Gear box for large-torque electric drill

Abstract

The gear box comprises a shell, a speed change mechanism, an inner gear ring, a wedging piece, a spring and an output mechanism used for clamping a drill bit, the inner gear ring is rotationally connected into the shell, the speed change mechanism is used for being connected with a motor, and the speed change mechanism is used for driving the inner gear ring to rotate at different torques; a protruding block is arranged on one side wall of the inner gear ring, the two sides of the protruding block are provided with a forward rotation inclined face and a reverse rotation inclined face respectively, the included angle between the forward rotation inclined face and the inner gear ring is smaller than the included angle between the reverse rotation inclined face and the inner gear ring, and the output mechanism is rotationally connected to the shell. The wedging piece is connected to the output mechanism in a sliding mode in the axis direction of the inner gear ring, and the spring is used for keeping the wedging piece abutting against the side wall, provided with the protruding blocks, of the inner gear ring. The reverse torque upper limit of the gearbox is smaller than the reverse torque upper limit, so that the effect that a bolt tightened by an electric drill at a gear can be directly unscrewed at the gear is achieved.

Description

Technical Field

[0001] The present application relates to the field of gearboxes, and in particular to a gearbox for a high-torque electric drill. Background Art

[0002] An electric drill is a drilling tool used to make holes in or penetrate objects. It is widely used in industries such as construction and decoration. The gearbox is the main component of the electric drill, which is used to adjust the speed, rotation direction, torque and other operations of the electric drill.

[0003] At present, the Chinese invention patent with publication number CN102431013A discloses an electric drill with drive mode switching, including a motor arranged in a shell and a rotatable function switching cup and a torque adjustment cup mounted outside the shell; the motor is connected to the output shaft through a planetary gear reduction mechanism installed in a gear box; a static impact ring with end face teeth and a fixed block with an end face boss are fixedly installed in the gear box; the output shaft is fixedly connected to a dynamic impact ring with end face teeth that tends to fit the end face of the static impact ring under pressure, and a moving block with a radial boss that forms a circumferential constraint with the function switching cup; the inner gear ring of the planetary gear reduction mechanism has a concave-convex structure on the end face, and is connected to one end of a fitting that is circumferentially constrained to the gear box; the invention has the characteristics of reducing costs and being easy to operate.

[0004] Since the inclination angles on both sides of the concave and convex structures on the end face of the inner gear ring are the same, the pressure exerted on the mating parts by the forward and reverse rotation of the inner gear ring is the same, and the upper limits of the forward and reverse output torque of the gearbox are the same. However, there will be a certain impact force when tightening the bolts with an electric drill, which makes it impossible to loosen the bolts at the same gear position. The gear position needs to be adjusted to perform the loosening operation, which is inconvenient for the staff to operate. Utility Model Content

[0005] In order to ensure that the upper limit of the reverse torque of the gearbox is lower than the upper limit of the reverse torque, so that the bolts tightened by the electric drill in a gear position can be directly loosened using this gear position, the present application provides a gearbox for a high-torque electric drill.

[0006] This application provides a gearbox for a high-torque electric drill, which adopts the following technical solution:

[0007] A gearbox for a high-torque electric drill, comprising a housing, a speed change mechanism, an inner gear ring, a fitting, a spring, and an output mechanism for clamping a drill bit, wherein the inner gear ring is rotatably connected to the housing, the speed change mechanism is used to connect to the motor, and the speed change mechanism is used to drive the inner gear ring to rotate with different torques, a protrusion is provided on one side wall of the inner gear ring, and a forward rotation inclined surface and a reverse inclined surface are respectively provided on both sides of the protrusion, the angle between the forward rotation inclined surface and the inner gear ring is smaller than the angle between the reverse inclined surface and the inner gear ring, the output mechanism is rotatably connected to the housing, the fitting is slidably connected to the output mechanism along the axial direction of the inner gear ring, and the spring is used to keep the fitting against the side wall of the inner gear ring provided with the protrusion.

[0008] By adopting the above technical solution, the speed change mechanism is used to drive the inner gear ring to rotate, and the engaging piece is slidably connected to the output mechanism. When the electric drill rotates forward to tighten the bolt, the speed change mechanism drives the inner gear ring to rotate forward, and the engaging piece is kept in contact with the side wall of the inner gear ring under the action of the spring. Under the action of the forward rotation inclined surface of the protrusion, the output mechanism is driven to rotate, and the output mechanism can tighten the bolt. When the bolt needs to be tightened, the force on the output mechanism increases, and the engaging piece overcomes the elastic force of the spring and moves along the forward rotation inclined surface until it disengages from the forward rotation inclined surface, and the speed change mechanism cannot drive the output mechanism to rotate; when the bolt needs to be loosened, the staff starts the speed change mechanism in the reverse direction. Since tightening the bolt will bring impact, loosening the bolt requires greater force. The angle of the reverse rotation inclined surface of the cam is greater than the angle of the forward rotation inclined surface, so that the reverse torque is greater than the forward torque, so that the upper limit of the reverse torque of the electric drill is greater than the upper limit of the forward torque of the motor. The speed change mechanism can output greater force through the inner gear ring and the engaging piece to drive the output mechanism to reverse, so that the tightened bolt can be directly loosened with the same gear of the electric drill.

[0009] Optionally, the included angle between the forward-rotating inclined surface and the inner gear ring is 35°-36°, and the included angle between the reverse-rotating inclined surface and the inner gear ring is 65°-66°.

[0010] By adopting the above technical solution, the angle between the forward-rotating inclined surface and the inner gear ring is smaller than the angle between the reverse-rotating inclined surface and the inner gear ring, so that the reverse torque of the electric drill is greater than the forward torque, so that the bolts tightened in this gear can be directly loosened using this gear.

[0011] Optionally, the speed change mechanism includes a first-stage planetary gear, a second-stage planetary gear, a third-stage planetary gear, a first-stage planetary carrier, a second-stage planetary carrier, a third-stage planetary carrier, a first-stage inner ring gear and an adjusting member, wherein the first-stage inner ring gear is arranged in the housing, the first-stage planetary carrier is rotatably connected to the output shaft of the motor, the first-stage planetary gear is rotatably connected to the first-stage planetary carrier, the first-stage planetary gear is meshed with the first-stage inner ring gear, the third-stage planetary carrier is arranged on the output mechanism, the third-stage planetary gear is arranged on the third-stage planetary carrier, the third-stage planetary gear is meshed with the inner ring gear, the second-stage planetary carrier is located between the first-stage planetary carrier and the third-stage planetary carrier, the second-stage planetary carrier is rotatably connected in the housing, the second-stage planetary gear is rotatably connected to the second-stage planetary carrier, the second-stage planetary gear is meshed with the first-stage planetary carrier, the second-stage planetary carrier is meshed with the third-stage planetary gear, and the adjusting member is used to limit the rotation of the second-stage planetary gear relative to the second-stage planetary carrier.

[0012] By adopting the above technical solution, the electric drill can be rotated at different speeds through the speed change mechanism for use in different working conditions; when a low speed is required, the adjusting part causes the secondary planetary gear to rotate with the secondary planetary carrier. At this time, the motor drives the primary planetary carrier to rotate, and the primary planetary carrier drives the primary planetary gear to rotate relative to the primary inner ring gear. The primary planetary gear drives the secondary planetary carrier to rotate, and the secondary planetary carrier drives the third planetary gear to rotate. The third planetary gear drives the inner ring gear to rotate, and the inner ring gear drives the output mechanism to rotate through the mating part; when a high speed is required, the adjusting part causes the secondary planetary gear to mesh with the first planetary gear and the secondary planetary carrier. At this time, the transmission ratio of the speed change mechanism changes, and the motor drives the inner ring gear to rotate faster through the speed change mechanism, and the inner ring gear increases its rotation speed through the electric output mechanism of the mating part.

[0013] Optionally, the adjusting part includes a secondary inner gear ring, a limiting ring and a shift wire, the limiting ring is arranged on the shell, the secondary inner gear ring is rotatably connected in the shell, a limiting block is provided on the outer wall of the secondary inner gear ring, and the shift wire can be used to put the secondary inner gear ring in a locked state or a rotating state, when the secondary inner gear ring is in a locked state, the limiting block and the limiting ring are in a clamping state, and when the secondary inner gear ring is in a rotating state, the secondary inner gear ring is engaged with the primary planetary carrier and the secondary planetary gear at the same time.

[0014] By adopting the above technical solution, when the staff needs to adjust the speed, they turn the shift wire, and the shift wire drives the secondary inner ring gear to slide. When a low speed is required, the limit block on the secondary inner ring gear is engaged with the limiting ring, so that the secondary inner ring gear and the secondary planetary carrier rotate together, the secondary planetary gear cannot rotate, and the primary planetary carrier directly drives the secondary planetary carrier to rotate; when a high speed is required, the secondary inner ring gear is engaged with the primary planetary carrier and the secondary inner ring gear at the same time, the primary planetary carrier drives the secondary inner ring gear to rotate, the secondary inner ring gear drives the secondary planetary gear to rotate, and the secondary planetary gear can drive the secondary planetary carrier to rotate, thereby realizing a change in the transmission ratio. The adjustment part has a simple structure and is easy to operate.

[0015] Optionally, the number of teeth of the first-stage inner ring gear is 48, the number of teeth of the first-stage planetary gear is 15, the number of teeth of the first-stage planetary carrier is 12, the number of teeth of the second-stage inner ring gear is 40, the number of teeth of the second-stage planetary gear is 14, the number of teeth of the second-stage planetary carrier is 17, the number of teeth of the inner ring gear is 38, and the number of teeth of the third-stage planetary gear is 11.

[0016] By adopting this technical solution, the motor uses a 16-tooth gear output and a 48-tooth primary ring gear, controlling the primary gear ratio to 4.0, with speed and torque transmitted through the 15-tooth primary planetary gear. A 12-tooth primary planetary carrier and a 40-tooth secondary ring gear control the secondary gear ratio to 4.333, with speed and torque transmitted through the 14-tooth secondary planetary gear. A 17-tooth secondary planetary carrier and a 38-tooth internal gear control the tertiary gear ratio to 3.235, with speed and torque transmitted through the 11-tooth third-stage planetary gear. This achieves a low-speed ratio of 1:56.07 and a high-speed ratio of 1:12.94.

[0017] Optionally, the mating part includes a support plate and a plurality of pins, the support plate is slidably connected to the output mechanism along the axial direction of the inner gear ring, the plurality of pins are circumferentially distributed along the axis of the support plate, the pins are arranged on the support plate, and the spring is used to keep the pins in contact with the side wall of the inner gear ring where the protrusion is provided.

[0018] By adopting the above technical solution, several pins can contact the inner gear ring at multiple points, thereby improving the smoothness of the sliding of the support plate, reducing the contact area between the inner gear ring and the support plate, and reducing sliding friction.

[0019] Optionally, the mating part also includes a torque cup and a screw sleeve, the torque cup is rotatably connected to the shell, the screw sleeve is slidingly connected to the shell along the axis of the torque cup, the screw sleeve is threadedly connected to the torque cup, and one end of the spring is arranged on the screw sleeve.

[0020] By adopting the above technical solution, the rotation of the torque cup can change the position of the screw sleeve in the shell, so that the distance between the support plate and the inner ring gear changes, and the degree of pressure on the spring changes. The elastic potential energy of the spring on the support plate can be changed through the torque cup and the screw sleeve, and multi-speed torque output can be achieved.

[0021] Optionally, a needle roller bearing is provided between the first-stage planetary gear and the first-stage planetary carrier, and an oil-containing bearing is provided between the second-stage planetary gear and the second-stage planetary carrier, and between the third-stage planetary gear and the third-stage planetary carrier.

[0022] By adopting the above technical solution, the rotation speed between the first-stage planetary gear and the first-stage planetary carrier is low, the torque is large, the needle bearing has strong load-bearing capacity and friction resistance, which can extend the service life of the first-stage planetary gear. The rotation speed of the second-stage planetary gear and the second-stage planetary carrier, as well as the third-stage planetary gear and the third-stage planetary carrier is fast, the torque is small, and the surrounding temperature is high. High temperature will cause the grease of ordinary bearings to deteriorate and the lubrication effect is poor. By adopting oil-containing bearings, lubricating oil will overflow during high speed and enter the gap of the oil-containing bearings, reducing friction and thus lowering the surrounding temperature, greatly extending the service life of the second-stage planetary gear and the third-stage planetary gear.

[0023] In summary, this application includes at least one of the following beneficial technical effects:

[0024] 1. The inner gear ring convex block is provided with a forward rotation inclined surface and a reverse rotation inclined surface on both sides, so that the torque upper limit of the output mechanism is different. The reverse rotation torque upper limit is greater than the forward rotation torque upper limit, so that the tightened bolts can be loosened while the electric drill is in the same gear.

[0025] 2. The speed change mechanism can realize the output of various speeds of the output mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a cross-sectional view of a gearbox for a high-torque electric drill, showing the positional relationship between the speed change mechanism and the adjustment parts.

[0027] Figure 2 yes Figure 1 The exploded view is used to show the matching relationship of each component.

[0028] Figure 3 yes Figure 2 Schematic diagram of the structure of the secondary internal gear ring.

[0029] Figure 4 yes Figure 2 Schematic diagram of the structure of the inner ring gear.

[0030] Figure numerals: 1. Housing; 2. Speed ​​changing mechanism; 21. Primary planetary gear; 22. Secondary planetary gear; 23. Third-stage planetary gear; 24. Primary planetary carrier; 25. Secondary planetary carrier; 26. Third-stage planetary carrier; 27. Primary inner ring gear; 28. Adjusting part; 281. Secondary inner ring gear; 282. Limiting ring; 283. Shift wire; 284. Limiting block; 285. Limiting groove; 286. Ring groove; 3. Inner ring gear; 31. Protrusion; 32. Forward inclined plane; 33. Reverse inclined plane; 4. Fitting part; 41. Support plate; 42. Pin; 43. Torque cup; 44. Screw sleeve; 5. Spring; 6. Output mechanism; 7. Needle roller bearing; 8. Oil-containing bearing. DETAILED DESCRIPTION

[0031] The following is combined with Figure 1-4 This application is described in further detail.

[0032] The present application discloses a gearbox for a high torque electric drill. Figure 1 and Figure 2 A gearbox for a high-torque electric drill includes a housing 1, a speed change mechanism 2, an inner ring gear 3, a fitting 4, a plurality of springs 5 ​​and an output mechanism 6. The speed change mechanism 2, the inner ring gear 3, the fitting 4, the springs 5 ​​and the output mechanism 6 are all located in the housing 1. The speed change mechanism 2 is used to connect to the motor. The speed change mechanism 2 drives the inner ring gear 3 to rotate, the inner ring gear 3 drives the fitting 4 to rotate, and the fitting 4 drives the output mechanism 6 to rotate. A plurality of springs 5 ​​are used to keep the fitting 4 in contact with the inner ring gear 3.

[0033] Reference Figure 1 and Figure 2 The speed change mechanism 2 includes four primary planetary gears 21, four secondary planetary gears 22, five tertiary planetary gears 23, a primary planetary carrier 24, a secondary planetary carrier 25, a tertiary planetary carrier 26, a primary inner gear ring 27 and an adjusting member 28. The primary inner gear ring 27 is coaxially arranged with the output mechanism 6. The primary inner gear ring 27 is fixedly arranged in the housing 1. The primary planetary carrier 24 is coaxially arranged with the primary inner gear ring 27. The primary planetary carrier 24 is rotatably connected to the housing 1. The four primary planetary gears 21 are circumferentially along the axis of the primary planetary carrier 24. Evenly distributed, the axis of the first-stage planetary gear 21 is parallel to the axis of the first-stage planetary carrier 24, the first-stage planetary gear 21 is rotatably connected to the frame, the first-stage planetary gear 21 is engaged with the first-stage inner ring 27, the number of teeth of the first-stage inner ring 27 is 48, the number of teeth of the first-stage planetary gear 21 is 15, and the number of teeth of the first-stage planetary carrier 24 is 12. When a motor gear with a tooth number of 16 is used, the first-level speed ratio is 4, and the speed and torque are transmitted through the first-stage planetary gear 21. A needle roller bearing 7 is arranged between the first-stage planetary gear 21 and the first-stage planetary carrier 24.

[0034] Reference Figure 2 and Figure 3, the secondary planet carrier 25 is coaxially arranged with the primary planet carrier 24, the secondary planet carrier 25 is rotatably connected to the housing 1, the four secondary planetary gears 22 are evenly distributed circumferentially along the axis of the secondary planet carrier 25, the axis of the secondary planetary gear 22 is parallel to the axis of the secondary planet carrier 25, the secondary planetary gear 22 is rotatably connected to the secondary planet carrier 25, the secondary planetary gear 22 is meshed with the primary planet carrier 24, the adjustment member 28 includes a secondary inner gear ring 281, a limiting ring 282 and a shift wire 283, the limiting ring 282 is coaxially arranged with the secondary planet carrier 25, the limiting ring 282 is fixedly arranged in the housing 1, the secondary inner gear ring 281 is slidably connected to the housing 1 along the axis of the secondary planet carrier 25, the secondary inner gear ring 281 can be sleeved on the secondary planet carrier 25 or meshed with the primary planet carrier 24 and the secondary planetary gear 22 at the same time, a plurality of limit blocks 284 are provided on the outside of the secondary inner gear ring 281, the limit blocks 28 4 are evenly distributed along the circumference of the axis of the secondary inner gear ring 281. A plurality of limiting grooves 285 are opened on the inner side wall of the limiting ring 282. The limiting grooves 285 are evenly distributed along the circumference of the axis of the limiting ring 282. The end surface of the limiting block 284 facing the limiting groove 285 is provided with a guiding inclined surface for facilitating entry into the limiting groove 285. When the second inner gear ring 3 is sleeved on the second planetary carrier, the limiting groove 285 is engaged with the limiting block 284. The number of teeth of the secondary inner gear ring 281 is 40, the second-level speed ratio is 4.333, the number of teeth of the secondary planetary gear 22 is 14, the speed and torque are transmitted through the secondary planetary gear 22, the outer wall of the secondary inner gear ring 281 is provided with an annular groove 286, the shift wire 283 is rotatably connected to the housing 1, one end of the shift wire 283 is located in the annular groove 286, the shift wire 283 is connected to the shift toggle block of the electric drill, and an oil-containing bearing 8 is provided between the secondary planetary gear 22 and the secondary planetary carrier 25.

[0035] Reference Figure 1 and Figure 2 The three-stage planetary carrier 26 is coaxially arranged with the two-stage planetary carrier 25. The three-stage planetary carrier 26 is fixedly arranged on the output mechanism 6. The five three-stage planetary gears 23 are evenly distributed circumferentially along the axis of the three-stage planetary carrier 26. The axis of the three-stage planetary gear 23 is parallel to the axis of the three-stage planetary carrier 26. The three-stage planetary gear 23 is rotatably connected to the three-stage planetary carrier 26. The three-stage planetary gear 23 is meshed with the two-stage planetary carrier 25. The inner ring gear 3 is coaxial with the three-stage planetary gear 23. The inner ring gear 3 is meshed with the third planetary gear. The number of teeth of the inner ring gear 3 is 38, and the third layer speed is controlled to be 3.235. The number of teeth of the three-stage planetary gear 23 is 11. The speed and torque are transmitted through the three-stage planetary gear 23 to achieve a low-speed gear ratio of 1:56.07 and a high-speed gear ratio of 1:12.94. An oil-containing bearing 8 is arranged between the three-stage planetary gear 23 and the three-stage planetary carrier 26.

[0036] Reference Figure 2 and Figure 4, a plurality of protrusions 31 are provided on the side of the inner gear ring 3 facing the output mechanism 6, and the plurality of protrusions 31 are evenly distributed along the circumference of the axis of the inner gear ring 3. A forward inclined surface 32 and a reverse inclined surface 33 are respectively provided on both sides of the protrusion 31. The angle between the forward inclined surface 32 and the inner gear ring 3 is 35°-36°, and the angle between the reverse inclined surface 33 and the inner gear ring 3 is 65°-66°. The fitting 4 includes a support plate 41, a plurality of pins 42, a torsion cup 43 and a screw sleeve 44. The torsion cup 43 is coaxially arranged with the housing 1. The torsion cup 43 is rotatably connected to the housing 1, and the screw sleeve 44 is slidably connected to the housing 1 along the axis direction of the three-stage planetary gear 23. The sleeve 44 is threadedly connected to the inner wall of the torque cup 43, the support plate 41 is located between the inner gear ring 3 and the screw sleeve 44, the support plate 41 and the inner gear ring 3 are coaxially arranged, a number of springs 5 ​​are evenly distributed circumferentially along the axis of the support plate 41, the length of the spring 5 is parallel to the axis of the support plate 41, one end of the spring 5 is fixedly set on the support plate 41, and the other end of the spring 5 is fixedly set on the screw sleeve 44, a number of pins 42 are evenly distributed circumferentially along the axis of the support plate 41, the pin 42 is located on the side of the support plate 41 away from the screw sleeve 44, the length of the pin 42 is parallel to the length direction of the support plate 41, and the pin 42 abuts against the side wall of the inner gear ring 3.

[0037] The implementation principle of a gearbox for a high-torque electric drill in an embodiment of the present application is as follows: the motor of the electric drill is connected to the speed change mechanism 2, and the adjustment part 28 of the speed change mechanism 2 can make the inner ring gear 3 have two different speeds. The fitting part 4 and the spring 5 enable the rotation and torque of the inner ring gear 3 to be transmitted to the output mechanism 6. The protrusion 31 on the inner ring gear 3 has a forward rotation inclined surface 32 and a reverse rotation inclined surface 33, and the angle between the forward rotation inclined surface 32 and the inner ring gear 3 is smaller than the angle between the reverse rotation inclined surface 33 and the inner ring gear 3, so that the reverse rotation torque upper limit of the motor is greater than the forward rotation torque upper limit of the motor, and the originally tightened bolts can be loosened without rotating the torque cup 43 of the electric drill.

[0038] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A gearbox for a high-torque electric drill, characterized by: The invention comprises a housing (1), a speed change mechanism (2), an inner gear ring (3), a fitting (4), a spring (5), and an output mechanism (6) for clamping a drill bit, wherein the inner gear ring (3) is rotatably connected to the housing (1), the speed change mechanism (2) is used to be connected to a motor, and the speed change mechanism (2) is used to drive the inner gear ring (3) to rotate at different torques, a convex block (31) is provided on one side wall of the inner gear ring (3), and a positive rotation cam is provided on both sides of the convex block (31). An inclined surface (32) and a reverse inclined surface (33) are provided, wherein the angle between the forward inclined surface (32) and the inner gear ring (3) is smaller than the angle between the reverse inclined surface (33) and the inner gear ring (3); the output mechanism (6) is rotatably connected to the housing (1); the engaging member (4) is slidably connected to the output mechanism (6) along the axial direction of the inner gear ring (3); and the spring (5) is used to keep the engaging member (4) in contact with the side wall of the inner gear ring (3) provided with the protrusion (31).

2. The gearbox for a high-torque electric drill according to claim 1, characterized in that: The included angle between the forward-rotating inclined surface (32) and the inner gear ring (3) is 35°-36°, and the included angle between the reverse-rotating inclined surface (33) and the inner gear ring (3) is 65°-66°.

3. A gearbox for a high-torque electric drill according to claim 1, wherein the speed change mechanism (2) comprises a first-stage planetary gear (21), a second-stage planetary gear (22), a third-stage planetary gear (23), a first-stage planetary carrier (24), a second-stage planetary carrier (25), a third-stage planetary carrier (26), a first-stage inner gear ring (27) and an adjusting member (28), wherein the first-stage inner gear ring (27) is arranged in the housing (1), the first-stage planetary carrier (24) is rotatably connected to the output shaft of the motor, the first-stage planetary gear (21) is rotatably connected to the first-stage planetary carrier (24), the first-stage planetary gear (21) is meshed with the first-stage inner gear ring (27), and the third-stage planetary carrier (26) is arranged on the output mechanism (6), the third-stage planetary gear (23) is arranged on the third-stage planetary carrier (26), the third-stage planetary gear (23) is meshed with the inner gear ring (3), the second-stage planetary carrier (25) is located between the first-stage planetary carrier (24) and the third-stage planetary carrier (26), the second-stage planetary carrier (25) is rotatably connected to the housing (1), the second-stage planetary gear (22) is rotatably connected to the second-stage planetary carrier (25), the second-stage planetary gear (22) is meshed with the first-stage planetary carrier (24), the second-stage planetary carrier (25) is meshed with the third-stage planetary gear (23), and the adjustment member (28) is used to limit the rotation of the second-stage planetary gear (22) relative to the second-stage planetary carrier (25).

4. The gearbox for a high-torque electric drill according to claim 3, characterized in that: The adjusting member (28) includes a secondary inner gear ring (281), a limiting ring (282) and a shift wire (283), wherein the limiting ring (282) is arranged on the housing (1), and the secondary inner gear ring (281) is rotatably connected to the housing (1). A limiting block (284) is provided on the outer wall of the secondary inner gear ring (281), and the shift wire (283) can be used to lock the secondary inner gear ring (281) or rotate it. When the secondary inner gear ring (281) is in the locked state, the limiting block (284) and the limiting ring (282) are in a clamping state. When the secondary inner gear ring (281) is in the rotating state, the secondary inner gear ring (281) is meshed with the primary planet carrier (24) and the secondary planetary gear (22) at the same time.

5. The gearbox for a high-torque electric drill according to claim 4, characterized in that: The number of teeth of the first-stage inner gear ring (27) is 48, the number of teeth of the first-stage planetary gear (21) is 15, the number of teeth of the first-stage planetary carrier (24) is 12, the number of teeth of the second-stage inner gear ring (281) is 40, the number of teeth of the second-stage planetary gear (22) is 14, the number of teeth of the second-stage planetary carrier (25) is 17, the number of teeth of the inner gear ring (3) is 38, and the number of teeth of the third-stage planetary gear (23) is 11.

6. The gearbox for a high-torque electric drill according to claim 1, characterized in that: The fitting (4) includes a support plate (41) and a plurality of pins (42), wherein the support plate (41) is slidably connected to the output mechanism (6) along the axial direction of the inner gear ring (3), and the plurality of pins (42) are distributed circumferentially along the axis of the support plate (41). The pins (42) are arranged on the support plate (41), and the spring (5) is used to keep the pins (42) in contact with the side wall of the inner gear ring (3) provided with the protrusion (31).

7. The gearbox for a high-torque electric drill according to claim 6, characterized in that: The fitting (4) further comprises a torque cup (43) and a screw sleeve (44), wherein the torque cup (43) is rotatably connected to the housing (1), the screw sleeve (44) is threadedly connected to the torque cup (43), and one end of the spring (5) is disposed on the torque cup (43).

8. The gearbox for a high-torque electric drill according to claim 4, characterized in that: A needle roller bearing (7) is provided between the first-stage planetary gear (21) and the first-stage planetary carrier (24), and an oil-containing bearing (8) is provided between the second-stage planetary gear (22) and the second-stage planetary carrier (25), and between the third-stage planetary gear (23) and the third-stage planetary carrier (26).

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