A riveting control method for high-strength ring groove rivets

Abstract

The present invention discloses a riveting control method for high-strength ring groove rivets. The riveting tool used for riveting includes a gun head assembly, a driving mechanism, a transmission mechanism, a power source and a control module arranged in the riveting tool housing; the riveting control adopts a PI adjustment algorithm, and implements a double closed-loop control method for the motor speed and the line current. During the riveting force receiving process, the riveting control is performed by detecting the relationship between the line current and the set value. The drive and transmission structure of the present invention adopt a planetary roller screw as a component for converting rotational motion into linear motion, and adopts a current control scheme to achieve the adjustment of the riveting force; the output tension of the riveting control method of the present invention can reach 70kN, which can effectively complete the riveting installation of ring groove rivets with a diameter of 12mm, and can select the riveting installation mode for rivets of different specifications and models. The input current of the motor can be adjusted to control the size of the motor torque, and finally the output tension of the tool can be adjusted.

Description

Technical Field

[0001] The invention belongs to the technical field of riveting and fastening, in particular to the technical field of design and production of handheld cordless electric tools, and particularly relates to a riveting control method for high-strength ring groove rivets. Background Art

[0002] Ring groove rivets are widely used in new energy, bridges, steel structure buildings and other fields. If hydraulic tools or pneumatic tools are used, they are limited by on-site working conditions, such as high altitude and high voltage power supply. These tools are often difficult to meet the use conditions. If cordless rechargeable electric riveting tools can be used for installation, these problems can be better solved. At present, the output tension of electric riveting tools at home and abroad is less than 30kN, which cannot meet the installation requirements of large diameter ring groove rivets. Summary of the invention

[0003] The present invention discloses a riveting control method for high-strength ring groove rivets in view of the deficiencies of the prior art. The present invention provides a riveting tool and a riveting control method thereof which can overcome the defects of the prior riveting tools in completing the riveting of high-strength ring groove rivets, adopts a movable electric drive, has a maximum riveting tension of 70kN, and can control different riveting modes.

[0004] The present invention is achieved through the following technical solutions:

[0005] A riveting control method for high-strength ring groove rivets, characterized in that:

[0006] The riveting tool used in the riveting includes a gun head assembly, a driving mechanism, a transmission mechanism, a power source and a control module arranged in a riveting tool housing;

[0007] The gun head assembly includes a claw and anvil for extrusion riveting of annular groove rivets; the power source is a detachable and rechargeable battery; the driving mechanism includes a DC motor, a motor-driven reduction box and a driving shaft; the transmission mechanism is a planetary roller screw transmission mechanism, the planetary roller screw shaft of the star roller screw transmission mechanism is coaxially driven and connected with the claw of the gun head assembly, and the planetary roller screw shaft is driven and connected with the driving shaft of the driving mechanism through gears installed respectively; the control module includes: STM32 main controller circuit, current sampling circuit, brushless DC motor drive circuit, Hall stroke protection circuit, overcurrent protection circuit, Hall limit circuit, and blocking protection circuit;

[0008] The riveting control adopts PI adjustment algorithm and implements double closed-loop control of motor speed and line current. During the riveting force receiving process, the riveting control is carried out by detecting the relationship between the line current and the set value.

[0009] The riveting control for short-tail ring groove rivets includes: setting the motor reversal current Ia and time t; when the anvil is against the ring, the force on the motor suddenly increases, and the current collected by the current sampling circuit surges. When the current is greater than the set current Ia, the main controller determines that the anvil has been against the ring, and the main controller starts timing. After t time, the main controller controls the drive circuit to drive the motor to brake and reverse until it reaches the front Hall limit, and all parameters are reset to complete the riveting.

[0010] The riveting control for the break-off type ring groove rivet includes: dividing the riveting process into the following time sequence: riveting combination section, ring bulging deformation section, ring bulging deformation rear section, anvil extrusion ring section, extrusion ring deformation rear section, break pre-tightening section, break rear section; obtaining the minimum first-order difference value K1 of the current in the ring bulging deformation rear section, obtaining the minimum first-order difference value K2 of the current in the extrusion ring deformation rear section, setting the first-order difference value of the current in the break rear section to K3, and making K3 less than or equal to K1 or K2; after the ring groove rivet is broken, the current drops sharply, and the main controller circuit performs a first-order difference operation on the collected current value. When the obtained first-order difference of the current is greater than the K3 value, the main controller determines that the riveting is completed, drives the motor to brake and reverse, until the front Hall limit is reached, and all parameters are reset to complete the riveting.

[0011] The planetary roller screw shaft of the present invention is arranged to be driven in parallel with the driving shaft.

[0012] Furthermore, the transmission mechanism also includes a roller planetary screw nut that cooperates with the planetary roller screw shaft drive, and a large gear is mounted on the outer periphery of the roller planetary screw nut; the diameter of the small gear mounted on the drive shaft of the driving mechanism is smaller than the diameter of the large gear, and the small gear mounted on the drive shaft is drivingly connected to the large gear mounted on the planetary screw nut.

[0013] Furthermore, a planar thrust roller bearing is arranged on the front end surface of the roller planetary screw nut, a thrust needle roller bearing is arranged on the rear end surface, and a group of needle roller bearings are arranged at the front and rear of the outer circumference.

[0014] Furthermore, a group of needle bearings are arranged at the front and rear of the outer periphery of the driving shaft.

[0015] The riveting tool used in the riveting control method of the present invention can have an output tension of up to 70kN, and can effectively complete the riveting installation of ring groove rivets with a diameter of 12mm; the present invention has a human-computer interaction interface, and can select the riveting installation mode for rivets of different specifications and models; the input current of the motor can be adjusted to control the size of the motor torque, and finally the output tension of the tool can be adjusted.

[0016] The drive and transmission structure of the present invention adopts a planetary roller screw as a component for converting rotational motion into linear motion, applies the planetary roller screw to the design of a handheld lithium-powered riveting tool, and adopts a current control scheme to adjust the riveting force. Compared with the ball screw used in conventional electric tools, the planetary roller screw shaft and the screw nut are in line contact, while the ball screw shaft and the screw nut are in point contact. Line contact has better force than point contact. For two screws of the same diameter, the planetary roller screw can theoretically reach three times the load capacity and six times the service life of an ordinary ball screw. Therefore, in the design of electric riveting tools with large pulling forces, a planetary roller screw with a smaller diameter can meet the design requirements and effectively reduce the weight of the whole machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the cross-sectional structure of the riveting tool of the present invention;

[0018] Figure 2 yes Figure 1 A partial enlarged schematic diagram;

[0019] Figure 3 This is a control block diagram of the short-tail rivet riveting of the present invention;

[0020] Figure 4 This is a control block diagram of the pull-off rivet riveting of the present invention;

[0021] Figures 5 to 8 This is a schematic diagram of the riveting process of short-tail ring groove rivets;

[0022] Fig. 9 It is a current variation curve diagram of the riveting process of the short-tail ring groove rivet of the riveting tool of the present invention;

[0023] Figures 10 to 13 It is a schematic diagram of the riveting process of the pull-off type ring groove rivet;

[0024] Fig.14 It is a curve diagram of current variation during the riveting process of the riveting tool of the present invention for pulling off the ring groove rivet.

[0025] In the figure, 1 is the claw, 2 is the anvil, 3 is the outer sleeve, 4 is the connecting shaft, 5 is the left end cover, 6 is the base, 7 is the steel ring, 8 is the needle bearing, 9 is the large gear, 10 is the needle bearing, 11 is the right end cover, 12 is the thrust needle bearing, 13 is the motor drive circuit board, 14 is the cooling fan, 15 is the steel ring, 16 is the LCD screen, 17 is the button, 18 is the motor, 19 is the control circuit board, 20 is the lithium battery, 21 is the switch, 22 is the reduction box, 23 is the button battery, 24 is the pinion, 25 is the LED lamp, 26 is the needle bearing, 27 is the roller planetary screw nut, 28 is the plane thrust roller bearing, 29 is the planetary roller screw shaft, T is the collar, G is the riveted workpiece, M is the rivet, F is the tension, t, t1 to t6 are the riveting time, and I is the current. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with specific implementation methods. The specific implementation methods are further descriptions of the principles of the present invention and do not limit the present invention in any way. Technologies that are the same or similar to the present invention do not exceed the scope of protection of the present invention.

[0027] Combined with the attached pictures.

[0028] The high-strength ring groove rivet riveting tool of the present invention is driven by a built-in storage battery and comprises a gun head assembly, a driving mechanism, a transmission mechanism, a power source and the like.

[0029] The gun head assembly comprises a clamping claw 1 and an anvil 2. The anvil 2 is fixedly arranged on an outer sleeve 3 of the gun body. The clamping claw 1 is connected to a transmission mechanism through a thread.

[0030] The power source is provided by a rechargeable lithium battery 20. The driving mechanism is a reduction motor 18 driven by the rechargeable lithium battery 20.

[0031] The transmission mechanism is a planetary roller screw transmission mechanism. The reduction motor 18 drives the planetary roller screw nut 27 to rotate through gear transmission, so that the planetary roller screw shaft 29 performs axial linear motion to generate pulling force or thrust.

[0032] The present invention adopts a planetary roller screw as a component for converting rotational motion into linear motion, applies the planetary roller screw to the design of a handheld lithium-powered riveting tool, and adopts a current control scheme to adjust the riveting force.

[0033] Compared with the ball screw transmission used in electric tools, the ball screw and the screw nut are point contact structures; in the riveting tool structure of the present invention, the planetary roller screw shaft 29 and the planetary roller screw nut 27 are line contact, and line contact has better force than point contact; for two screws of the same diameter, the planetary roller screw can theoretically reach three times the load capacity and six times the service life of the ordinary ball screw. In the design of the electric riveting tool with high pulling force of the present invention, a planetary roller screw with a smaller diameter can meet the design requirements and effectively reduce the weight of the whole machine.

[0034] The tool has a human-machine interactive interface, through which riveting parameters can be set, such as current size, riveting stroke, etc.

[0035] The control module of the present invention comprises an STM32 main controller circuit, a current sampling circuit, a brushless DC motor drive circuit, a Hall stroke protection circuit, an overcurrent protection circuit, a Hall limit circuit, and a blocking protection circuit.

[0036] The present invention designs different riveting control methods according to the riveting principles and riveting characteristics of different rivets.

[0037] like Figure 3 , Figures 5 to 9 As shown, for the riveting characteristics of short-tail ring groove rivets, in this example, in the riveting control method of short-tail ring groove rivets, a current value Ia and time t are set, such as the current value Ia set to 27A and the time t to 0.8s for 12mm rivets. The control principle block diagram is shown in Figure 3 As shown, the current sampling circuit transmits the collected current value Ib to the main controller. When Ib>Ia, the motor is controlled to continue running at constant power for t time. After the time is reached, the motor starts to brake and reverse, thereby achieving a precise riveting control.

[0038] like Fig. 9 As shown, Fig. 9 This is a current variation curve for the riveting process of short-tail ring groove rivets;

[0039] In the figure, the ordinate represents the current, the abscissa represents the riveting time, and the curve shows the change of the riveting current value with the riveting time.

[0040] Compared with the direct stroke control method, this control method has the following advantages: it can avoid excessive wear of the anvil and unstable rivet quality. In the existing riveting control, direct stroke control often cannot accurately determine whether the riveting is in place, resulting in possible wear of the anvil, increased friction, or high hardness of the rivet collar, which slows down the riveting speed and fails to meet the riveting quality requirements; or because the anvil is too large due to too many riveting, the inner wall of the anvil is pulled, or the collar is too soft, the riveting force is too small, and the riveting speed is accelerated, resulting in the tail teeth being broken.

[0041] like Figure 4 , Figures 10 to 14 As shown, for the break - off type grooved rivet, due to its different riveting structures and characteristics, the current change curve presented by the break - off type grooved rivet is as Fig.14 shown. The current is a discrete change amount. Taking the first - order difference of it, it can be seen from the figure that at the moment of break - off, that is, at time t5, its current value decreases instantaneously, and the first - order difference value k3 of its current is less than the minimum values k1 and k2 of the first - order difference at times t1 - t2 and t3 - t4, that is, k3 << k1 or k2. Therefore, according to the magnitude of the k3 value, it can be judged whether the rivet is broken, so as to quickly control the reverse rotation of the motor brake and achieve the purpose of automatic reverse rotation after break - off.

[0042] As Fig.14 shown, Fig.14 is the current change curve graph of the break - off type grooved rivet during the riveting process; the vertical coordinate represents the current, the horizontal coordinate represents the riveting time, the curve is the change of the riveting current value with the change of the riveting time, and the lower part of the figure is the first - order difference schematic diagram.

[0043] The working process of the riveting tool of the present invention is as follows: Press the start switch 21, the motor 18 is powered on and starts to run. After being decelerated by the reduction gearbox 22 to increase the torque, the planetary roller screw nut 27 is installed with the large gear 9. The large gear 9 meshes with the small gear 24 on the shaft of the reduction gearbox 22 for transmission, further decelerating to increase the torque of the screw nut 27. The rotation of the small gear 24 drives the rotation of the large gear 9, which drives the rotation of the planetary roller screw nut 27. The rotational motion is converted into the linear motion of the planetary roller screw shaft 29 through the planetary roller screw, so that the claw 1 generates a pulling force, and this pulling force acts on the grooved rivet. And the force is mutual, so the anvil 2 on the gun head generates a thrust force and squeezes the collar to deform. When the system detects that the current of the motor 18 reaches the preset value, the control module gives a signal and starts timing until the preset conditions in the program are reached, then the motor 18 brakes and reverses to the initial state, thus completing a riveting cycle.

[0044] Before using the riveting tool, install the lithium battery 20 on the base of the electric riveting tool, and then select the program on the parameter setting page according to the required rivets to be installed, and press the switch 21 button to install the grooved rivet.

[0045] When performing the riveting operation, first select the corresponding riveting mode according to different rivets through the 17 key; insert the claw 1 into the tail of the rivet to ensure that the pull groove inside the claw 1 engages with the pull groove at the tail of the rivet; hold down the switch 21 button, and the motor 18 is powered on and starts to run; through the power transmission of the driving mechanism and the transmission mechanism, the roller planetary screw shaft 29 generates Figure 5 or Fig.10Tension F in the direction indicated by the arrow; the roller planetary screw shaft 29 is threadedly connected to the connecting shaft 4, and the other end of the connecting shaft 4 is connected to the claw 1. In this process, when the claw 1 bites and pulls the rivet tail and moves upward, the anvil 2 presses against the outer edge of the collar, causing the anvil 2 to move in the opposite direction relative to the claw 1 and squeeze the collar surface. In the process of squeezing the collar, the force of the anvil 2 squeezing the collar and making it reach a certain deformation requirement is the riveting force, which is equal to the tension generated by the roller planetary screw shaft 29. The magnitude of the riveting force changes in real time and gradually increases. The current of the motor during the riveting process is detected by the current detection sensor on the motor drive circuit board, and the detected current value is fed back to the PLC program for data judgment: when the detected current value I and / or time t meet the set riveting mode, the motor 18 immediately brakes and reverses, and the roller planetary screw shaft 29 moves downward to cause the claw 1 to push the rivet out of the claw head 1, and the anvil 2 also detaches from the ring. At this point, the rivet installation is completed.

Claims

1. A riveting control method for high-strength ring groove rivets, characterized in that: The riveting tool used in the riveting includes a gun head assembly, a driving mechanism, a transmission mechanism, a power source and a control module arranged in a riveting tool housing; The gun head assembly includes a claw and anvil for extrusion riveting of annular groove rivets; the power source is a detachable and rechargeable battery; the driving mechanism includes a DC motor, a motor-driven reduction box and a driving shaft; the transmission mechanism is a planetary roller screw transmission mechanism, the planetary roller screw shaft of the planetary roller screw transmission mechanism is coaxially driven and connected with the claw of the gun head assembly, and the planetary roller screw shaft is driven and connected with the driving shaft of the driving mechanism through gears installed respectively; the control module includes: STM32 main controller circuit, current sampling circuit, brushless DC motor drive circuit, Hall stroke protection circuit, overcurrent protection circuit, Hall limit circuit, and blocking protection circuit; The riveting control adopts PI adjustment algorithm, and implements double closed-loop control of motor speed and line current. During the riveting force receiving process, the riveting control is carried out by detecting the relationship between the line current and the set value; The riveting control for short-tail ring groove rivets includes: setting the motor reversing current Ia and time t; when the anvil is against the collar, the force on the motor suddenly increases, and the current collected by the current sampling circuit surges. When the current is greater than the set current Ia, the main controller determines that the anvil has been against the collar, and the main controller starts timing. After t time, the main controller controls the drive circuit to drive the motor to brake and reverse until it reaches the Hall limit, and all parameters are reset to complete the riveting; The riveting control for the break-off type ring groove rivet includes: setting the riveting process in chronological order: riveting combination section, ring bulging deformation section, ring bulging deformation rear section, anvil extrusion ring section, extrusion ring deformation rear section, break pre-tightening section, break rear section; obtaining the minimum first-order difference value K1 of the current in the ring bulging deformation rear section, obtaining the minimum first-order difference value K2 of the current in the extrusion ring deformation rear section, setting the first-order difference value of the current in the break rear section to K3, and making K3 less than or equal to K1 or K2; after the ring groove rivet is broken, the current drops sharply, and the main controller circuit performs a first-order difference operation on the collected current value. When the obtained first-order difference of the current is greater than the K3 value, the main controller determines that the riveting is completed, and drives the motor to brake and reverse until the Hall limit is reached, and all parameters are reset to complete the riveting.

2. The riveting control method for high-strength ring groove rivets according to claim 1, characterized in that: The planetary roller screw shaft is arranged to be driven in parallel with the driving shaft.

3. The riveting control method for high-strength ring groove rivets according to claim 2, characterized in that: The transmission mechanism also includes a roller planetary screw nut that cooperates with the planetary roller screw shaft drive, and a large gear is mounted on the outer periphery of the roller planetary screw nut; the diameter of the small gear mounted on the drive shaft of the driving mechanism is smaller than the diameter of the large gear, and the small gear mounted on the drive shaft is drivingly connected to the large gear mounted on the planetary screw nut.

4. The riveting control method for high-strength ring groove rivets according to claim 3, characterized in that: The front end surface of the roller planetary screw nut is provided with a plane thrust roller bearing, the rear end surface is provided with a thrust needle roller bearing, and the outer periphery is provided with a group of needle roller bearings at the front and rear.

5. The riveting control method for high-strength ring groove rivets according to claim 3, characterized in that: A set of needle bearings are arranged at the front and rear of the outer periphery of the driving shaft.

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