A shiftable planetary gear reducer

Abstract

The application belongs to the field of speed reducers, and particularly relates to a gear-shiftable planetary gear reducer. The gear-shiftable planetary gear reducer comprises a shell, an input shaft, a movable shaft, a sun gear, a planet carrier, a fixed gear ring and an output shaft which are coaxially arranged in the shell; the planet carrier is fixedly connected with the output shaft, a plurality of planet gear mechanisms are arranged on the planet carrier in an array around the rotation direction of the planet carrier, the fixed gear ring is arranged around the planet gear mechanisms and is in mesh with the planet gear mechanisms; an axial hole is arranged on the planet carrier, an inner tooth part is arranged on one end of the axial hole, and a space is formed on the other end of the axial hole; an outer tooth part is arranged on the outer wall of the movable shaft, the sun gear is arranged on one end of the movable shaft and extends forward, the movable shaft rotates synchronously with the input shaft, and the movable shaft can be moved to a first position or a second position along the axis direction of the input shaft to realize gear-shifting operation of the speed reducer.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of speed reducers, in particular to a shiftable planetary gear reducer. BACKGROUND

[0002] A speed reducer is an independent component composed of gear transmission, worm transmission and gear-worm transmission enclosed in a rigid shell, commonly used as a speed reduction transmission device between a prime mover and a working machine. It plays a role in matching the speed and transmitting the torque between the prime mover and the working machine or actuator, and is widely used in modern machinery. Speed reducers are various, and can be divided into gear reducers, worm reducers and planetary gear reducers according to the type of transmission. Among them, the planetary gear reducer drives the planetary gear to rotate in the gear ring through the sun gear connected with the motor spindle, so that the planetary gear drives the output shaft to rotate to obtain greater torque and achieve the effect of speed reduction. The planetary gear reducer has compact structure, small size and long service life, and is applied to complex environments with small space, and does not need frequent maintenance and inspection. When the transmission ratio needs to be changed, it is difficult to replace due to small installation space and complex reducer structure, which needs to be improved. SUMMARY

[0003] The purpose of the application is to overcome the shortcomings of the prior art and provide a shiftable planetary gear reducer.

[0004] The application adopts the following technical scheme:

[0005] A shiftable planetary gear reducer comprises a shell, an input shaft, a movable shaft, a sun gear, a planet carrier, a fixed gear ring and an output shaft arranged coaxially in the shell.

[0006] The planet carrier is fixedly connected with the output shaft, and a plurality of planetary gear mechanisms are arranged in an array around the rotation direction of the planet carrier. The fixed gear ring is arranged outside the planetary gear mechanisms and meshes with the planetary gear mechanisms. The planet carrier is provided with an axial hole, one end of which is provided with an inwardly protruding inner tooth portion, and the other end forms a space for accommodation.

[0007] The outer wall of the movable shaft is provided with an outwardly protruding outer tooth portion, and the sun gear is arranged at one end of the movable shaft and extends forward. The movable shaft rotates synchronously with the input shaft, and can move to a first position or a second position along the axis direction of the input shaft.

[0008] When the movable shaft is in the first position state, the outer tooth portion of the movable shaft meshes with the inner tooth portion of the planet carrier, and at the same time, the sun gear is in the accommodation space and the sun gear is separated from each planetary gear mechanism. When the movable shaft is in the second position state, the outer tooth portion of the movable shaft is in the accommodation space and separated from the inner tooth portion, and at the same time, the sun gear is arranged between each planetary gear mechanism and meshes with each planetary gear mechanism.

[0009] Preferably, the planetary gear mechanism comprises wheel shafts and planetary gears, the wheel shafts are arranged on the planet carrier in a circumferential array in the direction of rotation of the planet carrier, and the planetary gears are arranged on the wheel shafts in one-to-one correspondence and in meshing engagement with the fixed ring gear.

[0010] Preferably, the planet carrier comprises a rotating disc, a connecting ring and a connecting member, the rotating disc is connected to the end of the output shaft, the wheel shafts are arranged on the rotating disc, the connecting ring is connected to the rotating disc and rotates synchronously therewith, the planetary gears are arranged between the connecting ring and the rotating disc, and the inner tooth portion is formed on the connecting ring, and the connecting member is connected between the rotating disc and the connecting ring.

[0011] Preferably, the gear shifting mechanism is further provided, the gear shifting mechanism is capable of driving the movable shaft to move to the first position or the second position on the output shaft, the gear shifting mechanism comprises a driving member and a positioning member, the driving member is capable of driving the movable shaft to move back and forth on the output shaft, and the positioning member is arranged on the movable shaft for positioning the first position and the second position and comprises a sliding ring, a first positioning hole, a second positioning hole and a positioning assembly, the sliding ring is connected between the driving member and the movable shaft and is capable of switching between the first position and the second position along with the driving member, the first positioning hole and the second positioning hole are formed outwardly from the inner wall of the housing and are distributed along the direction of the rotation axis and are respectively opposite to the position of the sliding ring in the first position and the second position, and the positioning assembly is capable of extending into the first positioning hole and the second positioning hole in the first position and the second position respectively to play a positioning role.

[0012] Preferably, the positioning assembly comprises a positioning groove, a positioning spring and a positioning ball, the positioning groove is formed inwardly from the outer side of the sliding ring and is opposite to the first positioning hole and the second positioning hole in the first position and the second position respectively, the positioning spring is arranged in the positioning groove, and the positioning ball is arranged in the positioning groove and is capable of being embedded in the positioning groove under the action of the positioning spring.

[0013] Preferably, the driving member comprises a first bearing, a sleeve, a driving rod and a sliding groove, the first bearing is sleeved between the sliding ring and the movable shaft and is capable of moving back and forth along with them, the sliding groove is formed on the housing to communicate the space inside and outside the housing, the sleeve is sleeved on the housing to seal the sliding groove, the driving rod extends into the housing through the sleeve and the sliding groove in sequence and is connected with the sliding ring, the driving rod is capable of moving back and forth along the extension direction of the sliding groove and drives the movable shaft to move to the first position or the second position.

[0014] Preferably, the outer side of the movable shaft is recessed upwardly from the bottom surface to form a first shaft shoulder, the first shaft shoulder is provided with a first limiting ring, the inner side surface of the first bearing is clamped between the first shaft shoulder and the first limiting ring, the inner side of the sliding ring is recessed upwardly from the bottom surface to form a second shaft shoulder, the second shaft shoulder is provided with a second limiting ring, and the outer side surface of the first bearing is clamped between the second shaft shoulder and the second limiting ring.

[0015] Preferably, the movable shaft and the input shaft are connected through a spline, the movable shaft is formed with a first key groove for the spline to pass through, the input shaft is formed with a second key groove for the spline to pass through, one end of the spline is fixedly connected with the second key groove, and the other end is slidably connected with the first key groove, so that the movable shaft can be moved along the axial direction to the first position or the second position while keeping synchronous transmission with the input shaft.

[0016] Preferably, the connecting piece comprises a first screw hole, a second screw hole, a limiting sleeve and a fixing bolt, the first screw hole is formed through the connecting ring, the second screw hole is formed on the rotating disc and opposite to the first screw hole, the limiting sleeve is connected between the rotating disc and the connecting ring and makes the first screw hole and the second screw hole communicate, and the fixing bolt passes through the first screw hole, the limiting sleeve and the second screw hole in sequence to fix the connecting ring on the rotating disc, so that a space for accommodating the planetary gear is formed between the connecting ring and the rotating disc.

[0017] Preferably, the width of the outer tooth part and the inner tooth part is less than the distance from the first position to the second position.

[0018] As can be seen from the above description of the present application, compared with the prior art, the beneficial effects of the present application are: by switching the movable shaft between the first position and the second position, the transmission ratio is changed, the transmission ratio can be adjusted without disassembling the reducer, which is efficient and convenient, and the planetary gear transmission is accurate and does not need to be verified after adjusting the transmission ratio;

[0019] When the sliding ring drives the movable shaft to move to the first position or the second position, the positioning assembly extends into the first positioning hole and the second positioning hole respectively under the action of the spring to achieve the fixing effect;

[0020] The positioning member is driven by the spring to move into the positioning hole to achieve the fixing effect, the force applied to the driving member is gradually increased when shifting gears, so that the positioning ball slides out of the positioning hole and reenters the positioning groove, realizing the switching from the fixed state to the free state;

[0021] The driving rod extending out of the housing is pushed to move the sliding ring, drive the movable shaft to move and realize gear shifting, which is simple to operate and does not need to open the reducer, and the sleeve is sleeved outside the sliding groove to avoid the lubricant in the reducer flowing out of the sliding groove;

[0022] The first bearing is fixed on the outer tooth part through the cooperation of the shaft shoulder and the limiting ring, avoiding the bearing from falling off when the driving rod is pushed to move, and improving the safety and stability of the device;

[0023] The movable shaft is movably arranged on the spline, the spline transmission is accurate and has large load, and the transmission efficiency is ensured while the movable shaft is movable;

[0024] The limiting sleeve is connected between the connecting ring and the rotating disc, plays a limiting role, makes the connecting ring and the rotating disc keep a certain gap when the bolt is locked with the connecting ring, avoids the connecting ring contacting the planetary gear and affecting the use of the speed reducer;

[0025] The width of the outer tooth part and the inner tooth part is less than the distance from the first position to the second position, so that only one pair of gears is engaged when switching between the first position and the second position, that is, only the sun gear and the planetary gear are engaged or the inner tooth part and the outer tooth part are engaged. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The figure is a structural schematic diagram of the application;

[0027] Figure 2 The figure is a partial cross section of the application Figure 1 ;

[0028] Figure 3 The figure is a partial cross section of the application Figure 2 ;

[0029] Figure 4 The figure is a transverse cross section of the application Figure 1 ;

[0030] Figure 2 The figure is a transverse cross section of the application Figure 6 ;

[0031] Figure 1 The figure is a longitudinal cross section of the application Figure 7 ;

[0032] Figure 2 The figure is a longitudinal cross section of the application Figure 8 ;

[0033] Figure 2 The figure is Figure 9 a partial enlarged view of A in the figure;

[0034] Figure 3 The figure is Figures 1 to 7 a partial enlarged view of B in the figure;

[0035] In the figure: 1 - housing, 11 - second bearing, 2 - output shaft, 3 - planet carrier, 31 - planetary gear mechanism, 311 - axle, 312 - planetary gear, 32 - shaft hole, 33 - inner tooth part, 34 - rotating disc, 35 - connecting ring, 351 - mounting groove, 36 - connecting piece, 361 - first screw hole, 362 - second screw hole, 363 - limiting sleeve, 364 - fixing bolt, 4 - fixed gear ring, 5 - movable shaft, 51 - outer tooth part, 52 - first key groove, 53 - mounting hole, 54 - first shaft shoulder, 55 - first limiting ring, 56 - second shaft shoulder, 57 - second limiting ring, 6 - sun gear, 7 - input shaft, 71 - spline, 72 - second key groove, 73 - third bearing, 8 - shifting mechanism, 81 - driving piece, 811 - first bearing, 812 - sleeve, 813 - driving rod, 814 - sliding slot, 82 - positioning piece, 821 - sliding ring, 822 - first positioning hole, 823 - second positioning hole, 824 - positioning assembly, 8241 - positioning groove, 8242 - positioning spring, 8243 - positioning ball. DETAILED DESCRIPTION

[0036] The application is further described below through specific embodiments.

[0037] REFERENCE ​ As shown in the figure, a shiftable planetary gear reducer includes a housing 1, an output shaft 2, a planet carrier 3, a fixed gear ring 4, a movable shaft 5, a sun gear 6, an input shaft 7, and a shifting mechanism 8.

[0038] The output shaft 2, the planet carrier 3, the fixed gear ring 4, the movable shaft 5, the sun gear 6, and the input shaft 7 are arranged in the housing 1 and along the same axis.

[0039] The planet carrier 3 is fixedly connected with the output shaft 2, and a plurality of planetary gear mechanisms 31 are arranged in an array around the rotation direction of the planet carrier 3. The fixed gear ring 4 is arranged around the planetary gear mechanisms 31 and meshes with the planetary gear mechanisms 31. The planetary gear mechanism 31 includes an axle 311 and a planetary gear 312. The axle 311 is arranged in an array around the circumference of the planet carrier 3 in the rotation direction of the planet carrier 3. The planetary gear 312 meshes with the fixed gear ring 4 and is arranged on the axle 311 one by one.

[0040] The planet carrier 3 is provided with a shaft hole 32 arranged in the axial direction. The shaft hole 32 is provided with an inner tooth part 33 protruding inward at one end and a space for accommodation at the other end.

[0041] Specifically, the planet carrier 3 comprises a rotating disc 34, a connecting ring 35 and a connecting piece 36, the rotating disc 34 is connected with the end of the output shaft 2, and the wheel shaft 311 is arranged on the rotating disc 34; the connecting ring 35 is connected with the rotating disc 34 and rotates synchronously with the rotating disc 34, the planet wheel 312 is arranged between the connecting ring 35 and the rotating disc 34, and the inner tooth portion 33 is formed on the connecting ring 35; the connecting piece 36 is connected between the rotating disc 34 and the connecting ring 35. The connecting piece 36 comprises a first screw hole 361, a second screw hole 362, a limiting sleeve 363 and a fixing bolt 364, the first screw hole 361 is formed through the connecting ring 35; the second screw hole 362 is formed on the rotating disc 34 and opposite to the first screw hole 361; the limiting sleeve 363 is connected between the rotating disc 34 and the connecting ring 35 and makes the first screw hole 361 and the second screw hole 362 communicate; the fixing bolt 364 passes through the first screw hole 361, the limiting sleeve 363 and the second screw hole 362 in sequence to fix the connecting ring 35 on the rotating disc 34, so that the space for accommodating the planet wheel 312 is formed between the connecting ring 35 and the rotating disc 34. Further, the mounting groove 351 coaxially arranged with the first screw hole 361 and used for positioning the limiting sleeve 363 is formed on the connecting ring 35, which facilitates the installation of the limiting sleeve 363.

[0042] The outer wall of the movable shaft 5 is provided with an outwardly protruding outer tooth portion 51, the sun gear 6 is arranged at one end of the movable shaft 5 and extends forward, the movable shaft 5 rotates synchronously with the input shaft 7, and the movable shaft 5 can move to a first position or a second position along the axis direction of the input shaft 7. When the movable shaft 5 is in the first position state: the outer tooth portion 51 of the movable shaft 5 is engaged with the inner tooth portion 33 of the planet carrier 3, at the same time, the sun gear 6 is in the accommodation space and is separated from each planet wheel mechanism 31; when the movable shaft 5 is in the second position state: the outer tooth portion 51 of the movable shaft 5 is in the accommodation space and is separated from the inner tooth portion 33, at the same time, the sun gear 6 is arranged between each planet wheel mechanism 31 and is engaged with each planet wheel mechanism 31. By driving the movable shaft 5 to move on the input shaft 7, fast gear shifting is realized, and the reducer does not need to be disassembled, which has high practicability.

[0043] Specifically, the movable shaft 5 and the input shaft 7 are connected through the spline 71, the first key groove 52 for the spline 71 to pass through is formed on the movable shaft 5, the second key groove 22 for the spline 21 to pass through is formed on the input shaft 7, one end of the spline 21 is fixedly connected with the second key groove 22, and the other end is slidably connected with the first key groove 52, so that the movable shaft 5 can move to the first position or the second position along the axis direction in the synchronous transmission state with the input shaft 7, the movable shaft 5 can be movably arranged on the spline 21, the spline 21 has high transmission precision and large load, and the transmission efficiency is ensured while the movable shaft 5 is movable. The first key groove 52 is upwardly formed from the bottom surface of the movable shaft 5, the mounting hole 53 for mounting the sun gear 6 is downwardly formed on the top surface of the movable shaft 5, and the sun gear 6 is arranged in the mounting hole 53 in an interference fit.

[0044] Further, the width of the outer tooth part 51 and the inner tooth part 33 is less than the distance from the first position to the second position, which ensures that only one pair of gears is engaged when switching between the first position and the second position, i.e. only the sun gear 6 and the planetary gear 312 are engaged or the inner tooth part 33 and the outer tooth part 51 are engaged.

[0045] The shift mechanism 8 can drive the movable shaft 5 to move on the input shaft 7 to the first position or the second position, and the shift mechanism 8 includes a driving part 81 and a positioning part 82. The driving part 81 can drive the movable shaft 5 to move back and forth on the input shaft 7. The positioning part 82 is arranged on the movable shaft 5 to position the first position and the second position, and includes a sliding ring 821, a first positioning hole 822, a second positioning hole 823, and a positioning assembly 824. The sliding ring 821 is connected between the driving part 81 and the movable shaft 5, and can switch between the first position and the second position with the driving part 81. The first positioning hole 822 and the second positioning hole 823 are formed outward from the inner wall of the housing 1, and are distributed along the direction of the rotation axis and respectively correspond to the positions of the sliding ring 821 in the first position and the second position. The positioning assembly 824 can extend into the first positioning hole 822 and the second positioning hole 823 in the first position and the second position respectively to play a positioning role. When the sliding ring 821 drives the movable shaft 5 to move to the first position or the second position, the positioning assembly 824 extends into the first positioning hole 822 and the second positioning hole 823 respectively to achieve the fixed effect.

[0046] The positioning assembly 824 includes a positioning groove 8241, a positioning spring 8242, and a positioning ball 8243. The positioning groove 8241 is formed inward from the outer side of the sliding ring 821, and can correspond to the first positioning hole 822 and the second positioning hole 823 in the first position and the second position respectively. The positioning spring 8242 is arranged in the positioning groove 8241. The positioning ball 8243 is arranged in the positioning groove 8241, and can be embedded in the positioning groove 8241 under the action of the positioning spring 8242. The diameter of the positioning ball 8243 is greater than the hole diameter of the positioning groove 8241. The positioning part 82 is driven by the spring to move into the positioning hole to achieve the fixed effect. When shifting, the force applied to the driving part 81 is gradually increased, so that the positioning ball 8243 slides out of the positioning hole and re-enters the positioning groove 8241, realizing the switching from the fixed state to the free state.

[0047] The driving member 81 comprises a first bearing 811, a sleeve 812, a driving rod 813 and a sliding slot 814. The first bearing 811 is sleeved between the sliding ring 821 and the movable shaft 5 and can move back and forth with the sliding ring 821. The sliding slot 814 is formed on the housing 1 to communicate the space inside and outside the housing 1. The sleeve 812 is sleeved on the housing 1 to seal the sliding slot 814. The driving rod 813 extends into the housing 1 through the sleeve 812 and the sliding slot 814 in sequence and is connected with the sliding ring 821. The driving rod 813 can move back and forth along the extension direction of the sliding slot 814 and drives the movable shaft 5 to move to the first position or the second position. The movement of the sliding ring 821 is realized by pushing the driving rod 813 extending outside the housing 1, which drives the movable shaft 5 to move and thus realizes gear shifting. The operation is simple and the reducer does not need to be opened. Meanwhile, the sleeve 812 sleeved outside the sliding slot 814 can prevent the lubricant in the reducer from flowing out of the sliding slot 814.

[0048] Specifically, the first shaft shoulder 54 is formed on the outer side of the movable shaft 5 and recessed upward from the bottom surface. The first limiting ring 55 is arranged on the first shaft shoulder 54. The inner side of the sliding ring 821 is recessed upward from the bottom surface and the second shaft shoulder 56 is formed thereon. The second limiting ring 57 is arranged on the second shaft shoulder 56. The outer side surface of the first bearing 811 is clamped between the second shaft shoulder 56 and the second limiting ring 57. The first bearing 811 is fixed on the outer tooth part through the cooperation of the shaft shoulder and the limiting ring, which avoids the bearing from falling off when the driving rod 813 is pushed to move, and improves the safety and stability of the device.

[0049] The input shaft 7 is specifically a shaft coupling connectable with the motor shaft, which is not the focus of the present application and will not be further described here. Meanwhile, the device further comprises a second bearing 11 arranged between the output and the housing 1 and a third bearing 73 arranged between the input shaft 7 and the housing 1.

[0050] The reducer is installed on the motor shaft. When it is necessary to shift from high speed to low speed (i.e. to move from the first position to the second position), the motor is stopped and the driving rod 813 is manually driven to move upward, so that the positioning ball 8243 gradually moves out of the first positioning hole 822 under the action of external force and the sliding ring 821 returns to the free state. At this time, the spring is in a compressed state. The driving rod 813 drives the sliding ring 821 to move the movable shaft 5 upward, and the outer tooth part 51 and the inner tooth part 33 gradually separate, and the sun gear 6 gradually cooperates with the planetary gear 312. When the movable shaft 5 moves to the second position, the positioning ball 8243 enters the second positioning hole 823 under the action of the spring to play a positioning role. At this time, the outer tooth part 51 and the inner tooth part 33 are completely separated, the sun gear 6 is completely meshed with the planetary gear 312, and the shifting of the reducer from high speed to low speed is completed.

[0051] When the speed change from low speed to high speed (i.e. moving from the second position to the first position) is needed, the motor is stopped, the driving rod 813 is manually driven to move downward, the positioning ball 8243 is gradually moved out of the second positioning hole 823 under the action of external force, and the sliding ring 821 is restored to the free state, at this time the spring is in the compressed state. The driving rod 813 drives the sliding ring 821 to move the movable shaft 5 downward, at the same time the sun gear 6 and the planetary gear 312 are gradually separated, and the outer tooth part 51 gradually matches with the inner tooth part 33. When the movable shaft 5 moves to the first position, the positioning ball 8243 enters the first positioning hole 822 under the action of the spring to play a positioning role, at this time the sun gear 6 and the planetary gear 312 are completely separated, the outer tooth part 51 and the inner tooth part 33 are completely meshed, that is, the speed change of the speed reducer from low speed to high speed is completed.

[0052] The speed change can be realized without long time shutdown or disassembly and replacement of the speed reducer, the structure is compact, the volume is small, the operation is simple, the maintenance is convenient, the speed change operation can be quickly performed in a complex environment, and the speed change operation has high practicability.

[0053] The above is only a preferred embodiment of the present application, and therefore cannot limit the scope of the present application. Equivalent changes and modifications made according to the scope of the present application and the content of the specification should still be within the scope of the present application.

Claims

1. A changeable-gear planetary gear reducer, characterized by: The transmission comprises a housing, an input shaft, a movable shaft, a sun gear, a planet carrier, a fixed ring gear, and an output shaft arranged coaxially in the housing; The planet carrier is fixedly connected with the output shaft, and a plurality of planetary gear mechanisms are arranged in an array around the rotation direction of the planet carrier. The fixed ring gear is arranged outside the planetary gear mechanisms and is in mesh with the planetary gear mechanisms. The planet carrier is provided with an axial hole, one end of which is provided with an inwardly protruding inner tooth portion, and the other end is formed with a space for accommodation. The outer wall of the movable shaft is provided with an outwardly protruding outer tooth portion. The sun gear is arranged at one end of the movable shaft and extends forward. The movable shaft rotates synchronously with the input shaft and can move to a first position or a second position along the axis of the input shaft. When the movable shaft is in the first position, the outer tooth portion of the movable shaft is in mesh with the inner tooth portion of the planet carrier, the sun gear is in the space for accommodation, and the sun gear is separated from the planetary gear mechanisms. When the movable shaft is in the second position, the outer tooth portion of the movable shaft is in the space for accommodation and is separated from the inner tooth portion, and the sun gear is arranged between the planetary gear mechanisms and is in mesh with the planetary gear mechanisms. The transmission further comprises a shifting mechanism. The shifting mechanism can drive the movable shaft to move to the first position or the second position on the output shaft. The shifting mechanism comprises a driving member and a positioning member. The driving member can drive the movable shaft to move back and forth on the output shaft. The positioning member is arranged on the movable shaft to position the first position and the second position. The positioning member comprises a sliding ring, a first positioning hole, a second positioning hole, and a positioning assembly. The sliding ring is connected between the driving member and the movable shaft and can switch between the first position and the second position with the driving member. The first positioning hole and the second positioning hole are formed outward from the inner wall of the housing and are distributed along the rotation axis and correspond to the positions of the sliding ring in the first position and the second position, respectively. The positioning assembly can extend into the first positioning hole and the second positioning hole in the first position and the second position, respectively, to play a positioning role. The driving member comprises a first bearing, a sleeve, a driving rod, and a sliding groove. The first bearing is sleeved between the sliding ring and the movable shaft and can move back and forth with them. The sliding groove is formed on the housing to connect the space inside and outside the housing. The sleeve is sleeved on the housing to seal the sliding groove. The driving rod passes through the sleeve and the sliding groove in sequence, extends into the housing, and is connected with the sliding ring. The driving rod can move back and forth along the extension direction of the sliding groove and drive the movable shaft to move to the first position or the second position. The outer side of the movable shaft is recessed upward from the bottom surface to form a first shoulder. The first shoulder is provided with a first limiting ring. The inner side of the first bearing is clamped between the first shoulder and the first limiting ring. The inner side of the sliding ring is recessed upward from the bottom surface to form a second shoulder. The second shoulder is provided with a second limiting ring. The outer side of the first bearing is clamped between the second shoulder and the second limiting ring.

2. A changeable gear planetary gear reducer according to claim 1, characterized in that: The planetary gear mechanism comprises an axle and a planetary gear. The axle is arranged in a circumferential array on the planet carrier in the rotation direction of the planet carrier. The planetary gear is in mesh with the fixed ring gear and is arranged one-to-one on the axle.

3. A changeable gear planetary gear reducer according to claim 2, characterized in that: The planet carrier comprises a rotating disc, a connecting ring and a connecting piece, the rotating disc is connected with the end of the output shaft, the wheel shaft is arranged on the rotating disc, the connecting ring is connected with the rotating disc and rotates synchronously, the planet wheel is arranged between the connecting ring and the rotating disc, the inner tooth part is formed on the connecting ring, and the connecting piece is connected between the rotating disc and the connecting ring.

4. A changeable gear planetary gear reducer according to claim 1, characterized in that: The positioning assembly comprises a positioning slot, a positioning spring and a positioning ball, the positioning slot is formed inwardly from the outer side of the sliding ring, and is opposite to the first positioning hole and the second positioning hole in the first position and the second position respectively, the positioning spring is arranged in the positioning slot, and the positioning ball is arranged in the positioning slot and can be embedded in the positioning slot under the action of the positioning spring.

5. A changeable gear planetary gear reducer according to claim 1, characterized in that: The movable shaft is connected with the input shaft through the spline, the first key groove through which the spline passes is formed on the movable shaft, the second key groove through which the spline passes is formed on the input shaft, one end of the spline is fixedly connected with the second key groove, and the other end is slidably connected with the first key groove, so that the movable shaft can be moved to the first position or the second position along the axial direction in the synchronous transmission state with the input shaft.

6. A changeable gear planetary gear reducer according to claim 3, characterized in that: The connecting piece comprises a first screw hole, a second screw hole, a limiting sleeve and a fixing bolt, the first screw hole is formed through the connecting ring, the second screw hole is formed on the rotating disc and opposite to the first screw hole, the limiting sleeve is connected between the rotating disc and the connecting ring and communicates the first screw hole with the second screw hole, and the fixing bolt passes through the first screw hole, the limiting sleeve and the second screw hole in sequence to fix the connecting ring on the rotating disc, so that the space for accommodating the planet wheel is formed between the connecting ring and the rotating disc.

7. A changeable gear planetary gear reducer according to claim 1, characterized in that: The width of the outer tooth part and the inner tooth part is less than the distance from the first position to the second position.

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