CN216299137U - Electric screwdriver and torque transmission mechanism thereof - Google Patents

Abstract

The utility model discloses an electric screwdriver and a torque transmission mechanism thereof. The torque transmission mechanism of the electric screwdriver comprises a striking shaft, a motor, a driving shaft, a clutch sleeve, a steel ball and a displacement detector; the circular truncated cone-shaped inner wall of the clutch sleeve, the clutch end I of the striking shaft and the clutch end II of the driving shaft are sequentially sleeved from outside to inside; a plurality of steel ball channels are arranged at the circumferential direction of the clutch end I; a plurality of convex parts are arranged on the circumferential direction of the clutch end II; the bulge is in contact fit with the inner wall of the clutch end I when the working torque of the electric screwdriver does not reach a set value I, and rotates and pushes the steel ball to extrude the circular truncated cone-shaped inner wall outwards along the steel ball channel when the working torque reaches the set value I. The torque transmission mechanism can convert the torque change between the driving shaft and the striking shaft into displacement change, so that the displacement of the clutch sleeve is detected by using the displacement detector, whether the actual working torque of the striking shaft reaches a set value or not is judged, and the motor is automatically turned off after the working torque reaches the set value, so that torque setting is realized.

Description

Electric screwdriver and torque transmission mechanism thereof

Technical Field

The utility model relates to the field of electric tools, in particular to a torque transmission mechanism of an electric screwdriver. Still relate to an electric screwdriver, include aforementioned electric screwdriver's torque transmission mechanism.

Background

The electric screwdriver is an electric tool which can convert kinetic energy generated by the rotation of an electric motor into deformation energy of a thread connecting piece in the outside, is used for screwing and disassembling the thread connecting piece, and can be widely applied to industries such as household appliances, automobiles, motorcycles and the like.

In order to ensure the assembly quality of the product, an operator often needs to enable the electric screwdriver to complete the installation of the internal thread connecting piece of the product with a specific torque, in other words, the electric screwdriver with the torque fixing function can ensure the installation effect of the internal thread connecting piece of the product, and further ensure the assembly quality of the product.

However, in the two types of common electric screwdrivers, the electric screwdriver with the metal block impacting device as the striking structure has stable torque and cannot realize fixed torque; the electric screwdriver with the oil pressure pulse unit as the striking structure realizes operation based on hydraulic oil, and the temperature change of the hydraulic oil can affect the precision and the stability of the output torque of the striking mechanism. Therefore, the electric screwdriver in the prior art has low torque precision and poor stability, so that the difference between the actual working state of the electric screwdriver and the expected working state of an operator is large, and the assembly effect of a product at a threaded connector is difficult to improve.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a torque transmission mechanism of an electric screwdriver, which can accurately monitor the working state of a transmission part in the electric screwdriver in real time so as to realize fixed-torque control. Another object of the present invention is to provide an electric screwdriver including the torque transmission mechanism of the electric screwdriver.

In order to achieve the purpose, the utility model provides a torque transmission mechanism of an electric screwdriver, which comprises a striking shaft, a motor, a driving shaft, a clutch sleeve, a steel ball and a displacement detector, wherein the driving shaft is connected with the motor;

the circular truncated cone-shaped inner wall of the clutch sleeve, the clutch end I of the striking shaft and the clutch end II of the driving shaft are sequentially sleeved from outside to inside; a plurality of steel ball channels which are annularly distributed and are penetrated along the radial direction are arranged in the circumferential direction of the clutch end I; a plurality of annularly distributed and radially extending protrusions are arranged on the circumferential direction of the clutch end II; the number of the steel balls, the number of the steel ball channels and the number of the convex parts are equal; any one of the convex parts is in contact fit with the inner wall of the clutch end I when the working torque of the electric screwdriver does not reach a set value I, and rotates and pushes the steel ball to move outwards along the steel ball channel to squeeze the circular truncated cone-shaped inner wall when the working torque reaches the set value I; and the displacement detector automatically shuts down the motor when the displacement of the clutch sleeve reaches a set value II.

Preferably, the striking shaft, the driving shaft and the output shaft of the motor are connected in sequence; the small-diameter end of the circular truncated cone-shaped inner wall faces the striking shaft.

Preferably, the drive shaft is connected to an output shaft of the motor through a speed reducer.

Preferably, the number of the steel balls is three, and the three steel balls are uniformly distributed around the clutch end I.

Preferably, the device further comprises a reference block which is relatively static with the beating shaft along the axial direction; the reference block, the clutch sleeve and the motor are sequentially distributed along the axial direction of the striking shaft, and a spring I which stretches along the axial direction of the clutch sleeve is arranged between the reference block and the clutch sleeve.

Preferably, the reference block is fixed to the striking shaft; the spring I is sleeved on the striking shaft.

Preferably, a retainer ring is sleeved on the periphery of the clutch end I, and the retainer ring slides along the axial direction of the striking shaft; ejector rods distributed in parallel are arranged on one side of the striking shaft; the clutch sleeve pushes the ejector rod to move along the axial direction of the ejector rod through the retainer ring; the displacement detector is arranged next to the ejector rod.

Preferably, the displacement detector comprises a proximity switch; the proximity switch is aligned with the rod body shaft end of the ejector rod.

Preferably, the device further comprises a casing; the ejector rod is sleeved with a spring II; one axial end of the spring II is fixed relative to the shell, and the other axial end of the spring II is abutted against the stopper in the middle of the ejector rod; the proximity switch is arranged at one end, far away from the spring II, of the ejector rod.

The utility model also provides an electric screwdriver which comprises the torque transmission mechanism.

Compared with the prior art, the torque transmission mechanism of the electric screwdriver comprises a striking shaft, a motor, a driving shaft, a clutch sleeve, a steel ball and a displacement detector; the motor, the driving shaft, the clutch sleeve, the steel ball and the displacement detector can be arranged in the casing, the head of the striking shaft can extend out of the casing and is used for being connected with external screw connectors such as screws and bolts, and the tail of the striking shaft can be positioned in the casing and is connected to an output shaft of the motor through the driving shaft.

In the torque transmission mechanism, a circular truncated cone-shaped inner wall and a through cavity defined by the circular truncated cone-shaped inner wall are arranged in a clutch sleeve; the tail part of the striking shaft is provided with a clutch end I, and the driving shaft is provided with a clutch end II. The circular truncated cone-shaped inner wall, the clutch end I and the clutch end II are sleeved in sequence from outside to inside.

A plurality of steel ball channels which are annularly distributed are arranged in the circumferential direction of the clutch end I, and any one steel ball channel is communicated along the radial direction of the clutch end I; the circumferential direction of the clutch end II is provided with a plurality of annularly distributed convex parts, any one of the convex parts extends along the radial direction of the clutch end II in a protruding mode, and meanwhile, the adjacent two convex parts limit and form a concave part on the circumferential side of the clutch end II. Since the clutch end I and the clutch end II are sleeved with each other, the radial direction of the clutch end I is also the radial direction of the clutch end II.

When the working torque transmitted to the driving shaft by the external workpiece through the striking shaft does not reach the set value I, the bulge part of the clutch end II abuts against the inner wall of the clutch end I at the moment, and the friction force between the bulge part and the inner wall is enough to maintain the relative rest of the clutch end I and the clutch end II, so that the driving shaft drives the striking shaft to synchronously rotate. In this state, the protruding portion of the clutch end II abuts against the inner wall of the clutch end I, the recessed portion of the clutch end II aligns with the steel ball channel of the clutch end I, and the steel ball in the steel ball channel can be closer to the clutch end II along the radial direction of the clutch end II and away from the circular truncated cone-shaped inner wall.

When the working torque transmitted to the drive shaft by the threaded coupling via the striking shaft reaches the set value I, the frictional force between the boss portion and the inner wall at this time is insufficient to maintain the relative standstill of the clutch end I and the clutch end II, causing the clutch end II to start rotating within the clutch end I. Under this state, the bulge rotates to aim at the steel ball channel gradually in the inner wall by the butt, compare in the depressed part that originally aims at with the steel ball channel, the bulge extends to the radial outside of separation and reunion end II and extrudes whole steel balls outward diffusion with separation and reunion end II as the center, and then applys the effort to round platform form inner wall by whole steel balls, makes separation and reunion cover and round platform form inner wall produce along the ascending displacement of separation and reunion cover axial.

Therefore, the torque transmission mechanism converts the torque change between the driving shaft and the striking shaft into the displacement change by using a clutch transmission structure assembled by a clutch sleeve, a clutch end I, a clutch end II and a steel ball, so that the displacement of the clutch sleeve is detected by using a displacement detector, and whether the working torque of the electric screwdriver comprising the mechanism reaches the set value of a user or not is judged. The displacement detector and the motor can be connected to the same controller, so that when the displacement detector detects that the displacement of the clutch sleeve reaches a set value II, the controller automatically stops the motor to prevent the striking shaft from continuously doing work under the driving of the motor.

In summary, in the torque transmission mechanism provided by the utility model, the clutch type transmission structure plays a role in transmitting a torque signal and detecting the torque signal, and can ensure that the torque signal is transmitted accurately, the torque sensing structure is stable and the detection result is accurate; the displacement detector can control the motor to start and stop according to the clutch type transmission structure, and the torque fixing function is realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1 is a schematic structural diagram of an electric screwdriver according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a torque-transmitting mechanism in a first state according to an embodiment of the present invention;

FIG. 3 is a cross-sectional view taken along line D-D of FIG. 2;

FIG. 4 is a schematic structural diagram of a torque-transmitting mechanism in a second state in accordance with an embodiment of the present invention;

FIG. 5 is a cross-sectional view taken along line E-E of FIG. 4;

FIG. 6 is a schematic view of a driving shaft according to an embodiment of the present invention in a first direction;

fig. 7 is a schematic structural diagram of a driving shaft in a second direction according to an embodiment of the present invention.

The device comprises a shell 1, a striking shaft 2, a clutch end I20, a steel ball channel 21, a motor 3, an output shaft 31, a driving shaft 4, a clutch end II40, a protrusion 41, a depression 42, a clutch sleeve 5, a steel ball 6, a proximity switch 7, a spring I9, a retainer ring 10, an ejector rod 11, a spring II12 and a speed reducer 14.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order that those skilled in the art will better understand the disclosure, the utility model will be described in further detail with reference to the accompanying drawings and specific embodiments.

Referring to fig. 1 to 7, fig. 1 is a schematic structural view of an electric screwdriver according to an embodiment of the present invention; FIG. 2 is a schematic structural diagram of a torque-transmitting mechanism in a first state according to an embodiment of the present invention; FIG. 3 is a cross-sectional view taken along line D-D of FIG. 2; FIG. 4 is a schematic structural diagram of a torque-transmitting mechanism in a second state in accordance with an embodiment of the present invention; FIG. 5 is a cross-sectional view taken along line E-E of FIG. 4; FIG. 6 is a schematic view of a driving shaft according to an embodiment of the present invention in a first direction; fig. 7 is a schematic structural diagram of a driving shaft in a second direction according to an embodiment of the present invention.

The utility model provides a torque transmission mechanism of an electric screwdriver, which comprises a motor 3, a striking shaft 2 and a driving shaft 4; the driving shaft 4 is connected between the motor 3 and the striking shaft 2, so that the motor 3 drives the striking shaft 2 to move. For convenience of description, the "torque transmission mechanism of the electric screwdriver" is also simply referred to as "the mechanism" or "the torque transmission mechanism" herein.

In the mechanism, a striking shaft 2 is provided with a clutch end I20, a plurality of steel ball channels 21 distributed in a circular array are arranged in the circumferential direction of the clutch end I20, and any one steel ball channel 21 is arranged in a penetrating way along the radial direction of the clutch end I20; the driving shaft 4 is provided with a clutch end II40, the clutch end II40 is circumferentially provided with a plurality of annularly distributed convex parts 41, and any one of the convex parts 41 extends to be protruded outwards along the radial direction of the clutch end II 40.

The clutch end I20 and the clutch end II40 are assembled with the clutch sleeve 5 and the steel ball 6 to form a clutch type transmission structure. The clutch sleeve 5 is internally provided with a circular truncated cone-shaped inner wall, the clutch end I20 is arranged in the circular truncated cone-shaped inner wall in a penetrating way, the clutch end II40 is arranged in the clutch end I20 in a penetrating way, in other words, the clutch sleeve 5, the clutch end I20 and the clutch end II40 are sleeved in turn from outside to inside. The steel ball 6 of the mechanism is loaded into the ball channel 21 of the clutch end I20.

The maximum diameter of the clutch end II40 refers to the diameter of the circular area surrounded by the tops of all the protrusions 41, and obviously matches the inner diameter of the clutch end II40 to satisfy the matching relationship between the clutch end I20 and the clutch end II 40. Because the plurality of the protruding portions 41 are arranged in the circumferential direction of the clutch end II40, a recessed portion 42 of the clutch end II40 is formed between two adjacent protruding portions 41, when the clutch end I20 is sleeved on the outer circumference of the clutch end II40, the protruding portions 41 contact the inner wall of the clutch end I20, and the recessed portion 42 is separated from the inner wall of the clutch end I20. Based on the foregoing structure, when the recess 42 of the clutch end II40 is aligned with the ball passage 21 of the clutch end I20, the ball 6 can be closer to the central axis of the clutch end II40 in the through direction of the ball passage 21; when the protrusion 41 of the clutch end II40 is aligned with the ball channel 21 of the clutch end I20, the protrusion 41 ejects the steel ball 6 outwardly along the through direction of the ball channel 21.

According to the stress condition of the striking shaft 2 and the driving shaft 4 under different working conditions, the clutch end I20 and the clutch end II40 have two motion states of relative rest and relative rotation. The above relative rest means that when the actual resistance torque transmitted from the external workpiece to the driving shaft 4 via the striking shaft 2 does not reach the preset resistance torque, the protruding portion 41 of the clutch end II40 abuts against the inner wall of the clutch end I20, and at this time, the friction force between the protruding portion 41 and the inner wall is sufficient to maintain the relative rest of the clutch end I20 and the clutch end II40, so that the driving shaft 4 drives the striking shaft 2 to rotate synchronously. The relative rotation means that when the actual resistance torque transmitted from the external workpiece to the driving shaft 4 via the striking shaft 2 reaches the preset resistance torque, the friction between the protrusions 41 and the inner wall is not enough to maintain the relative standstill of the clutch end I20 and the clutch end II40, so that the clutch end II40 starts to rotate in the clutch end I20.

Once clutch end II40 is rotated within clutch end I20 until boss 41 is aligned with ball channel 21, for a single boss 41, boss 41 will eject ball 6 outwardly in the direction of penetration of ball channel 21; for all the protrusions 41, all the protrusions 41 push all the steel balls 6 to spread outward around the clutch end II40 at the same time. Because the two ends of the steel ball channel 21 in the penetrating direction respectively face the clutch end II40 and the circular truncated cone-shaped inner wall of the clutch sleeve 5, all the steel balls 6 which are diffused outwards by taking the clutch end II40 as the center can apply acting force to the circular truncated cone-shaped inner wall, and on the premise that the steel balls 6 cannot generate axial displacement along the clutch sleeve 5 under the constraint of the steel ball channel 21, the acting force can cause the clutch sleeve 5 and the circular truncated cone-shaped inner wall to generate axial displacement along the clutch sleeve 5. In this mechanism, the number of the steel balls 6, the steel ball passages 21, and the bosses 41 is equal to each other; all of the steel balls 6 are fitted in all of the steel ball passages 21 in a one-to-one correspondence, and all of the bosses 41 are rotatable to be aligned with all of the steel ball passages 21 one by one.

According to the above description, the clutch sleeve 5, the clutch end I20 and the clutch end II40 are sequentially sleeved from the outside to the inside, so that the clutch sleeve 5 axially moves along itself, that is, the clutch sleeve 5 axially moves along both the striking shaft 2 and the driving shaft 4.

It can be seen that the mechanism utilizes a clutch transmission structure formed by assembling a clutch sleeve 5, a clutch end I20, a clutch end II40 and a steel ball 6 to convert the torque change between the driving shaft 4 and the striking shaft 2 into displacement change, so that the displacement detector is utilized to detect the displacement of the clutch sleeve 5, and whether the working torque of the electric screwdriver comprising the mechanism reaches the set value of a user is judged. In the mechanism, a displacement detector is connected with a motor 3, when the displacement detector detects that the displacement of a clutch sleeve 5 reaches a set value II, which means that the working torque of the electric screwdriver reaches a set value I, the motor 3 can be automatically shut down, and an output shaft 31 of the motor 3 does not work on a striking shaft 2 through a driving shaft 4 any more, so that a user can accurately control the actual working torque of the electric screwdriver at the set value I of the user.

The torque transmission mechanism of the electric screwdriver provided by the utility model is further described below with reference to the accompanying drawings and embodiments.

In the torque transmission mechanism provided by the present invention, the striking shaft 2, the drive shaft 4 and the output shaft 31 of the motor 3 are connected in sequence. Taking the orientation shown in fig. 1 and 2 as an example, the striking shaft 2, the driving shaft 4 and the output shaft 31 of the motor 3 are sequentially distributed and connected from left to right, and a user engages and disengages the left end of the striking shaft 2 to connect with an external workpiece, so as to apply work to the workpiece, and tighten or loosen the workpiece.

In the above structure, the small diameter end of the circular truncated cone shaped inner wall faces the striking shaft 2, and therefore, when all the steel balls 6 are pushed by all the protrusions 41 and spread outward to the peripheral side of the driving shaft 4, all the steel balls 6 push the clutch sleeve 5 and the circular truncated cone shaped inner wall to move toward the small diameter end of the clutch sleeve 5, that is, from right to left in the horizontal direction of fig. 1 and 2. This direction of movement of the clutch sleeve 5, which is adapted to the shape and size of the striking shaft 2 at the clutch end I20, facilitates the mounting and the arrangement of the displacement detector in the housing 1.

Further, the torque transmission mechanism further includes a speed reducer 14 provided between the motor 3 and the drive shaft 4; the input end of the speed reducer 14 is connected to the output shaft 31 of the motor 3, and the output end of the speed reducer 14 is connected to the drive shaft 4. The torque transmission mechanism utilizes the speed reducer 14 to realize low-rotation-speed high-torque operation of the electric screwdriver, and is also beneficial to accurately and reliably feeding back the relation between the working torque of the electric screwdriver and the set value I by utilizing the displacement detector.

In the torque transmission mechanism, three steel ball channels 21 are arranged in a clutch end I20, the through direction of any one steel ball channel 21 is parallel to the radial direction of a clutch end I20, and the central angles between any two steel ball channels 21 are the same and are all 120 degrees. Correspondingly, the clutch end II40 is provided with three protrusions 41, and the torque-transmitting mechanism is fitted with three steel balls 6 between the clutch end I20 and the clutch end II 40. Three steel balls 6 of the torque transmission mechanism simultaneously apply acting force to the circular truncated cone-shaped inner wall of the clutch sleeve 5, so that the clutch sleeve 5 is prevented from generating angular displacement to interfere the measurement accuracy of the clutch sleeve 5 along the axial linear displacement of the clutch sleeve.

Further, the torque transmission mechanism also includes a reference block and a spring I9. Viewed in the axial direction of the striking shaft 2, the reference block, the clutch sleeve 5 and the motor 3 are distributed in this direction in sequence. The spring I9 is arranged between the reference block and the clutch sleeve 5, and the two axial ends of the spring I9 are respectively abutted against the reference block and the clutch sleeve 5.

Therefore, when clutch sleeve 5 is pressed by steel ball 6 to undergo linear displacement in its own axial direction, clutch sleeve 5 compresses spring I9 toward the reference block. Once the motor 3 is automatically turned off, the spring I9 expands in return to push the clutch sleeve 5 to move toward the motor 3, and the clutch sleeve 5 applies a force to the clutch end II40 through the steel ball 6, so that the clutch end II40 rotates from the state shown in FIGS. 4 and 5 to the state shown in FIGS. 2 and 3.

In the above structure, the reference block may be fixed to the striking shaft 2, and the spring I9 is sleeved on the striking shaft 2, so as to satisfy the positioning of the spring I9 and restrict the expansion and contraction deformation direction of the spring I9 by using the striking shaft 2.

In addition, in the torque transmission mechanism, a retaining ring 10 is sleeved on the outer periphery of the clutch end I20, and the retaining ring 10 slides along the axial direction of the striking shaft 2; one side of the striking shaft 2 is provided with a mandril 11 which is parallel to the striking shaft 2. The clutch sleeve 5 pushes the ejector rod 11 to move through the retainer ring 10, and the displacement detector indirectly judges the displacement of the clutch sleeve 5 through the moving distance of the ejector rod 11.

Compare in the displacement that adopts displacement detector direct detection separation and reunion cover 5, add retaining ring 10 and ejector pin 11 between separation and reunion cover 5 and displacement detector, be favorable to the overall arrangement of the different spare parts of reasonable adjustment in casing 1, under the prerequisite of the displacement of realizing detecting separation and reunion cover 5, simplify the shape structure of separation and reunion cover 5, conveniently adopt among the prior art common all kinds of displacement detector to detect the displacement of separation and reunion cover 5 fast.

The displacement detector can be specifically set as a proximity switch 7, and the proximity switch 7 is aligned with the rod body shaft end of the mandril 11. When the push rod 11 moves under the action of the clutch sleeve 5 and the retainer ring 10, the rod body shaft end of the push rod 11 moves relative to the proximity switch 7, so that the proximity switch 7 acquires a moving signal of the push rod 11.

In order to improve the operation convenience of the electric screwdriver and the torque transmission mechanism, on the basis of the structure, the torque transmission mechanism further comprises a spring II 12. The spring II12 is sleeved on the ejector rod 11; one axial end of the spring II12 is fixed relative to the machine shell 1, and the other axial end of the spring II12 is abutted against the stopper in the middle of the ejector rod 11; the proximity switch 7 is arranged at one end of the ejector rod 11 far away from the spring II 12. The spring II12 can realize the reset of the ejector rod 11, and certainly, can also apply acting force to the clutch sleeve 5 through the ejector rod 11 and the check ring 10, thereby being beneficial to the reset of the clutch sleeve 5 and facilitating the reuse of the electric screwdriver and the torque transmission mechanism.

According to the examples provided above, the present invention also provides an electric screwdriver, wherein the torque transmission mechanism is disposed in the casing 1 of the electric screwdriver, the casing 1 can be provided with an operation handle at a side close to the motor 3, the electric screwdriver can be provided with a battery, a controller, a switch, an indicator light and other structures disposed on the handle, for example, the battery and the controller are disposed in the handle, and the switch and the indicator light are disposed on the surface of the handle.

The structure of the electric screwdriver except the torque transmission mechanism can refer to the prior art and is not specifically described herein.

In the electric screwdriver, a battery pack arranged in a handle can drive a motor 3, and the motor 3 drives a clutch type transmission structure to do work and output torque after speed change through a planetary speed reducing assembly. Wherein, the clutch type transmission structure comprises a sensor, and the position detector automatically controls the motor 3 to start and stop according to the axial displacement of the clutch sleeve 5 in the clutch type transmission structure. The torque transmission mechanism plays a role in transmitting torque signals and detecting the torque signals in the electric screwdriver, and the torque signals are transmitted accurately, the torque sensing structure is stable, and the detection result is accurate.

The electric screwdriver and the torque transmission mechanism thereof provided by the utility model are described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

Claims (10)

1. A torque transmission mechanism of an electric screwdriver comprises a striking shaft (2) and a motor (3), and is characterized by further comprising a driving shaft (4), a clutch sleeve (5), a steel ball (6) and a displacement detector;

the circular truncated cone-shaped inner wall of the clutch sleeve (5), the clutch end I (20) of the striking shaft (2) and the clutch end II (40) of the driving shaft (4) are sequentially sleeved from outside to inside; a plurality of steel ball channels (21) which are annularly distributed and are penetrated along the radial direction are arranged on the circumferential direction of the clutch end I (20); a plurality of annularly distributed and radially extending protrusions (41) are arranged on the circumferential direction of the clutch end II (40); the number of the steel balls (6), the number of the steel ball channels (21) and the number of the convex parts (41) are equal; any one of the convex parts (41) is in contact fit with the inner wall of the clutch end I (20) when the working torque of the electric screwdriver does not reach a set value I, and rotates and pushes the steel ball (6) to move outwards along the steel ball channel (21) to squeeze the circular truncated cone-shaped inner wall when the working torque reaches the set value I; and the displacement detector automatically shuts down the motor (3) when the displacement of the clutch sleeve (5) reaches a set value II.

2. The torque transmission mechanism of the electric screwdriver according to claim 1, wherein the striking shaft (2), the driving shaft (4) and the output shaft (31) of the motor (3) are connected in sequence; the small-diameter end of the circular truncated cone-shaped inner wall faces the striking shaft (2).

3. The torque transmission mechanism of the electric screwdriver according to claim 2, wherein said driving shaft (4) is connected to said output shaft (31) through a reducer (14).

4. The torque transmission mechanism of an electric screwdriver according to claim 1, characterized in that said steel balls (6) are three in number and three of said steel balls (6) are evenly distributed around said clutch end I (20).

5. The torque transmission mechanism of the electric screwdriver according to any one of claims 1 to 4, further comprising a reference block axially stationary with respect to the striking shaft (2); the reference block, the clutch sleeve (5) and the motor (3) are sequentially distributed along the axial direction of the striking shaft (2), and a spring I (9) which stretches along the axial direction of the clutch sleeve (5) is arranged between the reference block and the clutch sleeve (5).

6. The torque transmission mechanism of the electric screwdriver according to claim 5, wherein said reference block is fixed to said striking shaft (2); the spring I (9) is sleeved on the striking shaft (2).

7. The torque transmission mechanism of the electric screwdriver according to claim 5, wherein a retaining ring (10) is sleeved on the outer periphery of the clutch end I (20), and the retaining ring (10) slides along the axial direction of the striking shaft (2); ejector rods (11) which are distributed in parallel are arranged on one side of the striking shaft (2); the clutch sleeve (5) pushes the ejector rod (11) to move along the axial direction of the ejector rod (11) through the retainer ring (10); the displacement detector is arranged next to the ram (11).

8. The torque transmission mechanism of the electric screwdriver according to claim 7, wherein said displacement detector comprises a proximity switch (7); the proximity switch (7) is aligned with the rod body shaft end of the ejector rod (11).

9. The torque transmission mechanism of the electric screwdriver according to claim 8, further comprising a housing (1); the ejector rod (11) is sleeved with a spring II (12); one axial end of the spring II (12) is fixed relative to the shell (1), and the other axial end of the spring II abuts against a blocking body (111) in the middle of the ejector rod (11); the proximity switch (7) is arranged at one end, far away from the spring II (12), of the ejector rod (11).

10. An electric screwdriver characterized by comprising the torque transmission mechanism of the electric screwdriver according to any one of claims 1 to 9.

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