A sewing machine thread trimming control method

Abstract

The application provides a sewing machine thread trimming control method, comprising the following steps: setting an electric control module, a main shaft, an encoder for detecting the angle of the main shaft and a thread trimming mechanism in the sewing machine, the angle of the main shaft having an encoder edge zero position, a needle stop position angle and a thread separation starting angle of the main shaft, all of which are determined by the encoder edge zero position; when the sewing is finished and the thread is trimmed, after the main shaft rotates through a third preset angle from the needle stop position angle of the last round, the electric control module controls the motor shaft of the thread trimming motor to rotate in a first direction, the avoiding unit of the thread trimming mechanism makes the thread trimming transmission mechanism and the moving cutter have no power transmission, and the sewing machine performs a thread loosening action; the main shaft continues to rotate the last round, when the main shaft rotates to the thread separation starting angle, the avoiding unit of the thread trimming mechanism makes the thread trimming transmission mechanism and the moving cutter have power transmission, and with the continuous rotation of the motor shaft of the thread trimming motor in the first direction, the thread trimming mechanism sequentially performs a thread separation action and a thread trimming action. The application can avoid the influence of the needle stop position angle of the main shaft on the starting time of the thread trimming mechanism, and ensure the stability of thread trimming.

Description

Technical Field

[0001] This invention relates to the field of sewing machines, and in particular to a method for controlling thread cutting in sewing machines. Background Technology

[0002] Currently, sewing machines are equipped with automatic thread trimming mechanisms to automatically trim the thread after sewing, thereby improving the automation level of the sewing machine.

[0003] For example, the specification of Chinese invention patent application No. 201710215982.X discloses an automatic thread-cutting mechanism for a sewing machine. It uses an electromagnet to drive a drive cam to move left and right, achieving the engagement and disengagement of a roller and the drive cam. During thread cutting, the electromagnet activates, causing the roller to engage with the cam surface of the drive cam. The lower shaft in the sewing machine then drives the drive cam to rotate, driving the moving blade to achieve thread separation and cutting. Therefore, this automatic thread-cutting mechanism is a mechanical cam-driven structure. The shape of the mating surface on the outer periphery of the cam controls the thread-cutting action and the subsequent reset. The starting time of thread separation and thread cutting is controlled by adjusting the circumferential position of the cam.

[0004] For example, Chinese invention patent application No. 201610153124.2 discloses a wire-cutting mechanism, which includes a fixed blade, a wire-cutting blade that reciprocates relative to the fixed blade, a rotating shaft with a fixed axis, a wire-cutting motor, a transmission mechanism connected between the wire-cutting motor and the rotating shaft, and another transmission mechanism connected between the transmission shaft and the wire-cutting blade. By controlling the movement of the wire-cutting motor, the start time of wire cutting and the speed of the wire cutting action can be controlled. This motor-driven wire-cutting method has the following drawbacks:

[0005] 1. The start time of thread trimming is linked to the needle stop position of the sewing machine's main spindle. The angle of the thread trimming motor at the start of trimming is affected by the needle stop position of the main spindle. That is, the zero position of the thread trimming motor is determined based on the needle stop position of the main spindle, thus controlling the start time of thread trimming. The needle stop position of the main spindle refers to the position where the needle in the sewing machine is in the upper or lower needle stop position when the main motor controls the main spindle to rotate to a specified position. However, when the needle stop position of the main spindle deviates, it will cause a corresponding deviation in the zero position of the thread trimming motor, which in turn leads to a corresponding deviation in the start time of thread trimming, resulting in unstable thread trimming and poor thread trimming quality. Furthermore, users should not redefine the needle stop position during use, otherwise it may easily lead to thread trimming malfunctions or even other functional failures.

[0006] 2. The starting and ending points of the thread cutting when the thread cutting motor controls the thread splitting (i.e., the thread cutting start point) are not completely related to the spindle angle. When the spindle speed changes during thread cutting, the speed of the lower spindle in the sewing machine also changes accordingly, resulting in a mismatch between the speed of the thread cutting motor and the speed of the lower spindle, which can easily lead to unstable thread cutting.

[0007] 3. Without a forced reset structure, when the wire cutting motor jams, the needle may collide with the wire cutter, causing the needle to break. Summary of the Invention

[0008] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a sewing machine thread cutting control method that controls the output of the thread cutting motor based on the signal from the main shaft encoder, thereby eliminating the influence of the main shaft needle stop position on the thread cutting control.

[0009] To achieve the above objectives, the present invention provides a sewing machine thread-cutting control method, comprising the following steps:

[0010] S1. An electronic control module, a main shaft, an encoder for detecting the angle of the main shaft, and a thread-cutting mechanism are installed in the sewing machine;

[0011] The encoder is communicatively connected to the electronic control module, and the angle of the spindle has an encoder edge zero position that is uniquely determined based on the encoder output signal;

[0012] The wire cutting mechanism includes a wire cutting motor, a wire cutting transmission mechanism, a moving blade, and a fixed blade. The wire cutting motor is connected to the moving blade through the wire cutting transmission mechanism and drives the moving blade to reciprocate in a direction that approaches or moves away from the fixed blade. The wire cutting transmission mechanism is provided with an avoidance unit. The wire cutting motor is communicatively connected to the electronic control module.

[0013] S2. Determine the spindle stop angle and the spindle branch start angle:

[0014] The spindle stop angle = encoder edge zero position + first preset angle.

[0015] The spindle's starting angle = encoder edge zero position + second preset angle.

[0016] The first preset angle and the second preset angle are both pre-stored in the electronic control module;

[0017] S3. When sewing is finished, the electronic control module receives the thread-cutting signal and performs the following control:

[0018] When the main shaft rotates for the last revolution, after the main shaft has rotated through a third preset angle from the stop needle position angle of the last revolution, the electronic control module controls the motor shaft of the thread cutting motor to rotate in the first direction. The avoidance unit of the thread cutting mechanism makes the thread cutting transmission mechanism and the moving knife have no power transmission, and at the same time the sewing machine performs the thread loosening action.

[0019] As the main shaft continues to rotate for the last revolution, when the main shaft rotates to the starting angle of the splitting, the avoidance unit of the wire cutting mechanism enables power transmission between the wire cutting transmission mechanism and the moving blade. As the motor shaft of the wire cutting motor continues to rotate in the first direction, the wire cutting mechanism sequentially performs the splitting action and the wire cutting action.

[0020] Furthermore, during the wire-cutting mechanism's wire-splitting action, the motor shaft angle of the wire-cutting motor corresponds one-to-one with the angle of the main shaft through a first fitting curve, which is pre-stored in the electronic control module.

[0021] Furthermore, during the wire-cutting action of the wire-cutting mechanism, the motor shaft angle of the wire-cutting motor corresponds one-to-one with the angle of the main shaft through a second fitting curve, and the second fitting curve is pre-stored in the electronic control module.

[0022] Furthermore, during the wire-cutting action of the wire-cutting mechanism, the motor shaft of the wire-cutting motor rotates at a preset angular velocity, which is pre-stored in the electrical control module.

[0023] Furthermore, the thread-cutting transmission mechanism includes a first crank fixed to the motor shaft of the thread-cutting motor, a first connecting rod, a lever with a fixed swing fulcrum, a connecting pin fixed to the lever, a second connecting rod, a thread-cutting shaft rotatably supported in the sewing machine base plate, a second crank and a thread-cutting crank respectively fixed to both ends of the thread-cutting shaft, a thread-cutting connecting rod, and a moving blade holder rotatably supported in the sewing machine base plate around the lower shaft of the sewing machine. One end of the first connecting rod is hinged to the first crank, and the other end has a groove that rotatably and slidably engages with the connecting pin. Both ends of the second connecting rod are hinged to the lever and the first crank respectively. Both ends of the thread-cutting connecting rod are hinged to the thread-cutting crank and the moving blade holder respectively. The moving blade is fixed on the moving blade holder. The groove on the first connecting rod constitutes an avoidance unit. The groove extends along the length direction of the first connecting rod, and its two ends are the first groove end and the second groove end, respectively.

[0024] Furthermore, the thread-cutting mechanism also includes a return torsion spring sleeved on the thread-cutting shaft, with its two ends connected to the thread-cutting crank and the sewing machine base plate, respectively.

[0025] Furthermore, the motor shaft angle of the wire cutting motor has a loosening area, a wire separating area and a wire cutting area connected sequentially from the zero position along a first direction, and a first idle stroke area, a retraction area and a second idle stroke area connected sequentially from the end of the wire cutting area along a second direction opposite to the first direction.

[0026] When the motor shaft of the wire shearing motor is in the zero position, the connecting pins are located in the slide groove and are separated from the ends of the first and second grooves.

[0027] When the motor shaft of the thread-cutting motor rotates from zero to the end of the loosening zone in the first direction, the connecting pin and the slide slide relative to each other until the connecting pin abuts against the end of the first groove, the moving knife remains stationary, and the sewing machine performs the loosening action;

[0028] When the motor shaft of the wire cutting motor rotates from the starting point of the wire dividing area to the ending point of the wire dividing area along the first direction, the connecting pin is always in contact with the end of the first groove. The wire cutting motor drives the moving blade to move closer to the fixed blade through the wire cutting transmission mechanism, and the wire cutting mechanism performs the wire dividing action.

[0029] When the motor shaft of the wire cutting motor rotates from the starting point of the wire cutting area to the ending point of the wire cutting area along the first direction, the connecting pin always abuts against the end of the first groove. The wire cutting motor drives the moving blade to move closer to the fixed blade through the wire cutting transmission mechanism until the moving blade and the fixed blade mesh, and the wire cutting mechanism performs the wire cutting action.

[0030] When the motor shaft of the wire-cutting motor rotates along the second direction from the end of the wire-cutting area to the end of the first idle stroke area, the connecting pin and the slide groove slide relative to each other until the connecting pin abuts against the end of the second groove.

[0031] When the motor shaft of the wire shearing motor rotates from the starting point of the retraction zone to the ending point of the retraction zone along the second direction, and from the starting point of the second idle stroke zone to the ending point of the second idle stroke zone along the second direction, the connecting pin is always in contact with the end of the second groove, and the wire shearing motor drives the moving blade to move away from the fixed blade through the wire shearing transmission mechanism.

[0032] When the motor shaft of the wire shearing motor rotates from the end of the second idle travel zone to the zero position along the first direction, the connecting pin and the slide groove slide relative to each other, and the moving blade remains stationary.

[0033] Furthermore, the sewing machine thread cutting control method further includes the following step S4: After the thread cutting mechanism completes the thread cutting action, the electronic control module controls the motor shaft of the thread cutting motor to rotate sequentially from the end point of the thread cutting area through the first empty stroke area and the retraction area along the second direction to the second empty stroke area, and then rotates along the first direction to the zero position.

[0034] Furthermore, the sewing machine thread cutting control method also includes the following step S5: when the sewing machine is powered on, the electronic control module controls the motor shaft of the thread cutting motor to rotate from the zero position to the second idle travel area along the second direction, and then rotates back to the zero position along the first direction.

[0035] As described above, the sewing machine thread-cutting control method of the present invention has the following beneficial effects:

[0036] In this application, the starting angle of wire splitting when the wire cutting mechanism starts to perform the wire splitting action is determined according to the zero position of the encoder edge of the main shaft. The zero position of the encoder edge of the main shaft is determined by the mechanical position of the grating plate in the encoder, thereby eliminating the influence of the stop needle position angle of the main shaft on the starting time of the wire cutting mechanism (i.e. the starting time of wire splitting) and ensuring the stability of wire cutting. Attached Figure Description

[0037] Figure 1 and Figure 2 These are schematic diagrams of the wire-cutting mechanism in this application from different perspectives.

[0038] Figure 3 This is a schematic diagram showing the relationship between the spindle angle and the motor shaft angle of the wire shearing motor in this application.

[0039] Figure 4 This diagram illustrates the relationship between the spindle angle and the motor shaft angle of the wire-cutting motor during the wire-separating and wire-cutting actions of the wire-cutting mechanism. In this diagram, the horizontal axis represents the spindle angle, and the vertical axis represents the motor shaft angle of the wire-cutting motor.

[0040] Figure 5 This is a flowchart illustrating the sewing machine thread-cutting control method in this application.

[0041] Component designation explanation

[0042] 10 Wire Cutting Motor

[0043] 20. Surgery

[0044] 30 Fixed tool

[0045] 40 First Crank

[0046] 50 First Link

[0047] 51 Slide

[0048] 52 First groove end

[0049] 53 Second groove end

[0050] 60 leverage

[0051] 70 connecting pin

[0052] 80 Second Link

[0053] 90 thread cutter spool

[0054] 110 Second Crank

[0055] 120 Wire Cutting Crank

[0056] 130 Wire Cutting Rod

[0057] 140 Moving tool holder

[0058] 150 motor mount Detailed Implementation

[0059] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0060] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and objectives of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0061] This application provides a sewing machine, and more particularly a sewing machine thread-cutting control method for the sewing machine, wherein the sewing machine is a flatbed sewing machine. The sewing machine thread-cutting control method of this application includes the following steps:

[0062] Step S1: The sewing machine is equipped with an electronic control module, a main shaft, a main motor, an encoder for detecting the main shaft angle, and a thread-cutting mechanism. The main motor shaft is fixedly connected to the main shaft via a coupling, directly driving the main shaft rotation. The main motor communicates with the electronic control module, which controls the main shaft angle by controlling the main motor's output. The encoder includes a grating plate fixed to the main shaft and an optical coupler fixed to the machine housing. The grating plate includes a perforated section with multiple grating holes and a non-perforated section. The optical coupler and the grating plate cooperate, and the optical coupler communicates with the electronic control module. The main shaft angle corresponds to the encoder edge zero position α1 when the optical coupler detects the end of the perforated section of the grating plate. Therefore, after the grating plate is fixed to the main shaft, the encoder edge zero position α1 of the main shaft is uniquely determined by the mechanical mounting position of the grating plate. The main shaft angle has an encoder edge zero position α1 uniquely determined by the encoder output signal. Further, as... Figure 1 and Figure 2 As shown, the thread-cutting mechanism includes a thread-cutting motor 10, a thread-cutting transmission mechanism, a moving blade 20, and a fixed blade 30 fixed to the base plate of the sewing machine. The thread-cutting motor 10 is connected to the moving blade 20 through the thread-cutting transmission mechanism and drives the moving blade 20 to reciprocate in the direction of approaching or moving away from the fixed blade 30. The thread-cutting transmission mechanism is provided with an avoidance unit. The thread-cutting motor 10 is communicatively connected to the electronic control module. In this embodiment, the moving blade 20 moves by rotating around the lower shaft of the sewing machine.

[0063] Step S2: The encoder edge zero position α1 of the main shaft is uniquely determined. Therefore, the needle stop angle α2 and the thread splitting start angle α3 of the main shaft are determined based on the encoder edge zero position α1. The needle stop angle α2 refers to the main shaft angle corresponding to when the sewing machine needle stops above or below the needle plate. The needle stopping above the needle plate is the upper needle stop position, and the needle stopping below the needle plate is the lower needle stop position. In the following embodiments, the needle stop angle α2 of the main shaft always refers to the upper needle stop position. The thread splitting start angle α3 of the main shaft refers to the main shaft angle corresponding to when the moving blade 20 in the thread cutting mechanism begins to move towards the fixed blade 30. The movement of the moving blade 20 towards the fixed blade 30 in the thread cutting mechanism is also the thread cutting start time of the thread cutting mechanism, which is also the start time when the thread cutting mechanism performs the thread splitting action. Preferably, the determination method of the upper needle stop angle α2 and the thread splitting start angle α3 of the main shaft is as follows: Figure 3 As shown, the upper stop needle position angle α2 of the spindle is equal to the encoder edge zero position α1 + the first preset angle c1, and the spindle branch line starting angle α3 is equal to the encoder edge zero position α1 + the second preset angle c2. The first preset angle c1 and the second preset angle c2 are both pre-stored in the electronic control module.

[0064] Step S3, when sewing is finished, such as Figure 3 and Figure 5 As shown, the electronic control module receives the wire-cutting signal and performs the following control:

[0065] When the main shaft rotates for the last revolution, after the main shaft has rotated from the upper needle stop position angle α2 of the last revolution through a third preset angle c3, the electronic control module controls the motor shaft of the thread cutting motor 10 to rotate along the first direction. The third preset angle c3 is pre-stored in the electronic control module. First, the avoidance unit of the thread cutting mechanism ensures that there is no power transmission between the thread cutting transmission mechanism and the moving blade 20, so the moving blade 20 remains stationary, and the sewing machine performs the thread loosening action. Then, the main shaft continues to rotate for the last revolution. When the main shaft rotates along the first direction to the thread splitting starting angle α3, the avoidance unit of the thread cutting mechanism ensures that there is just enough power transmission between the thread cutting transmission mechanism and the moving blade 20. As the motor shaft of the thread cutting motor 10 continues to rotate along the first direction, the thread cutting motor 10 drives the moving blade 20 to rotate closer to the fixed blade 30 through the thread cutting transmission mechanism. The thread cutting mechanism sequentially performs the thread splitting action and the thread cutting action. The end point of the thread splitting action of the thread cutting mechanism is also the starting point of its thread cutting action.

[0066] In this application, the starting angle α3 for the wire cutting mechanism to start performing the wire splitting action is determined based on the encoder edge zero position α1 of the main shaft. The encoder edge zero position α1 of the main shaft is determined by the mechanical position of the grating plate in the encoder, thereby eliminating the influence of the upper stop needle position angle α2 of the main shaft on the wire cutting start time of the wire cutting mechanism (i.e., the start time of starting wire splitting). Regardless of how the upper stop needle position angle α2 of the main shaft is defined during production or use, the timing of the wire cutting mechanism starting to split can be precisely controlled, thereby ensuring the stability of wire cutting.

[0067] Furthermore, the preferred structure of the wire-cutting transmission mechanism is as follows: Figure 1 and Figure 2 As shown, the thread-cutting transmission mechanism includes a motor base 150 fixed to the sewing machine housing, a first crank 40 fixed to the motor shaft of the thread-cutting motor 10, a first connecting rod 50, a lever 60 with a fixed swing fulcrum, a connecting pin 70 fixed at the middle position of the lever 60, a second connecting rod 80, a thread-cutting shaft 90 rotatably supported in the sewing machine base plate, a second crank 110 and a thread-cutting crank 120 respectively fixed to the right and left ends of the thread-cutting shaft 90, a thread-cutting connecting rod 130, and a moving blade holder 140 rotatably supported in the sewing machine base plate around the lower shaft of the sewing machine; the thread-cutting motor 10 is fixed to the motor base 150; the right end of the lever 60 is hinged to the motor base 150 by a shaft screw extending forward and backward, and the hinge point of the lever 60 and the motor base 150 constitutes the fixed swing fulcrum of the lever 60; the first The upper end of the connecting rod 50 is hinged to the first crank 40. The lower end of the first connecting rod 50 is provided with a groove 51 extending along the length of the first connecting rod 50. The connecting pin 70 passes through the groove 51 and is rotatably and slidably engaged with the groove 51. The upper end of the second connecting rod 80 is hinged to the left end of the lever 60 by a axial screw extending forward and backward. The lower end of the second connecting rod 80 is hinged to the first crank 40 by a axial screw extending left and right. Therefore, the second connecting rod 80 is a spatial connecting rod with a twisted part in the middle. The two ends of the wire cutting connecting rod 130 are respectively hinged to the wire cutting crank 120 and the moving blade holder 140 by axial screws extending left and right. The moving blade 20 is fixed on the moving blade holder 140. The groove 51 on the first connecting rod 50 constitutes an avoidance unit. The upper and lower ends of the groove 51 are the first groove end 52 and the second groove end 53, respectively.

[0068] When the electrical control module controls the motor shaft of the wire-cutting motor 10 to rotate in the first direction, the wire-cutting motor 10 drives the first connecting rod 50 to move downwards via the first crank 40. After the first groove end 52 at the upper end of the first connecting rod 50 abuts against the connecting pin 70, the downward-moving first connecting rod 50 transmits power to the lever 60, ultimately driving the moving blade 20 to rotate towards the fixed blade 30. Therefore, the first direction in which the motor shaft of the wire-cutting motor 10 rotates is the wire-cutting direction. The direction opposite to the first direction is defined as the second direction. When the electrical control module controls the motor shaft of the wire-cutting motor 10 to rotate in the second direction, the wire-cutting motor 10 drives the first connecting rod 50 to move upwards via the first crank 40. After the second groove end 53 at the lower end of the first connecting rod 50 abuts against the connecting pin 70, the upward-moving first connecting rod 50 transmits power to the lever 60, ultimately driving the moving blade 20 to rotate away from the fixed blade 30. Therefore, the second direction in which the motor shaft of the wire-cutting motor 10 rotates is the blade-resetting direction. In addition, the thread cutting mechanism also includes a return torsion spring sleeved on the thread cutting shaft 90. The two ends of the return torsion spring are connected to the thread cutting crank 120 and the sewing machine base plate, respectively. When the thread cutting motor 10 drives the moving blade 20 to rotate closer to the fixed blade 30 through the thread cutting transmission mechanism, the return torsion spring is in an energy storage state. Thus, when the thread cutting motor 10 drives the moving blade 20 to rotate away from the fixed blade 30 through the thread cutting transmission mechanism, the return spring releases its energy and transmits torque to the moving blade holder 140 and the moving blade 20 through the thread cutting crank 120 and the thread cutting connecting rod 130, driving the moving blade 20 to rotate away from the fixed blade 30 for reset.

[0069] Furthermore, such as Figure 5As shown, during the operation of the sewing machine, the motor shaft of the thread-cutting motor 10 is in its initial position. The initial position of the motor shaft of the thread-cutting motor 10 is defined as the zero position T. At this time, the connecting pin 70 is located in the slide groove 51 and is separated from the end of the first groove 52 and the end of the second groove 53. In addition, the motor shaft angle of the wire-cutting motor 10 includes not only the zero position T, but also the wire loosening area X1, the wire splitting area X2, and the wire cutting area X3 connected sequentially from the zero position T along the first direction, and the first idle travel area X4, the tool retraction area X5, and the second idle travel area X6 connected sequentially from the end of the wire cutting area X3 along the second direction opposite to the first direction; the starting point of the wire loosening area X1 is the zero position T, the end of the wire loosening area X1 and the starting point of the wire splitting area X2 are both θ1, the end of the wire splitting area X2 and the starting point of the wire cutting area X3 are both θ2, the end of the wire cutting area X3 and the starting point of the first idle travel area X4 are both θ3, the end of the first idle travel area X4 and the starting point of the tool retraction area X5 are both θ4, the end of the tool retraction area X5 and the starting point of the second idle travel area X6 are both the zero position T, and the end of the second idle travel area X6 is θ5. When the electrical control module controls the wire cutting mechanism to cut the wire, the motor shaft of the wire cutting motor 10 starts from the zero position T and first rotates along the first direction to pass through the loose wire area X1, the wire separating area X2 and the wire cutting area X3 in sequence. Then, from the end point of the wire cutting area X3, it rotates along the second direction to pass through the first idle stroke area X4 and the retraction area X5 in sequence. The specific process is as follows.

[0070] First, as the motor shaft of the thread-cutting motor 10 rotates along the first direction from the zero position T to the end point θ1 of the loosening zone X1, the first connecting rod 50 moves downward, causing the connecting pin 70 to slide relative to the slide groove 51, while the moving blade 20 remains stationary, and the sewing machine performs the loosening action. When the motor shaft of the thread-cutting motor 10 rotates to the end point θ1 of the loosening zone X1, the connecting pin 70 just abuts against the end 52 of the first groove at the upper end of the slide groove 51, and the sewing machine has completed the loosening action.

[0071] Second, as the motor shaft of the wire-cutting motor 10 rotates along the first direction from the starting point θ1 to the ending point θ2 of the dividing area X2, the first connecting rod 50 moves downward, and the connecting pin 70 is always in contact with the end 52 of the first groove. Power is constantly transmitted between the first connecting rod 50 and the lever 60. Therefore, the wire-cutting motor 10 drives the moving blade 20 to move closer to the fixed blade 30 through the wire-cutting transmission mechanism, and the wire-cutting mechanism performs the wire-separating action. When the motor shaft of the wire-cutting motor 10 rotates to the ending point θ2 of the dividing area X2, the wire separation ends.

[0072] Third, as the motor shaft of the thread-cutting motor 10 rotates along the first direction from the starting point θ2 to the ending point θ3 of the thread-cutting area X3, the first connecting rod 50 moves downward, and the connecting pin 70 is always in contact with the end 52 of the first groove. Power is always transmitted between the first connecting rod 50 and the lever 60. Therefore, the thread-cutting motor 10 drives the moving blade 20 to continue moving closer to the fixed blade 30 through the thread-cutting transmission mechanism, and the thread-cutting mechanism performs the thread-cutting action. When the motor shaft of the thread-cutting motor 10 rotates to the ending point θ3 of the thread-cutting area X3, the moving blade 20 and the fixed blade 30 engage, cutting the thread, and the thread-cutting ends.

[0073] Fourth, as the motor shaft of the wire-cutting motor 10 rotates along the second direction from the end point θ3 of the wire-cutting zone X3 to the end point θ4 of the first idle stroke zone X4, the first connecting rod 50 moves upward, the connecting pin 70 slides relative to the slide groove 51, and the moving blade 20 slowly moves along the second direction under the release force of the return spring. When the motor shaft of the wire-cutting motor 10 rotates to the end point θ4 of the first idle stroke zone X4, the connecting pin 70 just abuts against the end of the second groove 53 at the lower end of the slide groove 51.

[0074] Fifth, during the process of the motor shaft of the wire cutting motor 10 rotating from the starting point θ4 of the retraction zone X5 to the zero position T along the second direction, the first connecting rod 50 moves upward, the connecting pin 70 always abuts against the end 53 of the second groove, and there is always power transmission between the first connecting rod 50 and the lever 60. Then the wire cutting motor 10 drives the moving blade 20 to move away from the fixed blade 30 through the wire cutting transmission mechanism, and the wire cutting mechanism performs the retraction action.

[0075] Furthermore, in order to achieve a greater repositioning effect for the moving tool 20, this application provides the following two preferred tool retraction methods:

[0076] Method 1, such as Figure 5As shown, the sewing machine thread cutting control method also includes the following step S4: After the thread cutting mechanism completes the thread cutting action, the electronic control module controls the motor shaft of the thread cutting motor 10 to rotate sequentially from the end point θ3 of the thread cutting area X3 through the first idle stroke area X4 and the retraction area X5 along the second direction, and then continue to rotate into the second idle stroke area X6, and then rotate back to the zero position T along the first direction. Thus, during the process of the motor shaft of the thread cutting motor 10 continuing to rotate from the zero position T to the end point θ5 of the second idle stroke area X6 along the second direction, the first connecting rod 50 moves upward, and the connecting pin 70 always abuts against the end 53 of the second groove at the lower end of the slide groove 51. There is always power transmission between the first connecting rod 50 and the lever 60, so the thread cutting motor 10 drives the moving blade 20 to continue moving away from the fixed blade 30 through the thread cutting transmission mechanism, and the thread cutting mechanism continues to perform the retraction action, thereby obtaining a greater resetting effect of the moving blade 20 and avoiding blade jamming. Subsequently, the motor shaft of the wire-cutting motor 10 rotates along the first direction from the end point θ5 of the second idle travel zone X6 to the zero position T. The first connecting rod 50 moves downwards, and the connecting pin 70 slides relative to the slide groove 51, while the moving blade 20 remains stationary. When the motor shaft of the wire-cutting motor 10 rotates to the zero position T, the connecting pin 70 is located at the middle position of the slide groove 51, separating from both the first groove end 52 and the second groove end 53 at both ends of the slide groove 51. The moving blade 20 remains in a state away from the fixed blade 30.

[0077] Method 2, such as Figure 5 As shown, the thread-cutting motor 10 is also used to drive the presser foot lifting mechanism in the sewing machine. The motor shaft angle of the thread-cutting motor 10 correspondingly includes the presser foot lifting area X7. The second idle stroke area X6 and the presser foot lifting area X7 are sequentially connected along the second direction. The starting point of the presser foot lifting area X7 is θ5, and the ending point is θ6. The sewing machine thread-cutting control method also includes the following step S6: After the thread-cutting mechanism completes the thread-cutting action, the electronic control module controls the motor shaft of the thread-cutting motor 10 to rotate along the second direction from the end point θ3 of the thread-cutting area X3, sequentially passing through the first idle stroke area X4, the retraction area X5, and the second idle stroke area X6, and then directly rotates to a turning angle value within the presser foot lifting area X7. Thus, the motor shaft of the thread-cutting motor 10 starts from the starting point θ4 of the retraction zone X5, and there is always power transmission between the first link 50 and the lever 60 until it reaches the starting point θ5 of the presser foot lifting zone X7. The first link 50 separates from the lever 60, and the thread-cutting crank 120 returns to its initial position through the return spring. In addition, it can also make the thread-cutting presser foot of the sewing machine respond faster.

[0078] Furthermore, such as Figure 5As shown, the sewing machine thread-cutting control method further includes the following step S5: When the sewing machine is powered on, the electronic control module controls the motor shaft of the thread-cutting motor 10 to rotate from zero position T to the second idle travel area X6 along the second direction, and then rotates back to zero position T along the first direction. Thus, during the rotation of the motor shaft of the thread-cutting motor 10 from zero position T to the second idle travel area X6 along the second direction, the first connecting rod 50 moves upward. First, the connecting pin 70 slides relative to the slide groove 51; second, when the connecting pin 70 abuts against the second groove end 53 at the lower end of the slide groove 51, the thread-cutting motor 10 drives the moving blade 20 to move away from the fixed blade 30 through the thread-cutting transmission mechanism, achieving forced reset of the moving blade 20 upon power-on, preventing the moving blade 20 from being in a jammed position. Afterward, the motor shaft of the thread-cutting motor 10 rotates to zero position T along the first direction, the first connecting rod 50 moves downward, the connecting pin slides relative to the slide groove 51, and the moving blade 20 remains stationary, maintaining a state away from the fixed blade 30.

[0079] Furthermore, during the initial thread separation process of the flatbed sewing machine, the relative positions of the moving blade 20 and the rotary hook in the sewing machine have important requirements. The position of the moving blade 20 is determined by the motor shaft angle of the thread-cutting motor 10, and the position of the rotary hook is determined by the lower shaft angle of the sewing machine, which in turn is determined by the main shaft angle. Therefore, in this application, during the thread separation action of the thread-cutting mechanism, the motor shaft angle of the thread-cutting motor 10 corresponds one-to-one with the main shaft angle, thereby ensuring the relative position between the moving blade 20 and the rotary hook and improving the accuracy and stability of thread cutting. Based on this, this application provides the following two preferred methods:

[0080] Method 1 is a fully follow-up type. Specifically, such as... Figure 4 As shown, during the wire-cutting mechanism's wire-splitting action, i.e., as the motor shaft angle of the wire-cutting motor 10 rotates from θ1 to θ2, the motor shaft angle of the wire-cutting motor 10 corresponds one-to-one with the angle of the main shaft through a first fitting curve, which is pre-stored in the electronic control module; the first fitting curve can be a linear curve or a fitted linear curve. During the wire-cutting mechanism's wire-cutting action, i.e., as the motor shaft angle of the wire-cutting motor 10 rotates from θ2 to θ3, the motor shaft angle of the wire-cutting motor 10 corresponds one-to-one with the angle of the main shaft through a second fitting curve, which is pre-stored in the electronic control module; the second fitting curve can be a linear curve or a fitted linear curve.

[0081] Method two is a semi-follower type. Specifically, such as... Figure 4As shown, during the wire-cutting mechanism's wire-splitting action, i.e., as the motor shaft angle of the wire-cutting motor 10 rotates from θ1 to θ2, the motor shaft angle of the wire-cutting motor 10 corresponds one-to-one with the angle of the main shaft through a first fitting curve, which is pre-stored in the electronic control module; the first fitting curve can be a linear curve or a fitted linear curve. During the wire-cutting mechanism's wire-cutting action, i.e., as the motor shaft angle of the wire-cutting motor 10 rotates from θ2 to θ3, the motor shaft of the wire-cutting motor 10 rotates at a preset angular velocity to complete the engagement of the moving blade 20 and the fixed blade 30; this preset angular velocity is also pre-stored in the electronic control module. In other words, during the wire-cutting action, the motor shaft angle of the wire-cutting motor 10 no longer has a one-to-one correspondence with the main shaft angle.

[0082] In summary, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0083] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A sewing machine thread-cutting control method, characterized in that: Includes the following steps: S1. An electronic control module, a main shaft, an encoder for detecting the angle of the main shaft, and a thread-cutting mechanism are installed in the sewing machine; The encoder is connected to the electronic control module. The angle of the spindle has an encoder edge zero position that is uniquely determined according to the encoder output signal. The wire cutting mechanism includes a wire cutting motor (10), a wire cutting transmission mechanism, a moving blade (20), and a fixed blade (30). The wire cutting motor (10) is connected to the moving blade (20) through the wire cutting transmission mechanism and drives the moving blade (20) to reciprocate in the direction of approaching or moving away from the fixed blade (30). The wire cutting transmission mechanism is provided with a clearance unit. The wire cutting motor (10) is connected to the electronic control module. S2. Determine the spindle stop angle and the spindle branch start angle: The spindle stop angle = encoder edge zero position + first preset angle. The spindle's starting angle = encoder edge zero position + second preset angle. The first preset angle and the second preset angle are both pre-stored in the electronic control module; S3. When sewing is finished, the electronic control module receives the thread-cutting signal and performs the following control: When the main shaft rotates for the last revolution, after the main shaft has rotated through a third preset angle from the stop needle position angle of the last revolution, the electrical control module controls the motor shaft of the thread cutting motor (10) to rotate in the first direction. The avoidance unit of the thread cutting mechanism makes the thread cutting transmission mechanism and the moving knife (20) have no power transmission. At the same time, the sewing machine performs the thread loosening action. The main shaft continues to rotate for the last revolution. When the main shaft rotates to the starting angle of the splitting, the avoidance unit of the wire cutting mechanism enables power transmission between the wire cutting transmission mechanism and the moving blade (20). As the motor shaft of the wire cutting motor (10) continues to rotate in the first direction, the wire cutting mechanism sequentially performs the splitting action and the wire cutting action.

2. The sewing machine thread-cutting control method according to claim 1, characterized in that: During the wire cutting mechanism's wire splitting action, the angle of the motor shaft of the wire cutting motor (10) corresponds one-to-one with the angle of the main shaft through a first fitting curve, which is pre-stored in the electrical control module.

3. The sewing machine thread-cutting control method according to claim 2, characterized in that: During the wire cutting action of the wire cutting mechanism, the angle of the motor shaft of the wire cutting motor (10) corresponds one-to-one with the angle of the main shaft through the second fitting curve, and the second fitting curve is pre-stored in the electrical control module.

4. The sewing machine thread cutting control method according to claim 2, characterized in that: During the wire cutting action of the wire cutting mechanism, the motor shaft of the wire cutting motor (10) rotates at a preset angular velocity, which is pre-stored in the electrical control module.

5. The sewing machine thread cutting control method according to claim 1, characterized in that: The thread-cutting transmission mechanism includes a first crank (40) fixed on the motor shaft of the thread-cutting motor (10), a first connecting rod (50), a lever (60) with a fixed swing fulcrum, a connecting pin (70) fixed on the lever (60), a second connecting rod (80), a thread-cutting shaft (90) rotatably supported in the sewing machine base plate, a second crank (110) and a thread-cutting crank (120) respectively fixed at both ends of the thread-cutting shaft (90), a thread-cutting connecting rod (130), and a moving blade holder (140) rotatably supported in the sewing machine base plate around the lower shaft of the sewing machine. One end of the first connecting rod (50) is connected to the first crank. The handle (40) is hinged, and the other end is provided with a groove (51) that is rotatably and slidably engaged with the connecting pin (70). The two ends of the second connecting rod (80) are respectively hinged to the lever (60) and the first crank (40). The two ends of the wire cutting connecting rod (130) are respectively hinged to the wire cutting crank (120) and the moving blade holder (140). The moving blade (20) is fixed on the moving blade holder (140). The groove (51) on the first connecting rod (50) constitutes a clearance unit. The groove (51) extends along the length direction of the first connecting rod (50), and the two ends are the first groove end (52) and the second groove end (53) respectively.

6. The sewing machine thread-cutting control method according to claim 5, characterized in that: The thread cutting mechanism also includes a reset torsion spring sleeved on the thread cutting shaft (90), and the two ends of the reset torsion spring are respectively connected to the thread cutting crank (120) and the sewing machine base plate.

7. The sewing machine thread cutting control method according to claim 5, characterized in that: The motor shaft angle of the wire cutting motor (10) has a loose wire area, a wire splitting area and a wire cutting area connected sequentially from the zero position along a first direction, and a first idle stroke area, a retraction area and a second idle stroke area connected sequentially from the end of the wire cutting area along a second direction opposite to the first direction. When the motor shaft of the wire cutting motor (10) is in the zero position, the connecting pin (70) is located in the slide groove (51) and is separated from the first groove end (52) and the second groove end (53); When the motor shaft of the thread-cutting motor (10) rotates from zero to the end of the loosening zone in the first direction, the connecting pin (70) and the slide (51) slide relative to each other until the connecting pin (70) abuts against the end (52) of the first groove, the moving knife (20) remains stationary, and the sewing machine performs the loosening action; When the motor shaft of the wire cutting motor (10) rotates from the starting point of the dividing area to the ending point of the dividing area along the first direction, the connecting pin (70) always abuts against the end of the first groove (52). The wire cutting motor (10) drives the moving blade (20) to move closer to the fixed blade (30) through the wire cutting transmission mechanism. The wire cutting mechanism performs the dividing action. When the motor shaft of the wire cutting motor (10) rotates from the starting point of the wire cutting area to the ending point of the wire cutting area along the first direction, the connecting pin (70) always abuts against the end of the first groove (52). The wire cutting motor (10) drives the moving blade (20) to move closer to the fixed blade (30) through the wire cutting transmission mechanism until the moving blade (20) and the fixed blade (30) mesh, and the wire cutting mechanism performs the wire cutting action. When the motor shaft of the wire cutting motor (10) rotates from the end of the wire cutting area to the end of the first idle stroke area in the second direction, the connecting pin (70) and the slide (51) slide relative to each other until the connecting pin (70) and the end of the second groove (53) come into contact. When the motor shaft of the wire cutting motor (10) rotates from the starting point of the retraction zone to the ending point of the retraction zone along the second direction, and from the starting point of the second idle stroke zone to the ending point of the second idle stroke zone along the second direction, the connecting pin (70) always abuts against the end of the second groove (53), and the wire cutting motor (10) drives the moving blade (20) to move away from the fixed blade (30) through the wire cutting transmission mechanism; When the motor shaft of the wire cutting motor (10) rotates from the end of the second idle travel zone to the zero position along the first direction, the connecting pin (70) and the slide groove (51) slide relative to each other, and the moving blade (20) remains stationary.

8. The sewing machine thread cutting control method according to claim 7, characterized in that: It also includes the following step S4: After the wire cutting mechanism completes the wire cutting action, the electrical control module controls the motor shaft of the wire cutting motor (10) to rotate along the second direction from the end of the wire cutting area through the first empty stroke area and the retraction area in sequence to the second empty stroke area, and then rotates along the first direction to the zero position.

9. The sewing machine thread cutting control method according to claim 7, characterized in that: It also includes the following step S5: When the sewing machine is powered on, the electrical control module controls the motor shaft of the thread cutting motor (10) to rotate from the zero position to the second idle stroke area along the second direction, and then rotates to the zero position along the first direction.

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