A transmission structure

Abstract

The invention discloses a transmission structure, including an input module, a speed change module and an output module, wherein the speed change module includes a first gear, a sliding guide sleeve, a shift mechanism and a second gear, the first gear is sleeved to the input shaft, and the second gear is sleeved on the output shaft; the speed change module also includes a third gear, a fourth gear and a driven shaft, the third gear is meshed with the first gear, the fourth gear is meshed with the second gear, the sliding guide sleeve is sleeved to the output shaft, the sliding guide sleeve is provided with an annular groove and the end surface of the sliding guide sleeve is respectively provided with a first transmission groove and a second transmission groove, the shift mechanism is engaged with the annular groove, the first gear is provided with a first transmission member, the second gear is provided with a second transmission member, the sliding guide sleeve is connected to the first gear by nesting the first transmission member in the first transmission groove or by nesting the second transmission member in the second transmission groove. The transmission structure of the invention is compact and simple, low in cost, smooth in gear shifting, convenient and reliable in speed shifting, and the problem of tooth collision or even tooth collapse is avoided.

Description

Technical Field

[0001] The present invention relates to the field of transmission technology, and more specifically, to a transmission structure. Background Art

[0002] Ordinary feeders generally have limited gears, resulting in fewer speed ranges. During the use of the feeder and the wood processing process, the user is unable to accurately obtain the required speed range due to various factors such as wood material, thickness, required processing shape, tool cutting depth, etc., and therefore cannot meet the more sophisticated speed requirements required for processing. Currently, users in the market will choose a frequency conversion speed feeder, which can achieve stepless speed change within the selected range to meet the user's more sophisticated speed requirements, but this feeder is more expensive, so the market coverage is small and not many users choose it.

[0003] Therefore, with the need of processing, a transmission structure that can be used with a feeder has appeared on the market, but the general transmission structure will use a multi-stage gear set to change speed, resulting in a complex transmission structure, large space occupation, and is not suitable for use with a feeder that is not large in size. In order to provide a speed change function and save space, the invention patent CN1369656A disclosed on September 18, 2002 describes a variable ratio coaxial transmission structure, which provides two optional speed gears through the outer gear moving on the coaxial axis and two speed gears. Therefore, the transmission structure retains all the speed segments of the current ordinary feeder, and can also provide an additional double speed segment when used with the feeder, further refining the segmentation of the feeding speed, meeting the fine needs of most users for the speed segment, and the speed change is convenient and fast, further improving the efficiency of the speed change, and the cost is greatly reduced compared with the feeder using variable frequency speed regulation. However, the disadvantages of this variable ratio coaxial transmission structure are that the overall structure is bulky and bloated, occupying a large space, and the direct drive gear engagement and disengagement to switch speeds can easily lead to problems such as uneven engagement, tooth collision, and even tooth breakage during the speed change process. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a transmission structure, which provides more precise speed stages, has a compact and simple structure, low cost, smooth gear shifting, convenient and reliable speed change, and avoids the problem of tooth collision or even tooth breakage.

[0005] The technical problem solved by the present invention is achieved by adopting the following technical scheme: a transmission structure, including an input module, a speed change module and an output module, the input module includes an input shaft, the output module includes an output shaft, wherein the speed change module includes a first gear, a sliding guide sleeve, a shift mechanism and a second gear arranged in sequence along the axial direction, the first gear is sleeved on the input shaft, the second gear is sleeved on the output shaft and can rotate relative to the output shaft; the speed change module also includes a third gear, a fourth gear and a driven shaft, the third gear and the fourth gear are respectively sleeved on both ends of the driven shaft, the third gear is meshed with the first gear, and the third gear is meshed with the first gear. The fourth gear is meshed with the second gear, the driven shaft is parallel to the output shaft, the sliding guide sleeve can be axially slidably sleeved on the output shaft, the radial outer surface of the sliding guide sleeve is provided with an annular groove and the two axial end faces of the sliding guide sleeve are respectively provided with a first transmission groove and a second transmission groove, the shifting mechanism is engaged with the annular groove, the end face of the first gear close to the output shaft is provided with a first transmission member, the end face of the second gear close to the input shaft is provided with a second transmission member, the sliding guide sleeve is connected to the first gear by nesting the first transmission member in the first transmission groove or is connected to the second gear by nesting the second transmission member in the second transmission groove.

[0006] In the transmission structure of the present invention, the first gear is sleeved on the input shaft, and the input shaft of the input module drives the first gear to rotate, so the speed of the input shaft is transmitted to the first gear. The third gear and the fourth gear are sleeved on both ends of the driven shaft, the first gear and the third gear are meshed, the first gear drives the third gear to rotate, and the number of teeth of the first gear and the number of teeth of the third gear may not be equal to achieve speed change. The third gear and the fourth gear rotate together and have the same speed. The fourth gear is meshed with the second gear, and the number of teeth of the second gear and the number of teeth of the fourth gear may not be equal, so that the fourth gear drives the second gear to achieve speed change again, when the number of teeth of the first gear is equal to the number of teeth of the third gear, the number of teeth of the second gear is not equal to the number of teeth of the fourth gear, and when the number of teeth of the second gear is equal to the number of teeth of the fourth gear, the number of teeth of the first gear is not equal to the number of teeth of the third gear, and the speed ratio can be adjusted and selected by adjusting the number of teeth of each gear according to actual needs, but it must be ensured that the sum of the pitch circle diameters of the third gear and the first gear is equal to the sum of the pitch circle diameters of the fourth gear and the second gear. When the sliding guide sleeve slides axially to the position where the second transmission groove is nested with the second transmission member, the second transmission member drives the second transmission groove to rotate, and the speed of the second gear after the speed change is thus transmitted to the sliding guide sleeve, and the sliding guide sleeve is sleeved on the output shaft to transmit the speed of the sliding guide sleeve to the output shaft, thereby realizing the speed change output. After the shift mechanism engaged on the annular groove of the sliding guide sleeve is dialed, the sliding guide sleeve slides axially along the output shaft, so when the sliding guide sleeve slides axially to the position where the first transmission groove is nested with the first transmission member, the first transmission member drives the first transmission groove to rotate, and the speed of the first gear is thus transmitted to the sliding guide sleeve, and the sliding guide sleeve transmits the speed to the output shaft, and the output shaft and the input shaft have the same speed, thereby realizing the constant speed output. The transmission structure provides additional speed gears, that is, it provides more required speed segments, which can meet more precise speed requirements. If more and more refined speed segments are required, the selection can be adjusted by adjusting the number of teeth of each gear according to actual needs to provide more speed gears. The transmission structure also adopts a coaxial speed change structure and a speed change driven by a transmission member. The meshing speed change of the gear set generally takes up a lot of space. At the same time, when shifting gears, problems such as tooth collision and tooth breakage are prone to occur before the gears mesh with each other, resulting in damage to the workpiece and uneven speed change. Since the transmission structure does not require changing the gear set for speed change, space is saved in the structure, and the structure is more compact and simple. At the same time, the speed change is driven by the transmission member, and the speed change is convenient and reliable, avoiding problems such as tooth collision and tooth breakage. Therefore, the gear shift can be smoothly transitioned, and the price is low compared with variable frequency speed regulation products.

[0007] In one embodiment, it also includes a housing, the speed change module and the output module are installed in the housing, the two axial end faces of the housing are respectively provided with a first support hole and a second support hole parallel to the sliding guide sleeve, the shift mechanism includes a support member, a sliding sleeve and a shift fork, the two ends of the support member are fixedly inserted into the first support hole and the second support hole, the shift fork can be axially slidably sleeved on the support member through the sliding sleeve and snapped into the annular groove. The support member is fixed in the first support hole and the second support hole of the housing, the shift fork is sleeved on the support member through the sliding sleeve, the support member provides radial support for the shift fork, the fork end of the shift fork snaps into the annular groove of the sliding guide sleeve, and can drive the sliding guide sleeve to slide axially along the output shaft. The housing protects the speed change module and the output module from being polluted by the external working environment, and can also prevent the workpiece from collapsing in the event of an accident in the speed change structure. Since the support member and the first support hole and the second support hole provide radial support, the shift fork can slide on the support member more smoothly, thereby driving the sliding guide sleeve to slide axially along the output shaft more stably. Since the gear shifting requires the sliding guide sleeve to slide on the output shaft and connect with the first transmission member and the second transmission member, because precise alignment is required, the size of the radial deviation needs to be very precise. The radial support provided by the support member reduces the radial deviation of the shift fork, allowing the gear shifting to be precisely aligned.

[0008] Preferably, the shift mechanism further comprises a shift shaft and a shift knob, a long groove is provided at one end of the shift fork away from the annular groove, a boss is provided at one end of the shift shaft close to the support member, the shift knob is provided at the other end of the shift shaft, and the boss is inserted into the long groove. Rotating the shift knob drives the boss to rotate, and the rotation of the boss pushes the inner side of the long groove, thereby driving the long groove on the shift fork to slide axially along the support member, so that the shift fork starts to slide axially, and the sliding of the shift fork drives the sliding guide sleeve to slide axially on the output shaft until it is connected with the first transmission member and the second transmission member to achieve gear shifting and speed change, and the rotation of the boss drives the shift fork to slide axially, so that the sliding guide sleeve can slide according to the rotation trajectory curve of the boss during gear shifting, and the gear shifting action is smooth, so the gear shifting and speed change is achieved more smoothly.

[0009] In one embodiment, the sliding guide sleeve is further provided with a spring plunger, the sliding guide sleeve is provided with a threaded hole, and the spring plunger passes through the threaded hole to press the output shaft. After the sliding guide sleeve slides to a certain position, the spring plunger presses the output shaft to fix it. During the sliding shifting process of the sliding guide sleeve, the spring plunger can press the output shaft to achieve axial fixation of the sliding guide sleeve, and the shift fork no longer bears the axial force of the sliding guide sleeve, thereby reducing the heat and wear caused by the mutual friction between the two, and ensuring smooth and stable shifting and speed change.

[0010] Preferably, the radial outer surface of the output shaft is provided with a groove, and the spring plunger passes through the threaded hole and is inserted into the groove. According to the gear position required for the speed change, a corresponding groove is provided at the position of the corresponding output shaft, and the spring plunger is inserted into the provided groove when the sliding guide sleeve slides to the required position. During the sliding shifting process of the sliding guide sleeve, the spring plunger can be inserted into the groove to achieve axial fixation of the sliding guide sleeve, and the shift fork no longer bears the axial force of the sliding guide sleeve, thereby reducing the heat and wear caused by the mutual friction between the two, and ensuring smooth and stable gear shifting.

[0011] In one embodiment, a first bearing is provided between the third gear, the fourth gear and the driven shaft, and the third gear and the fourth gear are sleeved to the driven shaft through the first bearing. The third gear and the driven shaft are connected through the first bearing, and the fourth gear and the driven shaft are also connected through the first bearing. The first bearing supports the radial load of the third gear and the fourth gear, and also reduces the friction between the third gear and the fourth gear and the driven shaft.

[0012] In one embodiment, the first gear is a boss gear, the boss of the boss gear is provided with an inner groove, the radial outer surface of the input shaft is provided with a key, and the input shaft and the boss gear are connected by the key and the slot key. The boss gear is provided with an inner groove, and the inner groove is key-connected, and the length of the key connection may include the length of the boss and the gear. The length of the boss lengthens the length of the key connection, so the effect of transmitting power is better, the force-bearing surface is increased, and the stress concentration is reduced.

[0013] In one embodiment, a second bearing is arranged between the first gear and the output shaft, a third bearing is arranged on the second gear, and the output shaft is also provided with a fourth bearing, a fifth bearing and an oil protection ring in sequence along the axial direction, a spacer is abutted between the third bearing and the fourth bearing, and the fifth bearing and the oil protection ring are arranged on both sides of the housing near the end face of the output shaft. An oil protection ring is arranged between the outer side of the housing and the output shaft to prevent the oil used for lubrication in the feeder used in conjunction with the speed change structure from leaking out. The second bearing supports the first gear during transmission, and the second transmission member and the sliding guide sleeve on the second gear are connected for transmission when the output shaft is output at a speed change. The second gear is supported by the third bearing between the transmission position and the housing, and the other end of the output shaft is supported by the fourth bearing and the fifth bearing between the housing, the second bearing and the third bearing can provide support at the transmission position, and the fourth bearing and the fifth bearing provide support at the longer output end of the output shaft, and the spacer abuts the third bearing and the fourth bearing to maintain the specified axial distance between the two bearings.

[0014] In one embodiment, the number of the first transmission grooves and the second transmission grooves is four, the first transmission grooves and the second transmission grooves are arc grooves, the four first transmission grooves and the four second transmission grooves are quartered arc grooves distributed along the circumference of the second gear, the first transmission member corresponds to the number of the first transmission grooves, and the second transmission member corresponds to the number of the second transmission grooves. When the four first transmission grooves and the four second transmission grooves are quartered arc grooves, power can be transmitted through the cooperation between the four first transmission grooves or the four second transmission grooves and the first transmission member or the second transmission member. The setting of the quartered arc grooves can make the power transmission more balanced and smoother, and at the same time prevent the radial load biased to one side from occurring during the power transmission process, causing damage to the shaft. The first transmission member corresponding to the number of the first transmission grooves and the second transmission member corresponding to the number of the second transmission grooves can better transmit torque.

[0015] In one embodiment, the output shaft is a six-tooth spline shaft, the sliding guide sleeve is a six-tooth spline sleeve, and the six-tooth spline shaft can be axially slidably connected to the six-tooth spline sleeve. The six-tooth spline shaft and the six-tooth spline sleeve are engaged to transmit the power of the second gear to the output shaft. The engagement of the six-tooth spline shaft and the six-tooth spline sleeve can increase the contact area, better transmit mechanical torque, and achieve better power transmission.

[0016] Compared with the prior art, the beneficial effects of the present invention are: the transmission structure of the present invention provides more precise speed stages, has a compact and simple structure, low cost, smooth gear shifting, and convenient and reliable speed change, while avoiding the problem of tooth collision or even tooth breakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the assembly of the transmission structure, the motor and the feeder;

[0018] Figure 2 It is an exploded assembly diagram of a speed change module and an output module of a transmission structure;

[0019] Figure 3 It is a schematic diagram of the assembly of the speed change module and the output module in the transmission structure without a housing;

[0020] Figure 4 It is a three-dimensional diagram of the transmission structure with a housing.

[0021] The drawings are only used for illustrative purposes and are not to be construed as limitations of the present invention. To better illustrate the embodiments, some parts of the drawings may be omitted, enlarged, or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the drawings. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with specific implementation modes and drawings, but the specific embodiments do not limit the present invention in any way.

[0023] like Figure 1 As shown, the transmission structure 10 includes an input module 40, a speed change module 20 and an output module 30. The input module 40 is a motor in this embodiment. Figure 2 As shown, the input module 40 includes an input shaft (not shown), the output module 30 includes an output shaft 301, and the speed change module 20 includes a first gear 201, a sliding guide sleeve 202, a shift mechanism 203, and a second gear 204 arranged in sequence along the axial direction. The first gear 201 is sleeved on the input shaft, and the input shaft of the input module 40 drives the first gear 201 to rotate, and the rotation speed of the input shaft is transmitted to the first gear 201. The sliding guide sleeve 202 is sleeved on the output shaft 301 and can slide axially on the output shaft 301.

[0024] like Figure 2 As shown, the sliding guide sleeve 202 is preferably a six-tooth spline sleeve, and six equally divided keyways 2021 are provided in the sliding guide sleeve 202. The sliding guide sleeve 202 can also be an arbitrary tooth spline sleeve, and a corresponding number of keyways 2021 are provided in the sliding guide sleeve 202. The six equally divided keyways 2021 are engaged with the six equally divided keys 3011 on the output shaft 301 to realize key connection to transmit power. The output shaft 301 can be an arbitrary tooth spline shaft, and the output shaft 301 is provided with keys 3011 corresponding to the number of keyways 2021. The sliding guide sleeve 202 and the output shaft 301 can also be ordinary components without keyways and keys, and the sliding guide sleeve 202 is directly sleeved on the output shaft 301 and can slide along the axial direction of the output shaft 301.

[0025] like Figure 2 , Figure 3 and Figure 4 As shown, the radial outer surface of the sliding guide sleeve 202 is provided with an annular groove 207 and the two end surfaces are respectively provided with four first transmission grooves 208 and four second transmission grooves 209. The four first transmission grooves 208 and the four second transmission grooves 209 are arranged at Figure 2The first transmission groove 208 and the second transmission groove 209 are respectively four equally divided arc grooves distributed along the circumference. The number of the first transmission groove 208 and the second transmission groove 209 can be selected according to the torque to be transmitted. The end surface of the first gear 201 close to the output shaft 301 is provided with four first transmission members 210, and the end surface of the second gear 204 close to the input shaft is provided with four second transmission members 211. The shift mechanism 203 is engaged with the annular groove 207. The number of the first transmission members 210 corresponds to the number of the first transmission grooves 208, and the number of the second transmission members 211 corresponds to the number of the second transmission grooves 209. The speed change module 20 also includes a third gear 2051 and a fourth gear 2052 and a driven shaft 206. The third gear 2051 and the fourth gear 2052 are sleeved on the driven shaft 206. The driven shaft 206 is parallel to the output shaft 301. The third gear 2051 and the fourth gear 2052 can be manufactured in one piece, for example, a double gear. The third gear 2051 and the fourth gear 2052 rotate on the driven shaft 206. The first gear 201 is meshed with the third gear 2051, and the first gear 201 drives the third gear 2051 to rotate. The number of teeth of the first gear 201 and the number of teeth of the third gear 2051 may not be equal to achieve speed change. The third gear 2051 and the fourth gear 2052 rotate together and have the same speed. The fourth gear 2052 is meshed with the second gear 204, and the number of teeth of the second gear 204 may not be equal to the number of teeth of the fourth gear 2052, so that the fourth gear 2052 drives the second gear 204 to change speed again. When the number of teeth of the first gear 201 is equal to the number of teeth of the third gear 2051, the number of teeth of the second gear 204 is not equal to the number of teeth of the fourth gear 2052. When the number of teeth of the second gear 204 is equal to the number of teeth of the fourth gear 2052, the number of teeth of the first gear 201 is not equal to the number of teeth of the third gear 2051. The speed ratio can be adjusted and selected by adjusting the number of teeth of each gear according to actual needs, but it must be ensured that the sum of the pitch circle diameters of the third gear 2051 and the first gear 201 is equal to the sum of the pitch circle diameters of the fourth gear 2052 and the second gear 204.

[0026] like Figure 2 , Figure 3 and Figure 4 As shown, the sliding guide sleeve 202 is also provided with two symmetrical threaded holes 212, and two spring plungers 213 are mounted on the threaded holes 212. The number of the threaded holes 212 and the number of the spring plungers 213 can be selected and correspond to each other according to the volume and weight of the driven components.

[0027] like Figure 2 , Figure 3 and Figure 4As shown, the first gear 201 is provided with an inner groove 214, and the inner groove 214 can be used for the key (not shown) on the input shaft to realize the key connection and power transmission. The speed change module 20 is also provided with two first bearings 215 between the third gear 2051, the fourth gear 2052 and the driven shaft 206, a second bearing 216 sleeved between the first gear 201 and the output shaft 301, and a third bearing 217 sleeved on the second gear 204. The output shaft 301 is also provided with a fourth bearing 219, a fifth bearing 220 and an oil protection ring 302 in sequence along the axial direction, a spacer 218 is abutted between the third bearing 217 and the fourth bearing 219, and the fifth bearing 220 and the oil protection ring 302 are arranged on both sides of the end surface of the housing 302.

[0028] like Figure 2 , Figure 3 and Figure 4As shown, the shift mechanism 203 includes a shift fork 2031, a support member 223 whose two ends are respectively fixed to the first support hole 221 and the second support hole 222 of the housing 302, and a shift shaft 225 installed on the housing 302. The U-shaped opening of the shift fork 2031 is clamped on the annular groove 207 of the sliding guide sleeve 202, the sliding sleeve 224 fixed on the shift fork 2031 is sleeved on the support member 223, and the boss 226 of the shift shaft 225, which is eccentric to the center of the main body at the front end, is inserted into the long groove 227 at the rear end of the shift fork 2031. When the shift knob 228 drives the shift shaft 225 to rotate 180 degrees, the rotation of the boss 226 drives the long slot 227 of the shift fork 2031 to slide along the support member 223, and the shift fork 2031 thus slides along the support member 223. The support member 223 is parallel to the input shaft, and the shift fork 2031 drives the sliding guide sleeve 202 to slide axially, thereby achieving speed shifting. The support member 223 provides additional radial support, and the shift fork 2031 can slide more smoothly on the support member 223, thereby driving the sliding guide sleeve 202 to slide axially more stably on the output shaft 301, so that the radially deviated size can be accurately aligned. The shift mechanism 203 can also be an ordinary shift handle or any other shift mechanism. When the spring plunger 213 follows the axial sliding of the sliding guide sleeve 202 to complete the gear shift, the ball inside it is inserted into the groove 229 or 230 provided on the output shaft 301 to lock the axial position of the sliding guide sleeve 202. When the spring plunger 213 is inserted into the groove 229, the first transmission member 210 drives the first transmission groove 209 to rotate, and the rotation speed of the first gear 201 is transmitted to the output shaft 301. The output shaft 301 and the input shaft have the same rotation speed, and the output speed is constant. When the spring plunger 213 is inserted into the groove 230, the second transmission member 211 drives the second transmission groove 209 to rotate, and the rotation speed of the second gear 204 is thus transmitted to the sliding guide sleeve 202, thereby transmitting the rotation speed of the sliding guide sleeve 202 to the output shaft 301, and the speed-shifted output is realized. The spring plunger 213 can also directly press the output shaft 301 to achieve axial fixation without the groove 229 or 230.

[0029] like Figure 1 and Figure 4 As shown, the transmission structure 10 is installed in the housing 302 as a whole. The housing protects the transmission module 20 and the output module 30 from being polluted by the external working environment, and can prevent the workpiece from collapsing in the event of an accident in the transmission structure. Figure 1 As shown, the transmission structure 10 can be used in conjunction with an input module 40 and a feeder 50 , and is adaptable to various types of input modules 40 and feeders 50 .

[0030] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A transmission structure, comprising an input module, a speed change module and an output module, wherein the input module comprises an input shaft, and the output module comprises an output shaft, wherein: The transmission module includes a first gear, a sliding guide sleeve, a shift mechanism and a second gear which are sequentially arranged along the axial direction, the first gear is sleeved on the input shaft, the second gear is sleeved on the output shaft and can rotate relative to the output shaft; the transmission module also includes a third gear, a fourth gear and a driven shaft, the third gear and the fourth gear are sleeved on both ends of the driven shaft respectively, the third gear is meshed with the first gear, the fourth gear is meshed with the second gear, the driven shaft is parallel to the output shaft, the sliding guide sleeve can be axially slidably sleeved on the output shaft, the radial outer surface of the sliding guide sleeve is provided with an annular groove, and the two end surfaces of the sliding guide sleeve along the axial direction are respectively provided with a first transmission groove and a second transmission groove, the shift mechanism is engaged with the annular groove, the end surface of the first gear close to the output shaft is provided with a first transmission member, the end surface of the second gear close to the input shaft is provided with a second transmission member, the sliding guide sleeve is connected to the first gear by nesting the first transmission member in the first transmission groove or is connected to the second gear by nesting the second transmission member in the second transmission groove; The transmission module and the output module are installed in the housing, and the two axial end surfaces of the housing are respectively provided with a first support hole and a second support hole parallel to the sliding guide sleeve, and the shift mechanism comprises a support member, a sliding sleeve and a shift fork, and the two ends of the support member are fixedly inserted into the first support hole and the second support hole, and the shift fork is axially slidably sleeved on the support member through the sliding sleeve and is engaged with the annular groove; The number of teeth of the first gear may be unequal to that of the third gear so as to achieve speed change, and the third gear and the fourth gear rotate together and at the same speed; the number of teeth of the second gear may be unequal to that of the fourth gear so that the fourth gear drives the second gear to achieve speed change again; when the number of teeth of the first gear is equal to that of the third gear, the number of teeth of the second gear is unequal to that of the fourth gear; when the number of teeth of the second gear is equal to that of the fourth gear, the number of teeth of the first gear is unequal to that of the third gear; the sum of the pitch circle diameters of the third gear and the first gear is equal to the sum of the pitch circle diameters of the fourth gear and the second gear.

2. According to the transmission structure of claim 1, the shift mechanism also includes a shift shaft and a shift knob, a long groove is formed at one end of the shift fork away from the ring groove, a boss is provided at one end of the shift shaft close to the support member, and the shift knob is provided at the other end of the shift shaft, and the boss is inserted into the long groove.

3. The transmission structure according to claim 1, characterized in that: The sliding guide sleeve is also provided with a spring plunger. The sliding guide sleeve is provided with a threaded hole. The spring plunger passes through the threaded hole to press the output shaft.

4. The transmission structure according to claim 3, characterized in that: A groove is arranged on the radial outer surface of the output shaft, and the spring plunger passes through the threaded hole and is inserted into the groove.

5. The transmission structure according to any one of claims 1 to 4, characterized in that: A first bearing is disposed between the third gear, the fourth gear and the driven shaft, and the third gear and the fourth gear are sleeved to the driven shaft through the first bearing.

6. The transmission structure according to any one of claims 1 to 4, characterized in that: The first gear is a boss gear, the boss of the boss gear is provided with an inner groove, the radial outer surface of the input shaft is provided with a key, and the input shaft and the boss gear are connected to the inner groove through the key.

7. The transmission structure according to any one of claims 1 to 4, characterized in that: A second bearing is arranged between the first gear and the output shaft, a third bearing is arranged on the second gear, and a fourth bearing, a fifth bearing and an oil protection ring are arranged on the output shaft in sequence along the axial direction, a spacer ring is abutted between the third bearing and the fourth bearing, and the fifth bearing and the oil protection ring are arranged on both sides of the housing close to the end face of the output shaft.

8. The transmission structure according to any one of claims 1 to 4, characterized in that: The number of the first transmission grooves and the second transmission grooves is four, the first transmission grooves and the second transmission grooves are arc grooves, the four first transmission grooves and the four second transmission grooves are four equally divided arc grooves distributed along the circumference of the second gear, the first transmission members correspond to the number of the first transmission grooves, and the second transmission members correspond to the number of the second transmission grooves.

9. The transmission structure according to any one of claims 1 to 4, characterized in that: The output shaft is a six-tooth spline shaft, the sliding guide sleeve is a six-tooth spline sleeve, and the six-tooth spline shaft can be axially slidably connected to the six-tooth spline sleeve.

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