driven shaft dynamic cone disc, and a motor-driven speed regulating mechanism, i.e., a spiral speed regulating mechanism, is provided on the back of the active shaft dynamic cone disc. The stiffness coefficient of the compression spring of the spiral speed regulating mechanism on the active shaft is greater than the stiffness coefficient of the compression spring on the driven shaft.

[0004] The following problems exist when using the continuously variable transmission in the above patent: 1. The compression spring needs to be large in size and have a large elastic force, which further causes the cone disc to be too large in size. 2. When adjusting the speed, whether the transmission ratio is from large to small or from small to large, it needs to be driven by a motor to achieve the spiral speed regulation mechanism. Therefore, a motor with forward and reverse rotation must be used, and at the same time, the elastic force of the spring needs to be overcome, resulting in too slow speed regulation. 3. The speed regulation system needs to coordinate the stiffness coefficients of the two sets of disc springs at the same time, resulting in complicated speed regulation; and the speed regulation cone disc is bidirectionally stressed, resulting in too slow speed regulation for small transmission ratios, and the bearing structure is complex, costly, and requires a large space. 4. The change in the clamping force of the flexible transmission element during transmission is opposite to the change in the elastic force of the compression spring on the driven shaft, which further leads to slow speed regulation and large speed regulation force. Summary of the invention

[0005] The object of the present invention is to provide a continuously variable transmission with low cost and simple and fast speed regulation.

[0006] In order to achieve the above-mentioned object, the present invention is implemented as follows: a continuously variable transmission, comprising a driving part and a driven part and a flexible element arranged between the driving part and the driven part, the driving part comprising a driving shaft and a pair of driving cone discs which are arranged on the driving shaft and used to clamp the flexible element, the driven part comprising a driven shaft and a pair of driven cone discs which are arranged on the driven shaft and used to clamp the flexible element; one of the driving cone discs is a driving fixed cone disc fixed on the driving shaft, and the other driving cone disc is a driving driving cone disc which can slide axially along the driving shaft, one of the driven cone discs is a driven fixed cone disc fixed on the driven shaft and opposite to the driving fixed cone disc, and the other driven cone disc is a driven driven cone disc which can slide axially along the driven shaft and opposite to the driving driven cone disc, characterized in that an elastic member is arranged between the back side of the driving driven cone disc and the axially fixed limiting member, and an elastic speed regulating mechanism which can axially push the driven driven cone disc is arranged on the back side of the driven driven cone disc, and the stiffness coefficient of the elastic member is K 1 , the stiffness coefficient of the elastic speed regulating mechanism is K 2 , and K 1 ≥K 2. In the continuously variable transmission arranged in the above manner, the elastic speed regulating mechanism is arranged on the driven shaft, the elastic member is arranged on the driving shaft, and the stiffness coefficient of the elastic speed regulating mechanism is set to be less than or equal to the stiffness coefficient of the elastic member. When adjusting the speed from a large transmission ratio to a small transmission ratio, it is only necessary to push the driven cone disc to move axially through the elastic speed regulating mechanism, and the force applied by the elastic speed regulating mechanism is consistent with the change direction of the clamping force of the flexible element, thereby improving the speed regulation rate. When adjusting the speed from a small transmission ratio to a large transmission ratio, the elastic speed regulating mechanism does not need to apply force, and only needs to push the driven cone disc through the axial return force of the elastic member on the driving shaft to achieve speed regulation. The speed regulating mechanism is simple, the speed regulating force requirement is small, and the speed regulating efficiency is high. In addition, in the continuously variable transmission arranged in the above manner, the elastic speed regulating mechanism does not need to overcome the elastic force of the elastic speed regulating mechanism when returning, so the volume and elastic force of the elastic speed regulating mechanism and the elastic member can be designed to be smaller, and further the cone disc can also be designed to be smaller, and more parts can be saved, thereby reducing the cost of the continuously variable transmission and reducing the volume of the continuously variable transmission.

[0007] Preferably, the elastic speed regulating mechanism includes a hollow speed regulating screw and a speed regulating nut; the hollow speed regulating screw is connected to the driven shaft via a first bearing, one end of the speed regulating nut is connected to the driven cone disk via a second bearing, and the other end is provided with an internal thread and is threadedly connected to the external thread of the hollow speed regulating screw, the hollow speed regulating screw is limited in circumferential rotation by a fixed limit block, the speed regulating nut is driven to rotate by a driving mechanism, and a disc spring assembly is sleeved on the driven shaft between the first bearing and the second bearing.

[0008] Preferably, the elastic member is a disc spring assembly, the limiting member is a sleeve fixed on the driving shaft, and the disc spring assembly is sleeved on the driving shaft.

[0009] In order to further realize the speed regulation range of the transmission ratio, the elastic member is composed of n disc springs, and the following relationship n≥4 is satisfied. In this way, the transmission ratio requirement can be realized in the range of four times from 0.5 to 2.

[0010] In order to further realize the speed regulation range of the transmission ratio, the inner diameter of the disc spring is d, the outer diameter of the disc spring is D, the thickness is t, and the outer diameter of the cone disk is D 0 , and there is the following relationship, D<D 0 +1, D / d<1.6, t>(D 0 +1) / d. This setting can realize the required curve of axial force and achieve the maximum to minimum transmission ratio.

[0011] In order to further ensure the speed regulation range and the stability of the disc spring, a retaining ring is set between the disc springs with opposite openings. The retaining ring has a diameter of d 0 , and the following conditions are met: t / 10<d 0<t. If the thickness of the retaining ring is too large, it will affect the transmission ratio range, resulting in a reduction in the transmission ratio range, while if it is too small, it will affect the stability of the disc spring force, so a special thickness selection is required.

[0012] In order to further improve the service life of the transmission, the speed regulating nut and the hollow speed regulating screw are rolling spiral or sliding spiral structures, and the diameter thereof is D L , and satisfy the following relationship: D L >D 0 / 2.

[0013] To further achieve the speed regulation range, the thread length L of the hollow speed regulating screw or the speed regulating nut satisfies the following relationship: L>2(D 0 / 2-D 0 / 3)tan(11π / 180).

[0014] In order to further reduce the space of the transmission, the driving mechanism includes a driving shaft, one end of which is provided with a driving gear, and the outer wall of the speed regulating nut is provided with a driven tooth meshing with the driving gear, and the other end of the driving shaft is driven by a motor and a worm gear mechanism. The motor drives the worm, which drives the turbine to rotate, and the turbine in turn drives the driving gear on the driving shaft to rotate, and the speed regulating nut is driven by meshing with the driving gear.

[0015] In order to further reduce the space of the transmission, the driving mechanism includes a driving shaft, a turbine is arranged on the driving shaft, and mutually meshing transmission teeth are arranged on the outer wall of the turbine and the outer wall of the speed regulating nut, and the turbine is driven by a motor and a worm. The motor drives the worm, and the worm drives the turbine to rotate, and the turbine in turn drives the speed regulating nut to rotate, so as to realize the axial movement of the speed regulating nut.

[0016] Beneficial effects:

[0017] The present invention realizes the speed adjustment of the entire transmission by adjusting the structure, setting an elastic speed regulating mechanism on the back of the driven cone disc of the driven shaft and setting a disc spring assembly on the back of the active cone disc of the driving shaft. The stiffness coefficient of the disc spring assembly of the elastic speed regulating mechanism is set to be less than or equal to the stiffness coefficient of the disc spring assembly on the driving shaft. In this way, the speed regulation method of the continuously variable transmission is simplified, the speed regulation speed is increased, the speed regulation force required by the elastic speed regulating mechanism is reduced, and the power required by the speed regulating motor is further reduced. In addition, the spatial layout of the transmission is optimized, the volume and components of the transmission are reduced, and the cost is reduced.

[0018] Specifically: 1. In the process of adjusting the transmission ratio from large to small, the continuously variable transmission of the present invention only needs to rely on the elastic speed regulating mechanism to pressurize the driven cone disc, and the force applied by the elastic speed regulating mechanism is consistent with the change direction of the clamping force required by the flexible element, which improves the speed regulation rate and reduces the force required by the speed regulating motor. In the process of adjusting the transmission ratio from small to large, the elastic speed regulating mechanism does not need to apply force, but only needs to transmit the axial return force of the disc spring assembly on the active drive cone disc to the driven cone disc through the flexible element, and then axially push the driven cone disc to increase the transmission ratio. In this process, there is no need to apply additional force to the elastic speed regulating mechanism through the speed regulating motor, nor is there any need to overcome the elastic force of the disc spring on the elastic speed regulating mechanism, so the speed regulation rate is high. Therefore, by reasonably configuring the disc spring, the speed regulation force is reduced, and the speed regulation in the direction of small transmission ratio is faster.

[0019] 2. Through the design of the speed regulating mechanism and disc spring assembly of the present invention, during the speed regulating process, the force that the driven cone disc needs to overcome is small, and the force condition of the driven cone disc is consistent with the direction of change of the clamping force described in the flexible element, so there is no need to design an excessively large elastic force for the disc spring. Therefore, the design volume of the cone disc can be further reduced, thereby reducing the overall volume of the continuously variable transmission.

[0020] 3. The continuously variable transmission of the present invention has a simple speed regulating structure. The cone disk driven by the speed regulating mechanism changes from bidirectional force to unidirectional force, the bearing type becomes simple, the positioning method is simplified, and the cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a structural diagram of a continuously variable transmission of the present invention;

[0022] Figure 2 for Figure 1 A partial enlarged view of . DETAILED DESCRIPTION

[0023] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings, but the present invention is not limited to these implementation modes, and any improvement or substitution based on the basic spirit of the present embodiment still falls within the scope of protection required by the claims of the present invention.

[0024] Example 1: Figure 1As shown, this embodiment provides a continuously variable transmission, including a driving part and a driven part and a flexible element 1 arranged between the driving part and the driven part, the driving part includes a driving shaft 2 and a pair of driving cone discs that are transmission-arranged on the driving shaft and used to clamp the flexible element, and the driven part includes a driven shaft 3 and a pair of driven cone discs that are transmission-arranged on the driven shaft and used to clamp the flexible element. One of the driving cone discs is a driving fixed cone disc 21 fixed on the driving shaft 2, and the other driving cone disc is a driving driven cone disc 22 that is axially slidable on the driving shaft. One of the driven cone discs is a driven fixed cone disc 31 that is fixed on the driven shaft 3 and is opposite to the driving fixed cone disc 21, and the other driven cone disc is a driven driven cone disc 32 that is axially slidable on the driven shaft 3 and is opposite to the driving driven cone disc. In addition, an elastic member is arranged between the back side of the active cone disc and the axially fixed limit member, and an elastic speed regulating mechanism 4 capable of axially pushing the driven cone disc is arranged on the back side of the driven cone disc, the stiffness coefficient of the elastic member is K1, the stiffness coefficient of the elastic speed regulating mechanism is K2, and K1≥K2.

[0025] The back side of the active drive cone disc refers to the side of the active drive cone disc facing away from the active fixed cone disc, and the side facing the active fixed cone disc is the front side. The back side of the driven drive cone disc refers to the side of the driven drive cone disc facing away from the driven fixed cone disc, and the side facing the driven fixed cone disc is the front side.

[0026] In this embodiment, the elastic member is a disc spring assembly B23 sleeved on the driving shaft, and the limiting member is a sleeve C24 fixed on the driving shaft.

[0027] In this embodiment, the elastic speed regulating mechanism 4 includes a driving mechanism 6 and an elastic push plate assembly 5 acting on the driven cone disc. As one of the implementation methods in this embodiment, the push plate assembly includes a hollow speed regulating screw 52 and a speed regulating nut 51. The outer end surface of the driven cone disc is provided with an integral or split and fixed sleeve A33, and one end of the speed regulating nut is fixed to the sleeve A through a bearing A53. The other end of the speed regulating nut is away from the driven cone disc and is threaded with the hollow speed regulating screw. Among them, a sleeve B55 is fixed on the driven shaft away from the end of the driven cone disc, and the hollow speed regulating screw is fixed on the sleeve B55 through a bearing B56. And the outer wall of the hollow speed regulating screw and the inner wall of the speed regulating nut are provided with external threads and internal threads that cooperate with each other, and a ball 54 is provided between the external threads and the internal threads. In addition, an axial disc spring assembly A57 is arranged in the cavity defined by the hollow speed regulating screw and the speed regulating nut. Specifically, the disc spring assembly A is sleeved on the driven shaft and abuts against the bearing A and the bearing B.

[0028] In addition, elements for axially and circumferentially limiting the hollow speed regulating nut are also provided. A stopper 58 is provided on the housing 100 of the continuously variable transmission, and the stopper can limit the circumferential rotation of the hollow speed regulating nut, and a truncated cone is provided on the inner wall of the hollow speed regulating nut, and the truncated cone is clamped on the end face of the bearing B56 facing the cone disk, further realizing the limit when the disc spring assembly A57 returns to its original position, thereby ensuring an accurate transmission ratio value.

[0029] As another implementation in this embodiment, the driving mechanism 6 includes a driving shaft 61, a driving gear 62 is fixed on the driving shaft, and a driven tooth 59 meshing with the driving gear is arranged on the outer wall of the speed regulating nut. A turbine assembly 63 is fixed on the driving shaft, and the driving shaft is driven by a motor driving a screw rod 64 matching the turbine assembly. As another implementation, a driving tooth meshing with the driven tooth 59 on the outer wall of the speed regulating nut can be directly arranged outside the turbine assembly.

[0030] When the continuously variable transmission of this embodiment is used, the disc spring assembly B is pre-mounted on the driving shaft, and all the cone disks, flexible elements and elastic drive mechanisms are assembled. When the transmission ratio is the largest, it is ensured that the disc spring assembly A and the disc spring assembly B are not subjected to compression force. When the continuously variable transmission of this embodiment is used, the transmission ratio of the continuously variable transmission needs to be gradually changed from the largest to the smallest. At this time, the driving motor causes the driving gear to drive the speed regulating nut on the driven shaft to rotate, thereby realizing the axial movement (towards the driven fixed cone disk) of the speed regulating nut, pushing the driven movable cone disk to squeeze the flexible element, so that the transmission ratio of the continuously variable transmission becomes smaller. At this time, the axial thrust of the driven movable cone disk is further transmitted to the active movable cone disk through the flexible element, so that the active movable cone disk axially compresses the disc spring assembly B, so that the disc spring assembly B accumulates force. In this speed regulation process, the force required for the flexible element to change speed gradually increases and is provided by the driven cone disc, and the force exerted on the driven cone disc also gradually increases. In other words, the force required for the flexible element to change speed and the force exerted on the driven cone disc both gradually increase, the force change trend is consistent, and the speed regulation is faster.

[0031] If it is necessary to change the speed from a small transmission ratio to a large transmission ratio, it is only necessary to stop the driving of the motor. The axial force released by the disc spring assembly B on the driving shaft when returning to its original position is transmitted to the driven cone disc on the driven shaft through the flexible element, thereby pushing the driven cone disc to move in a direction away from the driven fixed cone disc, releasing the squeezing of the flexible element, and realizing the speed regulation from a small transmission ratio to a large transmission ratio. Moreover, since the stiffness coefficient of the disc spring assembly B in this embodiment is greater than the stiffness coefficient of the disc spring assembly A, there is no need for the motor to provide external force during this speed regulation process, and due to the axial limit of the hollow speed regulating nut, there will be no inaccurate speed regulation. In this speed regulation process, the force required for the speed change of the flexible element is gradually reduced and provided by the driven cone disc, and the force received by the driven cone disc is also gradually reduced, that is, the force required for the speed change of the flexible element and the force received by the driven cone disc are both gradually reduced, so the speed regulation is faster. Moreover, the driven cone disc does not need to overcome the elastic force of the disc spring assembly A during the speed regulation process, which further improves the speed regulation rate.

[0032] Therefore, no matter it is a speed change from a large transmission ratio to a small transmission ratio or from a small transmission ratio to a large transmission ratio, the speed regulating force required is small, the disc spring assembly can also be designed to be small, and further the volume of the cone disk assembly can also be designed to be small. Not only the space size of the transmission is reduced, but also the bearing type becomes simple, the positioning method is simplified, and the cost is saved. Furthermore, since the speed regulating force is small, a motor with smaller power can be used, which further saves the cost.

[0033] As another implementation manner of this embodiment, the active fixed cone disc and the active shaft can be integrally provided or fixedly connected via a shoulder or a retaining spring, and the driven fixed cone disc and the driven shaft can be integrally provided or fixedly connected via a shoulder or a retaining spring.

[0034] This embodiment adjusts the structure by setting an elastic speed regulating mechanism on the back of the driven cone disc of the driven shaft and setting a disc spring assembly on the back of the active cone disc of the driving shaft to cooperate to achieve the speed adjustment of the entire transmission. And the stiffness coefficient of the disc spring assembly of the elastic speed regulating mechanism is set to be less than or equal to the stiffness coefficient of the disc spring assembly on the driving shaft. In this way, the speed regulation method of the continuously variable transmission is simplified, the speed regulation speed is increased, the speed regulation force required by the elastic speed regulating mechanism is reduced, and the power required by the speed regulating motor is further reduced. In addition, the spatial layout of the transmission is optimized, the volume and components of the transmission are reduced, and the cost is reduced.

[0035] Embodiment 2: This embodiment is an optimization choice made on the basis of embodiment 1.

[0036] In this embodiment, the disc spring assembly A is composed of n disc springs, and the following relationship n≥4 is met, and the selection may be but not limited to 4, 6, 8, 10, 12, 14, 16, 18, etc. In this embodiment, the disc spring assembly B is composed of 6 disc springs, and the disc spring assembly A is composed of 10 disc springs.

[0037] The inner diameter of the disc spring is d, the outer diameter of the disc spring is D, the thickness is t, and the outer diameter of the cone disk is D0. There is the following relationship: D<D0+1, D / d<1.6, t>(D0+1) / d.

[0038] In this embodiment, by limiting the thickness, inner diameter and outer diameter of the disc spring, the variation curve of the axial force of the cone disk and the variation curve of the transmission ratio are further balanced, so that their variation trends are basically consistent.

[0039] Embodiment 3: This embodiment is a further optimization based on Embodiment 1 or Embodiment 2.

[0040] In this embodiment, a retaining ring 25 is provided between the disc springs with openings facing each other. The diameter of the retaining ring is d0 and satisfies the following condition: t / 10<d0<t, where t is the thickness of the disc spring.

[0041] In this embodiment, if the thickness of the retaining ring is too large, it will affect the transmission ratio range, resulting in a reduction in the transmission ratio range, while if it is too small, it will affect the stability of the disc spring force. Therefore, it is necessary to select a special thickness to ensure the transmission ratio range and the stability of the disc spring.

[0042] Embodiment 4: This embodiment is a further optimization based on Embodiment 1, Embodiment 2 or Embodiment 3.

[0043] In this embodiment, the thread length L of the hollow speed regulating screw or the speed regulating nut satisfies the following relationship: L>2(D0 / 2-D0 / 3)tan(11π / 180).

[0044] As another implementation in this embodiment, the hollow speed regulating screw and the speed regulating screw mesh are rolling screw or sliding screw structures. The middle diameter is DL, and satisfies the following relationship: DL>D0 / 2. When a rolling screw is used, a ball is arranged between the nut and the screw, and the middle diameter refers to twice the distance from the center of the ball to the axis of the driven shaft.

[0045] In this embodiment, the hollow speed regulating screw and the speed regulating nut are specially set to ensure the realization of the speed regulating range and improve the service life of the transmission.

Claims

1. A continuously variable transmission, comprising a driving part and a driven part and a flexible element arranged between the driving part and the driven part, wherein the driving part comprises a driving shaft and a pair of driving cone discs which are arranged on the driving shaft and used to clamp the flexible element, and the driven part comprises a driven shaft and a pair of driven cone discs which are arranged on the driven shaft and used to clamp the flexible element; one of the driving cone discs is a driving fixed cone disc fixed on the driving shaft, and the other driving cone disc is a driving driven cone disc which can slide along the axial direction of the driving shaft, one of the driven cone discs is a driven fixed cone disc fixed on the driven shaft and opposite to the driving fixed cone disc, and the other driven cone disc is a driven driven cone disc which can slide along the axial direction of the driven shaft and opposite to the driving driven cone disc, characterized in that: An elastic member is provided between the back of the active cone disc and the axially fixed limiting member, and an elastic speed regulating mechanism capable of axially pushing the driven cone disc is provided on the back of the driven cone disc, the stiffness coefficient of the elastic member is K1, the stiffness coefficient of the elastic speed regulating mechanism is K2, and K1≥K2; The elastic speed regulating mechanism comprises a hollow speed regulating screw and a speed regulating nut; the hollow speed regulating screw is connected to the driven shaft through a first bearing, one end of the speed regulating nut is connected to the driven cone disk through a second bearing, and the other end is provided with an internal thread and is threadedly connected with the external thread of the hollow speed regulating screw, the hollow speed regulating screw is limited in circumferential rotation by a fixed limit block, the speed regulating nut is driven to rotate by a driving mechanism, and a disc spring assembly is sleeved on the driven shaft between the first bearing and the second bearing; The elastic member is a disc spring assembly, the limiting member is a shaft sleeve fixed on the driving shaft, and the disc spring assembly is sleeved on the driving shaft; The elastic member is composed of n disc springs, and the relationship is as follows: n≥4; The inner diameter of the disc spring is d, the outer diameter of the disc spring is D, the thickness is t, the outer diameter of the cone disk is D0, and the following relationship exists: D<D0+1, D / d<1.6, t>(D0+1) / d; A retaining ring is arranged between the disc springs with openings facing each other, the retaining ring diameter is d0, and the following conditions are satisfied: t / 10<d0<t; The speed regulating nut and the hollow speed regulating screw are rolling spiral or sliding spiral structures, and the spiral structure has a median diameter of D L , and satisfy the following relationship: D L >D0 / 2.

2. The continuously variable transmission according to claim 1, characterized in that: The thread length L of the hollow speed regulating screw or the speed regulating nut satisfies the following relationship: L>2(D0 / 2-D0 / 3)tan(11π / 180).

3. The continuously variable transmission according to claim 1 or 2, characterized in that: The driving mechanism comprises a driving shaft, one end of which is provided with a driving gear, an outer wall of the speed regulating nut is provided with a driven tooth meshing with the driving gear, and the other end of the driving shaft is driven by a motor and a worm gear mechanism.

4. The continuously variable transmission according to claim 1 or 2, characterized in that: The driving mechanism comprises a driving shaft, a turbine is arranged on the driving shaft, and mutually meshing transmission teeth are arranged on the outer wall of the turbine and the outer wall of the speed regulating nut. The turbine is driven by a motor and a worm.

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