Method for controlling the uniformity of the stitch of a sewing machine

Abstract

This invention provides a method for controlling uniform stitch length in a sewing machine, comprising the following steps: S1, preset multiple adjustable stitch length values ​​and multiple adjustable motor output swing angles in the controller; S2, during the nth feeding action of the feed dog, the moment when the feed dog emerges from the needle plate and lifts the fabric is recorded as t. 1n The moment when the feed tooth reaches its highest point is denoted as t. 2n , will be in t 1n and t 2n The time interval between times is denoted as t. 3n Thickness testing agency at t 1n Time and t 3n The thickness value H of the seam material is obtained at different times. 1n and H 3n The controller is based on H 1n and H 3n Obtain the adjustment stitch length value D n And control the output shaft of the regulating motor to be in the same position as D n The corresponding output swing angle, where n is a positive integer. The advantage of this invention is that, using the control method provided by this invention, the change in fabric thickness can be acquired in real time during each stitch of the sewing machine, and the stitch length can be adjusted promptly to ensure that there are no sudden changes in stitch length and to guarantee uniform stitch length on the fabric.

Description

Technical Field

[0001] This invention relates to the field of sewing machine control technology, and in particular to a method for controlling uniform stitch spacing in a sewing machine. Background Technology

[0002] According to the principle of lockstitch sewing machines (flat sewing machines), the stitch length changes with the thickness of the fabric. When the stitch length is set constant, an increase in fabric thickness causes the needle to penetrate the fabric prematurely before the feed dog has finished feeding, thus resulting in a smaller actual stitch length. In addition, other factors can also cause a smaller stitch length when sewing thicker fabrics, such as: thicker fabric may increase the resistance of the feed dog in pushing the fabric, preventing the feed dog from moving the fabric effectively and reducing the distance pushed with each stroke, thereby decreasing the stitch length; excessive thread tension may cause the fabric to shrink, visually reducing the stitch length, and so on.

[0003] To ensure uniform stitch spacing in sewing machines, thicker fabrics are often sewn by manually pushing and pulling the fabric to increase the stitch spacing. However, this manual pulling method cannot completely guarantee uniform stitch spacing and is highly dependent on the operator's skill. Some sewing machines have fabric thickness detection systems that compensate for stitch spacing based on the fabric thickness detected by these systems. The traditional compensation method involves detecting an increase in fabric thickness, determining whether a compensation threshold has been reached, and then compensating (adjusting) the stitch spacing by a fixed compensation value. This can lead to insufficient or excessive compensation if no compensation is made when the threshold is not reached, resulting in a stitch spacing smaller than the set value. If the threshold is reached, the fixed compensation value can also cause insufficient or excessive compensation. Lowering the compensation threshold to increase sensitivity and starting compensation even with slight changes in fabric thickness can also easily cause abrupt changes in stitch spacing. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the purpose of this invention is to provide a method for controlling uniform stitch length in a sewing machine, which can achieve uniform stitch length on fabrics of different thicknesses using existing stitch length adjustment mechanisms.

[0005] This invention provides a method for controlling uniform stitch length in a sewing machine. The sewing machine includes a main shaft motor, a main shaft rotating under the drive of the main shaft motor, a feed dog, feed dogs fixed to the feed dog, a feed mechanism connected to one end of the feed dog, a feed dog lifting mechanism connected to the other end of the feed dog, a stitch length adjustment mechanism, a thickness detection mechanism, and a controller. The stitch length adjustment mechanism includes an adjustment motor, which is connected to the feed mechanism. The thickness detection mechanism is used to detect the thickness of the sewing fabric. The main shaft motor, the adjustment motor, and the thickness detection mechanism are all communicatively connected to the controller. The control method includes the following steps:

[0006] S1. Multiple adjustment needle pitch values ​​and multiple output swing angles of the adjustment motors are preset in the controller, and the multiple adjustment needle pitch values ​​and multiple output swing angles of the adjustment motors correspond one-to-one.

[0007] S2. During the nth feeding action of the feed dog, the moment when the feed dog emerges from the needle plate and lifts the sewing fabric is recorded as t. 1n The moment when the feed tooth reaches its highest point is denoted as t. 2n , will be in t 1n and t 2n The time interval between times is denoted as t. 3n The thickness detection mechanism at t 1n Time and t 3n The thickness value H of the seam material is obtained at different times. 1n and H 3n The controller is based on H 1n and H 3n Obtain the adjustment stitch length value D n And control the output shaft of the regulating motor to be in the same position as D. n The corresponding output swing angle, where n is a positive integer.

[0008] Preferably, step S1 further includes: the controller further pre-setting multiple fabric thickness ranges, the multiple fabric thickness ranges corresponding one-to-one with multiple adjustable stitch length values; in step S2, the controller adjusts the stitch length according to H... 3n The stitch length adjustment value corresponding to the thickness range of the seam material that falls into the seam material is recorded as D. n .

[0009] Preferably, in step S2, the controller calculates the adjustment stitch length value D according to the formula. n :

[0010]

[0011] Where a0 is the empirical magnification ratio, T n For thickness slope, Ф 3n and Ф 1n t 3n The principal axis rotation angle at time t and t 1n The spindle rotation angle at any given time, and D0 is the set needle pitch value.

[0012] Preferably, in step S2, the controller calculates the adjustment stitch length value D according to the formula. n :

[0013]

[0014] Where a0, b0, c0, and e0 are all empirical magnification ratios, and T n For thickness slope, Ф 3n and Ф 1n t 3n The principal axis rotation angle at time t and t 1n The spindle rotation angle at any given time, D0 is the set needle pitch value, and r is the spindle speed.

[0015] Preferably, the sewing machine further includes a fixed bushing, a presser foot rod passing through the bushing, and a presser foot connected to the lower end of the presser foot rod.

[0016] Preferably, the upper end of the presser foot rod is provided with a compression spring.

[0017] Preferably, the thickness detection mechanism includes a test piece mounted on the presser foot bar via a connecting seat, and a detection piece fixedly mounted on the housing of the sewing machine.

[0018] Preferably, the detection element is a Hall sensor, which is communicatively connected to the controller; the detected element is a magnet.

[0019] The advantages of this invention are: by using the control method provided by this invention, the change in fabric thickness can be obtained in real time during each stitch of the sewing machine and the stitch length can be adjusted in a timely manner to ensure that there are no sudden changes in stitch length and to ensure that the stitch length on the fabric is uniform. Attached Figure Description

[0020] Figure 1 The curves are function curves of the feed dog's displacement Sx in the X direction and displacement Sy in the Y direction relative to the spindle rotation angle Ф;

[0021] Figure 2 This is a schematic diagram of the movement trajectory of the feed dog;

[0022] Figure 3 This is a perspective view of the sewing machine used in this invention;

[0023] Figure 4 This is a perspective view of the thickness detection mechanism used in this invention;

[0024] Figure 5 This is a diagram showing the status of the seam fabric thickness inspection.

[0025] Figure 6 A graph showing the relationship between fabric thickness and sewing time;

[0026] Figure 7 This is a diagram showing the relationship between the thickness of the sewing fabric and the angle of the main axis when the fabric is in the uphill phase.

[0027] Component designation explanation:

[0028] 1-Casing;

[0029] 2-Sleeve;

[0030] 3-Presser foot;

[0031] 4-Needle plate;

[0032] 5- Feeding teeth;

[0033] 6-Pressure foot bar;

[0034] 7-Pressure foot spring;

[0035] 8-Sewing material;

[0036] 100 - Thickness measuring mechanism; 101 - Component to be measured; 102 - Component to be measured; 103 - Connecting seat. Detailed Implementation

[0037] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0038] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0039] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0040] like Figure 1-5As shown, the sewing machine of this invention is equipped with a main shaft motor, a main shaft rotating under the drive of the main shaft motor, a feed dog, a feed dog 5 fixed on the feed dog, a feed mechanism connected to the front end of the feed dog, a lifting mechanism connected to the rear end of the feed dog, a stitch length adjustment mechanism, a thickness detection mechanism 100, a presser foot lifting mechanism, and a controller. During the sewing process, the main shaft motor drives the main shaft to rotate. The main shaft, through the lifting mechanism, drives the feed dog and feed dog 5 to move up and down reciprocally, and the feed dog 5 performs a lifting action. The main shaft, through the feed mechanism, drives the feed dog and feed dog 5 to move back and forth reciprocally, and the feed dog 5 performs a feeding action. Therefore, the feed dog 5 performs a composite motion of up-and-down reciprocating movement and back-and-forth reciprocating movement, and the motion trajectory is as follows: Figure 2 The shape shown is elliptical.

[0041] The stitch length adjustment mechanism includes an adjustment motor, which is connected to the feed mechanism. By adjusting the output swing angle of the adjustment motor, the amount of movement of the feed dog and feed dog 5 in the front-to-back direction can be changed, thereby achieving stitch length adjustment. The adjustment motor can be used solely for adjusting the stitch length, or it can be used to simultaneously adjust the stitch length and lift the feed dog.

[0042] The thickness detection mechanism 100 is used to detect the thickness of the seam material 8. For example... Figure 3-5 As shown, the presser foot lifting mechanism includes a bushing 2 fixedly installed inside the sewing machine housing 1, a presser foot bar 6 passing through the bushing 2, a presser foot 3 connected to the lower end of the presser foot bar 6, and a compression spring 7 connected to the upper end of the presser foot bar 6. Below the presser foot 3 is a needle plate 4, and below the needle plate 4 is a feed dog 5. The sewing fabric 8 passes through the space between the needle plate 4 and the presser foot 3. Therefore, the thickness of the sewing fabric 8 affects the lifting height of the presser foot 3. The thickness detection mechanism 100 can detect the axial movement distance of the presser foot bar 6 to provide feedback on the real-time thickness of the sewing fabric 8.

[0043] Specifically, the thickness detection mechanism 100 includes a sample 101 mounted on the presser foot rod 6 via a connecting seat 103, and a detection element 102 fixedly mounted on the housing 1. The detection element 102 is a Hall sensor, which is communicatively connected to the controller; the sample 101 is a magnet. When the sample 101 moves up and down with the presser foot rod 6, the detection element 102 can detect the height change of the sample 101 in real time. Figure 5 As shown, the height h of the presser foot 3 changes with the up-and-down movement of the feed dog 5, and its variation curve with respect to time T is as follows. Figure 6 As shown, the thickness variation of the seam material 8 can be obtained by detecting the height of the presser foot 3.

[0044] The relationship between the motion trajectory of feed dog 5 and the spindle rotation angle is as follows:

[0045] The oscillation of the feeding mechanism affects the feed teeth 5 in the front-to-back direction (i.e., Figure 2The displacement Sx in the X direction (middle X direction) affects the oscillation of the tooth lifting mechanism, which in turn affects the vertical displacement of the feed tooth 5 (i.e., vertical displacement). Figure 2 The displacements Sy, Sx, and Sy in the Y direction (in the middle) are function curves relative to the principal axis rotation angle Ф, as shown below. Figure 1 As shown. For each revolution of the main shaft, the sewing machine sews one stitch, and the feed dog 5 completes one feeding action. When the main shaft rotation angle is 185°, the sewing machine needle pierces into the fabric 8 and rises upward, and the feed dog 5 is below the needle plate 4; time t1 is the time when the feed dog 5 emerges from the needle plate 4, lifts the fabric 8, and begins to move the fabric 8 forward, at which time the main shaft rotation angle is 250°; time t2 is the time when the feed dog 5 is at its highest point (i.e., the displacement Sy is at its maximum value) and completes one feeding action from back to front, at which time the main shaft rotation angle is 360° (0°).

[0046] Combination Figure 6 It can be seen that h0 is the thickness of the sewing material, h is the real-time height of presser foot 3, and h max h is the maximum value. When the spindle rotation angle is 185° to 250°, the feed dog 5 is always below the needle plate 4, and h = h0. When the spindle rotation angle is 251° to 360°, the feed dog 5 is above the needle plate 4, and h changes with the height of the feed dog 5. Therefore, the height h of the presser foot 3 detected during this period needs to be filtered to remove the part caused by the height change of the feed dog 5, so as to obtain the actual thickness h0 of the sewing material 8.

[0047] In addition, such as Figure 4 As shown, the thickness detection mechanism 100 can also obtain the seam thickness by detecting the deformation of the compression spring 7. Since the presser foot rod 6 compresses the compression spring 7 during the lifting of the presser foot and the forward movement of the sewing material 8, the real-time thickness of the sewing material 8 can also be obtained by detecting the deformation of the compression spring 7.

[0048] The thickness detection mechanism 100 is not limited to the form of Hall sensors and magnets; it can also detect the thickness of seams through methods such as laser reflection.

[0049] The aforementioned spindle motor, adjusting motor, and thickness detection mechanism 100 are all communicatively connected to the controller. Specifically, the controller includes a storage module, a central processing module, a thickness acquisition module, a motor control module, and a parameter adjustment and display module. The thickness acquisition module is communicatively connected to both the thickness detection mechanism 100 and the central processing module. As the fabric thickness changes, the workpiece 101 mounted on the presser foot 6 moves up and down, causing displacement of the workpiece 101 relative to the detection piece 102 mounted on the machine housing 1. This results in a voltage change Vi on the detection piece 102, which serves as both the output signal of the thickness acquisition module and the input signal of the central processing module. The storage module stores data for adjusting the stitch length. The motor control module controls the output swing angle of the adjusting motor, acquires the spindle motor's speed information, and adjusts the stitch length. The parameter adjustment and display module is used for manual adjustments such as parameter modification (e.g., zero-point calibration) and parameter display. The storage module, motor control module, and parameter adjustment and display module are all communicatively connected to the central processing module. The central processing module is used to process the fabric thickness data collected by the thickness detection mechanism 100, obtain the stitch length adjustment value by calculating and / or reading the data from the storage module, control the adjustment motor, complete the analysis and action after parameter adjustment, and perform other related calculations required by the sewing machine.

[0050] The aforementioned main spindle motor, main spindle, feed dog 5, feed mechanism, feed dog lifting mechanism, stitch length adjustment mechanism, thickness detection mechanism 100, presser foot lifting mechanism, and controller are all existing technologies and are standard configurations for sewing machines to achieve sewing functions, and will not be described in detail here.

[0051] Based on the above-mentioned sewing machine, the present invention provides a method for controlling the uniform stitch length of a sewing machine, the method comprising the following steps:

[0052] S1. Multiple adjustable needle pitch values ​​and multiple adjustable motor output swing angles are preset in the controller, and the multiple adjustable needle pitch values ​​and multiple adjustable motor output swing angles correspond one-to-one.

[0053] S2. During the nth feeding action of the feed dog 5, the moment when the feed dog 5 emerges from the needle plate 4 and lifts the sewing material 8 is recorded as t. 1n The moment when the delivery tooth 5 reaches its highest point is denoted as t. 2n , will be in t 1n and t 2n The time interval between times is denoted as t. 3n Thickness testing agency 100 at t 1n Time and t 3n The thickness value H of the seam material is obtained at different times. 1n and H 3n The controller is based on H 1n and H 3n Obtain the adjustment stitch length value Dn And control the output shaft of the regulating motor to be in the same position as D n The corresponding output swing angle, where n is a positive integer.

[0054] In step S2 above, time t is set. 3n The corresponding spindle rotation angle is a fixed value. Combined with... Figure 1 and Figure 2 It can be seen that at time t 1n The corresponding spindle rotation angle is 250°, at time t 2n The corresponding spindle rotation angle is 360°. If the spindle rotation angle of 260° is set to the set time t3 when the feed dog 5 performs the first feed action, then every time the spindle rotates to 260° thereafter, the thickness detection mechanism 100 will acquire the fabric thickness value H. 3n .

[0055] The control method provided by this invention can acquire the changes in fabric thickness in real time during each stitch of the sewing machine and adjust the stitch length in a timely manner to ensure that there are no sudden changes in stitch length and to ensure that the stitch length on the fabric is uniform.

[0056] In step S2 above, the controller can obtain the adjustment needle pitch value D by looking up a table or by calculation. n .

[0057] In the first embodiment of the present invention, step S1 further includes: a plurality of fabric thickness ranges are preset in the controller, and the plurality of fabric thickness ranges correspond one-to-one with a plurality of adjustable stitch length values. In step S2, the controller determines the stitch length based on H. 3n The stitch length adjustment value corresponding to the fabric thickness range is obtained by reading a table and recorded as D. n If H 1n and H 3n If the thickness falls within the same seam thickness range, the output shaft of the control motor will maintain the current angle; if H 1n and H 3n If the stitch length falls within a range of different fabric thicknesses, the controller adjusts the stitch length value D accordingly. n Control the output shaft of the motor to rotate to the same position as D. n The corresponding output swing angle ensures that the actual stitch distance between two adjacent stitches remains unchanged before and after the change in fabric thickness.

[0058] When the fabric thickness changes rapidly, the compensation amount needs to be increased accordingly. Therefore, in the second embodiment of the present invention, in step S2, the controller calculates the adjustment stitch length value D according to formula (1). n :

[0059] (1)

[0060] Where a0 is the empirical magnification ratio, T n For thickness slope, Ф 3n and Ф 1n t 3n The principal axis rotation angle at time t and t 1n The spindle rotation angle at any given time, and D0 is the set needle pitch value.

[0061] like Figure 7 As shown, the fabric thickness remains unchanged from stage A to stage B, and the sewing machine sews normally; from stage B to stage C, the fabric is in an uphill phase, and the thickness gradually increases; after stage C, the fabric thickness remains unchanged, and the sewing machine continues to sew normally. The above embodiment two can determine whether the fabric 8 is in an uphill phase based on the relationship between the spindle angle change value ΔФ and the fabric thickness change value ΔH (i.e., the thickness slope T), and dynamically adjust the stitch length value based on the real-time calculated thickness slope T. The larger T is, the greater the compensation amount, ensuring that the actual stitch length value of two adjacent stitches remains unchanged before and after the fabric thickness change.

[0062] Furthermore, when the sewing speed of the sewing machine (i.e., the spindle speed) is faster, the instantaneous resistance of the fabric 8 increases, and the slippage phenomenon becomes more severe, requiring a corresponding increase in compensation. Therefore, in the third embodiment of the present invention, in step S2, the controller calculates the adjusted stitch length value D according to formula (2). n :

[0063] (2)

[0064] Where a0, b0, c0, and e0 are all empirical magnification ratios, and T n For thickness slope, Ф 3n and Ф 1n t 3n The principal axis rotation angle at time t and t 1n The spindle rotation angle at any given time, D0 is the set stitch length value, and r is the spindle speed. The above embodiment three can dynamically adjust the stitch length value based on the thickness slope T and spindle speed obtained in real time. The larger T and r are, the greater the compensation amount, ensuring that the actual stitch length value of two adjacent stitches on the sewing fabric 8 will not change abruptly.

[0065] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling uniform stitch spacing in a sewing machine, characterized in that, The sewing machine is equipped with a main shaft motor, a main shaft that rotates under the drive of the main shaft motor, a feed dog, a feed dog (5) fixed on the feed dog, a feed mechanism connected to one end of the feed dog, a feed dog lifting mechanism connected to the other end of the feed dog, a stitch length adjustment mechanism, a thickness detection mechanism (100), and a controller. The stitch length adjustment mechanism includes an adjustment motor, which is connected to the feed mechanism. The thickness detection mechanism (100) is used to detect the thickness of the sewing material (8). The main shaft motor, the adjustment motor, and the thickness detection mechanism (100) are all connected to the controller. The control method includes the following steps: S1. Multiple adjustment needle pitch values ​​and multiple output swing angles of the adjustment motors are preset in the controller, and the multiple adjustment needle pitch values ​​and multiple output swing angles of the adjustment motors correspond one-to-one; S2. During the nth feeding action of the feed dog (5), the moment when the feed dog (5) emerges from the needle plate (4) and lifts the sewing material (8) is recorded as t. 1n The moment when the feed tooth (5) is at its highest point is denoted as t. 2n , will be in t 1n and t 2n The time interval between times is denoted as t. 3n The thickness detection mechanism (100) at t 1n Time and t 3n The thickness value H of the seam material is obtained at different times. 1n and H 3n The controller is based on H 1n and H 3n Obtain the adjustment stitch length value D n And control the output shaft of the regulating motor to be in the same position as D. n The corresponding output swing angle, where n is a positive integer.

2. The control method according to claim 1, characterized in that, Step S1 further includes: multiple fabric thickness ranges are preset in the controller, and the multiple fabric thickness ranges correspond one-to-one with multiple adjustable stitch length values; in step S2, the controller adjusts according to H 3n The stitch length adjustment value corresponding to the thickness range of the seam material that falls into the seam material is recorded as D. n .

3. The control method according to claim 1, characterized in that, In step S2, the controller calculates the adjustment needle pitch value D according to formula (1). n : （1） Where a0 is the empirical magnification ratio, T n For thickness slope, Ф 3n and Ф 1n t 3n The principal axis rotation angle at time t and t 1n The spindle rotation angle at any given time, and D0 is the set needle pitch value.

4. The control method according to claim 1, characterized in that, In step S2, the controller calculates the adjustment needle pitch value D according to formula (2). n : （2） Where a0, b0, c0, and e0 are all empirical magnification ratios, and T n For thickness slope, Ф 3n and Ф 1n t 3n The principal axis rotation angle at time t and t 1n The spindle rotation angle at any given time, D0 is the set needle pitch value, and r is the spindle speed.

5. The control method according to claim 1, characterized in that, The sewing machine also includes a fixed bushing (2), a presser foot bar (6) passing through the bushing (2), and a presser foot (3) connected to the lower end of the presser foot bar (6).

6. The control method according to claim 5, characterized in that, The upper end of the presser foot rod (6) is provided with a compression spring (7).

7. The control method according to claim 5, characterized in that, The thickness detection mechanism (100) includes a test piece (101) mounted on the presser foot bar (6) via a connecting seat (103) and a detection piece (102) fixedly mounted on the housing (1) of the sewing machine.

8. The control method according to claim 7, characterized in that, The detection element (102) is a Hall sensor, which is connected in communication with the controller; the detected element (101) is a magnet.

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