A wrench capable of on-line monitoring and controlling axial force during bolt tightening

Abstract

The utility model discloses a wrench can carry out online monitoring and control to the axial force in the bolt tightening process, install transmission shaft and be used for driving transmission shaft rotation drive mechanism in shell subassembly can rotate relative to it, shell subassembly outside is provided with bolt sleeve that can rotate relative to it, the front end of transmission shaft is installed with the ultrasonic probe that is coaxial with it is arranged. Bolt head positioning groove is sleeved on the head of the bolt that needs to be tightened, the ultrasonic probe emits and captures the ultrasonic wave that returns, can real -time accurate inversion bolt axial force change through the change of ultrasonic wave speed, and feedback to operating personnel, or direct feedback to tightening force -exerting instrument, thereby realized accurate online monitoring and control to bolt axial force, and possess manual mode, bolt tightening axial force control mode, bolt tightening torque control mode, bolt tightening angle control mode and external control mode etc.

Description

Technical Field

[0001] This utility model relates to the field of bolt installation tool technology, specifically to a wrench that can monitor and control the axial force during the bolt tightening process online. Background Technology

[0002] Bolts are widely used connecting components. The axial force generated between the bolt and the connected parts along the bolt's axis is called axial force. Precise control of bolt axial force is directly related to the consistency of assembly performance and the stability of the overall machine performance.

[0003] Currently, when using a torque wrench to install (tighten) bolts, it is not possible to monitor the bolt axial force simultaneously. The axial force can only be detected after the bolt is tightened using a special tool. If the axial force is detected, the tightening degree of the bolt needs to be adjusted. This usually requires repeated adjustments to achieve high-precision control of the bolt axial force. This process is not only cumbersome and inefficient, but also unsuitable for scenarios where online monitoring of axial force is required during bolt tightening.

[0004] Solving these problems is now a top priority. Utility Model Content

[0005] To address the technical problem that existing torque wrenches lack online monitoring capabilities for bolt axial force, this invention provides a wrench capable of online monitoring and control of axial force during bolt tightening.

[0006] The technical solution is as follows:

[0007] The first aspect of this application relates to a wrench capable of online monitoring and control of axial force during bolt tightening, comprising a housing assembly, wherein a drive shaft rotatable relative to the housing assembly is installed and a drive mechanism for driving the drive shaft to rotate, and a bolt sleeve rotatable relative to the housing assembly is disposed outside the housing assembly, wherein the rear end of the bolt sleeve extends into the housing assembly and is synchronously rotatably connected to the front end of the drive shaft, wherein an ultrasonic probe coaxially disposed at the front end of the drive shaft is installed, and a bolt head positioning groove is recessed at the central axis position of the front end face of the bolt sleeve, wherein a probe protrusion hole adapted to the ultrasonic probe is opened at the bottom of the bolt head positioning groove, and the detection end of the ultrasonic probe extends into the probe protrusion hole.

[0008] The above-mentioned wrench, capable of online monitoring and control of axial force during bolt tightening, involves placing the bolt head positioning groove onto the head of the bolt to be tightened. An ultrasonic probe emits and captures the returning ultrasonic waves. By analyzing changes in ultrasonic speed, changes in bolt axial force can be accurately deduced in real time and fed back to the operator or directly to the tightening tool, thus achieving precise online monitoring and control of bolt axial force. Furthermore, this wrench, combined with its control program, is applicable to various bolt tightening control methods, including manual mode, bolt tightening axial force control mode, bolt tightening torque control mode, bolt tightening angle control mode, and external control mode. It boasts good versatility and is suitable for various application scenarios.

[0009] In some embodiments, the bolt sleeve is detachably mounted on the front end of the drive shaft.

[0010] In some embodiments, the front end of the drive shaft protrudes to form a prism-shaped sleeve joint, the end face of which is recessed to form a probe mounting hole adapted to the ultrasonic probe, the probe mounting hole communicating with the probe protrusion hole, the ultrasonic probe being installed in the probe mounting hole, and the rear end of the bolt sleeve being recessed to form a connector connection groove that engages with the sleeve joint.

[0011] In some embodiments, an electric slip ring is also included, comprising an electric slip ring rotor synchronously mounted on a drive shaft and an electric slip ring stator fixedly mounted on the inner wall of the housing assembly. The electric slip ring stator is rotatably mounted on the outside of the electric slip ring rotor and is electrically connected to the electric slip ring rotor. The cable of the ultrasonic probe passes through the wall of the probe mounting hole and is electrically connected to the electric slip ring rotor. The electric slip ring stator is powered through a wiring harness arranged in the housing assembly.

[0012] In some embodiments, the drive mechanism includes a motor and a two-stage reduction planetary gear system. The two-stage reduction planetary gear system includes an internal gear ring fixedly mounted on the inner wall of the housing assembly, a first-stage planetary carrier disposed in the internal gear ring, a first-stage sun gear synchronously mounted on the motor shaft of the motor, and a plurality of first-stage planetary gears distributed circumferentially around the first-stage sun gear. Each first-stage planetary gear is mounted on the side of the first-stage planetary carrier close to the first-stage sun gear and meshes with both the first-stage sun gear and the internal gear ring. A second-stage sun gear is disposed on the side of the first-stage planetary carrier close to the drive shaft and rotates synchronously therewith. The rear end of the drive shaft is integrally formed with a second-stage planetary carrier, on which a plurality of second-stage planetary gears are mounted evenly distributed along the second-stage sun gear. Each second-stage planetary gear meshes with both the second-stage sun gear and the internal gear ring.

[0013] In some embodiments, fan blades for directing airflow toward the motor rotor and stator are synchronously mounted on the motor shaft, and the housing assembly has an air outlet located next to the fan blades and an air inlet located at the end of the motor rotor away from the fan blades.

[0014] In some implementations, the motor has a self-locking function.

[0015] In some embodiments, the housing assembly includes a housing body, a quick-change housing, and a wrench holder connecting the housing body and the quick-change housing. The rear end of the wrench holder is detachably mounted to the front end of the housing body, and the rear end of the quick-change housing is detachably mounted to the front end of the wrench holder. The motor is mounted in the housing body, and the planetary gear train and drive shaft are both mounted in the wrench holder. The front end of the drive shaft extends into the quick-change housing, and the bolt sleeve extends rearward into the quick-change housing and connects to the front end of the drive shaft.

[0016] In some embodiments, a limiting seat is also included. The bottom of the outer shell body is integrally formed with a grip handle. A first connecting tooth is formed on the circumferential outer wall of the wrench seat. The inner end of the limiting seat has a limiting seat mounting ring fitted on the wrench seat. A second connecting tooth that meshes with the first connecting tooth is formed on the inner circumferential surface of the limiting seat mounting ring.

[0017] In some embodiments, a display screen is mounted on the housing assembly. Attached Figure Description

[0018] Figure 1 A structural diagram of a wrench from one perspective;

[0019] Figure 2 A structural diagram of a wrench from another perspective;

[0020] Figure 3 This is a cross-sectional view of the wrench;

[0021] Figure 4 This is a schematic diagram showing the fit between the drive shaft, drive mechanism, bolt sleeve, slip ring, and fan blades.

[0022] Figure 5 This is a schematic diagram showing the fit between a two-stage reduction planetary gear train and a drive shaft. Detailed Implementation

[0023] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0024] like Figures 1-5 As shown, a wrench capable of online monitoring and control of axial force during bolt tightening mainly includes a housing assembly 1, a drive shaft 2, a drive mechanism 3, a bolt sleeve 4, and an ultrasonic probe 5.

[0025] Both the drive shaft 2 and the drive mechanism 3 are installed in the housing assembly 1. The drive shaft 2 can rotate relative to the housing assembly 1 under the control of the drive mechanism 3. The bolt sleeve 4 is installed outside the housing assembly 1, and the rear end of the bolt sleeve 4 extends into the housing assembly 1 and is synchronously connected to the front end of the drive shaft 2. That is, the drive mechanism 3 can drive the drive shaft 2 and the bolt sleeve 4 to rotate synchronously. Since a bolt head positioning groove 4a is formed by a recess at the central axis position of the front end face of the bolt sleeve 4, the cross-section of the bolt head positioning groove 4a is usually a regular hexagon. After the bolt head is embedded in the bolt head positioning groove 4a, the drive mechanism 3 drives the bolt sleeve 4 to rotate through the drive shaft 2, which can drive the bolt to rotate and realize the bolt tightening operation.

[0026] In this embodiment, an ultrasonic probe 5 is coaxially mounted on the front end of the drive shaft 2. A probe protrusion hole 4b, adapted to the ultrasonic probe 5, is opened at the bottom of the bolt head positioning groove 4a. The probe end of the ultrasonic probe 5 extends into the probe protrusion hole 4b. The ultrasonic probe 5 emits and captures the returning ultrasonic waves. By analyzing the changes in ultrasonic speed, the change in bolt axial force can be accurately reflected in real time and fed back to the operator or directly to the tightening tool, thereby achieving precise online monitoring and control of the bolt axial force. Furthermore, the wrench and control program of this invention are applicable to various bolt tightening control methods, including manual mode, bolt tightening axial force control mode, bolt tightening torque control mode, bolt tightening angle control mode, and external control mode. It has good versatility and is suitable for various application scenarios.

[0027] The principle of using ultrasound to measure bolt axial force is based on the acoustoelastic effect. When the axial force of a bolt changes, the propagation speed of ultrasound will change accordingly. Therefore, there is a correspondence between the propagation time of ultrasound and the axial force of the bolt. By measuring the propagation time of ultrasound in the bolt, the axial force of the bolt can be measured.

[0028] Furthermore, in order to facilitate operators to monitor the changes in axial force during bolt tightening in real time, a display screen 9 is installed on the outer casing assembly 1. The display screen 9 is used not only to display the bolt axial force, but also to display information such as power and mode. It is also used to set parameters of the wrench via touch control.

[0029] Furthermore, the bolt sleeve 4 is preferably installed in a detachable manner, that is, the bolt sleeve 4 can be detachably installed at the front end of the drive shaft 2, so that the bolt sleeve 4 with different sized bolt head positioning grooves 4a can be adapted to the size of the bolt to be tightened.

[0030] Please see Figure 3 and Figure 5The front end of the drive shaft 2 protrudes to form a prism-shaped sleeve joint 2a. The sleeve joint 2a is generally made of a prism structure with a cross-section of a regular square prism or a regular hexagonal prism, which can ensure the coaxiality of the bolt sleeve 4 with the drive shaft 2 after installation. Correspondingly, the rear end of the bolt sleeve 4 is recessed to form a joint connection groove 4c that matches the sleeve joint 2a, so that the bolt sleeve 4 can be quickly installed by means of a snap-fit ​​engagement.

[0031] Meanwhile, the end face of the sleeve joint 2a is recessed to form a probe mounting hole 2b that is compatible with the ultrasonic probe 5. After the bolt sleeve 4 is installed at the front end of the drive shaft 2, the probe mounting hole 2b is connected to the probe protrusion hole 4b. The ultrasonic probe 5 is installed in the probe mounting hole 2b, and the detection end (front end) of the ultrasonic probe 5 extends into the probe mounting hole 2b. Typically, the end face of the detection end of the ultrasonic probe 5 is flush with or slightly lower than the bottom of the bolt head positioning groove 4a, which avoids interference with the bolt head and ensures the stability and reliability of the ultrasonic probe 5 in performing ultrasonic detection.

[0032] Please see Figure 3 and Figure 4 The wrench in this embodiment also includes an electric slip ring 7, which includes an electric slip ring rotor 7a synchronously mounted on the drive shaft 2 and an electric slip ring stator 7b fixedly mounted on the inner wall of the housing assembly 1. The electric slip ring stator 7b is rotatably mounted outside the electric slip ring rotor 7a and electrically connected to the electric slip ring rotor 7a. The cable of the ultrasonic probe 5 passes through the hole wall of the probe mounting hole 2b and is electrically connected to the electric slip ring rotor 7a. The electric slip ring stator 7b is connected to the power supply through a wire harness arranged in the housing assembly 1. Since the electric slip ring 7 is an electrical connection device for transmitting power and signals in rotating equipment, it can realize the transmission of power and signals under unrestricted continuous rotation. Therefore, it can avoid the problem of wire harness and cable tangling or breakage, thereby improving the overall durability.

[0033] Furthermore, a wire groove is formed in the inner wall of the housing assembly 1, which facilitates the arrangement of the wire harness and avoids interference with the internal components of the wrench.

[0034] Please see Figures 3-5 The drive mechanism 3 in this embodiment includes a motor 3a and a two-stage reduction planetary gear system 3b. The two-stage reduction planetary gear system 3b can achieve two large reduction ratios in a narrow space, thereby effectively increasing the torque of the wrench.

[0035] Specifically, the two-stage reduction planetary gear system 3b includes an internal gear ring 3b2 fixedly mounted on the inner wall of the housing assembly 1, a first-stage planetary carrier 3b3 disposed in the internal gear ring 3b2, a first-stage sun gear 3b1 synchronously mounted on the motor shaft 3a1 of the motor 3a, and a plurality of first-stage planetary gears 3b4 distributed circumferentially around the first-stage sun gear 3b1. Each first-stage planetary gear 3b4 is mounted on the side of the first-stage planetary carrier 3b3 near the first-stage sun gear 3b1 and meshes with both the first-stage sun gear 3b1 and the internal gear ring 3b2. A second-stage sun gear 3b5 is disposed on the side of the first-stage planetary carrier 3b3 near the drive shaft 2 and rotates synchronously therewith. A second-stage planetary carrier 3b6 is integrally formed at the rear end of the drive shaft 2. A plurality of second-stage planetary gears 3b7 are mounted on the second-stage planetary carrier 3b6 and evenly distributed along the second-stage sun gear 3b5. Each second-stage planetary gear 3b7 meshes with both the second-stage sun gear 3b5 and the internal gear ring 3b2. Therefore, the motor shaft 3a1 drives the first-stage sun gear 3b1 to rotate synchronously with it. The first-stage sun gear 3b1 drives the first-stage planetary carrier 3b3 to rotate through each first-stage planetary gear 3b4. The first-stage planetary carrier 3b3 drives the second-stage sun gear 3b5 to rotate synchronously with it. The second-stage sun gear 3b5 drives the second-stage planetary carrier 3b6 to rotate through each second-stage planetary gear 3b7. The second-stage planetary carrier 3b6 drives the transmission shaft 2 to rotate synchronously with it. The transmission shaft 2 drives the bolt sleeve 4 to rotate synchronously with it.

[0036] Since the wrench in this embodiment has a manual mode, that is, the operation of tightening bolts by manually rotating the wrench, the motor 3a in this embodiment has a self-locking function.

[0037] Please see Figure 3 and Figure 4 A fan blade 6 is synchronously mounted on the motor shaft 3a1 to direct airflow towards the motor rotor 3a2 and motor stator 3a3 of the motor 3a. The housing assembly 1 has an air outlet 1a1 located next to the fan blade 6 and an air inlet 1a2 located at the end of the motor rotor 3a2 away from the fan blade 6. Therefore, as soon as the motor 3a starts, the fan blade 6 will rotate synchronously with the motor shaft 3a1, thereby drawing in outside air through the air inlet 1a2, cooling the motor 3a, and then discharging it through the air outlet 1a1, thus preventing the motor 3a from overheating.

[0038] Please see Figure 1 and Figure 2The housing assembly 1 includes a housing body 1a, a quick-change housing 1c, and a wrench holder 1b connecting the housing body 1a and the quick-change housing 1c. The rear end of the wrench holder 1b is detachably mounted on the front end of the housing body 1a, and the rear end of the quick-change housing 1c is detachably mounted on the front end of the wrench holder 1b. The motor 3a is installed in the housing body 1a, and the planetary gear train 3b and the drive shaft 2 are both installed in the wrench holder 1b. The front end of the drive shaft 2 extends into the quick-change housing 1c, and the bolt sleeve 4 extends rearward into the quick-change housing 1c and connects to the front end of the drive shaft 2. With this design, when the bolt sleeve 4 needs to be replaced, only the quick-change housing 1c needs to be disassembled; when the planetary gear train 3b needs to be inspected and maintained, only the wrench holder 1b needs to be disassembled; and only when the motor 3a needs to be inspected and maintained does the housing assembly 1 need to be fully opened. Therefore, the housing assembly 1 adopts a split structure, ensuring ease of use.

[0039] Please see Figures 1-3 The wrench in this embodiment also includes a limiting seat 8. A handle 1a3 is integrally formed on the bottom of the outer shell 1a. A ring of first connecting teeth 1b1 is formed on the circumferential outer wall of the wrench seat 1b. The inner end of the limiting seat 8 has a limiting seat mounting ring 8a fitted onto the wrench seat 1b. A ring of second connecting teeth 8b, which meshes with the first connecting teeth 1b1, is formed on the inner circumferential surface of the limiting seat mounting ring 8a. Therefore, axial movement of the limiting seat mounting ring 8a can separate the first connecting teeth 1b1 and the second connecting teeth 8b. Then, the limiting seat 8 can be flexibly rotated according to the actual usage scenario. After reaching the correct position, the first connecting teeth 1b1 and the second connecting teeth 8b are engaged again, realizing flexible adjustment of the mounting angle of the limiting seat 8 and improving ease of use. Furthermore, the limiting seat 8 serves both a limiting function and can also be used as a grip.

[0040] In this embodiment, the wrench can be powered by either a lithium battery or by an external power source connected via a power cord.

[0041] The method for obtaining the bolt axial force based on the ultrasonic information collected by ultrasonic probe 5 is carried out according to the following steps:

[0042] Ignoring the change in medium density caused by changes in axial force, establish the longitudinal wave propagation velocity v of ultrasound without axial force. L0 Ultrasonic transverse wave propagation velocity v under axial force S0 The steps of the relational expression.

[0043] Specifically, bolts are typically made of metal, which is an isotropic solid medium. For an isotropic solid medium, the vector field can be expressed as the sum of the scalar gradient and the vector curl, therefore:

[0044] v=gradφ+rotψ (1)

[0045] divψ=0 (2)

[0046] In equations (1) and (2), v represents the velocity vector, φ represents the scalar potential, and ψ represents the vector potential. Separating the scalar potential and vector potential, we obtain:

[0047]

[0048] In equations (3) and (4), ρ represents the density of the bolt, and λ and μ are the second-order elastic coefficients of the bolt. Generally speaking, scalar potential and vector potential describe longitudinal and transverse waves, respectively. Therefore, under the action of no axial force, the propagation speeds of ultrasonic longitudinal and transverse waves in a metallic medium can be expressed as:

[0049]

[0050] In equations (5) and (6), v L0 and v S0 They represent the propagation speeds v of ultrasonic longitudinal waves under axial force-free conditions. L0 The propagation speed v of ultrasonic transverse waves under axial force S0 Depending on the direction of ultrasonic wave propagation, the acoustic elasticity equations for different propagation directions can be expressed as follows:

[0051]

[0052]

[0053] In equations (7)-(10), σ represents the bolt axial force, ρ0 represents the bolt density without axial force, l, m, and n represent the third-order elastic coefficients of the bolt, and v LII v represents the longitudinal wave propagation velocity of ultrasound parallel to the direction of the axial force. L⊥ v represents the longitudinal wave propagation velocity of ultrasound perpendicular to the direction of the axial force. SII v represents the propagation speed of ultrasonic longitudinal and transverse waves parallel to the direction of the axial force. S⊥ This represents the propagation velocity of the ultrasonic transverse wave perpendicular to the direction of the axial force. Since the ultrasonic transverse wave is a shear wave, its polarization direction is perpendicular to the axial force direction, but its propagation direction is not uniform. Because the ultrasonic longitudinal wave parallel to the axial force direction is most sensitive to changes in axial force, and ultrasonic longitudinal wave transducers are more commonly used and less expensive, most time-of-flight methods use ultrasonic longitudinal waves to detect the axial force of bolts. Therefore, combining equations (5) and (7), ignoring the change in medium density caused by the change in axial force state, i.e., ρ0 = ρ, we can obtain:

[0054]

[0055] make:

[0056]

[0057] In equations (11) and (12), K a Let be the acoustoelastic coefficient of the material. From equation (12), it can be seen that the acoustoelastic coefficient is only related to the second and third elastic coefficients of the material and is not affected by other factors. Therefore, substituting equation (12) into equation (11) yields:

[0058] v Lσ =v L0 (1+K a σ) (13)

[0059] Equation (13) is the longitudinal wave propagation velocity v of ultrasonic waves under the action of no axial force. L0 Ultrasonic transverse wave propagation velocity v under axial force S0 The relational expression.

[0060] Establish the ultrasonic transit time Δt under stress conditions σ The steps for determining the relationship between the ultrasonic transit time Δt0 under axial force and the equation.

[0061] Specifically, establish the relationship between the elongation of a bolt under axial force:

[0062]

[0063] In equation (14), L0 is the total length of the bolt when it is not under stress, and L σ E is the total length of the bolt under stress, and E is the elastic modulus of the bolt.

[0064] Combining equations (13) and (14), the transit time Δt of the ultrasonic wave under stress is calculated. σ The transit time Δt0 of an ultrasonic wave under axial force-free conditions is expressed as:

[0065]

[0066] For metallic materials, the acoustoelastic coefficient K a The order of magnitude is extremely small, typically K within the safe axial force range of the bolt. a σ << 1, therefore, equation (15) is approximately simplified to:

[0067]

[0068] Equation (17) is the formula for establishing the ultrasonic transit time Δt under stress. σ The relationship between the ultrasonic transit time Δt0 under the action of no axial force and the ultrasonic wave transit time Δt0.

[0069] Establish the ultrasonic transit time Δt under stress conditions σThe steps for calculating the relationship between the ultrasonic transit time Δt0 and the axial force coefficient K under no axial force to determine the bolt axial force σ.

[0070] Specifically, by extracting the bolt axial force σ from equation (17), we obtain:

[0071]

[0072] Therefore, the formula for calculating the bolt axial force σ is:

[0073]

[0074] In equation (19), K represents the axial force coefficient, which is obtained through calibration experiments and is related to the material properties of the bolt and the geometric dimensions of the bolt.

[0075] Equation (19) is based on the ultrasonic transit time Δt under stress. σ The relationship between the ultrasonic transit time Δt0 under no axial force and the axial force coefficient K for calculating the bolt axial force σ is given. Therefore, the ultrasonic transit time Δt0 acquired by ultrasonic probe 3... σ The axial force σ of the bolt can be obtained by using the ultrasonic transit time Δt0 under no axial force and the axial force coefficient K obtained through calibration experiments.

[0076] Finally, it should be noted that the above description is merely a preferred embodiment of the present utility model. Those skilled in the art, under the guidance of the present utility model, can make various similar representations without departing from the spirit and claims of the present utility model, and such modifications all fall within the protection scope of the present utility model.

Claims

1. A wrench capable of online monitoring and control of axial force during bolt tightening, comprising a housing assembly (1), characterized in that: The housing assembly (1) is equipped with a drive shaft (2) that can rotate relative to it and a drive mechanism (3) for driving the drive shaft (2) to rotate. The housing assembly (1) is provided with a bolt sleeve (4) that can rotate relative to it. The rear end of the bolt sleeve (4) extends into the housing assembly (1) and is synchronously connected to the front end of the drive shaft (2). The front end of the drive shaft (2) is equipped with an ultrasonic probe (5) that is coaxially arranged with it. The bolt head positioning groove (4a) is recessed at the center axis position of the front end face of the bolt sleeve (4). The bottom of the bolt head positioning groove (4a) is provided with a probe protrusion hole (4b) that is adapted to the ultrasonic probe (5). The detection end of the ultrasonic probe (5) extends into the probe protrusion hole (4b).

2. The wrench according to claim 1, characterized in that: The bolt sleeve (4) can be detachably installed at the front end of the drive shaft (2).

3. The wrench according to claim 2, characterized in that: The front end of the drive shaft (2) protrudes to form a prism-structured sleeve joint (2a). The end face of the sleeve joint (2a) is recessed to form a probe mounting hole (2b) that is compatible with the ultrasonic probe (5). The probe mounting hole (2b) communicates with the probe protrusion hole (4b). The ultrasonic probe (5) is installed in the probe mounting hole (2b). The rear end of the bolt sleeve (4) is recessed to form a connector connection groove (4c) that engages with the sleeve joint (2a).

4. The wrench according to claim 3, characterized in that: It also includes an electric slip ring (7), which includes an electric slip ring rotor (7a) that is synchronously mounted on the drive shaft (2) and an electric slip ring stator (7b) that is fixedly mounted on the inner wall of the housing assembly (1). The electric slip ring stator (7b) is rotatably mounted on the outside of the electric slip ring rotor (7a) and is electrically connected to the electric slip ring rotor (7a). The cable of the ultrasonic probe (5) passes through the hole wall of the probe mounting hole (2b) and is electrically connected to the electric slip ring rotor (7a). The electric slip ring stator (7b) is connected to the power supply through a wire harness arranged in the housing assembly (1).

5. The wrench according to claim 1, characterized in that: The drive mechanism (3) includes a motor (3a) and a two-stage reduction planetary gear train (3b). The two-stage reduction planetary gear train (3b) includes an internal gear ring (3b2) fixedly mounted on the inner wall of the housing assembly (1), a first-stage planet carrier (3b3) disposed in the internal gear ring (3b2), a first-stage sun gear (3b1) synchronously mounted on the motor shaft (3a1) of the motor (3a), and a plurality of first-stage planet gears (3b4) distributed circumferentially around the first-stage sun gear (3b1). Each first-stage planet gear (3b4) is mounted close to the first-stage planet carrier (3b3). On one side of the primary sun gear (3b1), it meshes with both the primary sun gear (3b1) and the internal gear ring (3b2). On the side of the primary planetary carrier (3b3) near the drive shaft (2), there is a secondary sun gear (3b5) that rotates synchronously with it. The rear end of the drive shaft (2) is integrally formed with a secondary planetary carrier (3b6). Multiple secondary planetary gears (3b7) are mounted on the secondary planetary carrier (3b6) and are evenly distributed along the secondary sun gear (3b5). Each secondary planetary gear (3b7) meshes with both the secondary sun gear (3b5) and the internal gear ring (3b2) simultaneously.

6. The wrench according to claim 5, characterized in that: The motor shaft (3a1) is synchronously mounted with fan blades (6) for directing airflow toward the motor rotor (3a2) and motor stator (3a3) of the motor (3a). The housing assembly (1) has an air outlet (1a1) located next to the fan blades (6) and an air inlet (1a2) located at the end of the motor rotor (3a2) away from the fan blades (6).

7. The wrench according to claim 5, characterized in that: The motor (3a) has a self-locking function.

8. The wrench according to claim 5, characterized in that: The housing assembly (1) includes a housing body (1a), a quick-change housing (1c), and a wrench holder (1b) connecting the housing body (1a) and the quick-change housing (1c). The rear end of the wrench holder (1b) is detachably mounted on the front end of the housing body (1a), and the rear end of the quick-change housing (1c) is detachably mounted on the front end of the wrench holder (1b). The motor (3a) is mounted in the housing body (1a). The planetary gear train (3b) and the drive shaft (2) are both mounted in the wrench holder (1b). The front end of the drive shaft (2) extends into the quick-change housing (1c), and the bolt sleeve (4) extends rearward into the quick-change housing (1c) and connects to the front end of the drive shaft (2).

9. The wrench according to claim 8, characterized in that: It also includes a limiting seat (8), and the bottom of the outer shell body (1a) is integrally formed with a grip handle (1a3). A first connecting tooth (1b1) is formed on the circumferential outer wall of the wrench seat (1b). The inner end of the limiting seat (8) has a limiting seat mounting ring (8a) fitted on the wrench seat (1b). A second connecting tooth (8b) that meshes with the first connecting tooth (1b1) is formed on the inner circumferential surface of the limiting seat mounting ring (8a).

10. The wrench according to claim 1, characterized in that: A display screen (9) is mounted on the housing assembly (1).

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