Sewing method for preventing needle breakage in a sewing machine

Abstract

This invention relates to a sewing method for preventing needle breakage in a sewing machine, comprising: a standard sewing mode: the feed dog moves along a set trajectory, the main shaft rotates at a uniform speed Va and drives the needle to move, and within one operating cycle time T, the time corresponding to when the needle tip is successively located at the needle plate plane, the highest position B, and the needle plate plane after the needle starts moving from the lowest point A is t. C t B and t D Thick-material anti-needle breakage sewing mode: The feed dog trajectory is the same as in the standard sewing mode, and the relationship between the spindle angle and the needle position is also the same; within the cycle time T, there are time points t0, t1, t2, t3, and t4. During the time period t0 to t2, the spindle decelerates; during the time period t0 to t1, the spindle speed is greater than Va; during the time period t1 to t2, the spindle speed is less than Va. The time when the needle tip is located on the needle plate plane is recorded as t. C0 , t C0 <t C During the time interval t2 to t4, the spindle accelerates; during the time interval t2 to t3, the spindle speed is less than Va; during the time interval t3 to t4, the spindle speed is greater than Va. The time when the needle tip is on the needle plate plane is recorded as t. D0 , t D0 >t D .

Description

Technical Field

[0001] This invention relates to the field of sewing technology, and more specifically to a sewing method for using a sewing machine that can prevent needle breakage. Background Technology

[0002] When sewing extremely thick materials, sewing machines often experience needle breakage due to the needle dragging on the fabric. Existing technologies often address this by altering the feed trajectory. For example, patent application CN201310021344.6 discloses a sewing machine that uses an independent feed motor to move the feed dog back and forth, while a main motor moves it up and down. These two motors can synthesize a specific feed trajectory. When the fabric is thick, the feed dog's back and forth movement is stopped earlier, preventing needle breakage caused by the needle dragging on the fabric. However, this solution uses a swing angle function with a noticeable inflection point in the solid line, and the discontinuous slope exacerbates the problem of electronic control over the swing angle, easily leading to poor trajectory matching and high noise at high speeds. Furthermore, this solution uses only one independent feed motor, and the power source for lifting the feed dog is still the main shaft. Mechanical transmission prevents the timing of the feed dog relative to the main shaft from being changed, limiting its adaptability to thick fabric stitches.

[0003] In existing flatbed sewing machines, a needle-piercing mechanism with increased needle travel has been specifically developed for thick fabric sewing. In terms of assembly, the lowest point of the needle remains consistent, and while ensuring the same stitching sequence, the needle's travel above the needle plate is increased. This extends the needle's travel time on the needle plate, giving the feeding mechanism sufficient time to complete fabric transfer and preventing the needle from rubbing against the fabric. The needle bar travel of a typical flatbed sewing machine is approximately 31mm, while that of a thick-fabric model is approximately 35mm. A larger needle bar travel can cause increased vibration and noise throughout the machine, negatively impacting the operator's experience.

[0004] Furthermore, in current flatbed sewing machines (including those with electronic feed), the power source for the feed end or feed dog lifting end generally originates from the main shaft. The main shaft transmits its power to the feed end or feed dog lifting end via mechanical transmission. The movement of the feed dog is a combination of the feed end and the feed dog lifting end, which means that the movement of the needle and the feed dog cannot be completely independent. Therefore, regardless of whether the fabric is thick or thin, the needle position is the same and cannot be adjusted according to the fabric thickness, resulting in the problem of the needle breaking when the fabric is too thick. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the technical problem to be solved by the present invention is to provide a sewing method for preventing needle breakage in a sewing machine, which can effectively eliminate the problem of needle breakage caused by the needle touching the moving fabric when sewing thick fabric without changing the feed dog trajectory.

[0006] To achieve the above objectives, the present invention provides a sewing method for preventing needle breakage in a sewing machine. The sewing machine needle is driven by a spindle, and the process of moving the needle from its lowest position A to its highest position B and then back to its lowest position A is recorded as one operating cycle, with a cycle time of T. The sewing method includes:

[0007] M. Standard sewing mode: The feed dog moves along the set trajectory, and the main shaft rotates at a constant speed Va, driving the needle. Within one operating cycle time T, the time t corresponds to the needle tip being successively at the needle plate plane, the highest position B, and the needle plate plane after the needle starts moving from the lowest point A. C t B and t D ;

[0008] N. Thick material anti-needle breakage sewing mode: The feed dog moves along the same trajectory as in the standard sewing mode, and the relationship between the spindle angle and the needle position is also the same as in the standard sewing mode; within the cycle time T, there are times t0, t1, t2, t3 and t4 in sequence, where t0 is the start time of the cycle and t4 is the end time of the cycle. The rotation process of the spindle (4) includes:

[0009] N1. During the time interval t0 to t2, the spindle decelerates. During the time interval t0 to t1, the spindle speed is greater than Va. During the time interval t1 to t2, the spindle speed is less than Va. The time when the needle moves upward from the lowest point A starting from time t0, and the needle tip is on the needle plate plane, is recorded as t. C0 , t C0 <t C ;

[0010] N2. During the time interval t2 to t4, the spindle accelerates; during the time interval t2 to t3, the spindle speed is less than Va; during the time interval t3 to t4, the spindle speed is greater than Va. The time when the needle descends from its highest point B to the point where the needle tip is on the needle plate plane is recorded as t. D0 , t D0 >t D .

[0011] Furthermore, in step N1 of the thick material anti-needle breakage sewing mode N, t C0 ≤t1; t in step N2 D0 ≥t3.

[0012] Furthermore, in the thick material anti-broken needle sewing mode N, t3 is the moment when the cycle time T is halfway through.

[0013] Furthermore, in the thick material anti-needle breakage sewing mode N, the speed curve of the spindle is set symmetrically around the time point T / 2.

[0014] Furthermore, in the thick material anti-needle breakage sewing mode N, the magnitude of the spindle acceleration gradually increases from zero during the time period t0 to t1, gradually decreases to zero during the time period t1 to t2, gradually increases during the time period t2 to t3, and gradually decreases to zero during the time period t3 to t4.

[0015] Furthermore, the movement of the feed dog and the main shaft are controlled by the electronic control system of the sewing machine. The sewing machine is also equipped with a fabric thickness detection mechanism for detecting the fabric thickness. Before sewing begins, the fabric thickness detection mechanism detects the thickness d of the fabric to be sewn. When the thickness d is less than or equal to the set thickness threshold d0, the sewing machine selects the standard sewing mode M for sewing. When the thickness d is greater than the set thickness threshold d0, the sewing machine selects the thick material anti-needle breakage sewing mode N for sewing.

[0016] Furthermore, in the thick material anti-needle breakage sewing mode N, the insertion advance time △T1=|t C0 -t C | and the delayed extraction time △T2=|t D -t D0 The system sets spindle speed control data corresponding to △T1 and △T2, establishes the relationship between △T1 and △T2 and the fabric thickness d, and automatically determines the corresponding △T1 and △T2 and the corresponding spindle speed control data based on the detected fabric thickness d, and controls the spindle rotation according to the spindle speed control data.

[0017] Furthermore, in the thick material anti-needle breakage sewing mode N, while controlling the spindle rotation, the real-time speed or angle of the spindle is simultaneously acquired and compared with the spindle speed control data to determine whether there is a deviation, and correction is made in a timely manner.

[0018] Furthermore, the feeding motion of the feed dog in the front-to-back direction is driven by the feeding drive mechanism, and the motion in the up-to-down direction is driven by the lifting drive mechanism. Both the feeding drive mechanism and the lifting drive mechanism adopt a drive source independent of the main shaft motion. The motion of the feeding drive mechanism, the lifting drive mechanism and the main shaft are all controlled by the sewing machine's electronic control system.

[0019] Furthermore, the driving source of the feeding drive mechanism is a feeding motor, the driving source of the tooth lifting drive mechanism is a tooth lifting motor, the main shaft is driven by a main shaft motor, and the electrical control system is connected to the feeding motor, the tooth lifting motor and the main shaft motor respectively.

[0020] As described above, the sewing method of the present invention has the following beneficial effects:

[0021] 1. By setting a thick material anti-needle breakage sewing mode, when sewing thick fabrics, there is no need to change the feed dog trajectory or other structural adjustments. Only by changing the spindle speed within the cycle, the movement of the needle relative to the existing standard sewing mode is to achieve earlier needle plate exit and delayed needle plate insertion. This extends the running time of the needle in the area above the needle plate (away from the fabric), giving the feeding system sufficient time to complete the fabric transfer action. Under the conventional elliptical trajectory, the situation where the needle touches the fabric during the transfer of thick materials can be avoided, thus eliminating the problem of needle breakage caused by contact with moving fabric.

[0022] 2. It can automatically adjust the spindle speed for fabrics of different thicknesses, thus broadening its adaptability to fabrics of different thicknesses. The overall structure remains unchanged, and it can adapt to fabrics of different thicknesses simply by changing the program. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the sewing method of the present invention.

[0024] Figure 2 This is a schematic diagram of the sewing machine in this invention.

[0025] Figure 3 This is a schematic diagram of the movement trajectory of the feed tooth in this invention.

[0026] Figure 4 This is a schematic diagram showing the needle position when the feed dog is located on the needle plate plane in the standard sewing mode of this invention.

[0027] Figure 5 This is a schematic diagram illustrating the feeding process during the standard sewing pattern of thick fabric in this invention.

[0028] Figure 6 This is a schematic diagram showing the needle position when the feed dog is located on the needle plate plane in the thick material anti-needle breakage sewing mode of the present invention.

[0029] Figure 7 This is a schematic diagram of the needle position change curves in the standard sewing mode and the thick material anti-needle breakage sewing mode of the present invention.

[0030] Figure 8 This is a schematic diagram of the spindle angle variation curves in the standard sewing mode and the thick material anti-needle breakage sewing mode of the present invention.

[0031] Figure 9 This is a schematic diagram of the spindle speed variation curves in the standard sewing mode and the thick material anti-needle breakage sewing mode of the present invention.

[0032] Explanation of icon numbers

[0033] 1. Feeding teeth

[0034] 2 needle plates

[0035] 3 needles

[0036] 4 spindles

[0037] 5. Spindle motor

[0038] 6. Tooth lifting drive mechanism

[0039] 61 Tooth-lifting motor

[0040] 7. Feeding drive mechanism

[0041] 71 Feeding motor

[0042] 8. Fabric

[0043] 9. Feeding tooth movement trajectory Detailed Implementation

[0044] 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.

[0045] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and are 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.

[0046] See Figures 1 to 9 This invention provides a sewing method for preventing needle breakage in a sewing machine. The sewing machine needle 3 is driven by the main shaft 4. The process of moving the needle 3 from the lowest point A to the highest point B and then back to the lowest point A is recorded as one operating cycle, with the operating cycle time being T. The angle rotated by the main shaft 4 is 2π. During the sewing process, the feed dog 1 feeds the fabric. The feed dog 1's forward and backward movement is driven by the feed drive mechanism 7, and its vertical movement is driven by the dog lifting drive mechanism 6. Through the coordinated work of the feed drive mechanism 7 and the dog lifting drive mechanism 6, the feed dog 1 is driven to cyclically move along a certain motion trajectory. See [link to relevant documentation]. Figure 3 and Figure 4The feed dog's trajectory 9 is preferably elliptical, but it can also be square or other shapes. The feed dog 1's movement above the needle plate 2 surface is the feeding process, driving the fabric 8 to move. Its movement below the needle plate 2 surface is the resetting process. The feeding and resetting actions are very close in time, with the feed dog 1 spending approximately half the time above the needle plate 2 surface. The feed dog 1, feed drive mechanism 7, lift drive mechanism 6, and needle 3 can all adopt conventional structures. In this embodiment, preferably, the main shaft 4 is driven by the main shaft motor 5. The movements of the feed drive mechanism 7, lift drive mechanism 6, and main shaft motor 5 are all controlled by the sewing machine's electronic control system. Therefore, the movement of the needle 3 and feed dog 1 is controlled through the electronic control system.

[0047] The sewing method of the present invention includes:

[0048] M. Standard sewing pattern:

[0049] The feed dog 1 moves along a set trajectory, and the main shaft 4 rotates at a uniform speed Va, where Va = 2π / T. The main shaft 4 drives the needle 3 to move. Within one cycle T, the needle tip of the needle 3 starts from the lowest point A and successively moves to the plane of the needle plate 2, the highest point B, and the plane of the needle plate 2. The position of the needle tip of the needle 3 on the plane of the needle plate 2 during the upward movement is recorded as position C, and the position of the needle tip of the needle 3 on the plane of the needle plate 2 during the downward movement is recorded as position D. That is, within one cycle, the needle 3 starts from the lowest point A and successively passes through position C, the highest point B, and position D, and the corresponding time is t. C t B and t D .

[0050] The standard sewing mode is used for normal sewing of relatively thin fabric 8. The feed dog trajectory can be set according to specific conditions. See the graph showing the changes in the spindle angle and speed over time within one operating cycle. Figure 8 and Figure 9 The solid line portion in the figure represents the position change curve of needle 3. (See also:) Figure 7 The solid line portion in the figure is a curve resembling an inverted cosine, with its highest and lowest positions set according to actual needs. Preferably, the upward and downward movements of the needle 3 are symmetrically arranged, that is, the position change curve of the needle 3 is symmetrically arranged about the time point T / 2. When the feed dog 1 starts the feed action (moves upward until it is just below the plane of the needle plate 2) and completes the feed action (moves downward until it is just below the plane of the needle plate 2), see... Figure 4 The needle tip of the sewing machine 3 has a fixed distance, denoted as H1, between it and the plane of the needle plate 2. At this distance, the needle tip of the sewing machine 3 is positioned on the fabric 8, preventing needle dragging. The specific size of H1 can be set according to the specific characteristics of the sewing machine.

[0051] N. Thick-material anti-needle breakage sewing mode:

[0052] This mode is used for sewing thick fabric 8. Specifically, when sewing in the standard sewing mode, the needle tip of the machine needle 3 may have already inserted into the fabric 8 before the feed dog 1 completes its feeding action. In the thick fabric anti-needle breakage sewing mode, the feed dog 1 moves along the same trajectory as in the standard sewing mode, and the relationship between the angle of the main shaft 4 and the position of the machine needle 3 is also the same as in the standard sewing mode. Therefore, when changing from the standard sewing mode to the thick fabric anti-needle breakage sewing mode, no hardware adjustments are required. Furthermore, the movement trajectory and control logic of the feed dog 1 do not need to be changed; only the rotation method of the main shaft 4 is altered to change the movement of the machine needle 3. Figure 7 , Figure 8 and Figure 9 As shown, within one operating cycle time T, there are sequentially defined times t0, t1, t2, t3, and t4, where t0 is the start time of the cycle and t4 is the end time of the cycle. The curves showing the changes in the rotation angle and speed of the spindle 4 over time are shown below. Figure 8 and Figure 9 The dotted line portion in the figure represents the position change curve of needle 3. (See also...) Figure 7 The dotted line section; the rotation process of spindle 4 includes the following steps:

[0053] N1. During the time interval t0 to t2, the main shaft 4 decelerates. During the time interval t0 to t1, the rotational speed of the main shaft 4 is greater than Va. During the time interval t1 to t2, the rotational speed of the main shaft 4 is less than Va. Starting from time t0, the needle 3 moves upward from the lowest point position A, and the state position when the needle tip of the needle 3 is on the plane of the needle plate 2 is recorded as position C0, and the corresponding time is recorded as t. C0 , t C0 <t C See Figure 8 and Figure 9 Because the spindle speed of the main shaft 4 is greater than 2π / T during the time period t0 to t1, the needle tip of the needle 3 will leave the plane of the needle plate 2 earlier than in the standard sewing pattern, that is, t C0 <t C And preferably t C0 ≤t1, compared to the standard sewing mode, the needle 3 will reach the height position of the upper surface of the fabric 8 earlier. At the beginning of the feeding process of the feed dog 1 (when the feed dog 1 moves upward and just reaches the plane of the needle plate 2), the distance H2 between the needle tip of the needle 3 and the plane of the needle plate 2 is larger, which is greater than the distance H1 in the standard mode. See [reference needed]. Figure 4 and Figure 6 When sewing fabric 8 with a thickness less than H2, the needle tip of the machine needle 3 has already left the upper surface height position of the thick fabric 8, and there will be no problem of needle dragging. The distance H2 can be determined as needed by controlling the rotation of the main shaft 4.

[0054] In this embodiment, the time when the tip of the needle 3 moves from the lowest point A to the highest point B is denoted as t. B0 Preferably, the rotational speed of spindle 4 is at its minimum at this time, i.e., t B0 =t2, during the time interval t0 to t2, the needle 3 moves upward from the lowest point A to the highest point B, which facilitates the control of the position of the needle 3. Preferably, this is exactly half of the cycle time T, i.e., t B0 =t2=T / 2.

[0055] N3. During the time interval t2 to t4, the main shaft 4 accelerates its rotation. During the time interval t2 to t3, the rotational speed of the main shaft 4 is less than Va. During the time interval t3 to t4, the rotational speed of the main shaft 4 is greater than Va. When the needle 3 descends from its highest point position B to the point where the needle tip is located on the plane of the needle plate 2, this state position is recorded as position D0, and the corresponding time is recorded as t. D0 , t D0 >t D See Figure 7 , Figure 8 and Figure 9 Because the spindle 4 rotates at a speed less than Va during the time interval t2 to t3, relative to the standard sewing pattern, the spindle 4 will rotate with a delay until it reaches the angle corresponding to when the needle 3 is at position D0. Therefore, the needle tip of the needle 3 will reach the plane of the needle plate 2 with a delay during its descent, i.e., t... D0 >t D And preferred t D0 ≥t3, meaning that the spindle speed 4 reaches position D0 before Va. Therefore, compared to the standard sewing mode, the needle tip of the needle 3 will reach the upper surface height position of the fabric 8 later.

[0056] In this embodiment, see Figure 7 , Figure 8 and Figure 9 The speed curve of the main shaft 4 is symmetrically set around the time point T / 2, and the feeding action and reset action of the feed dog 1 are basically the same. Therefore, when the feed dog 1 completes its action (i.e., when the feed dog 1 moves downwards just below the plane of the needle plate 2), the distance between the needle tip of the needle 3 and the plane of the needle plate 2 is also basically H2, which is greater than the distance H1 in the standard mode. See [reference needed]. Figure 4 and Figure 6 At that time, when sewing fabric 8 with a thickness less than H2, the needle tip of the machine needle 3 has not yet reached the height position of the upper surface of the thick fabric 8.

[0057] In this embodiment, see Figure 7 , Figure 8 and Figure 9As a preferred design, the magnitude of the acceleration of the main shaft 4 in N2 gradually increases from zero in the time interval t0 to t1, gradually decreases to zero in the time interval t1 to t2, gradually increases in the time interval t2 to t3, and gradually decreases to zero in the time interval t3 to t4. The entire speed curve of the main shaft 4 is similar to a cosine curve, which makes the main shaft 4 more stable during the speed change operation.

[0058] In this way, compared with the standard sewing mode, the thick material anti-needle breakage sewing mode can obviously meet the sewing needs of thicker fabrics 8, and avoid the problem of the fabric 8 dragging the needle 3 and causing needle breakage.

[0059] In this embodiment, see Figure 2 As a preferred design, both the feeding drive mechanism 7 and the tooth-lifting drive mechanism 6 employ drive sources independent of the main shaft 4. The feed drive mechanism 7 is driven by a feed motor 71, and the tooth-lifting drive mechanism 6 is driven by a tooth-lifting motor 61. The main shaft 4 is driven by a main shaft motor 5. The electrical control system is connected to the feed motor 71, the tooth-lifting motor 61, and the main shaft motor 5, respectively, thereby independently controlling the movements of the feed drive mechanism 7, the tooth-lifting drive mechanism 6, and the main shaft 4. This effectively achieves complete separation between the feeding system and the needle 3's feeding system, allowing for flexible timing definition. Alternatively, the feed drive mechanism 7 and the tooth-lifting drive mechanism 6 can employ other suitable structures, ensuring that the movements of the feed dog 1 and the main shaft 4 are independent of each other.

[0060] In this embodiment, as a preferred design, a fabric thickness detection mechanism for detecting the thickness of fabric 8 is also provided. This fabric thickness detection mechanism can employ a displacement sensor, which is positioned above the presser foot assembly of the sewing machine to automatically sense the thickness of the fabric 8. Before sewing begins, the fabric thickness detection mechanism detects the desired thickness d of the fabric 8 to be sewn. When the thickness d is less than or equal to a set thickness threshold d0, the sewing machine selects the standard sewing mode M for sewing. When the thickness d is greater than the set thickness threshold d0, the sewing machine selects the thick-material anti-needle-breakage sewing mode N for sewing.

[0061] In this embodiment, preferably, in the thick material anti-needle breakage sewing mode N, the insertion advance time △T1=|t C0 -t C | and the delayed extraction time △T2=|t D -t D0The system is equipped with spindle speed control data corresponding to △T1 and △T2. This data can be an angular velocity versus time function ω = f(t), or a correspondence with the position of the feed tooth 1. The position of the feed tooth 1 is determined by the rotation angles of the feed motor 71 and the lifting motor 61. Therefore, the spindle speed control data represents the correspondence between the rotation angles of the spindle 4 and the rotation angles of the feed motor 71 and the lifting motor 61. A relationship is established between △T1 and △T2 and the thickness d of the fabric 8. The larger the thickness d, the larger △T1 and △T2. Based on the detected thickness d of the fabric 8, the electronic control system automatically determines the corresponding △T1 and △T2 and the corresponding spindle speed control data. The spindle 4 is then controlled to rotate according to this data, achieving intelligent automated control. In the sewing machine, the relative positional relationship between the spindle 4 angle and the needle 3 is fixed. When △T1 and △T2 are determined, the distance H2 between the needle tip 3 and the needle plate 2 plane when the feed dog 1 moves exactly to the needle plate 2 plane can be indirectly determined, thus determining whether it will insert into the fabric 8 at this time. Furthermore, when controlling the rotation of the spindle 4, the real-time speed or rotation angle of the spindle 4 is simultaneously acquired and compared with the spindle speed control data. Specifically, when the spindle speed control data adopts the correspondence between the rotation angle of the spindle 4 and the rotation angles of the feed motor 71 and the lifting dog motor 61, the actual rotation angle of the spindle 4 at a certain moment can be compared with the spindle 4 rotation angle that the rotation angles of the feed motor 71 and the lifting dog motor 61 should correspond to at that moment, thereby judging whether there is a deviation and adjusting the spindle motor 5 in time to correct the speed of the spindle 4.

[0062] In this embodiment, preferably, in the standard sewing mode M, when the main shaft 4 rotates, the control system also obtains the real-time rotation angle and speed of the main shaft 4 in real time, judges the angle that it should rotate under the standard uniform speed Va, compares it to see if there is a deviation, and corrects it in time. Specifically, it can be compared with the actual rotation angle by comparing the rotation angle of the main shaft 3 corresponding to the rotation angle of the feeding motor 71 and the lifting motor 61 at a certain moment.

[0063] As can be seen from the above, the sewing method of the present invention has the following beneficial effects:

[0064] 1. By setting a thick material anti-needle breakage sewing mode, when sewing thick fabric 8, it is not necessary to change the trajectory of the feed dog 1 or other structural adjustments. Only by changing the spindle speed within the cycle, the movement of the needle 3 relative to the existing standard sewing mode can achieve earlier exit from the needle plate 2 and delayed insertion into the needle plate 2. This extends the running time of the needle 3 in the area above the needle plate 2 (away from the fabric), giving the feeding system sufficient time to complete the fabric 8 transfer action. Under the normal elliptical trajectory, the situation where the needle 3 touches the fabric 8 during the thick material transfer process can be avoided, thus eliminating the needle breakage problem caused by touching the moving fabric 8.

[0065] 2. It can automatically adjust the spindle speed of the main shaft 4 for fabrics 8 of different thicknesses, thus broadening its adaptability to fabrics 8 of different thicknesses. The overall structure remains unchanged, and it can adapt to fabrics 8 of different thicknesses simply by changing the program.

[0066] In summary, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0067] 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 method for preventing needle breakage in a sewing machine, wherein the sewing machine needle (3) is driven by a spindle (4), and the process of moving the needle (3) from the lowest point position A to the highest point position B and then back to the lowest point position A is recorded as one operating cycle, and the operating cycle time is T; the sewing method includes: M. Standard sewing mode: The feed dog (1) moves along the set trajectory, the main shaft (4) rotates at a constant speed Va and drives the needle (3) to move. Within one running cycle time T, the time corresponding to when the needle (3) starts moving from the lowest point A and the needle tip is successively located on the needle plate (2) plane, the highest point B, and the needle plate (2) plane is t. C t B and t D ; N. Thick material anti-needle breakage sewing mode: The feed dog (1) moves along the same trajectory as in the standard sewing mode, and the relationship between the angle of the main shaft (4) and the position of the needle (3) is also the same as in the standard sewing mode; within the cycle time T, there are times t0, t1, t2, t3 and t4 in sequence, where t0 is the start time of the cycle and t4 is the end time of the cycle. The rotation process of the main shaft (4) includes: N1. During the time interval t0 to t2, the spindle (4) decelerates and rotates. During the time interval t0 to t1, the spindle (4) rotates at a speed greater than Va. During the time interval t1 to t2, the spindle (4) rotates at a speed less than Va. Starting from time t0, the needle (3) moves upward from the lowest point A, and the time when the needle tip of the needle (3) is located on the plane of the needle plate (2) is recorded as t. C0 , t C0 <t C ; N2. During the time interval t2 to t4, the spindle (4) accelerates its rotation. During the time interval t2 to t3, the spindle (4) rotates at a speed less than Va. During the time interval t3 to t4, the spindle (4) rotates at a speed greater than Va. The time when the needle (3) descends from the highest point B to the point where the needle tip is on the plane of the needle plate (2) is recorded as t. D0 , t D0 >t D .

2. The sewing method according to claim 1, characterized in that: In step N1 of the thick material anti-needle breakage sewing mode N, t C0 ≤t1; t in step N2 D0 ≥t3.

3. The sewing method according to claim 1, characterized in that: In the thick material anti-broken needle sewing mode N, t3 is the moment when the cycle time T is halfway through.

4. The sewing method according to claim 1 or 3, characterized in that: In the thick material anti-needle breakage sewing mode N, the speed curve of the main shaft (4) is set symmetrically around the time point T / 2.

5. The sewing method according to claim 1, characterized in that: In the thick material anti-needle breakage sewing mode N, the magnitude of the acceleration of the main shaft (4) gradually increases from zero in the time period t0 to t1, gradually decreases to zero in the time period t1 to t2, gradually increases in the time period t2 to t3, and gradually decreases to zero in the time period t3 to t4.

6. The sewing method according to claim 1, characterized in that: The movement of the feed dog (1) and the main shaft (4) is controlled by the electronic control system of the sewing machine. The sewing machine is also equipped with a fabric thickness detection mechanism for detecting the thickness of the fabric (8). Before sewing begins, the thickness d of the fabric (8) to be sewn is detected by the fabric thickness detection mechanism. When the thickness d is less than or equal to the set thickness threshold d0, the sewing machine selects the standard sewing mode M for sewing. When the thickness d is greater than the set thickness threshold d0, the sewing machine selects the thick material anti-needle breakage sewing mode N for sewing.

7. The sewing method according to claim 6, characterized in that: In the thick-material anti-needle breakage sewing mode N, the insertion advance time △T1=|t C0 -t C | and the delayed extraction time △T2=|t D -t D0 | and set spindle speed control data corresponding to △T1 and △T2, establish the relationship between △T1 and △T2 and the thickness d of the fabric (8), the electronic control system automatically determines the corresponding △T1 and △T2 and the corresponding spindle speed control data according to the detected thickness d of the fabric (8), and controls the spindle (4) to rotate according to the spindle speed control data.

8. The sewing method according to claim 7, characterized in that: In the thick material anti-broken needle sewing mode N, when controlling the rotation of the main shaft, the real-time speed or rotation angle of the main shaft (4) is simultaneously acquired and compared with the main shaft speed control data to determine whether there is a deviation and make timely corrections.

9. The sewing method according to claim 1 or 6, characterized in that: The feeding motion of the feed dog (1) in the front-to-back direction is driven by the feeding drive mechanism (7), and the motion in the up-down direction is driven by the lifting drive mechanism (6). The feeding drive mechanism (7) and the lifting drive mechanism (6) both adopt a drive source independent of the main shaft (4). The motion of the feeding drive mechanism (7), the lifting drive mechanism (6) and the main shaft (4) are all controlled by the sewing machine's electronic control system.

10. The sewing method according to claim 9, characterized in that: The feeding drive mechanism (7) is driven by a feeding motor (71), the tooth lifting drive mechanism (6) is driven by a tooth lifting motor (61), the main shaft (4) is driven by a main shaft motor (5), and the electrical control system is connected to the feeding motor (71), the tooth lifting motor (61) and the main shaft motor (5) respectively.

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