JP2012176182A - Sewing machine - Google Patents

Abstract

There is provided a sewing machine capable of preventing thread dropout at the start of sewing without imposing a load on a sewing needle even when a needle thread remaining length is short.
When using a sewing machine, an operator reduces the remaining length of a needle thread as much as possible in order to reduce "bird's nest" generated in a cloth. The amount of upper thread drawn into the back side of the fabric 10 is reduced by the stitch forming operation of the sewing machine. The sewing machine of the present embodiment makes the cloth feed amount at the start of sewing larger than usual. A part of the upper thread 8A is bent, and the bent portion Q can be quickly submerged under the presser foot 15 with respect to the reference feed amount. Since the upper thread 8A is in a state where the bent portion Q is stepped on by the presser foot 15, the resistance on the cloth side of the upper thread becomes large, and even if the upper thread 8A is pulled up by a balance, it is possible to reliably prevent the thread from coming off.
[Selection] Figure 8

Description

  The present invention relates to a sewing machine.

  Industrial sewing machines form stitches on work cloths. In order to prevent the formation of the stitches at the start of sewing from failing (thread removal), the operator sets the remaining upper thread amount (the remaining length of the needle thread plate) to be 3 cm or more extending from the stitch hole of the sewing needle at the start of sewing. Had secured. However, the upper thread end remains on the back of the fabric and is sewn into the second and subsequent stitches, resulting in a “bird's nest” state. The sewing machine disclosed in Patent Document 1 feeds the cloth in the cloth feeding direction by a minute predetermined amount with the sewing needle penetrating the work cloth. As a result, the cloth resistance of the end side upper thread portion with respect to the work cloth is greater than the cloth resistance of the balance side upper thread portion with respect to the work cloth.

JP 2003-275487 A

  Since the sewing machine disclosed in Patent Document 1 feeds the cloth with the sewing needle penetrating the work cloth, a load is applied to the sewing needle. When a load is applied to the sewing needle, there is a problem in that the position of the sewing needle with respect to the work cloth is displaced and a beautiful seam cannot be formed.

  An object of the present invention is to provide a sewing machine that can prevent thread dropout at the start of sewing without imposing a load on the sewing needle even when the remaining length of the needle thread is short.

  The sewing machine according to the first aspect of the present invention includes a sewing needle having a hole through which an upper thread passes and moves up and down, a needle plate on which a sewing product is placed and through which the sewing needle passes, and the sewing product A presser foot that presses the needle on the needle plate, a feed dog that feeds the workpiece on the needle plate in cooperation with the presser foot, and a feed that drives the feed dog in synchronization with the vertical movement of the sewing needle. A sewing machine comprising: a mechanism; and a feed amount adjusting means capable of adjusting a feed amount of the sewing product per cycle of the vertical movement of the sewing needle in the feed mechanism, wherein the sewing material is An adjustment driving means for driving the feed amount adjusting means to adjust the feed amount; and the adjustment driving means for making the feed amount larger than a reference amount which is a preset feed amount of the sewing product at the start of sewing. Control means for controlling.

  In the sewing machine according to the first aspect, the feed amount is set larger than a preset reference amount of the sewing product at the start of sewing. Part of the thread is bent. The bent portion sinks between the sewing object and the presser foot. The cloth presser holds the bent part of the thread. Therefore, the first mode can prevent the thread from coming off at the start of sewing without imposing a load on the sewing needle.

  In the first aspect, the control means may control the adjustment driving means to adjust the reference amount after sewing a predetermined number of stitches from the start of sewing. Therefore, the seam can be reliably formed at the start of sewing.

  Further, in the first aspect, the control means adjusts the reference amount to the reference amount when the feed dog is positioned below the needle plate after sewing the predetermined number of stitches from the start of sewing. The driving means may be controlled. Since the reference amount does not return while the workpiece is being sent, the stitches can be formed beautifully on the workpiece.

  In the first aspect, when the first stitch of the sewing needle first stabbed into the sewing product from the start of sewing is the first stitch, the predetermined number of stitches may be at least two. By increasing the feed amount until at least two stitches are sewn, a part of the thread can be bent and the bent part can be pressed with a cloth presser, so that it is possible to reliably prevent the thread from coming off at the start of sewing.

1 is a perspective view of a sewing machine 1. FIG. 3 is a cross-sectional view showing the periphery of the sewing needle 14 and the periphery of the shuttle mechanism 30. FIG. FIG. 4 is a cross-sectional view showing a part of the internal structure of the pedestal 3. 2 is a block diagram showing an electrical configuration of the sewing machine 1. FIG. It is a flowchart of the sewing process by CPU71. 6 is a flowchart showing a continuation of FIG. It is a figure which shows the relationship between an upper-axis angle, and the movement locus | trajectory of the needle plate 11 and the balance. FIG. 6 is a view showing a state where a bent portion Q of an upper thread 8A has entered under the presser foot 15; FIG. 9 is an enlarged view of a portion surrounded by a two-dot chain line W in FIG. 8.

  Hereinafter, a sewing machine 1 according to an embodiment of the present invention will be described with reference to the drawings. The drawings to be referred to are used for explaining the technical features that can be adopted by the present disclosure, and the configuration and flowcharts of the apparatus described are not intended to be limited only to them, but are merely illustrative examples. is there. The x direction shown in FIGS. 2 and 8 indicates the normal feed direction of the cloth 10. In the following description, the remaining length on the free end side of the upper thread 8A extending from the eye hole 14A of the sewing needle 14 shown in FIG. 2 is referred to as “needle thread remaining length”. The sewing machine 1 of the present embodiment is characterized in that the thread can be reliably prevented from coming off even if the remaining length of the needle thread at the start of sewing is shortened.

  The physical configuration of the sewing machine 1 will be described with reference to FIG. The left side, the right side, the upper left side, and the lower right side in FIG. The sewing machine 1 is fitted in a recess (not shown) provided in the table 6. A controller 70 that controls the operation of the sewing machine 1 is attached to the lower surface of the table 6. A step-down pedal 91 is connected to the control device 70 via a rod 90. When the operator depresses the pedal 91 to the toe side or to the heel side, a switch (not shown) is appropriately turned on and off, and the sewing work 1 starts or stops, or the thread trimming work by the thread trimming mechanism, etc. Is done.

  As shown in FIG. 1, the sewing machine 1 includes a bed portion 2 as a base, a columnar leg column portion 3 erected in the vertical direction on the right end portion of the upper surface of the bed portion 2, and the leg column portion 3. An arm portion 4 is provided extending from the upper end portion to the left side and facing the upper surface of the bed portion 2. A head 49 that protrudes downward is provided at the distal end of the arm portion 4 in the extending direction.

  A needle plate 11 is provided on the upper left end side of the bed portion 2. As shown in FIG. 2, a needle hole 11 </ b> A is provided in the needle plate 11 immediately below the sewing needle 14. Further, the needle plate 11 is provided with a square hole 12 through which a feed dog 32 (described later) moves back and forth. A hook mechanism 30 is provided below the needle plate 11 in the bed portion 2. The shuttle mechanism 30 accommodates a bobbin for lower thread (not shown). Above the shuttle mechanism 30 and below the needle plate 11, a sewing object (hereinafter referred to as a cloth 10 in FIG. 2 as an example) is arranged behind the sewing machine 1 with a predetermined feed amount (forward feed direction) and A feed dog 32 is provided to be transferred either forward (reverse feed direction). The feed dog 32 is driven by a cloth feed mechanism described later.

  As shown in FIG. 1, a sewing machine motor 87 (see FIG. 4) having a columnar pulley 5 that manually rotates the upper shaft (not shown) of the sewing machine 1 is provided on the upper right side of the pedestal 3. It has been. A feed amount adjustment pulley 21 for adjusting the feed amount of the cloth 10 by the feed dog 32 is provided at the center of the front surface of the pedestal 3. A feed amount adjusting motor 22, which is a pulse motor, is fixed to a lower portion of the right side surface of the pedestal portion 3 via a fixing member 25. A drive pulley 23 is fixed to the tip of the output shaft 22A (see FIG. 3) of the feed amount adjusting motor 22. A timing belt 24 is bridged between the feed amount adjusting pulley 21 and the driving pulley 23. The feed amount adjusting motor 22 is connected to a control device 70 (see FIGS. 1 and 4) via a drive circuit 83 (see FIG. 4) described later. The control device 70 controls driving of the feed amount adjusting motor 22. The driving force of the feed amount adjusting motor 22 is transmitted from the drive pulley 23 to the feed amount adjusting pulley 21 via the timing belt 24. Therefore, the feed amount of the cloth 10 is adjusted with the rotation of the feed amount adjustment pulley 21. A mechanism for adjusting the feed amount of the fabric 10 will be described later. The cloth feed amount can be set on the operation panel 7 described later. The feed amount adjusting pulley 21, the feed amount adjusting motor 22, the drive pulley 23, and the timing belt 24 correspond to the “adjustment driving means” of the present invention.

  As shown in FIGS. 1 and 2, a needle bar 13 is provided below the head 49 so as to be movable in the vertical direction. A sewing needle 14 is attached to the lower end of the needle bar 13. A presser foot 15 for pressing the cloth is provided behind the needle bar 13. In the head 49, a needle bar vertical movement mechanism (not shown) for moving the needle bar 13 up and down and a balance mechanism (not shown) for moving the balance 18 (see FIG. 1) for lifting the upper thread 8A up and down are provided. It has been.

  A sewing machine motor 87 (see FIG. 4) for driving the sewing machine 1 is provided below the pedestal 3 shown in FIG. The driving force of the sewing machine motor 87 is transmitted to the upper shaft (not shown) via a joint (not shown). The upper shaft extends in the left-right direction within the arm portion 4. The driving force of the sewing machine motor 87 is also transmitted to the lower shaft (not shown) by a transmission mechanism (not shown) provided in the middle of the upper shaft. The lower shaft extends in the left-right direction within the bed portion 2. When the operator depresses the pedal 91, the sewing machine motor 87 is driven, and the elements including the needle bar 13, the balance mechanism, the shuttle mechanism 30, and the feed mechanism are synchronously driven, and a stitch is formed on the cloth 10. .

  As shown in FIG. 1, a rectangular operation panel 7 that is horizontally long when viewed from the front is provided at the center of the upper surface of the arm portion 4. A liquid crystal display 7A (hereinafter referred to as LCD 7A) is provided on the front surface of the operation panel 7. The LCD 7A displays function names and various messages for executing various functions necessary for sewing work such as selection and editing of a sewing pattern and setting of a cloth feed amount during sewing. A touch panel 7B is provided on the front surface of the LCD 7A. The LCD 7A and the touch panel 7B are connected to the control device 70. The operator selects an item displayed on the LCD 7A with a finger or a touch pen. The touch panel 7B senses the selected item. The operator can input various instructions to the sewing machine 1 via the LCD 7A and the touch panel 7B.

  The relationship between the movement locus of the sewing needle 14 and the phase of the upper shaft will be described with reference to FIG. The top dead center of the sewing needle 14 is set to a rotation phase of 0 ° on the upper axis. The sewing needle 14 reciprocates up and down over a rotation phase of 0 ° to 360 °. When the rotation phase is approximately 110 °, it is the timing when the tip of the sewing needle 14 enters the needle hole 11A (see FIG. 2) of the needle plate 11. The rotational phase of 180 ° is the timing when the sewing needle 14 reaches the bottom dead center. When the rotation phase is approximately 201 °, it is the timing when the blade mechanism (not shown) of the shuttle mechanism 30 is met. When the rotational phase is about 250 °, it is the timing at which the tip of the sewing needle 14 comes out of the needle hole 11A of the needle plate 11 upward. When the rotation phase is 360 °, it is the timing when the sewing needle 14 returns to the top dead center. When the upper axis angle is 0 ° to 360 °, one cycle is obtained.

  In order to detect these various timings, an encoder disk (not shown) in which a large number of thin lines are printed radially is fixed to the upper shaft. An encoder 88 (see FIG. 4) that detects individual thin lines printed on the encoder disk and generates a timing signal is mounted inside the arm portion 4. The signal (encoder pulse) output from the encoder 88 is updated and stored in the pulse number memory of the RAM 73 (see FIG. 4) of the control device 70. The encoder pulse number is reset every rotation of the upper shaft.

  The relationship between the movement locus of the sewing needle 14 and the movement locus of the balance 18 will be described with reference to FIG. When the sewing needle 14 enters the cloth 10, the balance 18 (see FIG. 1) moves downward to allow the upper thread 8A to have a margin. A loop is formed in the upper thread 8A. The inner hook of the hook mechanism 30 comes out of the loop and the lower thread (not shown) passes. When the sewing needle 14 is pulled out from the cloth 10, the balance 18 moves upward to pull up the upper thread 8A. The entanglement of the upper thread 8A and the lower thread is located in the middle of the cloth 10. Thus, a seam is formed in the cloth 10 by the cooperation of the vertical movement of the sewing needle 14 and the vertical movement of the balance 18.

  The cloth feed mechanism will be briefly described with reference to FIG. The cloth feed mechanism of the present embodiment is a conventional well-known mechanism that drives the feed dog 32. For example, the feed dog 32 is given a backward movement (in the x direction in FIG. 2) and a forward movement by a horizontal feed shaft (not shown) rotatably supported at both ends of the bed portion 2. A vertical movement is given by a vertical feed shaft (not shown) interlocked with a feed base (not shown) to which the feed dog 32 is fixed. The cloth 10 can be fed in the front-rear direction by such known means. The switching of the feeding direction of the cloth 10 is determined by the inclination of a switch (not shown) provided in the bed portion 2. The cloth 10 is fed in the reverse feed direction (the reverse direction to the x direction in FIG. 2) by the inclination of the switch, and reverse stitching or the like is performed.

  A known mechanism for adjusting the inclination of the switch will be briefly described. 1 includes a reverse solenoid 58 (see FIG. 4), a solenoid lever (not shown), a reverse stitching lever shaft (not shown), a lever (not shown), and a switch linkage assembly ( (Not shown). When the reverse solenoid 58 is turned on, the reverse stitching lever shaft is rotated via a solenoid lever (not shown). The lever (not shown) swings according to the rotation of the reverse stitching lever shaft, and the switch linkage assembly (not shown) swings up and down. Thereby, the inclination of the switch is changed to a symmetrical position, and the feed direction of the cloth 10 is switched from the normal feed direction to the reverse feed direction. At this time, the feed amount of the cloth 10 does not change. A reverse stitching lever 9 (see FIG. 1) arranged on the lower side of the front surface of the leg post 3 is connected to the reverse stitching lever shaft. Also by manually operating the reverse stitching lever 9 downward, the reverse stitching lever shaft is rotated to change the inclination of the switch to the symmetrical position, and the cloth 10 is fed in the reverse feed direction.

  A mechanism for adjusting the feed amount of the cloth 10 will be described with reference to FIG. In the pedestal 3, the feed adjusting cam 50 is pivotally supported around the shaft 54 at a position facing the feed amount adjusting pulley 21. The feed adjustment cam 50 is connected to a feed adjustment stand 57 via a link 56. The feed adjustment stand 57 is a well-known one connected to a switcher via a link (not shown), and is provided in the bed portion 2 so as to be rotatable. The feed adjustment stand 57 is rotated by the vertical movement of the link 56, and the inclination of the switch is changed. By changing the tilt angle of the switch, the amount of swing of the horizontal feed shaft (not shown) is changed to vary the feed amount by the feed dog 32 (see FIG. 2).

  A cam surface 51 having a V-shape in a side view is formed at the front end portion of the feed adjusting cam 50. The rear end portion of the feed adjusting cam 50 is rotatably connected to the upper end portion of a link 56 that is an element constituting the above-described switch linkage group. An adjusting shaft 41 that protrudes rearward from the center of the feed amount adjusting pulley 21 is screwed into the screw hole 3 </ b> A provided in the upper portion of the front surface of the pedestal 3. The distal end portion 42 of the adjustment shaft 41 engages with the cam surface 51 of the feed adjustment cam 50.

The cam surface 51 includes a forward feed control surface 52 located on the lower side and a reverse feed control surface 53 located on the upper side. The link 56 is urged downward in FIG. 3 by a spring, and the forward feed control surface 52 is urged toward the tip end portion 42 of the adjustment shaft 41. When the adjustment shaft 41 is turned, the adjustment shaft 41 moves in and out, the contact position of the tip 42 with the forward feed control surface 52 changes, and the swing angle of the switch changes via the link 56. For this reason, the feed amount of one pitch by the feed dog 32 can be adjusted.
The structure using such a feed adjusting cam 50 is the same as the conventional one.

  FIG. 3 shows a state where the reverse solenoid 58 (see FIG. 4) is OFF. The tip end portion 42 of the adjustment shaft 41 abuts on the forward feed control surface 52. In a state where the reverse solenoid 58 is turned on, the link 56 rises against the spring force, and the tip 42 of the adjustment shaft 41 contacts the reverse feed control surface 53. At this time, the swing angle of the switch is switched from the forward feed angle to the reverse feed angle, and the feed direction of the feed dog 32 is reversed. The feed amount adjusting mechanism of the cloth 10 corresponds to the “feed amount adjusting means” of the present invention.

  The electrical configuration of the sewing machine 1 will be described with reference to FIG. As described above, the sewing machine 1 includes the control device 70. The control device 70 includes a CPU 71 (corresponding to “control means” of the present invention). A ROM 72, a RAM 73, an EEPROM (registered trademark) 74, and an I / O interface (hereinafter referred to as I / O) 76 are connected to the CPU 71 via a bus 77. The I / O 76 of the control device 70 having such a configuration includes a pedal 91, a touch panel 7B, a drive circuit 81 for driving the LCD 7A, a drive circuit 82 for driving the sewing machine motor 87, and a feed amount. A drive circuit 83 for driving the adjusting motor 22, a drive circuit 84 for driving the reverse solenoid 58, a drive circuit 85 for driving the thread trimming solenoid 65, and an encoder for detecting the rotation angle of the upper shaft 88 etc. are connected to each other.

  The sewing process in the sewing machine 1 will be described with reference to the flowcharts of FIGS. 5 and 6 and FIGS. In FIG. 7, the movement trajectory of the sewing needle 14 and the movement trajectory of the balance 18 are indicated by solid lines, the vertical feed phase of the feed dog 32 is indicated by a dotted line, and the horizontal feed phase of the feed dog 32 is indicated by a two-dot chain line. Yes. Further, the operation of the feed dog 32 is divided into a horizontal feed phase and a vertical feed phase. When the operator turns on the power of the sewing machine 1, the CPU 71 calls a “sewing control program” stored in the ROM 72 and executes this processing. Prior to the start of sewing, the operator reduces the remaining length of the needle thread as much as possible (for example, about 15 mm) in order to reduce the “bird's nest” generated in the cloth 10.

  The CPU 71 determines whether or not feed data has been input (S11). The feed data includes a reference feed amount (M) of the fabric 10, an enlargement rate (S) for increasing the reference feed amount (M) at the start of sewing, and an enlargement obtained by multiplying the reference feed amount (M) by the enlargement rate (S). The number of stitches (N) that triggers the return of the feed amount (MS) to the reference feed amount (M). The operator inputs feed data (M, S, N) to the control device 70 through the operation panel 7 before starting sewing. For example, the reference feed amount (M) is 3 mm, the enlargement ratio (S) is 1.6, and the number of stitches (N) is 2. In this case, the enlarged feed amount (MS) is 4.8 mm. In this input example, the feed amount is set to 4.8 mm at the first stitch, and the sewing machine 1 is controlled to return to 3 mm when the feed dog 32 moves below the needle plate 11 at the second stitch.

  The CPU 71 returns to S11 and enters a standby state until it determines that the feed data has been input (S11: NO). When the CPU 71 determines that the feed data has been input (S11: YES), the CPU 71 stores the input feed data in the RAM 73 (S12). The CPU 71 determines whether or not input of all feed data (M, S, N) has been completed (S13). When the CPU 71 determines that there is feed data that has not been input yet (S13: NO), the CPU 71 returns to S11 and waits until the remaining feed data is input. The sewing machine 1 does not drive unless feed data is input.

  When the CPU 71 determines that all the feed data has been input (S13: YES), the CPU 71 determines whether the pedal 91 is turned on (S14). Until the pedal 91 is turned on (S14: NO), the CPU 71 returns to S14 and enters a standby state. The operator depresses the pedal 91 toward the toe side to start sewing in order to start sewing. When the CPU 71 determines that the pedal 91 is turned on (S14: YES), the CPU 71 starts driving the sewing machine motor 87 (S15). The sewing machine 1 starts a sewing operation. For example, as shown in FIG. 7, when the sewing machine 1 starts a sewing operation when the upper shaft is near 45 °, the CPU 71 feeds the cloth 10 in the X direction with the reference feed amount (M) stored in the RAM 73 and the sewing needle 14 Is lowered.

  The CPU 71 determines whether or not the sewing needle 14 has entered the first needle that pierces the cloth 10 (S17). Here, it is determined whether or not the upper shaft angle at which the sewing needle 14 reaches the needle plate 11 has reached 110 °. The CPU 71 feeds the fabric 10 in the normal feed direction with the reference feed amount (M) as it is until the first stitch is entered (S17: NO).

  When the CPU 71 determines that the sewing needle 14 has entered the first stitch (S17: YES), the CPU 71 performs a feed amount enlargement process (S16). In the feed amount enlargement process, the CPU 71 calculates an enlarged feed amount (MS) by multiplying the feed amount (M) stored in the RAM 73 by the enlargement rate (S) stored in the RAM 73. The CPU 71 drives the feed amount adjusting motor 22 (see FIG. 4) so that the feed amount of the cloth 10 is changed from the reference feed amount (M) to the enlarged feed amount (MS). The EEPROM 74 stores a feed table (not shown) in which a correspondence relationship between the rotation phase of the feed amount adjusting motor 22 and the feed amount is set. Therefore, the CPU 71 refers to the feed table to adjust the feed amount by controlling the drive of the feed amount adjusting motor 22. The driving force of the feed amount adjusting motor 22 is transmitted from the drive pulley 23 to the feed amount adjusting pulley 21 via the timing belt 24. As the feed amount adjusting pulley 21 rotates, the adjusting shaft 41 rotates. The adjustment shaft 41 moves rearward as it rotates. The contact position of the front end portion 42 with the forward feed control surface 52 changes, and the swing angle of the switch changes via the link 56. Therefore, the CPU 71 controls the rotational phase of the feed amount adjusting motor 22 to change the swing angle of the switch, so that the feed amount of one pitch by the feed dog 32 can be adjusted to the enlarged feed amount (MS). .

  The sewing needle 14 is pulled up from the needle plate 11. Next, the feed dog 32 moves upward from the needle plate 11 and moves in an enlarged feed amount (MS) in the forward feed direction. The cloth 10 is transported in the forward feed direction at an enlarged feed amount (MS). At this time, as shown in FIGS. 8 and 9, a part of the upper thread 8A (Q portion in FIG. 9) bends in the forward feed direction. The bent portion Q is submerged between the cloth 10 and the presser foot 15. The upper thread 8 </ b> A is stepped on by the presser foot 15.

  Here, when the upper shaft angle exceeds 360 °, the sewing needle 14 descends again (see FIG. 7). As shown in FIGS. 8 and 9, the yarn having the smaller yarn resistance is pulled up with the balance on the main tone side and the fabric side. Since the thread resistance on the fabric side is very small compared to the thread resistance on the main tone side at the start of sewing, the upper thread on the fabric side is quickly pulled up. At this time, the upper thread is lifted more than the static lifting amount of the balance by the inertia moment of the thread. The upper thread 8A is stepped on the bent portion Q by the presser foot 15 more quickly than when sewing with the reference feed amount. Therefore, the resistance against the moment of inertia is increased, and the thread dropout can be reliably prevented.

  Returning to the flow of FIG. 5, the CPU 71 determines whether or not the pedal 91 is ON (S18). When the operator stops the sewing operation, the operator removes his / her foot from the pedal 91 and turns it off. When the CPU 71 determines that the pedal 91 is turned off (S18: NO), the CPU 71 stops driving the sewing machine motor 87 (S20) and ends the sewing process.

  On the other hand, when the CPU 71 determines that the pedal 91 is still ON (S18: YES), the CPU 71 determines whether or not the sewing needle 14 has entered the Nth stitch (S19). In the present embodiment, the number N of stitches stored in the RAM 73 is 2. Therefore, in this embodiment, the CPU 71 determines whether or not the sewing needle 14 has entered the second stitch (S19). The CPU 71 returns to S18 until the second stitch is entered (S19: NO), and continues the sewing operation while the pedal 91 is ON (S18: YES). When it is determined that the CPU 71 has entered the second needle (S19: YES), the CPU 71 determines whether or not the feed dog 32 is below the needle plate 11 as shown in the flow of FIG. 8 (S22). While the feed dog 32 is above the needle plate 11, the cloth 10 is being transferred in the forward feed direction. If the feed amount is returned to the reference feed amount (M) during the transfer of the fabric 10, the fabric 10 may be relied on and a beautiful seam may not be formed. Therefore, until the CPU 71 determines that the feed dog 32 is below the needle plate 11 (S22: NO), the CPU 71 returns to S22 and enters a standby state.

  When the CPU 71 determines that the feed dog 32 is below the needle plate 11 (S22: YES), the CPU 71 executes a feed amount return process (S23). In the feed amount return processing, the CPU 71 drives the feed amount adjustment motor 22 to return the feed amount of one pitch by the feed dog 32 to the reference feed amount (M). As shown in FIG. 7, the horizontal feed phase of the feed dog 32 is smaller in the second stitch than in the first stitch. Furthermore, since the feed dog 32 is below the needle plate 11, the cloth 10 is not fed. By returning the feed amount to the reference feed amount (M) in this state, the cloth 10 can be normally transferred when the feed dog 32 moves above the needle plate 11 in the next cycle. Therefore, the stitches after the second stitch can be formed beautifully.

  The CPU 71 determines whether or not the pedal 91 is ON (S24). When the CPU 71 determines that the pedal 91 is turned off (S24: NO), the CPU 71 stops driving the sewing machine motor 87 (S27), and ends the sewing process. On the other hand, if the CPU 71 determines that the pedal 91 is still ON (S24: YES), the CPU 71 then determines whether or not the pedal 91 has been depressed (S25). The operator performs thread trimming to finish the seam in the fabric 10. In order to perform thread trimming, for example, the operator depresses the pedal 91 to the heel side. When the CPU 71 determines that there is no stepping back (S25: NO), the CPU 71 returns to S24 and continues to monitor the ON / OFF state of the pedal 91 and the presence / absence of the stepping operation.

  When the CPU 71 determines that the operator has stepped back to the heel side (S25: YES), the CPU 71 outputs a thread trimming signal and executes a thread trimming operation by a thread trimming mechanism (not shown) (S26). ). The thread trimming mechanism cuts both the upper thread 8A and the lower thread in response to the thread trimming signal. When the thread trimming by the thread trimming mechanism is finished, the CPU 71 stops driving the sewing machine motor 87 and finishes the sewing process.

  As described above, when using the sewing machine 1 of the present embodiment, the operator shortens the remaining length of the needle thread as much as possible in order to reduce the “bird's nest” generated in the cloth 10. The amount of the upper thread drawn into the back side of the cloth 10 by the seam forming operation of the sewing machine 1 is reduced. The sewing machine 1 makes the cloth feed amount at the start of sewing larger than usual. Then, a part of the upper thread 8A is bent, and the bent portion Q can be quickly submerged under the presser foot 15 with respect to the reference feed amount. Since the upper thread 8A is in a state where the bent portion Q is stepped on by the presser foot 15, the resistance on the cloth side of the upper thread becomes large, and even if the upper thread 8A is pulled up by a balance, it is possible to reliably prevent the thread from coming off.

  Further, in the present embodiment, in particular, after adjusting to the enlarged feed amount at the start of sewing, after the second stitch from the start of sewing, when the feed dog 32 moves below the needle plate 11, the reference feed amount is restored. . Therefore, since the cloth does not return to the reference feed amount while the cloth 10 is being fed (for example, after feeding more than the reference feed amount), the seam can be formed cleanly on the cloth 10.

  Furthermore, in this embodiment, in particular, since at least two stitches are sewn from the start of sewing and then adjusted to the reference feed amount (M), the upper thread 8A is quickly bent at the first stitch from the reference feed amount, and the bent portion Q can be stepped on with the presser foot 15.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, in the above embodiment, the CPU 71 returns to the reference feed amount (M) when the feed dog 32 is positioned below the needle plate 11 after sewing the second stitch from the start of sewing. You may return to reference | standard feed amount (M) after sewing the above. The timing for returning to the reference feed amount (M) may be appropriately changed according to the operating conditions of the sewing machine 1, the material of the sewing object, and the like.

In the above embodiment, the “adjustment drive means” of the present invention is constituted by the feed amount adjusting pulley 21, the feed amount adjusting motor 22, the drive pulley 23, and the timing belt 24. May be.

DESCRIPTION OF SYMBOLS 1 Sewing machine 8A Upper thread 11 Needle plate 14 Sewing needle 15 Work clamp 21 Feed amount adjustment pulley 22 Feed amount adjustment motor 23 Drive pulley 24 Timing belt 32 Feed dog 70 Controller 71 CPU
72 ROM
73 RAM
87 Sewing machine motor

Claims (4)

A sewing needle having a hole through which the upper thread passes and moving up and down;
A needle plate on which a workpiece is placed and has a hole through which the sewing needle passes;
A presser foot for holding the sewing product on the needle plate,
A feed dog that feeds the workpiece in cooperation with the presser foot on the needle plate;
A feed mechanism for driving the feed dog in synchronization with the vertical movement of the sewing needle;
A sewing machine comprising: a feed amount adjusting means capable of adjusting a feed amount of the sewing product per cycle of the vertical movement of the sewing needle in the feed mechanism;
Adjustment driving means for driving the feed amount adjusting means so as to adjust the feed amount of the sewing product by the feed mechanism;
A sewing machine comprising: control means for controlling the adjustment driving means so as to make the feed amount larger than a reference amount which is a preset feed amount of the sewing product at the start of sewing.   The sewing machine according to claim 1, wherein the control means controls the adjustment driving means so as to adjust the reference amount after sewing a predetermined number of stitches from the start of sewing.   The control means controls the adjustment driving means to adjust the reference amount when the feed dog is positioned below the needle plate after sewing the predetermined number of stitches from the start of sewing. The sewing machine according to claim 2, wherein the sewing machine is characterized in that:   4. The sewing machine according to claim 2, wherein the predetermined number of stitches is at least two when the sewing needle first pierces the sewing product from the start of sewing as one stitch. 5.

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