JP5487674B2 - sewing machine - Google Patents

Description

  The present invention relates to a sewing machine having a needle hook timing adjustment mechanism.

  As a prior-art sewing machine equipped with a needle hook timing adjustment mechanism, the needle bar swings by swinging the needle bar by rotating the main shaft so that the needle bar swings to form a staggered stitch. And a first sun gear having a gear formed on the inner periphery, fixed to a rotary shaft connected to the shuttle, and one end loosely fitted to the rotary shafts of the first sun gear and the second sun gear. A planetary gear that is rotatably attached to the other end of the gear holder and is engaged with the first and second sun gears, and a lever mechanism that transmits the needle swinging motion of the needle bar swinging base to the gear holder. A sewing machine including a shuttle speed adjusting device is disclosed (for example, refer to Patent Document 1).

Japanese Patent Publication No. 7-28976

  According to Patent Document 1, the phase of the main shaft (upper shaft) and the rotation shaft (lower shaft) is adjusted in proportion to the swinging amount of the needle bar by the hook speed adjusting device (needle hook timing adjusting mechanism) The timing of encounters with the kettle's sword is always constant. Therefore, when sewing a cloth that is difficult to bend, even if the maximum swing amount of the needle is increased, sewing can be performed without any problem, and a sewing machine having a cloth presser provided with a needle hole through which a wide needle passes can be provided. However, when sewing a soft and stretchy fabric like a jersey fabric, when the needle pierces the fabric and reaches the lowest point, it turns upward and the upper thread forms a loop. The cloth also rises as the needle rises. For this reason, there is a problem in that a loss occurs in the needle up amount, and loops are not often formed and skipping occurs. In particular, with a cloth presser with a wide needle hole, the fabric tends to bend near the center of the needle hole, increasing the needle up amount and increasing the needle up amount in a small swing range, forming a loop. There is a problem that skips frequently.

  The present invention has been made in view of the above problems, and when sewing a cloth that is soft and stretchable like a jersey fabric and is easy to bend, a loop is formed to suppress the occurrence of skipping, An object of the present invention is to provide a sewing machine that can be satisfactorily sewn and is inexpensive.

  In order to solve the above problems, the invention described in claim 1 is a machine frame, an upper shaft that is rotatably supported by the machine frame and drives a needle bar, and a hook that is rotatably supported by the machine frame and drives a hook. A timing belt that connects the upper shaft and the lower shaft to synchronize the rotation of the upper shaft and the rotation of the lower shaft, and a pulley that constantly contacts the timing belt. A sewing machine having a needle hook timing adjustment mechanism for changing the phase, and adjusting the timing of the encounter between the needle and the hook according to the needle drop position of the needle fixed to the needle bar.

According to the first aspect of the present invention, of the adjustment of the timing of the encounter between the needle and the hook, the needle up adjustment amount with respect to the deflection of the cloth is larger at the center needle drop position and smaller at the both ends needle drop position side.

  According to the first aspect of the present invention, the timing of the encounter between the needle and the shuttle is adjusted according to the needle drop position in consideration of the amount of deflection of the cloth stuck by the needle fixed to the needle bar. As a result, the timing of the needle-to-hook encounter takes into account the deflection of the cloth with respect to the needle drop position, changes the swing width of the pulley by the needle hook timing adjustment mechanism according to the needle drop position, forms a loop, It is adjusted to suppress the occurrence of blinking. Therefore, it is possible to provide a sewing machine that can be satisfactorily sewn even when the cloth is warped when sewing a cloth that is soft, stretchable and flexible, such as a jersey cloth, and has a thickness that is difficult to remove.

  In addition, when sewing a cloth that is easy to bend, taking into account the amount of flexure of the cloth, the needle hook timing adjustment mechanism provided in the conventional sewing machine allows the needle swing timing adjustment mechanism to adjust the pulley swing width according to the needle drop position. Is adjusted to form a loop and suppress the occurrence of skipping. As a result, a low-cost sewing machine that can be satisfactorily sewn can be provided.

In addition, when sewing a fabric that is easy to bend, the needle up adjustment amount for preventing the occurrence of stitch skipping is larger at the center needle drop position where the needle falls to the center. The smaller the both-end needle drop position side falls on the both ends of. Therefore, even in the range where the swing width is small in the vicinity of the center needle drop position where the cloth is easily bent, the loop is formed and the occurrence of the skipping is suppressed, so that the suppression of the skipping is improved.

It is explanatory drawing which shows the structure of the front of the sewing machine which concerns on the Example of this invention. It is explanatory drawing which shows the structure of the right side surface of FIG. It is a disassembled perspective view of the principal part concerning a tension pulley. It is explanatory drawing which shows formation of the loop at the time of sewing. It is explanatory drawing which shows the timing of an encounter of a needle and a hook. It is explanatory drawing seen from the right side surface which shows typically the operation | movement which adjusts the phase of the upper shaft and lower shaft by the timing pulley by the needle hook timing adjustment mechanism of the sewing machine of this invention. It is explanatory drawing which shows after adjustment of the timing of the needle | hook of the sewing machine of this invention and a shuttle in the case of the cloth which is hard to bend. It is a schematic sectional drawing of the needle hole center of the cloth presser perpendicular | vertical to the feed direction of a cloth. It is a figure which shows the deflection amount of the cloth by the difference in a needle hole width, and the difference in a needle drop position. It is a figure which shows the needle up amount and the needle up amount adjustment amount of a prior art. It is a figure which shows the needle up amount and the needle up adjustment amount of a conventional sewing machine and the sewing machine of the present invention. It is a block diagram which shows the control structure of a sewing machine.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  Hereinafter, embodiments of the present invention will be described in detail.

  1 and 2 show a sewing machine 100 according to the present invention. FIG. 1 is an explanatory diagram showing a front configuration, and FIG. 2 is an explanatory diagram showing a configuration on the right side of FIG. The sewing machine 100 includes an outer shell 1 and a machine casing 2. The upper shaft 3 is rotatably supported by a pair of bearings 4 a and 4 b fixed to the machine casing 2. A hand wheel 5 and a pulley 6 are fixed to one end of the upper shaft 3. A large-diameter driven pulley 6a and a first timing pulley 6b are formed on the pulley 6. A drive belt 7 is hung on the motor pulley 8 and the driven pulley 6a fixed to the upper shaft driving motor 9 fixed to the machine frame 2, and the rotation of the upper shaft driving motor 9 is decelerated and transmitted to the upper shaft 3. . A needle bar crank 10 is fixed to the other end of the upper shaft 3, and the needle bar 12 moves up and down by the crank rod 11. A needle clamp 38 is attached to the tip of the needle bar 12, and the needle 39 is fixed to the needle bar 12. The lower shaft 17 is rotatably supported by bearings 18 and 19 fixed to the machine casing 2. A second timing pulley 20 is fixed to one end of the lower shaft 17 by a set screw 21. The second timing pulley 20 and the first timing pulley 6b are set to the same number of teeth. On the other hand, a screw gear (not shown) is fixed to the other end of the lower shaft 17, and a hook (not shown) is doubled and rotated. A timing belt 22 is wound around the first timing pulley 6b and the second timing pulley 20, and the upper shaft 3 and the lower shaft 17 normally rotate at a constant speed.

  A needle hook timing adjustment mechanism 23 is provided near the first timing pulley 6b and the second timing pulley 20, and the tension pulleys 13 and 14 (pulleys) of the needle hook timing adjustment mechanism 23 are always in contact with the timing belt 22. Yes. FIG. 3 is an exploded perspective view of the main parts related to the tension pulleys 13 and 14. The needle hook timing adjustment mechanism 23, the lower shaft 17, the first timing pulley 6 b (FIG. 1), the second timing pulley 20, and FIG. Indicates. In the machine frame 2, a shaft 15 is protruded in the vicinity of the timing belt 22 traveling approximately in the middle between the first timing pulley 6 b and the second timing pulley 20. The tension pulley bracket 56 has a substantially triangular shape, and a bush 57 that engages with the shaft 15 projects from the upper corner, and a shaft 28 projects from the lower corner. A tension pulley 13 is rotatably coupled to the shaft 28. The other corner is bent at a right angle, a female screw 56 a is bored, and the worm screw 29 is screwed and locked by the nut 30.

  The tension pulley bracket 31 is bent in a U-shape at the top and has holes 31a and 31a, is rotatably engaged with the outer periphery of the bush 57, and has a shaft 32 protruding at the lower end. The tension pulley 14 is rotatably coupled to the shaft 32. In addition, a pin 33 protrudes on the opposite side of the shaft 32 at the substantially central portion. The tension pulley bracket 56 and the tension pulley bracket 31 are supported coaxially on the machine frame 2. Similar to the tension pulley bracket 31, the cam follower arm 34 is bent in a U shape at the top, and the holes 34 b and 34 b are opened. The cam follower arm 34 is rotatably engaged with the outer periphery of the bush 57. Further, the cam driven arm 34 is sandwiched between the U-shaped bent portions of the tension pulley bracket 31. The spacer 36 is provided to make the movement of the cam driven arm 34 smooth. The cam follower arm 34 is provided with a pin 35 at its lower end and a projection 34a. The tension pulley bracket 56, the tension pulley bracket 31, and the cam follower arm 34 are rotatable about the shaft 15 of the machine casing 2, respectively. Then, it is locked in the axial direction by a retaining ring 37. The needle hook timing adjusting motor 24 is screwed to the bracket 59 by a screw 61. Further, the bracket 59 is screwed to the machine frame 2 by screws 62 (FIG. 2).

  The cam 58 is a plate cam and has two cam surfaces 58a and 58b that are substantially symmetrical with respect to the vertical axis and are press-fitted and fixed to the rotary shaft 24a of the needle hook timing adjusting motor 24. ing. The cam surface 58 a is in contact with the pin 35 of the cam driven arm 34. The cam surface 58 b is in contact with the pin 33 of the tension pulley bracket 31. Further, the tip of the worm screw 29 attached to the tension pulley bracket 56 is in contact with the protrusion 34 a of the cam driven arm 34. As a result, when the needle hook timing adjusting motor 24 rotates, the pair of tension pulleys 13 and 14 swing left and right about the shaft 15 in FIG. Although not shown, the needle hook timing adjusting motor 24 is operated by computer control in accordance with information such as the rotation and swing amount of the upper shaft 3, the yarn type, the fabric type, and the like. The needle hook timing adjustment mechanism 23 is configured as described above. The needle hook timing adjustment mechanism 23 changes the phase of the upper shaft 3 and the lower shaft 17 according to the swing width of the tension pulleys 13 and 14.

  As shown in FIG. 1, a presser bar 25 having a presser bar holding 26 and a presser holder 27 at the lower end is attached to the machine frame 2 by a bush so as to be movable up and down, behind the needle bar 12 of the machine frame 2. ing. The presser bar 25 is urged downward by a presser bar spring (not shown) provided between the machine casing 2 and the presser bar holder 26. A cloth presser 40 is rotatably attached to the presser holder 27 and conveys the cloth in the feed direction in cooperation with a feed dog (not shown) during sewing.

  FIG. 4 is an explanatory view showing formation of a loop at the time of sewing. A loop is formed in the upper thread 16 by raising the needle 39 from the lowest point. The seam is formed by the sword tip 41a (FIG. 5) of the hook 41 catching the loop of the upper thread 16 that is formed when the needle 39 pierces the cloth and reaches the lowest point and then turns upward. If the raising amount H (FIG. 4) of the needle 39 from the lowest point until the sword tip 41a of the hook 41 reaches the position of the needle and catches the loop is small, the loop is not formed or the loop becomes small. The tip of the sword 41a cannot catch the loop, causing the eyes to skip. Further, if the pressing force of the cloth is not sufficient when the needle 39 pierces the cloth and reaches the lowest point, the cloth also rises as the needle 39 rises, causing a loss in the needle up amount H. When the loop is not formed or becomes small, the sword tip cannot catch the loop, and the seam is not formed, resulting in skipping. Here, the loss of the needle up amount is obtained by subtracting the needle up amount of the bent fabric from the needle up amount of the unsagable cloth, with the needle up amount as a reference when the needle 39 is pulled up. The value is equal to the amount of deflection of the fabric.

  FIG. 5 is an explanatory diagram showing the timing of encounter between the needle 39 of the sewing machine 100 and the sword tip 41a of the shuttle 41. As shown in FIG. When the zigzag sewing is performed, the needle up amount is −θ earlier when the needle 41 and the sword tip 41a of the hook 41 meet with each other depending on the swing width, and −θ earlier when the right needle is dropped. Therefore, in the center needle drop, the right needle drop, and the left needle drop, the needle up amount for loop formation is hM, hR, and hL, respectively, and the size of the loop necessary for sewing is not constant.

  FIG. 6 is an explanatory view schematically showing an operation of adjusting the phases of the upper shaft 3 and the lower shaft 17 by the timing pulleys 13 and 14 by the needle hook timing adjusting mechanism 23 (FIG. 1) of the sewing machine 100 of the present invention. The phase of the upper shaft 3 and the lower shaft 17 is changed by swinging the tension pulleys 13 and 14 left and right with the shaft 15 as a fulcrum by the needle hook timing adjusting motor 24 (FIG. 1). In the case of the left needle drop, the second timing pulley 20 is advanced with respect to the first timing pulley 6b by + θ / 2 for the case of the center needle drop. In the case of the right needle drop, the second timing pulley 20 is retarded with respect to the first timing pulley 6b by −θ / 2 minutes with respect to the case of the center needle drop.

  FIG. 7 is an explanatory diagram showing a state after adjusting the timing of encounter between the needle 39 of the sewing machine 100 of the present invention and the sword tip 41a of the shuttle 41 when sewing a cloth that is difficult to bend. The needle hook timing adjustment mechanism 23 adjusts the swing width of the timing pulleys 13 and 14 to adjust the phases of the upper shaft 3 and the lower shaft 17. By this adjustment, the needle up amount ho can be kept constant at the center needle drop, the right needle drop, and the left needle drop.

  By the way, the cause of “jumping” is due to the expansion and contraction of the cloth, as well as the difference in the needle up amount due to the timing difference between the needle 39 and the sword tip 41a of the hook 41 due to the swing width as described above. There is a loss of needle up amount. In the case of a cloth that is difficult to bend, the stitch jump caused by the timing difference between the contact between the needle 39 and the sword tip 41a of the hook 41 is caused by the needle hook timing adjustment mechanism 23 with respect to the needle drop position with the central needle drop position as the origin. This can be resolved by adjusting the needle up adjustment amount in proportion. However, in the case of sewing a cloth that is soft and stretchable, such as a jersey fabric, and is thick and difficult to remove the needle 39, the needle due to the expansion and contraction of the cloth and the deflection can be obtained only by proportional adjustment of the above-mentioned needle up adjustment amount. Blindness frequently occurs due to loss of the amount of uplink. Hereinafter, the adjustment of the needle up when sewing a cloth that is easily bent will be described.

  FIG. 8 is a schematic cross-sectional view of the center of the needle hole 40a of the presser foot 40 perpendicular to the cloth feeding direction, and shows the expansion and contraction and deflection of the cloth. FIG. 8A shows the case of a cloth that is difficult to bend, and no loss in the needle up amount occurs. 8B to 8D show the case of a cloth (for example, a jersey cloth) that is stretchable and easy to bend. In FIG. 8B, when the needle 39 is stabbed into the cloth, the cloth is pulled by the tip of the needle 39 due to the resistance of the cloth, and the amount of deflection of the cloth becomes Δh1. In FIG. 8C, when the needle 39 rises after reaching the lowest point, the cloth stretched by Δh1 contracts and the amount of deflection becomes Δh2. During this time, since the needle 39 and the cloth rise together, no loop is formed. As shown in FIG. 8D, even after the lower surface of the cloth returns to the position of the upper surface 60b of the needle plate 60, the needle 39 and the thread rise together as the cloth is bent by the resistance of the needle 39 and the thread. In some cases, the amount of deflection becomes Δh3. During this time, the needle 39 and the cloth rise as a unit, so that no loop is formed.

  Further, in the sewing machine 100 of the present invention provided with the needle hook timing adjustment mechanism 23, when sewing a cloth which is difficult to bend as described above, the needle up amount is constant regardless of the swing width of the needle 39. The maximum swing width can be increased. Along with this, the presser foot 40 inevitably increases, and the widths of the needle hole 40a of the presser foot 40 and the needle hole 60a of the needle plate 60 (the width in the swing direction of the needle 39) also increase (FIG. 9). FIG. 9 shows the amount of deflection of the cloth due to the difference in the needle hole width and the difference in the needle drop position. In the figure, (a) shows the amount of deflection Δh3 of the cloth at the center needle drop position when the width of the cloth needle hole 40a and the width of the needle hole 60a are small. (B) and (c) are cases where the width of the needle hole 40a and the width of the needle hole 60a are large, (b) shows the deflection amount Δh4 of the cloth of the center needle drop, and (c) is the cloth of the right needle drop. The amount of deflection Δh5 is shown. The deflection amount Δh4 is larger than the deflection amount Δh5, and the loss of the needle up amount is also large. In the needle drop at both the left and right ends, the left and right ends of the needle hole press the cloth, so the amount of deflection Δh5 decreases. Further, the large deflection amount Δh4 of the needle holes 40a, 60a is larger than the small deflection amount Δh3 of the needle holes 40a, 60a. In this way, even if the needle up amount is made constant by the needle hook timing adjustment mechanism 23 regardless of the swing width of the needle 39, the needle up amount is lost due to the deflection of the cloth during actual sewing. With needle drop, the amount of needle rise changes, and the more the needle drop at the center, the easier it is to skip. Such skipping due to the cause is soft and stretchable like a jersey fabric, and is particularly likely to occur when sewing a thick cloth.

  FIG. 10 shows a needle drop position, a needle up amount and a needle up adjustment amount according to the prior art. As shown in FIG. 10, in a sewing machine that does not have a conventional needle hook timing adjustment mechanism, the needle up amount is larger as the left needle is dropped, and is smaller as the right needle is dropped. A downward straight line hn is obtained. In the sewing machine provided with the conventional needle hook timing adjustment mechanism shown in Patent Document 1, the needle hook timing adjustment mechanism (hook speed adjusting device) is configured by combining gears. It becomes a constant value ho connecting. In this case, the needle up adjustment amount Co is proportional to the center needle drop position as the origin, and the needle up position is proportional to the right as shown by the triangle mark.

  FIG. 11 shows the needle up amount and the needle up amount adjustment amount of the conventional sewing machine and the sewing machine 100 of the present invention, and FIG. 12 is a block diagram showing the control configuration of the sewing machine 100 of the present invention. The sewing machine 100 of the present invention adjusts the timing of the encounter between the needle 39 and the sword tip 41a of the shuttle 41 in anticipation of a needle up loss at the time of actual sewing in which the cloth bends. That is, when sewing a cloth that is easily bent, the needle up adjustment amount C in adjusting the timing of encounter between the needle 39 and the sword tip 41a of the hook 41 is a constant value ho (FIG. 7, FIG. 7). The needle up adjustment amount Cc due to the deflection of the cloth according to the position at which the needle falls is added to the needle up adjustment amount Co (FIG. 10) (FIG. 10). Accordingly, the needle up adjustment amount C according to the present invention is C = Co + Cc, and the needle up amount is a curve hc connecting black circles.

  As shown in FIG. 11, with the center needle drop position as the origin, adjustment of the needle up amount of the conventional sewing machine is a straight line that goes up to the right on the premise that the cloth does not bend, but when sewing a cloth that is easy to bend First, since the adjustment of the needle up amount of the sewing machine according to the present invention is made in consideration of the deflection of the cloth, it is set to a non-linear curve on the upper right. Then, the needle up adjustment amount C with respect to the deflection of the cloth is set to be larger at the center needle drop position and smaller at both the left and right ends where the needle 39 is swung. Accordingly, the needle up amount of the sewing machine 100 of the present invention becomes a substantially constant value for any needle drop position even when the cloth is bent.

  Specifically, an adjustment amount C is set for the needle drop position when sewing a soft, stretchable and thick fabric, for example, a jersey fabric, and this adjustment amount C is set in advance by the central processing unit 42 (FIG. 12). Enter in and store. For example, when the user selects the jersey fabric mode, this command is input to the central processing unit 42, and the central processing unit 42 transmits the stored adjustment amount C information to the needle drive timing adjusting motor drive circuit 47. The needle hook timing adjusting motor 24 is rotated. Then, the swing width of the tension pulleys 13 and 14 is changed, and the timing of the encounter between the needle 39 and the sword tip 41a of the hook 41 is adjusted so as to prevent the occurrence of skipping.

  As shown in FIG. 12, the central processing unit 42 (CPU) receives information such as a pattern type, a swing width, and a feed amount from a setting input device 52 and displays the information on a display device 51 that is a liquid crystal touch panel. Further, the central processing unit 42 stores in advance data of the needle up adjustment amount with respect to the needle drop position of a cloth (for example, a jersey cloth) that is easily bent. Information from the buttonhole switching detection means 53, the upper shaft rotation speed sensor 54, and the presser foot vertical position detection means 55 is also sent to the central processing unit 42. Based on the sent information, the central processing unit 42 uses the width-determining motor drive circuit 50 to set the width-determining motor 43, the feed-rate adjusting motor drive circuit 49 to set the feed-rate adjusting motor 44, and the upper-axis drive. The motor driving circuit 48 controls the upper shaft driving motor 9 and the needle hook timing adjusting motor driving circuit 47 controls the needle hook timing adjusting motor 24, respectively.

  As described above, when sewing a cloth such as a jersey fabric that is soft, stretchable and flexible, and has a thickness that is difficult to remove the needle 39, the central arithmetic unit 42 takes into account the needle hook timing adjustment mechanism 23 in consideration of the cloth deflection. The swing widths of the tension pulleys 13 and 14 are controlled, and the phases of the upper shaft 3 and the lower shaft 17 are adjusted. Thereby, the timing of the encounter between the needle 39 and the sword tip 41a of the hook 41 is adjusted according to the needle drop position in consideration of the amount of deflection of the cloth. Therefore, even if the cloth is deflected, the sewing machine 100 can be provided in which loops are formed and the occurrence of skipping is suppressed and good sewing can be performed.

  Further, even when the deflection occurs, the occurrence of skipping is suppressed, so that the maximum swing width of the needle 39 can be increased.

  Further, when sewing a cloth that is easily bent, the central processing unit 42 used in the conventional sewing machine takes into account the amount of bending of the cloth and the tension pulleys 13 and 14 of the conventional needle hook timing adjustment mechanism 23 are swung. Control the width. Accordingly, since the timing of encounter between the needle 39 and the sword tip 41a of the hook 41 is adjusted appropriately, a loop is formed when sewing a cloth that is easily bent, the occurrence of skipping is suppressed, and good sewing is possible. Inexpensive sewing machine 100 can be provided.

  Further, among the needle up adjustment amount C, the needle up adjustment amount Cc due to the deflection of the cloth is set to be larger at the center needle drop position and smaller at both the left and right ends. Therefore, even in the range where the swing width is small in the vicinity of the center needle drop position where the cloth is easily bent, the loop is formed and the occurrence of skipping is suppressed.

2 Machine frame 3 Upper shaft 12 Needle bar 13, 14 Tension pulley (pulley)
17 Lower shaft 22 Timing belt 23 Needle hook timing adjustment mechanism 39 Needle 41 Hook 100 Sewing machine

Claims (1)

The machine frame,
An upper shaft that is rotatably supported by the machine frame and drives the needle bar;
A lower shaft that is rotatably supported by the machine frame and drives the hook;
A timing belt that connects the upper shaft and the lower shaft and synchronizes the rotation of the upper shaft and the rotation of the lower shaft;
A sewing machine comprising a pulley that constantly contacts the timing belt, and a needle hook timing adjustment mechanism that changes a phase of the upper shaft and the lower shaft according to a swing width of the pulley;
Adjust the timing of the encounter between the needle and the hook according to the needle drop position of the needle fixed to the needle bar ,
Among the adjustments of the timing of encounter between the needle and the hook, the needle up adjustment amount for the deflection of the cloth is larger at the center needle drop position and smaller at the both ends needle drop position side,
A sewing machine characterized by that.

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