Electric screwdriver with current detection module

Abstract

The utility model discloses a kind of electric screwdrivers with current detection module, the electric screwdriver includes motor, speed reduction mechanism and bit assembly, it is characterized in that, current sampling resistance is connected in series in the power supply loop of the motor, and the current sampling resistance is electrically connected with MCU controller by operational amplifier circuit.The current sampling resistance and operational amplifier circuit are combined MCU controller to carry out real-time monitoring to motor current by being introduced, and the response speed and control accuracy of overload protection are significantly improved.Meanwhile, the intelligent algorithm of dynamic adjustment overcurrent threshold value can better adapt to complex working condition demand, avoid the occurrence of misjudgment and lag problem, thereby prolong the service life of equipment and improve operation safety, meet the application requirement of modern industry to intelligentization, high-precision electric tool.

Description

Technical Field

[0001] This utility model relates to the field of electric screwdrivers, and in particular to an electric screwdriver equipped with a current detection module. Background Technology

[0002] Existing electric screwdrivers suffer from problems such as high system complexity and lag in response speed and control accuracy for motor overload protection.

[0003] For example, the "Dual-Pulse Feedback Electric Screwdriver" in Chinese Invention Patent Publication No. CN106625371B employs a technical solution that determines load changes by detecting the rotational state of the inner and outer rotors. This solution generates two sets of waveform signals by setting detector components around the outer rotor sleeve and the inner rotor magnetic shaft, thereby acquiring speed and load information, which is then used by the controller for overload detection and motor shutdown. While this design effectively distinguishes between bit overload and motor stall, improving the overload protection response capability, it relies on a mechanical structure combined with magnetic induction elements for feedback control. This results in high system complexity, susceptibility to interference, and detection delays. Furthermore, it cannot achieve real-time and accurate monitoring of motor current, especially when the motor momentarily stalls, making it difficult to react quickly to prevent motor damage or screw damage.

[0004] Furthermore, the Chinese invention patent publication CN106584342B, "Magnetic Coupling Electric Screwdriver," also employs a similar magnetic coupling transmission method, using a detector assembly on a probe to test speed changes and determine if an overload has occurred. This scheme uses a reducer to drive the output shaft, rotating the inner rotor, which in turn drives the outer rotor and the screwdriver bit under magnetic coupling. When an abnormal speed is detected, the controller shuts off the motor for protection. However, this speed-change-based detection method is essentially an indirect feedback mechanism and cannot directly reflect the actual operating current changes of the motor. This means that in cases of slight motor overload or slow stall, the control system may not respond promptly, exhibiting a certain degree of lag and risk of misjudgment, thus affecting the overall control sensitivity and reliability.

[0005] None of the aforementioned existing technical solutions involve direct detection and feedback control of motor current, lacking a current detection module capable of acquiring motor operating current in real time and performing precise control accordingly. Therefore, existing electric screwdrivers often struggle to achieve rapid and accurate overload protection and motor control when facing high-precision tightening requirements under complex working conditions, limiting their application in high-end fields such as precision assembly and intelligent manufacturing. Utility Model Content

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0007] An electric screwdriver with a current detection module includes a motor, a reduction mechanism, and a bit assembly. A current sampling resistor is connected in series in the power supply circuit of the motor, and the current sampling resistor is electrically connected to an MCU controller through an operational amplifier circuit.

[0008] In a preferred embodiment of the present invention, a temperature sensor is embedded on the surface of the motor housing, and the temperature sensor is electrically connected to the MCU controller.

[0009] In a preferred embodiment of this utility model, the current sampling resistor is a low-resistance precision resistor with a resistance range of 0.01 ohms to 0.1 ohms.

[0010] In a preferred embodiment of this utility model, the operational amplifier circuit adopts a differential amplifier structure, with its input terminals connected to both ends of the current sampling resistor, and its output terminal connected to the ADC interface of the MCU controller through a filter circuit.

[0011] In a preferred embodiment of this utility model, the electric screwdriver further includes an alarm module, which is electrically connected to the MCU controller.

[0012] In a preferred embodiment of this utility model, the current sampling resistor is placed in a shielded cavity, and the shielded cavity is in communication with the outer shell of the electric screwdriver.

[0013] The beneficial effects of this utility model are as follows:

[0014] This invention provides an electric screwdriver equipped with a current detection module. By introducing a current sampling resistor and operational amplifier circuit combined with an MCU controller, it monitors the motor current in real time, significantly improving the response speed and control accuracy of overload protection. Simultaneously, through an intelligent algorithm that dynamically adjusts the overcurrent threshold, it can better adapt to complex working conditions, avoiding misjudgments and lag issues, thereby extending the equipment's service life and improving operational safety, meeting the application requirements of modern industry for intelligent, high-precision electric tools. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0016] Figure 1 This is a system structure diagram of this utility model. Detailed Implementation

[0017] In the description of this utility model, it should be noted that the terms "upper", "lower", "left", "right", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. The above description is for the purpose of simplifying the description of this utility model and does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this utility model.

[0018] Unless otherwise specified, the singular forms “a,” “the,” and “the” used in this specification include the plural forms. The terms “comprising,” “including,” and “containing” used in this specification indicate the presence of the claimed feature, but do not exclude the presence of one or more other features.

[0019] In the specification, when an element is described as being "on," "fixed" to, "connected" to, or "joined" to another element, the element may be directly located on, fixed to, connected to, joined to, or in contact with the other element, or there may be an intermediate element present. In the specification, the description of a feature being arranged "adjacent" to another feature may refer to a feature having a portion that overlaps with the adjacent feature or a portion located above or below the adjacent feature.

[0020] It is understood that although the terms "first," "second," etc., may be used herein to describe different elements, these elements should not be limited by these terms. These terms are merely used to distinguish one element from another. Therefore, a first element may be referred to as a second element without departing from the teachings of this application.

[0021] Exemplary embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that this application can be presented in many different ways and is not limited to the embodiments described below. It should also be understood that the embodiments disclosed herein can be combined in various ways to provide further additional embodiments. Throughout the drawings, the same reference numerals denote the same or functionally identical elements.

[0022] The electric screwdriver mainly consists of a motor (1), and an intelligent motor protection system is constructed by integrating core components such as a current sampling resistor (4), an operational amplifier circuit (5), an MCU controller (6), a temperature sensor (7), and an alarm module (8). This system enables comprehensive monitoring and protection of the motor's operating status, and its technological advantages are reflected in three aspects: intelligent response, anti-interference design, and multi-dimensional protection mechanisms.

[0023] Figure 1The internal system module structure of the screwdriver was demonstrated. The MCU controller 6, as the core control unit of the current detection module, incorporates an intelligent algorithm that dynamically adjusts the overcurrent threshold based on historical current data. This algorithm analyzes current fluctuation characteristics in real time and automatically optimizes the protection threshold for different operating conditions (such as load differences when tightening screws of different materials or sizes). Compared to traditional fixed threshold solutions, the dynamic adjustment mechanism effectively avoids misjudgments or lag issues, significantly improving the intelligence level of overload protection. Furthermore, the MCU controller 6 has real-time signal processing capabilities, enabling feature extraction and status identification of the acquired current signals. When abnormal operating conditions such as overload, stall, or short circuit are detected, the controller immediately triggers a control signal to cut off the motor power supply, effectively preventing equipment damage and safety accidents.

[0024] To address the complex monitoring requirements of motor operation, this embodiment embeds a temperature sensor 7 on the surface of the motor 1's housing. This sensor is electrically connected to the MCU controller 6, enabling real-time acquisition of motor winding temperature data and its fusion analysis with the current signal. When the motor experiences abnormal temperature rise due to prolonged high-load operation, even if the current signal has not yet reached the overload threshold, the system can still quickly identify overload or stall conditions through a temperature-current multi-dimensional judgment mechanism. This composite sensing strategy can improve protection response speed by 40% while reducing the probability of false triggering by more than 30%.

[0025] The current sampling resistor 4 is placed inside a shielded cavity (not shown in the figure), which is made of conductive material and is in communication with the outer shell of the electric screwdriver. When the operator holds the screwdriver, this communication acts as a grounding mechanism, reducing external electromagnetic interference.

[0026] At the human-machine interface level, the system is equipped with an alarm module 8 that integrates audible and visual alarm functions. This module works in conjunction with the MCU controller 6 to trigger differentiated alarm signals based on the type of anomaly: a continuous buzzing sound accompanied by a flashing red light during overload conditions, and an intermittent flashing mode during stall conditions. On-site testing shows that this design can reduce the anomaly recognition time to within 0.3 seconds, improving efficiency by 60% compared to traditional single visual prompt solutions. The modular design of the alarm module also supports subsequent functional expansion, such as the reserved wireless communication interface to support integration with remote monitoring systems.

[0027] In some implementations, the MCU controller 6 samples the operational amplifier voltage. Taking a motor operating current of I = 5A as an example, the sampling resistor is R = 10mR. Due to the motor's characteristics, when the motor stops at the stall position due to external force, the motor torque increases, and the current increases accordingly. Taking a stall current of I = 10A as an example, with a sampling resistor of R = 10mR and an operational amplifier amplification factor of 20, the voltage difference across the sampling resistor is V = 10A * 10mR * 20 = 2V. When the MCU controller 6 detects a voltage change from 1V to 2V, it considers the cutter motor to have encountered resistance and reached the stall position, immediately stopping the motor drive to protect the cutter head and screw from damage due to prolonged torque.

[0028] The electric screwdriver in this embodiment is particularly suitable for high-precision operations such as electronic assembly. Taking the screw fastening process on a mobile phone production line as an example, the system can dynamically optimize the current protection parameters to an accuracy range of ±2% for the fastening characteristics of tiny screws (M1-M2 size). The shielded cavity design enables the device to maintain stable operation in environments with strong electromagnetic interference, such as welding equipment and high-frequency testing instruments, effectively solving the industry pain point of high malfunction rate of traditional power tools in complex electromagnetic environments.

[0029] In summary, this embodiment achieves three major technological breakthroughs through hardware architecture innovation and the integration of intelligent algorithms: First, the MCU controller 6 based on the dynamic threshold algorithm shortens the overload protection response time to less than 5ms and achieves a control accuracy of ±1.5%; Second, the temperature-current dual-modal sensing mechanism reduces the system's false judgment rate to below 0.2%, thereby meeting the requirements for improved reliability.

Claims

1. A power screwdriver with a current detection module, the power screwdriver comprising a motor, a speed reduction mechanism and a bit assembly, characterized in that, A current sampling resistor is connected in series in the power supply circuit of the motor, and the current sampling resistor is electrically connected to the MCU controller through an operational amplifier circuit.

2. The electric screwdriver with a current detection module according to claim 1, wherein A temperature sensor is embedded in the surface of the motor housing, and the temperature sensor is electrically connected to the MCU controller.

3. The electric screwdriver with a current detection module according to claim 2, wherein, The current sampling resistor is a low-resistance precision resistor with a resistance range of 0.01 ohms to 0.1 ohms.

4. An electric screwdriver with a current detection module as described in claim 1, characterized in that, The operational amplifier circuit adopts a differential amplifier structure, with its input terminals connected to both ends of the current sampling resistor, and its output terminal connected to the ADC interface of the MCU controller through a filter circuit.

5. The electric screwdriver with a current detection module according to claim 1, wherein The electric screwdriver also includes an alarm module, which is electrically connected to the MCU controller.

6. A power screwdriver with a current detection module according to any one of claims 1 to 5, characterized in that, The current sampling resistor is placed in a shielded cavity, which is in communication with the outer shell of the electric screwdriver.

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