Low-reaction force electric pulse tool and control method thereof

Abstract

The application discloses a low-reaction-force electric pulse tool and a control method thereof. The tool comprises a shell, a motor, an output head, a torque transmission mechanism, a static torque sensor, a torque sampling module and a controller. The motor transmits a tightening torque to a side of a fastened part through the torque transmission mechanism and the output head, and a circumferential angle gap is formed in a torque transmission path between the motor rotor and the fastened part to allow the motor rotor to rotate relatively to the fastened part in a circumferential direction when the rotation of the fastened part is limited. The static torque sensor is arranged on the reaction force transmission path and outputs an analog signal corresponding to the reaction torque; the torque sampling module samples the analog signal at a preset sampling frequency to obtain a torque signal. The controller judges whether a preset trigger condition is reached according to the torque signal, and if the trigger condition is reached, it is determined that the fastened part reaches a collision state, and the driving current applied to the motor is stopped or reduced, and the continuous driving force transmitted to the operator's hand is reduced.

Description

Technical Field

[0001] This invention relates to the field of electric tightening tools, and in particular to a low-reaction electric pulse tool and its control method. Background Technology

[0002] Electric tightening tools are widely used in assembly operations to screw in and tighten screws, bolts, nuts, and other fasteners. Depending on the tightening method, electric tightening tools can include continuous tightening tools, impact tightening tools, and pulse tightening tools. Among these, electric pulse tightening tools typically use the coordination between a motor, transmission mechanism, and output head to convert the rotational motion of the motor output into pulse torque acting on the workpiece to be tightened, thereby completing the tightening operation in a relatively short time.

[0003] In electric pulse tools, the motor is typically connected to the output head via a reduction gear or other torque transmission mechanism. The output head can directly engage with the workpiece to be tightened, or it can engage with the workpiece through tightening actuators such as bit or socket. Before the workpiece is seated, the tool can usually screw it in quickly by continuous rotation. As the workpiece gradually comes into contact with the workpiece, the resistance on the output head increases, and the tool enters a high-load tightening stage.

[0004] For pulse tightening tools, the settling torque generated during the settling phase is not entirely the same as the pulse torque generated during the subsequent pulse tightening phase. The settling torque is typically used to characterize the transition of the workpiece from a low-load screw-in state to a fully engaged or near-fully engaged state; while the pulse torque is usually generated after the circumferential angular clearance present in the torque transmission path between the motor rotor and the workpiece is absorbed, i.e., when the relevant components contact or collide at the end of the circumferential angular clearance. This circumferential angular clearance can be formed between the transmission mechanism and the output head, or at the mating position between the output head, the bit, and the workpiece.

[0005] During pulse tightening, even when the rotation of the workpiece is restricted, the motor rotor may still experience a brief circumferential rotation relative to the workpiece, transmitting pulse torque to the workpiece side at the end of the circumferential angular gap. This pulse torque has a short duration and changes rapidly. If the motor continues to apply drive current during the pulse collision phase to output torque in the tightening direction, the continuous driving force of the motor may superimpose with the reaction force generated by the pulse collision, causing the reaction force to be transmitted to the operator's hand via the output head, transmission mechanism, housing, or motor casing.

[0006] Existing electric pulse tools typically focus more on seat placement detection, final torque control, or tightening efficiency. For example, some tools can detect the seat placement torque to enter the subsequent pulse tightening stage, or determine the tightening result based on the final tightening torque. However, during the pulse tightening stage, the pulse collision torque is characterized by its short duration and rapid change. If the tool does not sample enough of the torque changes during this stage or its judgment is delayed, it will be difficult to identify the pulse collision state in a timely manner, and it will also be difficult to adjust the drive current of the motor along the tightening direction in a timely manner.

[0007] For handheld electric pulse tools, the continuous driving current involved in the pulse collision phase increases the torsional reaction force felt by the operator, leading to increased grip burden and potentially affecting the comfort and stability of continuous operation. Especially under higher target torque conditions, the change in reaction force during the pulse collision phase is more pronounced. Without rapid sampling and corresponding control of the collision torque, there is still room for improvement in the tool's low-reaction-force operation performance. Summary of the Invention

[0008] The purpose of this invention is to provide a low-reaction electric pulse tool and its control method, so as to at least improve the problem that in the pulse tightening process of existing electric pulse tools, the motor continuously outputs driving current along the tightening direction, resulting in the continuous tightening force or impact reaction force being transmitted to the operator's hand through the housing, motor housing and other paths.

[0009] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A low-reaction electric pulse tool, characterized in that it comprises: a housing, a motor, an output head, a torque transmission mechanism, a static torque sensor, a torque sampling module, and a controller. The output head is used to engage with the part to be tightened; The motor is connected to the output head through the torque transmission mechanism and can transmit tightening torque to the part to be tightened via the output head; A circumferential angular gap for pulse tightening is formed in the torque transmission path between the rotor of the motor and the part to be tightened. The circumferential angular gap is used to allow the rotor of the motor to rotate circumferentially relative to the part to be tightened when the rotation of the part to be tightened is restricted, and to transmit pulse torque to the part to be tightened at the end of the circumferential angular gap. The static torque sensor is disposed on the reaction force transmission path between the torque transmission mechanism and the housing or the outer shell of the motor, and is used to output an analog signal corresponding to the reaction torque of the torque transmission mechanism; The torque sampling module is electrically connected to the static torque sensor and is used to sample the analog signal at a preset sampling frequency to obtain a torque signal. The controller is electrically connected to the motor and the torque sampling module; The controller is used to execute a reaction avoidance strategy based on the torque signal; The reaction avoidance strategy is to determine whether the torque signal reaches the preset trigger condition. If the preset trigger condition is reached, it is determined that the part to be tightened has reached the collision state, and the driving current applied to the motor to make the output head output torque in the tightening direction is stopped or reduced.

[0010] By employing the above technical solution, a static torque sensor positioned along the reaction force transmission path acquires the analog signal corresponding to the reaction torque. This analog signal is then sampled by a torque sampling module at a preset sampling frequency, enabling the controller to promptly identify pulse collision-related states based on the torque signal. When the torque signal reaches a preset trigger condition, the controller stops or reduces the drive current outputting torque along the tightening direction, thereby reducing the degree to which the continuous driving force of the motor participates in the reaction force transmission.

[0011] Further settings: The preset triggering conditions include at least one of the following: The torque signal reaches a preset collision torque threshold. The rate of change of the torque signal within the preset sampling window reaches a preset collision change rate threshold. The torque signal is within a preset collision torque range for a preset duration; The torque signal and the change in the motor speed satisfy a preset collision correlation condition.

[0012] By adopting the above technical solution, the controller can judge the pulse collision state from dimensions such as torque amplitude, torque change rate, torque duration range, and the correlation between torque and motor speed change, thereby improving the triggering stability of the reaction avoidance strategy.

[0013] Further configuration: The step of stopping or reducing the drive current applied to the motor to cause the output head to output torque in the tightening direction includes at least one of the following: Set the torque command of the motor to zero; Reduce the current command of the motor to below a preset ratio; Turn off the drive output of the motor; This puts the motor into a low electromagnetic force output state.

[0014] By adopting the above technical solutions, the continuous driving effect of the motor along the tightening direction can be reduced through torque command, current command, drive output or low electromagnetic force state, thereby weakening the transmission of continuous tightening force to the operator's hand.

[0015] Further configuration: The controller has a continuous tightening mode and a pulse tightening mode; In the continuous tightening mode, the controller controls the motor to drive the output head to rotate continuously through the torque transmission mechanism; When the controller determines whether the preset seating condition has been met based on the torque signal, if the preset seating condition has been met, it determines that the part to be tightened has reached the seating state, and the controller controls the motor to enter the pulse tightening mode to perform pulse tightening operation on the part to be tightened.

[0016] By adopting the above technical solution, the low-reaction electric pulse tool can improve the screwing efficiency by continuously tightening before the part to be tightened is seated, and enter the pulse tightening mode after it is seated to complete the subsequent tightening process by pulse torque.

[0017] Further configuration: The torque transmission mechanism includes a planetary reduction mechanism, which includes a sun gear, planet gears, a ring gear, and a planet carrier; The sun gear is connected to the rotor of the motor for transmission, the planet gears mesh with the sun gear and the ring gear, and the planet carrier is used to support the planet gears; The planetary carrier and the output head form the circumferential angular gap.

[0018] By adopting the above technical solution, the motor output can be transmitted to the output head through the planetary reduction mechanism, and the pulse torque transmission condition is formed through the circumferential angular gap between the planetary carrier and the output head.

[0019] Further configuration: The planetary carrier includes a plurality of impact sections arranged circumferentially, and the output head includes an impact-bearing section corresponding to the impact sections; The circumferential angular gap is formed between the plurality of impact parts, and the impact-bearing part is located within the circumferential angular gap; When the torque transmission mechanism rotates relative to the output head within the circumferential angular gap to the end of the gap, the impact part contacts the impact receiving part to transmit pulse torque to the output head.

[0020] By adopting the above technical solution, the circumferential angle gap can provide a relative rotational stroke for the torque transmission mechanism relative to the output head, and pulse torque transmission is achieved at the end of the gap through the contact between the impact part and the bearing part.

[0021] Further configuration: The output head is connected to the part to be tightened via a screwdriver bit, and the circumferential angular gap is formed at least in part by a first mating angular gap between the output head and the screwdriver bit and / or a second mating angular gap between the screwdriver bit and the part to be tightened.

[0022] By adopting the above technical solution, the circumferential angular clearance is not limited to being formed between the torque transmission mechanism and the output head, but can also be formed or jointly formed by the mating angular clearance between the output head, the bit and the part to be tightened, thereby expanding the applicable range of the low reaction force pulse tightening structure.

[0023] On the other hand, this application also provides a control method for a low-reaction electric pulse tool, applied to the aforementioned low-reaction electric pulse tool, specifically including the following steps: The motor is controlled to drive the output head to rotate through the torque transmission mechanism, and the tightening torque is transmitted to the part to be tightened through the output head; When the rotation of the part to be tightened is restricted, the circumferential angle gap in the torque transmission path between the rotor of the motor and the part to be tightened is used to make the rotor of the motor rotate circumferentially relative to the part to be tightened, and to transmit pulse torque to the part to be tightened at the end of the circumferential angle gap. The static torque sensor outputs an analog signal corresponding to the reaction torque of the torque transmission mechanism. The torque signal is obtained by sampling the analog signal at a preset sampling frequency using the torque sampling module. The controller executes a reaction avoidance strategy based on the torque signal; The reaction avoidance strategy includes: determining whether the torque signal reaches a preset trigger condition; if the preset trigger condition is reached, determining that the part to be tightened has reached a collision state, and stopping or reducing the driving current applied to the motor to make the output head output torque in the tightening direction.

[0024] Further configuration: The low-reaction electric pulse tool is controlled to have a continuous tightening mode and a pulse tightening mode; In the continuous tightening mode, the motor is controlled to drive the output head to rotate continuously through the torque transmission mechanism; Determine whether the preset seating conditions have been met based on the torque signal; If the preset seating condition is met, it is determined that the part to be tightened has reached the seating state, and the motor is controlled to enter the pulse tightening mode to perform a pulse tightening operation on the part to be tightened.

[0025] In summary, the present invention has the following beneficial effects: First, this application places a static torque sensor on the reaction force transmission path between the torque transmission mechanism and the housing or motor housing, so that the collected analog signal can reflect the reaction torque received by the torque transmission mechanism, providing a signal basis for subsequent reaction avoidance control.

[0026] Secondly, this application obtains a torque signal by sampling the analog signal at a preset sampling frequency through a torque sampling module, enabling the controller to determine whether the preset triggering condition has been met based on the sampled torque signal, thus avoiding missing the opportunity to avoid continuous tightening force by relying solely on low-frequency or lagging torque judgment.

[0027] Third, when the torque signal reaches the preset trigger condition, this application stops or reduces the driving current applied to the motor to make the output head output torque in the tightening direction, which can reduce the continuous driving effect of the motor in the tightening direction, thereby reducing the continuous tightening force or pulse reaction force transmitted to the operator's hand through the housing, motor housing and other paths.

[0028] Fourth, this application enables the motor rotor to rotate relative to the part to be tightened in the circumferential angle gap by setting or utilizing the circumferential angle gap in the torque transmission path between the motor rotor and the part to be tightened, so that the motor rotor can still generate circumferential relative rotation with respect to the part to be tightened when the rotation of the part to be tightened is restricted, and transmit pulse torque to the part to be tightened at the end of the circumferential angle gap, thereby achieving pulse tightening after reducing the drive current along the tightening direction.

[0029] Fifth, this application combines continuous tightening mode and pulse tightening mode to continuously rotate and tighten the part before it reaches the seated state, and then enters pulse tightening mode after it reaches the seated state, which can take into account screwing efficiency, pulse tightening capability and low reaction force operation effect. Attached Figure Description

[0030] Figure 1 This is a cross-sectional view of the overall structure of Embodiment 1; Figure 2 This is a diagram showing the mating structure between the planetary carrier and the output end in Example 1; Figure 3 This is the working logic diagram of Example 1; Figure 4 This is the test curve graph from Example 3; Figure 5 This is a timing diagram of torque, speed and current commands under the reaction avoidance strategy provided in the embodiment.

[0031] In the diagram, 1 is the motor; 2 is the housing; 3 is the output head; 4 is the torque transmission mechanism; 5 is the static torque sensor; and 6 is the planetary carrier. Detailed Implementation

[0032] The present application will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the following embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application. Where there is no conflict, the technical features in the following embodiments can be combined with each other.

[0033] In this application, the "part to be tightened" can be a screw, bolt, nut, or other connecting part that needs to be screwed in or tightened. "Circumferential angular clearance" refers to the angular space allowed for circumferential rotation between the motor rotor and the part to be tightened in the torque transmission path between the motor rotor and the part to be tightened. This circumferential angular clearance can be formed between the torque transmission mechanism and the output head, or at the mating position between the output head, the bit, and the part to be tightened, or it can be formed by the mating angular clearances at multiple positions.

[0034] In this application, "collision state" refers to a state in which, after the rotation of the part to be tightened is restricted, the circumferential relative rotation of the motor rotor side with respect to the part to be tightened absorbs the circumferential angular gap, and related components in the torque transmission path make contact or collision at the end of the circumferential angular gap, transmitting pulse torque to the part to be tightened. This state can be identified by the amplitude, rate of change, duration range of the torque signal, or the correlation between the torque signal and the change in motor speed.

[0035] Example 1:

[0036] like Figure 1-4 As shown, a low-reaction electric pulse tool includes a housing, a motor, an output head, a torque transmission mechanism, a static torque sensor, a torque sampling module, and a controller.

[0037] The housing houses the motor, torque transmission mechanism, static torque sensor, torque sampling module, and control-related wiring. The housing can be handheld, such as a gun-type or cylindrical housing. An output head is located at the front of the housing and engages with the part to be tightened. Specifically, the output head engages with the part via a screwdriver bit, socket, or other tightening actuator.

[0038] The motor is connected to the output head via a torque transmission mechanism and can transmit tightening torque to the part to be tightened via the output head. The motor can be a servo motor, brushless motor, or other controllable motor. The controller can control the motor's start, stop, speed, torque command, current command, or drive output status.

[0039] A circumferential angular gap A is formed in the torque transmission path between the motor rotor and the part to be tightened for pulse tightening. This circumferential angular gap A allows the motor rotor to rotate circumferentially relative to the part to be tightened when the rotation of the part to be tightened is restricted, and transmits pulse torque to the part to be tightened at the end of the circumferential angular gap A.

[0040] Specifically, when the part to be tightened is not yet restricted, the motor can drive the part to be tightened to continuously screw in via the torque transmission mechanism, output head, and screwdriver bit. As the part to be tightened gradually comes into contact with the workpiece, the rotational resistance of the part to be tightened increases, and the movement of the part to be tightened is restricted. At this time, the rotor side of the motor can still generate a short-term circumferential relative rotation with respect to the part to be tightened within the allowable range of the circumferential angle gap A; when the circumferential angle gap A is absorbed, the relevant components in the torque transmission path contact or collide at the end of the gap, thereby transmitting pulse torque to the output head and the part to be tightened.

[0041] How circumferential angular clearance is formed In one implementation, such as Figure 2 As shown, a circumferential angular gap is formed between the torque transmission mechanism and the output head. The torque transmission mechanism is capable of rotating relative to the output head within the circumferential angular gap. When the torque transmission mechanism rotates relative to the output head to the end of the circumferential angular gap, the torque transmission mechanism transmits pulse torque to the output head.

[0042] In another embodiment, the output head is connected to the part to be tightened via a screwdriver bit, and the circumferential angular gap A is at least partially formed by a first mating angular gap A between the output head and the screwdriver bit. The first mating angular gap A can be formed by the assembly gap in a tenon-and-mortise fit, hexagonal fit, spline fit, or other non-circular fit structure between the output head and the screwdriver bit.

[0043] In another embodiment, the circumferential angular clearance A is at least partially formed by a second mating angular clearance A between the bit and the part to be tightened. The second mating angular clearance A may be formed by an assembly clearance between the bit and a screw slot, hexagon socket, Torx hole, or other mating part.

[0044] In practical use, the total circumferential angular clearance A between the motor rotor and the workpiece to be tightened can be formed by one or more of the following: the internal angular clearance between the torque transmission mechanism and the output head, the first mating angular clearance A between the output head and the bit, and the second mating angular clearance A between the bit and the workpiece to be tightened. As long as the circumferential angular clearance A allows the motor rotor to rotate circumferentially relative to the workpiece to be tightened when the rotation of the workpiece to be tightened is restricted, and transmits pulse torque to the workpiece side at the end of the clearance, it falls under the implementation of the circumferential angular clearance A described in this application.

[0045] In one specific embodiment, the torque transmission mechanism includes a planetary reduction gear. The planetary reduction gear includes a sun gear, planet gears, a ring gear, and a planet carrier.

[0046] The sun gear is driven by the rotor of the motor. In some embodiments, the rotor of the motor can be connected to the sun gear via a splined sleeve, coupling, or other transmission connection. The planet gears mesh with the sun gear and the ring gear, and are mounted on and supported by the planet carrier. The planet carrier, as the output component of the planetary reduction mechanism, transmits the reduced torque to the output head.

[0047] In this embodiment, a circumferential angular gap A is formed between the planetary carrier and the output head. The planetary carrier is capable of rotating relative to the output head within the circumferential angular gap A. When the output head is restricted in its rotation due to obstruction by the component to be tightened, the planetary carrier can rotate relative to the output head within the circumferential angular gap A; when this relative rotation reaches the end of the circumferential angular gap A, the planetary carrier contacts or collides with the output head, thereby transmitting pulse torque to the output head.

[0048] In one specific structure, the planetary carrier includes multiple impact sections arranged circumferentially, and the output head includes impact-bearing sections corresponding to the impact sections. A circumferential angular gap A is formed between the multiple impact sections, and the impact-bearing sections are located within the circumferential angular gap A. When the planetary carrier rotates relative to the output head within the circumferential angular gap A, the impact-bearing sections can generate circumferential displacement relative to adjacent impact sections; when the impact-bearing sections contact the corresponding impact sections, the circumferential angular gap A is absorbed, and the planetary carrier transmits pulse torque to the output head through the impact sections and the impact-bearing sections.

[0049] In some embodiments, the planetary carrier may have a toothed spline segment, with multiple impact portions formed on this spline segment. The output head may have an inner circumferential groove, with an impact-bearing portion formed on the circumferential end face of the inner circumferential groove. The toothed spline segment extends at least partially into the inner circumferential groove, forming a circumferential angular clearance A between the segment and the groove. The planetary carrier and the output head may also maintain coaxiality through a hole-shaft fit structure to reduce off-center loading during pulse collisions.

[0050] It should be noted that the planetary reduction mechanism, impact section, and impact bearing section described above are only one specific implementation of the torque transmission mechanism and the circumferential angular clearance A. In other implementations, the torque transmission mechanism may also employ other structures capable of transmitting torque and allowing the formation of the circumferential angular clearance A.

[0051] Static torque sensor and reaction force transmission path A static torque sensor is positioned on the reaction force transmission path between the torque transmission mechanism and the housing or motor casing. The static torque sensor outputs an analog signal corresponding to the reaction torque of the torque transmission mechanism.

[0052] In embodiments where the torque transmission mechanism includes a planetary reduction mechanism, a static torque sensor can be disposed between the gear ring and the housing or the outer casing of the motor. The static torque sensor may have a first connecting end and a second connecting end. The first connecting end is circumferentially connected to the gear ring, and the second connecting end is circumferentially connected to the housing or the outer casing of the motor. When the output head applies a tightening torque to the component to be tightened, the reaction torque generated by the component is transmitted to the gear ring via the output head and the torque transmission mechanism. The gear ring applies a corresponding reaction torque to the static torque sensor, and the static torque sensor outputs an analog signal corresponding to this reaction torque.

[0053] Specifically, during the pulse tightening process, the part to be tightened exerts a reaction force on the output head in the opposite direction to the tightening. Part of this reaction force can act on the rotor of the motor and the torque transmission mechanism, while another part can be transmitted to the operator's hand via the gear ring, housing, or motor casing. By arranging a static torque sensor on this reaction force transmission path F, the analog signal output by the static torque sensor can reflect the change in the reaction torque experienced by the torque transmission mechanism.

[0054] Torque sampling module The torque sampling module is connected between the static torque sensor and the controller. The static torque sensor outputs an analog signal Sa corresponding to the reaction torque of the torque transmission mechanism. The torque sampling module samples and converts this analog signal Sa to digital, and then outputs the torque signal Sd to the controller.

[0055] In one embodiment, the torque sampling module includes an analog-to-digital converter (ADC) and a programmable gain amplifier (PGA). The PGA amplifies the analog signal Sa output by the static torque sensor, and the ADC samples the amplified analog signal Sa at a preset sampling frequency and converts it into a digital torque signal Sd. The controller can communicate with the torque sampling module via an SPI communication link to obtain the torque signal Sd.

[0056] In one specific implementation, the analog-to-digital converter (ADC) can be a 32-bit ADC, with selectable data rates ranging from 1.875 kSPS to 61.44 kSPS. The gain of the programmable gain amplifier can be selected from 1x, 2x, 4x, 8x, 16x, 32x, and 64x. By configuring the programmable gain amplifier, the analog signal Sa output by the static torque sensor can be adapted to the input range of the ADC, improving the ability of the torque signal Sd to characterize changes in pulse-impact torque.

[0057] In one implementation, the preset sampling frequency is 32 kSPS. When the pulse width of the pulse collision torque is approximately 1 ms, the torque sampling module can collect approximately 32 sampling points within this 1 ms pulse width. Therefore, the controller can identify the rising edge, peak range, and falling edge of the torque signal Sd based on multiple sampling points, thereby determining whether the torque signal Sd has reached the preset trigger condition.

[0058] Specifically, the controller can determine whether the torque signal Sd reaches a preset collision torque threshold based on multiple sampling points within a 1ms pulse width, or it can determine whether the rate of change of the torque signal Sd reaches a preset collision change rate threshold based on the torque change within adjacent sampling points or the sampling window. Compared to obtaining only a single or a small number of torque points through low-frequency sampling, this implementation can more completely acquire the rising segment, peak segment, and falling segment of the pulse collision torque, thereby improving the timeliness of collision state recognition.

[0059] When the controller determines that the preset trigger condition has been met based on the torque signal Sd, it executes a reaction avoidance strategy, stopping or reducing the drive current applied to the motor to output torque in the tightening direction. This reduces the transmission of the motor's continuous tightening drive force to the operator's hand via the housing or motor casing during the pulse collision phase.

[0060] Controller and reaction avoidance strategy The controller is electrically connected to the motor and the torque sampling module. The controller is used to execute a reaction avoidance strategy based on the torque signal output by the torque sampling module.

[0061] The reaction avoidance strategy includes: determining whether the torque signal has reached the preset trigger condition; if the preset trigger condition is reached, it is determined that the part to be tightened has reached the collision state, and the drive current applied to the motor to make the output head output torque in the tightening direction is stopped or reduced.

[0062] In this embodiment, the object to be stopped or reduced is not necessarily the entire current of the motor, but rather the drive current used to output torque in the tightening direction. In other words, the controller can stop or reduce the forward drive action in the same direction as the tightening, thereby reducing the extent to which the motor continues to apply a continuous tightening force to the output head during the pulse collision phase.

[0063] Preset trigger conditions may include at least one of the following.

[0064] First, the torque signal reaches the preset collision torque threshold. That is, when the amplitude of the torque signal reaches the preset collision torque threshold, the controller determines that the part to be tightened has reached a collision state.

[0065] Second, the rate of change of the torque signal within the preset sampling window reaches the preset collision rate of change threshold. That is, when the torque signal rises rapidly within a short sampling window, the controller determines that a pulse collision has occurred in the torque transmission path.

[0066] Third, the torque signal remains within a preset collision torque range for a preset duration. This method avoids false triggering due to a single abnormal sampling point, improving the stability of collision state judgment.

[0067] Fourth, the torque signal and the motor speed change satisfy the preset collision correlation conditions. For example, when the torque signal rises rapidly and the motor speed signal decreases, changes abruptly, or reverses, it can be determined that a pulse collision has occurred at the end of the circumferential angular clearance A.

[0068] When the preset triggering conditions are met, the controller can stop or reduce the drive current applied to the motor to make the output head output torque in the tightening direction by at least one of the following methods: setting the motor torque command to zero; reducing the motor current command to below a preset ratio; turning off the motor drive output; or putting the motor into a low electromagnetic force output state.

[0069] In this way, under pulse collision conditions, the continuous driving force of the motor along the tightening direction is weakened, making it difficult for the reaction force generated by the part to be tightened to be superimposed with the continuous tightening force of the motor and transmitted to the housing and the operator's hand, thereby reducing the reaction force felt by the operator.

[0070] like Figure 5 As shown, during a pulse tightening test, the torque signal, speed signal, and current command of a low-reaction electric pulse tool are synchronously acquired. Figure 5 In the diagram, the upper curve represents the torque signal, the middle curve represents the speed signal, and the lower curve represents the current command. t1, t2, t3, and t4 represent different control moments during the pulse tightening process.

[0071] exist Figure 5 In the illustrated embodiment, time t1 corresponds to the moment when the controller determines, based on the torque signal or the trend of its change, that the preset triggering condition has been met. At time t1, the controller stops or reduces the drive current applied to the motor to cause the output head to output torque in the tightening direction, thus switching the current command from an active drive state to a low electromagnetic force output state or a stopped output state.

[0072] During the t1 to t2 stage, the drive current of the motor along the tightening direction has been stopped or reduced, and the motor rotor side can still generate circumferential relative rotation with respect to the part to be tightened within the allowable range of the circumferential angle clearance. Figure 5 In this case, the duration of the t1 to t2 phase can be approximately 4 ms. This value is only for a specific test case and is not intended to limit the scope of protection of this application.

[0073] During the period from t2 to t3, the speed signal drops rapidly or changes abruptly, while the torque signal rises rapidly and forms a pulse peak near t3. This phenomenon indicates that the torque transmission path between the motor rotor and the part to be tightened enters a pulse collision process during this period, the circumferential angular clearance is absorbed, and the relevant components transmit pulse torque to the part to be tightened at the end of the circumferential angular clearance. Figure 5 In this case, the duration of the t2 to t3 phase can be approximately 2.8 ms.

[0074] During the t3 to t4 phase, the torque signal gradually decreases from its peak value, the speed signal enters the recovery process after the collision, and the current command remains in a stopped or reduced state. Therefore, during the generation and decline of the torque peak, the motor does not continuously apply the drive current that outputs torque in the tightening direction, thereby reducing the superposition of the motor's continuous driving force and the pulse collision reaction force transmitted to the operator's hand through the housing or motor casing. Figure 5 In this case, the duration of the t3 to t4 phase can be approximately 10.1 ms.

[0075] After time t4, the controller can resume or reapply the current command according to the tightening process requirements, target torque status, or subsequent pulse control strategy, to execute the next pulse tightening or end the tightening process.

[0076] pass Figure 5 The test results show that the reaction avoidance strategy does not simply shut down the motor after tightening, but rather controls the drive current used to output torque in the tightening direction before and after the pulse collision torque is formed, stopping or reducing it. This control method can reduce the degree to which the continuous positive drive of the motor participates in the transmission of pulse collision reaction force, thereby achieving low reaction force operation.

[0077] It should be noted that, Figure 5 The time intervals t1 to t2, t2 to t3, and t3 to t4 shown are only examples under specific test conditions. The above time intervals may vary depending on the tool model, target torque, circumferential angular clearance, specifications of the part to be tightened, sampling frequency, and control parameters. Figure 5 This is used to illustrate the timing correspondence between torque signals, speed signals, and current commands, and is not intended to limit the scope of protection of this application. Continuous tightening mode and pulse tightening mode The controller has a continuous tightening mode and a pulse tightening mode.

[0078] In continuous tightening mode, the controller controls the motor to drive the output head to rotate continuously via the torque transmission mechanism. Continuous tightening mode is primarily used during the rapid screwing-in stage before the part to be tightened is seated. During this stage, the resistance to the part is relatively small, allowing the output head to continuously drive its rotation.

[0079] The controller determines whether the preset seating conditions have been met based on the torque signal. If the preset seating conditions are met, it is determined that the part to be tightened has reached the seating state, and the controller controls the motor to enter the pulse tightening mode to perform pulse tightening operation on the part to be tightened.

[0080] The preset seating condition can be different from the preset trigger condition. The preset seating condition is used to determine whether the part to be tightened has entered a contact or near-contact state from a low-load screw-in state; the preset trigger condition is used to determine whether a collision torque occurs or a collision state is entered during the pulse tightening process. In other words, the seating state can be used as the basis for switching from continuous tightening mode to pulse tightening mode, and the collision state can be used as the basis for stopping or reducing the drive current along the tightening direction in the reaction avoidance strategy.

[0081] In pulse tightening mode, when the rotation of the part to be tightened is restricted, the motor rotor can rotate circumferentially relative to the part and transmit pulse torque to the part at the end of the circumferential angle gap A. The controller continuously or periodically acquires the torque signal through the torque sampling module and executes a reaction avoidance strategy when the torque signal reaches the preset trigger condition.

[0082] Example 2:

[0083] A control method for a low-reaction electric pulse tool can be applied to the aforementioned low-reaction electric pulse tool. The control method includes the following steps.

[0084] S1 controls the motor to drive the output head to rotate through the torque transmission mechanism, and transmits the tightening torque to the part to be tightened through the output head.

[0085] Specifically, before the part to be tightened is seated, the controller can put the low-reaction electric pulse tool into continuous tightening mode. In continuous tightening mode, the controller controls the motor to drive the output head to rotate continuously through the torque transmission mechanism, so that the part to be tightened is screwed in quickly.

[0086] S2, when the rotation of the part to be tightened is restricted, the circumferential angle gap A in the torque transmission path between the motor rotor and the part to be tightened is used to make the motor rotor rotate relative to the part to be tightened in a circumferential direction, and transmit pulse torque to the part to be tightened at the end of the circumferential angle gap A.

[0087] Specifically, when the part to be tightened is in contact with the workpiece or subjected to the reaction force of the workpiece, the rotation of the part to be tightened is restricted. At this time, the rotor side of the motor can generate relative rotation within the circumferential angular gap A, and make contact or collision at the end of the gap, thereby generating a pulse torque acting on the side of the part to be tightened.

[0088] S3 outputs an analog signal corresponding to the reaction torque of the torque transmission mechanism through a static torque sensor.

[0089] The static torque sensor is positioned on the reaction force transmission path, so its output analog signal can reflect the change in the reaction torque experienced by the torque transmission mechanism.

[0090] S4, the torque signal is obtained by sampling the analog signal at a preset sampling frequency through the torque sampling module.

[0091] In one implementation, the torque sampling module converts the analog signal into a torque signal via an analog-to-digital converter. The preset sampling frequency can be determined based on the duration of the pulse collision phase and the rate of torque change.

[0092] S5 executes a reaction avoidance strategy based on the torque signal through the controller.

[0093] Specifically, the controller determines whether the torque signal has reached the preset trigger condition. If the preset trigger condition has not been reached, the controller continues to control according to the current tightening mode. If the preset trigger condition has been reached, the controller determines that the part to be tightened has reached a collision state and stops or reduces the drive current applied to the motor to make the output head output torque in the tightening direction.

[0094] S6, after executing the reaction avoidance strategy, the controller can continue to control the low reaction force electric pulse tool to perform subsequent pulse tightening or end the tightening process based on the target torque, torque signal or tightening process parameters.

[0095] In the above steps, the order of S1 to S6 can be adjusted according to the actual control process. For example, the analog signal acquisition of the static torque sensor and the sampling of the torque sampling module can be continuously executed in the continuous tightening mode and the pulse tightening mode; the reaction avoidance strategy can be judged for each collision torque in the pulse tightening mode.

[0096] Example 3:

[0097] In one specific embodiment, the low-reaction electric pulse tool may include the PHP.025 model and the PHP.050 model.

[0098] The PHP.025 model has an applicable torque range of 8 N·m to 25 N·m, a maximum output speed of 1800 rpm, and an output head size of Sq.3 / 8". The PHP.050 model has an applicable torque range of 10 N·m to 50 N·m, a maximum output speed of 2400 rpm, and an output head size of Sq.3 / 8".

[0099] In one specific embodiment, the PHP.025 model employs a servo motor and a planetary reduction gear mechanism. The planetary reduction gear mechanism has a speed ratio of 6.6, the motor's maximum speed limit is 13980 rpm, and the maximum output torque at the motor end is 1.5655 N·m. These parameters are merely examples of specific models and are not intended to limit the scope of protection of this application.

[0100] During the experiment, the correspondence between motor speed, output speed, and impact torque can be established. Table 1 shows one such correlation between impact speed and torque.

[0101]

[0102] Table 1: Relationship between impact speed and torque As shown in Table 1, in this specific embodiment, the impact torque generated at the output end increases accordingly with the increase of motor speed. The controller can select the corresponding motor speed or output strategy based on the target tightening torque and tool parameters. In practical applications, the values ​​in the table can be calibrated according to different tool models, different reduction ratios, different output head structures, and different working conditions of the parts to be tightened.

[0103] To verify the usability of the torque signal acquired by the static torque sensor during the continuous tightening phase, a continuous tightening accuracy test was conducted on a low-reaction electric pulse tool. During the test, the torque value inside the tool housing and the torque value measured by the external torque sensor were recorded respectively. The test results are shown in Table 2.

[0104]

[0105] Table 2: Results of continuous tightening accuracy test As shown in Table 2, during the continuous tightening test, the average torque of the chassis changes accordingly with the target torque, and the standard deviation is small. This indicates that the torque signal collected by the static torque sensor can be used for torque monitoring and seat status judgment during the continuous tightening phase. There is a difference between the torque value of the external sensor and the torque value of the chassis. This difference is related to the different detection positions and torque transmission paths of the two sensors and does not affect the use of the static torque sensor 5 to identify the seat status and execute the reaction avoidance strategy.

[0106] To verify the correspondence between the torque signal acquired by the static torque sensor and the target torque in pulse tightening mode, a pulse tightening accuracy test was conducted on a low-reaction electric pulse tool. During the test, the average torque value of the machine casing and the average torque value of the external torque sensor were recorded. The test results are shown in Table 3.

[0107]

[0108] Table 3: Results of Pulse Tightening Accuracy Test As shown in Table 3, there is a correlation between the average torque of the chassis and the target torque in the pulse tightening test, indicating that the torque signal collected by the static torque sensor can be used for torque monitoring during the pulse tightening process. The average torque of the external sensors is generally higher than that of the chassis, and the data fluctuation of the external sensors increases under higher target torques. This indicates a difference between the torque signal on the chassis side and the torque signal from the external sensor on the output side, caused by measurement position, impact response, and transmission path. In practical implementation, the chassis torque signal can be calibrated according to the tool model and process requirements to improve the stability of the final tightening control.

[0109] like Figure 4 As shown, during a pulse tightening test, the torque, speed, and angle signals of a low-reaction electric pulse tool are simultaneously acquired. Figure 4 In the diagram, the upper curve represents the torque variation, the middle curve represents the speed variation, and the lower curve represents the angle variation. The horizontal axis represents time.

[0110] Depend on Figure 4 It can be seen that after the part to be tightened transitions from the continuous screwing stage to the high-load tightening stage, the angle change curve gradually flattens out, indicating that the rotation of the part to be tightened is restricted. Simultaneously, the torque change curve exhibits multiple sharp pulses, and the speed change curve shows periodic fluctuations corresponding to the torque pulses. This test result demonstrates that when the rotation of the part to be tightened is restricted, there is circumferential relative motion in the torque transmission path between the motor rotor and the part to be tightened. Furthermore, after the circumferential angular gap is absorbed, pulse collisions are formed, thereby transmitting pulse torque to the part to be tightened.

[0111] Figure 4 The vertical dashed lines in the diagram represent the pulse collision identification window, while the horizontal dashed lines represent torque or speed reference values. Within this pulse collision identification window, the torque signal exhibits a rapid rise and peak change, while the speed signal synchronously shows abrupt or periodic changes. The controller can determine whether the torque signal meets preset trigger conditions based on the torque signal sampled by the torque sampling module at a preset sampling frequency. For example, it can determine whether the torque signal reaches a preset collision torque threshold, or whether the rate of change of the torque signal within the preset sampling window reaches a preset collision rate of change threshold, or combine the torque signal with changes in motor speed to determine whether preset collision correlation conditions are met.

[0112] When the controller according to Figure 4When the torque signal change of the type shown indicates that the part to be tightened has reached a collision state, the controller stops or reduces the drive current applied to the motor to output torque in the tightening direction. Therefore, during the pulse collision phase, the continuous drive action of the motor in the tightening direction is weakened, reducing the extent to which this continuous drive action and the pulse collision reaction force are transmitted to the operator's hand through the housing, motor housing, or handle. It should be noted that... Figure 4 The test waveforms shown are only used to illustrate the corresponding changes in torque, speed and angle during pulse tightening, and are not intended to limit the scope of protection of this application. Figure 4 The torque threshold, speed reference value, angle reference value, pulse collision identification window position, and specific values ​​of each curve can be calibrated according to the model of the electric pulse tool, the target torque, the structure of the torque transmission mechanism, the specifications of the part to be tightened, and the sampling frequency.

[0113] Taking the forward tightening of screws as an example, after the operator starts the low-reaction electric pulse tool, the controller controls the motor to drive the output head to rotate continuously through the torque transmission mechanism. The output head drives the part to be tightened into the workpiece through the bit.

[0114] Before the part to be tightened is seated, the low-reaction electric pulse tool is in continuous tightening mode. The controller acquires the torque signal obtained from the static torque sensor and torque sampling module, and determines whether the preset seating condition has been met based on the torque signal. When the preset seating condition is met, the controller determines that the part to be tightened has reached the seated state and controls the motor to enter pulse tightening mode.

[0115] In pulse tightening mode, the rotation of the part to be tightened is restricted, and the rotor side of the motor rotates relative to the part through a circumferential angular gap. When the circumferential angular gap is absorbed, the relevant components in the torque transmission path transmit pulse torque to the part to be tightened at the end of the gap. This pulse torque causes a short-term change in the analog signal output by the static torque sensor, and the torque sampling module samples this analog signal at a preset sampling frequency to obtain the torque signal.

[0116] The controller determines whether the torque signal has reached the preset trigger condition. When the torque signal reaches the preset trigger condition, the controller determines that the part to be tightened has reached a collision state and stops or reduces the drive current applied to the motor to make the output head output torque in the tightening direction. As a result, the continuous driving force of the motor in the tightening direction is reduced, making it less likely that the reaction force generated during the pulse collision phase will be superimposed with the continuous tightening force of the motor and transmitted to the housing and the operator's hand.

[0117] The embodiments described above do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the above embodiments should be included within the scope of protection of this technical solution.

Claims

1. A low-reaction electric pulse tool, characterized in that, include: Housing, motor, output head, torque transmission mechanism, static torque sensor, torque sampling module, and controller. The output head is used to engage with the part to be tightened; The motor is connected to the output head through the torque transmission mechanism and can transmit tightening torque to the part to be tightened via the output head; A circumferential angular gap for pulse tightening is formed in the torque transmission path between the rotor of the motor and the part to be tightened. The circumferential angular gap is used to allow the rotor of the motor to rotate circumferentially relative to the part to be tightened when the rotation of the part to be tightened is restricted, and to transmit pulse torque to the part to be tightened at the end of the circumferential angular gap. The static torque sensor is disposed on the reaction force transmission path between the torque transmission mechanism and the housing or the outer shell of the motor, and is used to output an analog signal corresponding to the reaction torque of the torque transmission mechanism; The torque sampling module is electrically connected to the static torque sensor and is used to sample the analog signal at a preset sampling frequency to obtain a torque signal. The controller is electrically connected to the motor and the torque sampling module; The controller is used to execute a reaction avoidance strategy based on the torque signal; The reaction avoidance strategy is to determine whether the torque signal reaches the preset trigger condition. If the preset trigger condition is reached, it is determined that the part to be tightened has reached the collision state, and the driving current applied to the motor to make the output head output torque in the tightening direction is stopped or reduced.

2. The low-reaction electric pulse tool according to claim 1, characterized in that, The preset triggering conditions include at least one of the following: The torque signal reaches a preset collision torque threshold. The rate of change of the torque signal within the preset sampling window reaches a preset collision change rate threshold. The torque signal is within a preset collision torque range for a preset duration; The torque signal and the change in the motor speed satisfy a preset collision correlation condition.

3. The low-reaction electric pulse tool according to claim 1, characterized in that, The stopping or reducing of the drive current applied to the motor to cause the output head to output torque in the tightening direction includes at least one of the following: Set the torque command of the motor to zero; Reduce the current command of the motor to below a preset ratio; Turn off the drive output of the motor; This puts the motor into a low electromagnetic force output state.

4. The low-reaction electric pulse tool according to claim 1, characterized in that, The controller has a continuous tightening mode and a pulse tightening mode; In the continuous tightening mode, the controller controls the motor to drive the output head to rotate continuously through the torque transmission mechanism; When the controller determines whether the preset seating condition has been met based on the torque signal, if the preset seating condition has been met, it determines that the part to be tightened has reached the seating state, and the controller controls the motor to enter the pulse tightening mode to perform pulse tightening operation on the part to be tightened.

5. The low-reaction electric pulse tool according to claim 1, characterized in that, The torque transmission mechanism includes a planetary reduction mechanism, which includes a sun gear, planet gears, a ring gear, and a planet carrier. The sun gear is connected to the rotor of the motor for transmission, the planet gears mesh with the sun gear and the ring gear, and the planet carrier is used to support the planet gears; The planetary carrier and the output head form the circumferential angular gap.

6. The low-reaction electric pulse tool according to claim 5, characterized in that, The planetary carrier includes a plurality of impact sections arranged circumferentially, and the output head includes an impact-bearing section corresponding to the impact section; The circumferential angular gap is formed between the plurality of impact parts, and the impact-bearing part is located within the circumferential angular gap; When the torque transmission mechanism rotates relative to the output head within the circumferential angular gap to the end of the gap, the impact part contacts the impact receiving part to transmit pulse torque to the output head.

7. The low-reaction electric pulse tool according to claim 1, characterized in that, The output head is connected to the part to be tightened via a screwdriver bit, and the circumferential angular gap is formed at least in part by a first mating angular gap between the output head and the screwdriver bit and / or a second mating angular gap between the screwdriver bit and the part to be tightened.

8. A control method for a low-reaction electric pulse tool, applied to the low-reaction electric pulse tool according to any one of claims 1 to 7, characterized in that, Specifically, the steps include the following: The motor is controlled to drive the output head to rotate through the torque transmission mechanism, and the tightening torque is transmitted to the part to be tightened through the output head; When the rotation of the part to be tightened is restricted, the circumferential angle gap in the torque transmission path between the rotor of the motor and the part to be tightened is used to make the rotor of the motor rotate circumferentially relative to the part to be tightened, and to transmit pulse torque to the part to be tightened at the end of the circumferential angle gap. The static torque sensor outputs an analog signal corresponding to the reaction torque of the torque transmission mechanism. The torque signal is obtained by sampling the analog signal at a preset sampling frequency using the torque sampling module. The controller executes a reaction avoidance strategy based on the torque signal; The reaction avoidance strategy includes: determining whether the torque signal reaches a preset trigger condition; if the preset trigger condition is reached, determining that the part to be tightened has reached a collision state, and stopping or reducing the driving current applied to the motor to make the output head output torque in the tightening direction.

9. The control method for a low-reaction electric pulse tool according to claim 8, characterized in that, The low-reaction electric pulse tool is controlled to have a continuous tightening mode and a pulse tightening mode; In the continuous tightening mode, the motor is controlled to drive the output head to rotate continuously through the torque transmission mechanism; Determine whether the preset seating conditions have been met based on the torque signal; If the preset seating condition is met, it is determined that the part to be tightened has reached the seating state, and the motor is controlled to enter the pulse tightening mode to perform a pulse tightening operation on the part to be tightened.

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