Sewing machine

Abstract

A sewing machine (100) includes a lower feed mechanism (20) that feeds a workpiece from below a throat plate (101) by conveyor belts (21 to 24) driven by lower feed motors (24 and 25), a needle up-and-down movement mechanism (80) that moves up and down, by a sewing machine motor (16), a needle bar (12) holding a stitch needle (11), a needle feed mechanism (50) that swings, by the sewing machine motor (16), the needle bar (12) holding the stitch needle (11) along a feed direction of the workpiece, and a control device (90) that controls the lower feed motors (24 and 25) to feed the conveyor belts (21 to 24) in accordance with a feed amount of the stitch needle (11) along the feed direction of the workpiece, the feed amount being caused by swinging of the needle bar (12).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a sewing machine that performs belt feed and needle feed.BACKGROUND ART

[0002] There is a needle feed sewing machine that performs feed while piercing a workpiece on a throat plate with a swinging stitch needle, in order to feed the workpiece with high conveying force (see, for example, Patent Literature 1).CITATION LISTPATENT LITERATURE

[0003] Patent Literature 1: JP2020-188825ASUMMARY OF INVENTIONTECHNICAL PROBLEM

[0004] A sewing machine provided with a lower feed mechanism using a belt has the advantages in that the belt does not damage a workpiece, the feed speed can be easily varied, and the number of components of the mechanism is small.

[0005] Accordingly, in needle feed sewing machines as well, it is considered to mount the lower feed mechanism for belt feed.

[0006] However, since the needle feed mechanism is configured to swing the needle bar that moves up and down, the feed speed of the workpiece varies with each upper shaft angle, whereas the lower feed mechanism for belt feed has a constant feed speed, potentially resulting in a mismatch between the respective feed speeds.

[0007] An object of the present disclosure is to smoothly feed a workpiece.SOLUTION TO PROBLEM

[0008] The present disclosure provides a sewing machine including: a lower feed mechanism configured to feed a workpiece from below a throat plate by a conveyor belt driven by a lower feed motor, a needle up-and-down movement mechanism configured to move up and down, by a sewing machine motor, a needle bar configured to hold a stitch needle, a needle feed mechanism configured to swing, by the sewing machine motor, the needle bar configured to hold the stitch needle along a feed direction of the workpiece, and a control device configured to control the lower feed motor to feed the conveyor belt in accordance with a feed amount of the stitch needle along the feed direction of the workpiece, the feed amount being caused by swinging of the needle bar. ADVANTAGEOUS EFFECTS OF INVENTION

[0009] The sewing machine of the present disclosure enables smooth feed of a workpiece by the above configuration.BRIEF DESCRIPTION OF DRAWINGS

[0010] [FIG. 1] FIG. 1 is a rear view of a sewing machine according to an embodiment of the present disclosure. [FIG. 2] FIG. 2 is a left side view of the sewing machine. [FIG. 3] FIG. 3 is a perspective view of the sewing machine. [FIG. 4] FIG. 4 is a perspective view showing an upper surface of a left end portion of a sewing machine bed portion (a presser foot is not shown). [FIG. 5] FIG. 5 is a perspective view of a guide frame of a lower feed mechanism. [FIG. 6] FIG. 6 is a perspective view of a feed mechanism in which four conveyor belts are in a front-and-rear differential feed state. [FIG. 7] FIG. 7 is a perspective view of the feed mechanism in which the four conveyor belts are in a left-and-right differential feed state. [FIG. 8] FIG. 8 is a diagram showing a needle up-and-down movement mechanism and a needle feed mechanism. [FIG. 9] FIG. 9 is an exploded perspective view of the needle up-and-down movement mechanism and the needle feed mechanism. [FIG. 10] FIG. 10 is a diagram illustrating a principle of a needle feed adjustment mechanism. [FIG. 11] FIG. 11 is a diagram illustrating the principle of the needle feed adjustment mechanism. [FIG. 12] FIG. 12 is a block diagram showing a control system of the sewing machine. [FIG. 13] FIG. 13 is a diagram illustrating a relationship between a feed amount, in a front-and-rear direction, of a stitch needle fed by the needle feed mechanism and a shaft angle of an upper shaft. [FIG. 14] FIG. 14 is a flowchart showing feed operation control of the sewing machine. [FIG. 15] FIG. 15 is a plan view of an example in which a detection device for detecting a position of a stitch needle on a throat plate is provided. DESCRIPTION OF EMBODIMENTS[Schematic Configuration of Embodiment]

[0011] Hereinafter, a sewing machine, which is an embodiment of the present disclosure, will be described in detail.

[0012] FIG. 1 shows a rear view of a sewing machine 100, FIG. 2 shows a left side view of the sewing machine 100, and FIG. 3 shows a perspective view of the sewing machine 100.

[0013] Hereinafter, the downstream side of the feed direction of the workpiece is referred to as "front", the upstream side of the feed direction is referred to as "rear", the left side when facing forward is referred to as "left", the right side is referred to as "right", the vertically upward direction is referred to as "up", and the vertically downward direction is referred to as "down". The front-and-rear, left-and-right, and up-and-down directions are orthogonal to each other.

[0014] In the following description, it is assumed that the sewing machine 100 is installed on a horizontal plane, and the front-and-rear and left-and-right directions are horizontal.

[0015] As the sewing machine 100, which is an embodiment of the present disclosure, a so-called lockstitch sewing machine is exemplified.

[0016] The sewing machine 100 includes a sewing machine frame 110, a needle up-and-down movement mechanism 80, a needle feed mechanism 50, a lower feed mechanism 20, a cloth presser mechanism 70 as a presser mechanism, a shuttle mechanism, and a control device 90.

[0017] The needle up-and-down movement mechanism 80 applies an up-and-down movement to a needle bar 12 that holds a stitch needle 11.

[0018] The needle feed mechanism 50 applies a swinging motion, in a feed direction of a workpiece, to the needle bar 12 that holds the stitch needle 11.

[0019] The lower feed mechanism 20 applies a feed movement, in the front-and-rear direction, from below to the workpiece on the throat plate 101.

[0020] The cloth presser mechanism 70 applies pressing pressure to the workpiece on the throat plate 101.

[0021] The shuttle mechanism captures a loop of upper thread from the stitch needle 11 and entwines it with a lower thread, thereby forming a seam.

[0022] The control device 90 executes operation control of each of the above components.

[0023] Note that the sewing machine 100 includes various components, such as a thread tensioner, which are included in general lockstitch sewing machines. However, the descriptions thereof are omitted as they are well-known in the art.[Sewing Machine Frame]

[0024] The sewing machine frame 110 supports or houses each component of the sewing machine 100 described above.

[0025] The sewing machine frame 110 includes a sewing machine bed portion 111, an upright drum portion 112, and a sewing machine arm portion 113.

[0026] The sewing machine bed portion 111 is located at a lower portion of the sewing machine 100 and extends in the left-and-right direction.

[0027] The upright drum portion 112 is erected from a right end portion of the sewing machine bed portion 111.

[0028] The sewing arm portion 113 extends leftward from an upper end portion of the upright drum portion 112.

[0029] FIG. 4 is a perspective view showing an upper surface of a left end portion of the sewing machine bed portion 111. In FIG. 4, a presser foot described below is omitted.

[0030] A combined opening portion 102 is formed at a stitch point position of the stitch needle 11 with respect to the throat plate 101. In the combined opening portion 102 of the throat plate 101, an eye member 30 having an eye 13, a rear left lower belt 21, a front left lower belt 22, a front right lower belt 23, and a rear right lower belt 24 of the lower feed mechanism 20 described below are arranged to be exposed upward. That is, the combined opening portion 102 has a shape in which a plurality of rectangular opening portions through which the eye member 30 and each of the lower belts 21 to 24 are exposed are integrally combined.[Shuttle Mechanism]

[0031] As shown in FIGS. 2 and 3, the shuttle mechanism includes an outer shuttle 14 and an inner shuttle 15 provided on a lower side of the eye member 30 of the throat plate 101, and a shuttle shaft (not shown) for rotating the inner shuttle 15.

[0032] The shuttle shaft is rotatably supported within the sewing machine bed portion 111, while extending in the left-and-right direction. Rotation about an axis extending in the left-and-right direction, which is transmitted from the upper shaft and increased to a speed twice that of the upper shaft via a gear mechanism or a belt mechanism, is input to the shuttle shaft.

[0033] The inner shuttle 15 is housed inside the outer shuttle 14. Additionally, the inner shuttle 15 houses a bobbin (not shown) that supplies a lower thread inside the inner shuttle 15.

[0034] The outer shuttle 14 is connected to a left end portion of the shuttle shaft and rotates around the inner shuttle 15. The inner shuttle 15 is restricted from rotating so as not to rotate together with the outer shuttle 14. The outer shuttle 14 has a hook for capturing a loop of upper thread from the stitch needle 11 at an outer periphery thereof. By rotating, the outer shuttle 14 is capable of capturing a loop of upper thread with its hook and passing the loop under a lower thread reeled out from inside the inner shuttle 15.

[0035] The outer shuttle 14 and the inner shuttle 15 are arranged in a housed state within a substantially cylindrical guide frame 29 of the lower feed mechanism 20 described below.[Lower Feed Mechanism]

[0036] FIG. 5 is a perspective view of the guide frame 29 of the lower feed mechanism 20, and FIGS. 6 and 7 are perspective views of the lower feed mechanism 20. FIGS. 6 and 7 show different wrapping states of the respective lower belts 21 to 24 described below.

[0037] Below, the lower feed mechanism 20 will be described in detail based on FIGS. 1 to 7.

[0038] As shown in each drawing, the lower feed mechanism 20 includes each of the lower belts 21 to 24 as conveyor belts, a first motor 25 and a second motor 26 as lower feed motors, rotation shafts 27 and 28, a first pulley 31, and a second pulley 32.

[0039] In addition, the lower feed mechanism 20 includes a guide frame 29 that guides each of the lower belts 21 to 24 to come into contact with a lower surface of a workpiece, a first pressurizing mechanism 33, and a second pressurizing mechanism 34.

[0040] Both the first motor 25 and the second motor 26 are motors whose operation amount can be arbitrarily controlled. The first motor 25 and the second motor 26 are, for example, stepping motors or servo motors. Both the first motor 25 and the second motor 26 are arranged on an inner side of a right end portion of the sewing machine bed portion 111 in a state of being aligned in the front-and-rear direction, with output shafts oriented leftward.

[0041] The first pulley 31 is connected to the output shaft of the front-side first motor 25 via the rotation shaft 27.

[0042] The second pulley 32 is connected to the output shaft of the rear-side second motor 26 via the rotation shaft 28.

[0043] Both the rotation shafts 27 and 28 are parallel in the left-and-right direction and are rotatably supported within the sewing machine bed portion 111.

[0044] The first pulley 31 and the second pulley 32 are rotatably supported about axes extending in the left-and-right directions within a left end portion of the sewing machine bed portion 111. The first pulley 31 and the second pulley 32 are rotationally driven by the first motor 25 and the second motor 26 via the rotation shafts 27 and 28, respectively.

[0045] The first pulley 31 and the second pulley 32 are arranged in an overlapping manner when viewed from the front-and-rear direction. That is, the first pulley 31 and the second pulley 32 are positioned at the same height and at the same location in the left-and-right direction. Additionally, the first pulley 31 is arranged forward of the second pulley 32.

[0046] Both the first pulley 31 and the second pulley 32 can be wrapped with all of the lower belts 21, 22, 23, and 24, which are arranged in parallel in the left-and-right direction.

[0047] That is, the first pulley 31 has, on its outer peripheral surface, a left groove 311 for wrapping the rear left lower belt 21 and the front left lower belt 22, and a right groove 312 for wrapping the front right lower belt 23 and the rear right lower belt 24.

[0048] The second pulley 32 has, on its outer peripheral surface, a left groove 321 for wrapping the rear left lower belt 21 and the front left lower belt 22, and a right groove 322 for wrapping the front right lower belt 23 and the rear right lower belt 24.

[0049] Each of the lower belts 21 to 24 has the same width, and the left grooves 311 and 321 and the right grooves 312 and 322 all have a width corresponding to at least two belts.

[0050] Accordingly, each of the lower belts 21 to 24 can be selectively wrapped around the first pulley 31 or the second pulley 32.

[0051] Each of the lower belts 21, 22, 23 and 24 has an endless loop shape and is wrapped between the guide frame 29 and the first pulley 31 or between the guide frame 29 and the second pulley 32.

[0052] In addition, the respective lower belts 21, 22, 23, and 24 are arranged in parallel in the order from left to right.

[0053] As shown in FIG. 2, the guide frame 29 (guide member) is arranged so as to substantially coincide with the first pulley 31 and the second pulley 32 in the left-and-right direction and to be located between the first pulley 31 and the second pulley 32 in the front-and-rear direction. Additionally, the guide frame 29 is arranged above the first pulley 31 and the second pulley 32, and directly below the throat plate 101.

[0054] As shown in FIG. 5, the guide frame 29 includes a bracket portion 295 for fixing the guide frame 29 within the sewing machine bed portion 111, and a cylindrical main body portion 296 for guiding each of the lower belts 21 to 24.

[0055] The guide frame 29 is arranged directly below the throat plate 101 with a central axis of the main body portion 296 oriented in the left-and-right direction.

[0056] A fitting groove 297 extending in the front-and-rear direction is formed at a center, in the left-and-right direction, of an upper portion of an outer peripheral surface of the main body portion 296. The plate-shaped eye member 30, which is elongated in the front-and-rear direction, is fixedly fitted and arranged inside the fitting groove 297. The eye member 30 is formed with an eye 13 penetrating in the up-and-down direction at a stitch point position. Note that since the needle bar 12 swings in the front-and-rear direction by the needle feed mechanism 50, the eye 13 into which the stitch needle 11 enters is formed in a long hole shape, which is elongated in the front-and-rear direction.

[0057] A surface of the eye member 30 where the eye 13 is formed is flush with or slightly higher than an upper surface of the throat plate 101.

[0058] In addition, the main body portion 296 allows each of the lower belts 21 to 24 to circumferentially slide on the upper portion of its outer peripheral surface, thereby feeding a workpiece. To this end, a first guide portion 291, a second guide portion 292, a third guide portion 293, and a fourth guide portion 294 are provided on the upper portion of the outer peripheral surface of the main body portion 296 to respectively guide the lower belts 21 to 24.

[0059] The first guide portion 291 is provided at the left rear of the eye 13, the second guide portion 292 is provided at the left front of the eye 13, the third guide portion 293 is provided at the right front of the eye 13, and the fourth guide portion 294 is provided at the right rear of the eye 13.

[0060] Each of the guide portions 291 to 294 is a projection extending in the front-and-rear direction. A width in the left-and-right direction of each of the guide portions 291 to 294 is equal to or slightly greater than a width of each of the lower belts 21 to 24. A rear end portion of each of the guide portions 291 to 294 forms a slope in which an amount of protrusion radially outward from the outer peripheral surface of the main body portion 296 gradually increases toward the front. In addition, a front end portion of each of the guide portions 291 to 294 forms a slope in which an amount of protrusion radially outward from the outer peripheral surface of the main body portion 296 gradually decreases toward the front.

[0061] The first guide portion 291 is located to the left of the eye 13 and rearward of the center position in the front-and-rear direction of the eye 13 over almost its entire length.

[0062] The first guide portion 291 has a guide surface 291a (a portion indicated by dots in FIG. 5) that is flat and horizontal forward of its maximum protruding portion in the radially outward direction of the main body portion 296. The guide surface 291a is arranged to face the combined opening portion 102 of the throat plate 101 when viewed from above.

[0063] The guide surface 291a is set such that an outer surface of the rear left lower belt 21, which passes in sliding contact on the guide surface 291a, is slightly higher than the upper surface of the throat plate 101.

[0064] The guide surface 291a is formed such that a front end portion of the guide surface 291a is located slightly rearward of the center position in the front-and-rear direction of the eye 13, and the rear left lower belt 21 comes into contact with a workpiece rearward of the center position in the front-and-rear direction of the eye 13.

[0065] The second guide portion 292 is located to the left of the eye 13, to the right of the first guide portion 291, and forward of the center position in the front-and-rear direction of the eye 13 over almost its entire length.

[0066] The second guide portion 292 has a guide surface 292a (a portion indicated by dots in FIG. 5) that is flat and horizontal rearward of its maximum protruding portion in the radially outward direction of the main body portion 296. The guide surface 292a is arranged to face the combined opening portion 102 of the throat plate 101 when viewed from above.

[0067] The guide surface 292a is set such that an outer surface of the front left lower belt 22, which passes in sliding contact on the guide surface 292a, is slightly higher than the upper surface of the throat plate 101.

[0068] The guide surface 292a is formed such that a rear end portion of the guide surface 292a is located slightly forward of the center position in the front-and-rear direction of the eye 13, and the front left lower belt 22 comes into contact with a workpiece forward of the center position in the front-and-rear direction of the eye 13.

[0069] The third guide portion 293 is located to the right of the eye 13 and forward of the center position in the front-and-rear direction of the eye 13 over almost its entire length.

[0070] The third guide portion 293 has a guide surface 293a (a portion indicated by dots in FIG. 5) that is flat and horizontal rearward of its maximum protruding portion in the radially outward direction of the main body portion 296. The guide surface 293a is arranged to face the combined opening portion 102 of the throat plate 101 when viewed from above.

[0071] The guide surface 293a is set such that an outer surface of the front right lower belt 23, which passes in sliding contact on the guide surface 293a, is slightly higher than the upper surface of the throat plate 101.

[0072] The guide surface 293a is formed such that a rear end portion of the guide surface 293a is located slightly forward of the center position in the front-and-rear direction of the eye 13, and the front right lower belt 23 comes into contact with a workpiece forward of the center position in the front-and-rear direction of the eye 13.

[0073] The fourth guide portion 294 is located to the right of the eye 13 and the third guide portion 293 and rearward of the center position in the front-and-rear direction of the eye 13 over almost its entire length.

[0074] The fourth guide portion 294 has a guide surface 294a (a portion indicated by dots in FIG. 5) that is flat and horizontal forward of its maximum protruding portion in the radially outward direction of the main body portion 296. The guide surface 294a is arranged to face the combined opening portion 102 of the throat plate 101 when viewed from above.

[0075] The guide surface 294a is set such that an outer surface of the rear right lower belt 24, which passes in sliding contact on the guide surface 294a, is slightly higher than the upper surface of the throat plate 101.

[0076] The guide surface 294a is formed such that a front end portion of the guide surface 294a is located slightly rearward of the center position in the front-and-rear direction of the eye 13, and the rear right lower belt 24 comes into contact with a workpiece rearward of the center position in the front-and-rear direction of the eye 13.

[0077] The guide surfaces 291a and 294a are provided rearward of the center position in the front-and-rear direction of the eye 13, and the guide surfaces 292a and 293a are provided forward of the center position in the front-and-rear direction of the eye 13. For this reason, when a speed difference (difference in conveying amount) is provided between the rear left lower belt 21 and rear right lower belt 24 on the rear side and the front left lower belt 22 and front right lower belt 23 on the front side, the respective lower belts 21 to 24 can apply a conveying force caused by the front-and-rear feed speed difference (difference in conveying amount) to the workpiece without interfering with each other. Accordingly, a seam as intended is formed during differential feed in the front-and-rear direction, making it possible to improve stitch quality.

[0078] The first pressurizing mechanism 33 applies tension to all of the belts, among the lower belts 21 to 24, wrapped between the guide frame 29 and the first pulley 31, thereby suppressing sagging.

[0079] The first pressurizing mechanism 33 includes a left pressurizing roller 331, a right pressurizing roller 332, a support plate 333, and a base block 334, as shown in FIGS. 2, 3, and 6.

[0080] The support plate 333 has an elongated flat plate shape extending in the front-and-rear and up-and-down directions, and is supported by the base block 334 with its longitudinal direction oriented obliquely upward and forward.

[0081] Additionally, the support plate 333 concentrically and rotatably supports the left pressurizing roller 331 and the right pressurizing roller 332 on left and right surfaces of an upper end portion of the support plate 333. The support plate 333 is arranged such that the left pressurizing roller 331 and the right pressurizing roller 332 come into contact with the outer surface of the belt extending between the guide frame 29 and the first pulley 31 from a lower rear side.

[0082] The base block 334 is shared with the second pressurizing mechanism 34 described below, and supports the structures of the first pressurizing mechanism 33 and the second pressurizing mechanism 34. The base block 334 is fixedly provided below the guide frame 29 within the sewing machine bed portion 111.

[0083] The support plate 333 has an elongated hole extending in the longitudinal direction of the support plate 333, and is fastened and fixed to the base block 334 by two bolts inserted into the elongated hole. The longitudinal direction of the support plate 333 is oriented in a direction approximately orthogonal to the belt that is wrapped around the first pulley 31. Accordingly, the press-contact forces of the left pressurizing roller 331 and the right pressurizing roller 332 against the belt can be adjusted by loosening the bolts and moving the support plate 333 along the elongated hole. In other words, the tension of the belt extending between the guide frame 29 and the first pulley 31 can be adjusted.

[0084] The left pressurizing roller 331 and the right pressurizing roller 332 have the same outer diameter and are supported by the support plate 333 so as to be rotatable about the same axis extending in the left-and-right direction. In addition, the left pressurizing roller 331 and the right pressurizing roller 332 each have a width in the left-and-right direction that is equal to or greater than twice a width of each of the lower belts 21 to 24.

[0085] Accordingly, the left pressurizing roller 331 can be brought into contact with either the rear left lower belt 21 or the front left lower belt 22 wrapped between the guide frame 29 and the first pulley 31.

[0086] Similarly, the right pressurizing roller 332 can be brought into contact with either the front right lower belt 23 or the rear right lower belt 24 wrapped between the guide frame 29 and the first pulley 31.

[0087] The second pressurizing mechanism 34 applies tension to all of the belts, among the lower belts 21 to 24, wrapped between the guide frame 29 and the second pulley 32, thereby suppressing sagging.

[0088] The second pressurizing mechanism 34 includes a left pressurizing roller 341, a right pressurizing roller 342, a support plate 343, and the base block 334 described above, as shown in FIGS. 2, 3, and 6.

[0089] The support plate 343 has the same structure as that of the support plate 333 described above, and is supported by the base block 334 with its longitudinal direction oriented obliquely upward and rearward.

[0090] Additionally, the support plate 343 concentrically and rotatably supports the left pressurizing roller 341 and the right pressurizing roller 342 on left and right surfaces of an upper end portion of the support plate 343. The support plate 343 is arranged such that the left pressurizing roller 341 and the right pressurizing roller 342 come into contact with the outer surface of the belt extending between the guide frame 29 and the second pulley 32 from an upper rear side.

[0091] The support plate 343 also has an elongated hole, and the support plate 343 can be moved along the elongated hole. Accordingly, the contact-press forces of the left pressurizing roller 341 and the right pressurizing roller 342 against the belt wrapped around the second pulley 32 can be adjusted. Therefore, the tension of the belt extending between the guide frame 29 and the second pulley 32 can be adjusted.

[0092] The left pressurizing roller 341 and the right pressurizing roller 342 have the same outer diameter and are supported by the support plate 343 so as to be rotatable about the same axis extending in the left-and-right direction. In addition, the left pressurizing roller 341 and the right pressurizing roller 342 each have a width in the left-and-right direction that is equal to or greater than twice a width of each of the lower belts 21 to 24.

[0093] Accordingly, the left pressurizing roller 341 can be brought into contact with either the rear left lower belt 21 or the front left lower belt 22 wrapped between the guide frame 29 and the second pulley 32.

[0094] Similarly, the right pressurizing roller 342 can be brought into contact with either the front right lower belt 23 or the rear right lower belt 24 wrapped between the guide frame 29 and the second pulley 32.

[0095] Both the left pressurizing roller 331 of the first pressurizing mechanism 33 and the left pressurizing roller 341 of the second pressurizing mechanism 34 can be brought into contact with the rear left lower belt 21 and the front left lower belt 22. Similarly, both the right pressurizing roller 332 of the first pressurizing mechanism 33 and the right pressurizing roller 342 of the second pressurizing mechanism 34 can be brought into contact with the front right lower belt 23 and the rear right lower belt 24.

[0096] Accordingly, each of the lower belts 21 to 24 is provided with tension by either the first pressurizing mechanism 33 or the second pressurizing mechanism 34, regardless of whether it is wrapped around the first pulley 31 or the second pulley 32.

[0097] FIG. 6 shows a state in which the front left lower belt 22 and the front right lower belt 23, which perform feed forward of the stitch point position, are wrapped around the first pulley 31, and the rear left lower belt 21 and the rear right lower belt 24, which perform feed rearward of the stitch point position, are wrapped around the second pulley 32.

[0098] FIG. 7 shows a state in which the rear left lower belt 21 and the front left lower belt 22, which perform feed leftward of the stitch point position, are wrapped around the first pulley 31, and the front right lower belt 23 and the rear right lower belt 24 are wrapped around the second pulley 32.

[0099] When the bolts are loosened and each of the pressurizing rollers 331, 332, 341, and 342 is retracted, each of the lower belts 21 to 24 can be easily removed from each of the pulleys 31 and 32 for replacement and rewrapping.

[0100] Accordingly, it is possible to easily select and perform sewing in the wrapping state of FIG. 6 and sewing in the wrapping state of FIG. 7.

[0101] For example, in the wrapping state of FIG. 6 (a front-and-rear differential feed state), it is possible to perform a so-called shirring stitch in which feed is performed faster on a side forward of the stitch point position than on a side rearward of the stitch point position.

[0102] In addition, in the front-and-rear differential feed state, it is also possible to perform sewing in which feed is performed slower on a side forward of the stitch point position than on a side rearward of the stitch point position and tension is applied to a workpiece.

[0103] In the wrapping state of FIG. 7 (a left-and-right differential feed state), when feed is performed faster on the left side, a curved stitch turning to the right can be performed, and when feed is performed faster on the right side, a curved stitch turning to the left can be performed.

[0104] In addition, since the curvature can be changed depending on the magnitude of the speed difference (difference in conveying amount) between the left and right sides, various curved stitches can be performed.[Cloth Presser Mechanism]

[0105] As shown in FIGS. 1 to 4, the cloth presser mechanism 70 includes a presser foot 71, a presser bar 72, a presser motor 73 (see FIG. 12), and a height sensor 74 (see FIG. 12) as a presser height detection unit.

[0106] The presser bar 72 is arranged in front of and adjacent to the needle bar 12 and is supported so as to be movable up and down within the sewing machine arm portion 113 with oriented in the up-and-down direction.

[0107] An upper end portion of the presser bar 72 is pressed downward by a presser spring (not shown) within the sewing machine arm portion 113. An amount of expansion and contraction of the presser spring can be adjusted by the presser motor 73 whose operation amount can be arbitrarily controlled. Therefore, by controlling the presser motor 73, a pressing pressure of the presser foot 71 can be arbitrarily set.

[0108] In addition, the height sensor 74 that detects a height of the presser bar 72 is provided in association with the presser bar 72. Therefore, after setting the pressing pressure of the presser foot 71 to a specified value, when the height sensor 74 detects that a height of the presser foot 71 varies due to a change in thickness of a workpiece, the pressing pressure can be maintained at a constant set value by controlling the presser motor 73 so that the amount of expansion and contraction of the presser spring does not vary.

[0109] The presser foot 71 is arranged above the combined opening portion 102 of the throat plate 101. The presser foot 71 presses a workpiece from above to appropriately transmit a conveying force caused by each of the lower belts 21 to 24 to the workpiece.

[0110] As shown in FIGS. 1 to 3, the presser foot 71 includes a bottom plate that presses a workpiece from above, and a connecting portion attached to a lower end portion of the presser bar 72.

[0111] The bottom plate is formed in a so-called boat shape with a smooth bottom surface and an upstream side (rear end portion) in a cloth feeding direction curved upward.

[0112] The connecting portion is erected on an upper surface of a front end portion of the bottom plate, and is connected to the bottom plate so as to be swingable to some extent about an axis extending in the left-and-right direction. An upper end portion of the connecting portion is connected to the lower end portion of the presser bar 72.[Needle Up-and-Down Movement Mechanism]

[0113] FIG. 8 is a drawing showing the needle up-and-down movement mechanism 80 and the needle feed mechanism 50, and FIG. 9 is an exploded perspective view of the needle up-and-down movement mechanism 80 and the needle feed mechanism 50.

[0114] As shown in FIGS. 8 and 9, the needle up-and-down movement mechanism 80 includes a needle bar 12 that holds a stitch needle 11, a sewing machine motor 16 that serves as a drive source for up-and-down movement of the needle bar 12, an upper shaft 82 that is connected to an output shaft of the sewing machine motor 16 and performs rotational driving, a needle bar crank 83 that is fixedly provided at a left end portion of the upper shaft 82, a crankshaft 84 that is provided at a position eccentric with respect to a center of rotation of the needle bar crank 83, a crank rod 85 that is rotatably connected, at its upper end portion, to the crankshaft 84 about an axis extending in the left-and-right direction, and a needle bar clamp 86 that clamps and holds the needle bar 12 and is rotatably connected to a lower end portion of the crank rod 85 about an axis extending in the left-and-right direction.

[0115] The sewing machine motor 16 is composed of, for example, a servo motor.

[0116] In addition, a reference sign 87 shown in FIG. 9 indicates a thread take-up lever rotatably supported with respect to the crankshaft 84.

[0117] The upper shaft 82 is rotatably supported within the sewing machine arm portion 113, while extending in the left-and-right direction. The upper shaft 82 is connected to the output shaft of the sewing machine motor 16 and rotates about an axis extending in the left-and-right direction.

[0118] The needle bar crank 83 is connected to the upper end portion of the crank rod 85 via the crankshaft 84 at a position eccentric with respect to the upper shaft 82. Accordingly, the upper end portion of the crank rod 85 can be caused to perform a circular motion.

[0119] The needle bar 12 is supported so as to be reciprocally movable along a longitudinal direction of the needle bar 12 by the needle feed mechanism 50 described below.

[0120] Accordingly, the circular motion at the upper end portion of the crank rod 85 connected to the needle bar 12 via the needle bar clamp 86 is converted into a reciprocating motion along the needle bar 12 and transmitted to the needle bar 12. As a result, the needle bar 12 and the stitch needle 11 perform an up-and-down movement.[Needle Feed Mechanism]

[0121] As shown in FIGS. 8 and 9, the needle feed mechanism 50 includes a needle feed shaft 51 to which a reciprocating rotational motion is input from the upper shaft 82 via the needle feed adjustment mechanism 60, a swing arm 52 that is fixedly provided at a left end portion of the needle feed shaft 51, a swing base 53 that slidably supports the needle bar 12 along its longitudinal direction, a square piece 54 serving as a roller provided on a shaft portion of the needle bar clamp 86 of the needle bar 12, a guide base 55 that slidably guides the square piece 54, a connecting link 56 that connects the swing arm 52 and the guide base 55, and a guide member 57 that guides swinging of the swing base 53.

[0122] The needle feed shaft 51 is rotatably supported within the sewing machine arm portion 113, while extending in the left-and-right direction. In addition, the needle feed shaft 51 is capable of reciprocally swinging a pivoting end portion of the swing arm 52 extending downward from a left end portion thereof, in the front-and-rear direction.

[0123] The swing base 53 is a frame body that slidably holds the needle bar 12 at two vertically spaced positions. A shaft portion 531 extending in the left-and-right direction is provided near a lower end portion of the swing base 53. The swing base 53 is capable of swinging, by the shaft portion 531, about an axis in the left-and-right direction within the sewing machine arm portion 113. Note that a reference sign 58 shown in FIG. 9 indicates a sleeve that slidably supports the shaft portion 531, and a reference sign 59 shown in FIG. 9 indicates a rolling bearing that rotatably supports the shaft portion 531.

[0124] In addition, an upper end portion of the swing base 53 is provided with a guide shaft 532 having a prismatic shape and extending rearward. The guide shaft 532 is inserted in a guide groove 571 provided in the guide member 57 and extending along the front-and-rear direction. Insertion of the guide shaft 532 in the guide groove 571 of the guide member 57 enables suppression of rattling in the left-and-right direction during swinging of the swing base 53.

[0125] The guide base 55 includes an insertion hole 551 for inserting, clamping, and fixing the shaft portion 531 of the swing base 53, and a slide groove 552 for slidably guiding the square piece 54.

[0126] The insertion hole 551 is provided in a lower end portion of the guide base 55. With the shaft portion 531 of the swing base 53 inserted, clamped, and fixed in the insertion hole 551, the guide base 55 and the swing base 53 integrally perform a swinging operation.

[0127] The slide groove 552 is formed in a direction parallel to the needle bar 12 supported by the swing base 53. The slide groove 552 can slidably guide the square piece 54 along the same direction during up-and-down movement of the needle bar 12 along its longitudinal direction.

[0128] In addition, a rear end portion of the connecting link 56 is rotatably connected to an upper end portion of the guide plate 55 about an axis extending in the left-and-right direction.

[0129] Since the connecting link 56 is rotatably connected, at its front end portion, to a lower end portion of the swing arm 52 about an axis extending in the left-and-right direction, a swinging motion of the swing arm 52 along the front-and-rear direction, caused by the reciprocating rotation of the needle feed shaft 51, is transmitted to the guide base 55.

[0130] Then, the swing base 53 swings about the shaft portion 531 together with the guide base 55, thereby swinging the needle bar 12 along the front-and-rear direction to perform a needle swinging operation.[Needle Feed Adjustment Mechanism]

[0131] The needle feed mechanism 50 includes a needle feed adjustment mechanism 60 that adjusts a needle feed amount. FIGS. 10 and 11 are diagrams illustrating a principle of the needle feed adjustment mechanism 60.

[0132] As shown in FIGS. 8 and 10, the needle feed adjustment mechanism 60 includes an eccentric cam 61, a needle feed connecting rod 62, a needle feed input arm 63, a first needle feed link member 64, a second needle feed link member 65, a needle feed adjuster 66, a support shaft 661, a driven arm 67, a needle feed adjustment motor 68, a driving arm 69, and a connecting link 691. The eccentric cam 61 is fixedly provided on the upper shaft 82. The needle feed connecting rod 62 rotatably holds the eccentric cam 61 at its upper end portion. The needle feed input arm 63 is fixedly provided at a right end portion of the needle feed shaft 51. The first needle feed link member 64 is a transmission member that connects the needle feed connecting rod 62 and the needle feed input arm 63. The needle feed adjuster 66 varies a posture of the second needle feed link member 65. The support shaft 661 rotates the needle feed adjuster 66 about an axis extending in the left-and-right direction. The driven arm 67 extends radially (approximately upward) from the support shaft 661. The needle feed adjustment motor 68 rotates the needle feed adjuster 66 to an arbitrary rotation angle. The driving arm 69 is provided on an output shaft of the needle feed adjustment motor 68. The connecting link 691 connects a pivoting end portion of the driving arm 69 and a pivoting end portion of the driven arm 67.

[0133] The needle feed adjustment motor 68 is composed of, for example, a stepping motor.

[0134] The needle feed connecting rod 62 is oriented approximately in the front-and-rear direction. When a rear end portion performs a circular motion by rotation of the upper shaft 82 through the eccentric cam 61, a swinging motion in the front-and-rear direction can be input to an upper end portion of the first needle feed link member 64 at a front end portion of the needle feed connecting rod 62.

[0135] The first needle feed link member 64 is provided as a pair. The upper end portions of the respective first needle feed link members 64 are rotatably connected to the left and right sides of the front end portion of the needle feed connecting rod 62 about an axis extending in the left-and-right direction. The first needle feed link members 64 are arranged approximately along the up-and-down direction. The lower end portions of the respective first needle feed link members 64 are rotatably connected to the left and right sides of the pivoting end portion of the needle feed input arm 63 about an axis extending in the left-and-right direction.

[0136] The second needle feed link member 65 is provided as a pair, and the second needle feed link members are arranged outside the first needle feed link members 64 on the left and right sides. Upper end portions of the respective second needle feed link members 65 are individually and rotatably connected to the upper end portions of the first needle feed link members 64 about an axis extending in the left-and-right direction. That is, the upper end portion of the second needle feed link member 65 and the front end portion of the needle feed connecting rod 62 are connected to the upper end portion of the first needle feed link member 64 by a common pivot shaft.

[0137] In addition, lower end portions of the respective second needle feed link members 65 are rotatably connected to the needle feed adjuster 66 about an axis extending in the left-and-right direction.

[0138] The needle feed adjuster 66 is rotatable about an axis extending in the left-and-right direction, with the support shaft 661 provided at the upper portion of the needle feed adjuster 66 serving as a center of rotation. The support shaft 661 may be concentric with a center of rotation of a connecting portion between the first needle feed link member 64 and the second needle feed link member 65. The rotational motion of the needle feed adjuster 66 is input from the needle feed adjustment motor 68 via the driving arm 69, the connecting link 691, and the driven arm 67.

[0139] As shown in FIG. 10, the needle feed adjuster 66 sets a state in which the first needle feed link member 64 and the second needle feed link member 65 overlap each other (a state in which their longitudinal directions coincide with each other) as a neutral position.

[0140] FIG. 10 shows an example in which a length of the first needle feed link member 64 and a length of the second needle feed link member 65 are approximately equal. However, the length of the first needle feed link member 64 and the length of the second needle feed link member 65 need not be completely equal.

[0141] At the neutral position of the needle feed adjuster 66, a center of rotation C1 on the lower end portion side of the first needle feed link member 64 and a center of rotation C2 on the lower end portion side of the second needle feed link member 65 are close to or coincide with each other when viewed from the left-and-right direction.

[0142] In this case, the lower end portion of the second needle feed link member 65 is connected to and supported by the needle feed adjuster 66, so its center of rotation C2 is maintained at a constant position. Accordingly, when a reciprocating motion is input by the needle feed connecting rod 62, the upper end portions of the first needle feed link member 64 and the second needle feed link member 65 rotate along an arc R1 about the centers of rotation C1 and C2 that coincide with each other.

[0143] In this case, when a reciprocating motion is input by the needle feed connecting rod 62 from the upper end portion side of the first needle feed link member 64 and the upper end portion side of the second needle feed link member 65, both the first needle feed link member 64 and the second needle feed link member 65 rotate about the centers of rotations C1 and C2 on their lower end portion sides. For this reason, the rotational motion is not input to the needle feed input arm 63 connected to the lower end portion of the first needle feed link member 64, and the needle feed shaft 51 remains in a stationary state.

[0144] On the other hand, as shown in FIG. 11, when the needle feed adjuster 66 rotates about the support shaft 661 from the neutral position, the center of rotation C1 of the lower end portion of the first needle feed link member 64 and the center of rotation C2 of the lower end portion of the second needle feed link member 65 separate from each other.

[0145] Also in this case, the lower end portion of the second needle feed link member 65 is connected to and supported by the needle feed adjuster 66, so the center of rotation C2 of the second needle feed link member 65 is maintained at a constant position. Accordingly, when a reciprocating motion is input by the needle feed connecting rod 62, the upper end portions of the first needle feed link member 64 and the second needle feed link member 65 rotate along an arc R2 about the center of rotation C2 of the front end portion of the second needle feed link member 64. Since the arc R2 does not overlap the arc centered on the center of rotation C1 of the lower end portion of the first needle feed link member 64, a reciprocating motion having a component in a direction orthogonal to the needle feed input arm 63 is input to the needle feed input arm 63.

[0146] As a result, a reciprocating rotational motion is input from the needle feed input arm 63 to the needle feed shaft 51.

[0147] A range of a reciprocating rotation angle input to the needle feed shaft 51 can be varied in accordance with an amount of angular change of the needle feed adjuster 66 relative to the neutral position. Accordingly, by controlling an amount of rotation angle of the needle feed adjuster 66 caused by the needle feed adjustment motor 68, the range of the reciprocating rotation angle input to the needle feed shaft 51 can be arbitrarily adjusted, and a needle feed amount of the stitch needle 11 can be arbitrarily adjusted.

[0148] Additionally, phases can be made opposite to each other between when the needle feed adjuster 66 is rotated clockwise and when it is rotated counterclockwise. By controlling a rotation direction of the needle feed adjuster 66 caused by the needle feed adjuster motor 68, the needle feed direction of the stitch needle 11 can be freely selected between a forward feed direction and a reverse feed direction of a workpiece.

[0149] Note that when a difference in length between the first needle feed link member 64 and the second needle feed link member 65 is not large, an amount of rotational motion generated in the needle feed input arm 63 is small at the neutral position where the longitudinal directions of the two link members 64 and 65 overlap. Therefore, the first needle feed link member 64 and the second needle feed link member 65 may differ in length to some extent.[Control System of Sewing Machine]

[0150] FIG. 12 is a block diagram showing a control system of the sewing machine 100.

[0151] As shown in FIG. 12, the sewing machine 100 includes the control device 90 that controls an operation of each configuration. The sewing machine motor 16, the presser motor 73, the first motor 25, the second motor 26, and the needle feed adjustment motor 68 are connected to the control device 90 via motor drive circuits 16a, 73a, 25a, 26a, and 68a, respectively.

[0152] In addition, the sewing machine motor 16, the presser motor 73, the first motor 25, and the second motor 26 are respectively provided with encoders 161, 732, 251, and 261 for detecting their respective rotational speeds. The encoders 161, 732, 251, and 261 are also connected to the control device 90 via motor drive circuits 16a, 73a, 25a, and 26a.

[0153] The control device 90 includes a CPU 91, a ROM 92, a RAM 93, and an EEPROM 94 (registered trademark), and executes various operation controls described below.

[0154] A basic system program is stored in the ROM 92.

[0155] Additionally, various setting data, other programs, and the like are stored in the EEPROM 94. Note that the various setting data and programs may be stored in a nonvolatile memory device such as a flash memory, an EPROM, an HDD, or the like, instead of the EEPROM.

[0156] The CPU 91 executes various programs in the ROM 92 and the EEPROM 94. The RAM 93 is a memory that serves as a working area for the CPU 91.

[0157] Additionally, an operation input unit 96 is connected to the control device 90 via an interface 96a.

[0158] The operation input unit 96 includes an input screen 961 on which information necessary for inputting various settings is displayed.

[0159] In addition, settings for a stitch pitch, a speed difference (difference in conveying amount) between the first motor 25 and the second motor 26, a set value of a pressing pressure during sewing by the cloth presser mechanism 70, and the like can be input from the operation input unit 96.

[0160] In addition, a pedal 95 that inputs operations such as start and stop of sewing and increase / decrease in sewing speed by a depression operation is connected to the control device 90 via an interface 95a.

[0161] Additionally, the height sensor 74 that detects a height of the presser foot 71 is connected to the control device 90 via an interface 74a.[Needle Feed Control]

[0162] Here, needle feed control of a workpiece performed based on a control program 941 stored in the EEPROM 94 will be described.

[0163] FIG. 13 is a diagram illustrating a relationship between a feed amount, in the front-and-rear direction, of the stitch needle 11 fed by the needle feed mechanism 50 and a shaft angle (phase) of the upper shaft 82. In FIG. 13, the horizontal axis represents the phase of the upper shaft 82, the vertical axis represents the amount of movement of the stitch needle 11, and the lower side of the vertical axis corresponds to the forward feed direction. In FIG. 13, the variation in the amount of movement of the tip of the stitch needle 11 is indicated by the solid line L1. In addition, for comparison, in FIG. 13, the feed amount by the lower belts 21 to 24 with a constant feed speed is indicated by the two-dot chain line L2.

[0164] Note that the phase of the upper shaft 82 is defined such that the top dead point of the stitch needle 11 is 0° and the bottom dead point is 180°. Additionally, FIG. 13 mainly shows a section of 90° to 270° related to feed of the workpiece. Note that, strictly speaking, the angle at which the stitch needle 11 reaches the workpiece on the throat plate 101 and performs feed is within a section of about 100° to 260°.

[0165] A reciprocating rotational motion is input to the needle feed mechanism 50 from the upper shaft 82, which performs full rotation, via the needle feed adjustment mechanism 60 that constitutes a cam-crank mechanism. Accordingly, when the upper shaft 82 rotates at a constant rotation speed, as shown in FIG. 13, the feed amount in the front-and-rear direction at the tip of the stitch needle 11 varies, and the feed amount also varies in accordance with a sinusoidal curve.

[0166] In contrast, as indicated by the two-dot chain line L2, if the lower belts 21 to 24 perform feed at a constant feed speed, there is a risk that the sewing quality deteriorates because the needle feed amount and the belt feed amount do not match, which may cause slippage of the lower belts 21 to 24 or looseness or tension in the workpiece.

[0167] Therefore, the CPU 91 that executes the control program 941 performs control to drive the first motor 25 and the second motor 26 only within the upper shaft angle section in which needle feed is performed (referred to as the needle feed section; for example, 100° to 260°), and to convey the workpiece in accordance with the feed amount of the tip of the stitch needle 11 along the front-and-rear direction.

[0168] The feed amount at the tip of the stitch needle 11 exhibits a variation along a sinusoidal curve, and can be calculated from design data such as the set stitch pitch and the dimensions of respective members of the needle feed mechanism 50.

[0169] Accordingly, the CPU 91 performs control to drive the first motor 25 and the second motor 26 within the needle feed section, based on the calculated needle feed amount at the tip of the stitch needle 11.

[0170] In addition, it is also possible to use a feed table 942 in which the range from the upper shaft angle (100°) of the feed start of the stitch needle 11 to the upper shaft angle (260°) of the feed end is divided into a plurality of sections (e.g., every 20°) and a feed amount is set for each section. In this case, the CPU 91 detects the upper shaft angle and controls the operation amounts of the first motor 25 and the second motor 26 so that the target feed amount set for each section in the feed table 942 is achieved.

[0171] Note that the feed table 942 needs to be prepared for each set stitch pitch. In addition, the width of the section is not limited to 20° and can be arbitrarily set.

[0172] Note that the example in which the first motor 25 and the second motor 26 are controlled in accordance with the feed amount along the front-and-rear direction of the tip of the stitch needle 11 has been described, but no such limitation is intended.

[0173] That is, the feed amount in the front-and-rear direction at the tip of the stitch needle 11 and the feed amount in the front-and-rear direction of the workpiece on the throat plate 101 do not strictly match. Since the stitch needle moves up and down during needle feed, a displacement in the front-and-rear direction may occur between the tip of the stitch needle 11 and a portion of the stitch needle 11 located at the height of the upper surface of the needle plate 101.

[0174] Accordingly, it is desirable to preliminarily measure the position of the stitch needle 11 in the front-and-rear direction at the height of the upper surface of the needle plate 101 within each upper shaft angle section (100°, 120°, 140°, 160°, 180°, and 200°), and to create the feed table 942 from the measured values.

[0175] Note that, in the lower feed mechanism 20, when performing left-and-right differential feed, the feed amount of the stitch needle 11 is set to the median value of feed amounts of left and right belt feeds. The differential amount is set such that the average of the feed amounts of left and right belt feeds becomes the median value.

[0176] In addition, when performing front-and-rear differential feed, the feed amount of the stitch needle 11 may be set to the median value of feed amounts of front-and-rear belt feeds. Alternatively, the feed amount of the stitch needle 11 may be matched to either the front-side feed amount or the rear-side feed amount.

[0177] Below, the operation control of the sewing machine 100 that is performed by the CPU 91 based on the control program 941 will be described based on the flowchart of FIG. 14.

[0178] Note that while the upper shaft 82 rotates once, the following processing of steps S3 to S19 is performed.

[0179] When the pedal 95 is depressed and the sewing machine motor 16 starts driving, the CPU 91 reads the set value of the stitch pitch currently set for feeding a workpiece (step S1).

[0180] Then, the CPU 91 detects the current upper shaft angle from the encoder 161 of the sewing machine motor 16 and determines whether it is a rotational speed detection angle (step S3). The rotational speed detection angle refers to a predetermined upper shaft angle at which the rotational speed (rotation speed) of the upper shaft 82 for each needle is detected.

[0181] If the rotational speed detection angle has not yet been reached, the CPU 91 repeatedly executes the determination, and if the rotational speed detection angle is reached, the CPU 91 acquires the rotational speed (rotation speed) from the output of the encoder 161 (step S5).

[0182] Then, the CPU 91 calculates the feed amount in the front-and-rear direction at the tip of the stitch needle 11 from the set value of the stitch pitch.

[0183] In addition, when using the feed table 942, the CPU 91 reads the feed table 942 corresponding to the set stitch pitch and specifies the feed amount of the stitch needle 11 within the first section (step S7).

[0184] Then, the CPU 91 detects the current upper shaft angle from the encoder 161 and determines whether it is a feed start angle (100°) (step S9).

[0185] If the feed start angle has not yet been reached, the CPU 91 repeatedly executes the determination, and if the feed start angle is reached, the CPU 91 starts belt feed by driving the first motor 25 and the second motor 26 (step S11).

[0186] During belt feed, the operation amounts of the first motor 25 and the second motor 26 are controlled such that the feed amount obtained in step S7 is achieved.

[0187] In addition, when using the feed table 942, the first motor 25 and the second motor 26 are controlled such that the feed amount specified in the feed table 942 is achieved within each section of the upper shaft angle (step S13).

[0188] Then, the CPU 91 detects the current upper shaft angle from the encoder 161 and determines whether it is a feed end angle (260°) (step S15).

[0189] If the feed end angle has not yet been reached, the CPU 91 returns the process to step S13 and continues to control the operation amounts of the first motor 25 and the second motor 26.

[0190] In addition, when the feed end angle is reached, the CPU 91 stops driving the first motor 25 and the second motor 26 and ends belt feed (step S17).

[0191] Then, the CPU 91 determines whether the depression on the pedal 95 has been released and sewing has been completed (step S19).

[0192] If the completion state of sewing is not detected, the CPU 91 returns the process to step S3 and repeats the processing of steps S3 to S19.

[0193] In addition, when the release of the depression on the pedal 95 is detected, the CPU 91 stops the sewing machine motor 16, thereby terminating the operation control of sewing.[Technical Effects of Embodiment of Present Disclosure]

[0194] The sewing machine 100, under the control of the control device 90, controls the first motor 25 and the second motor 26 of the lower feed mechanism 20 to convey the workpiece by belt in accordance with the feed amount of the stitch needle 11 along the front-and-rear direction caused by the swinging of the needle bar 12.

[0195] Accordingly, the difference between the needle feed amount by the stitch needle 11 and the feed amount by each of the lower belts 21 to 24 of the lower feed mechanism 20 is reduced, making it possible to smoothly feed the workpiece. As a result, it becomes possible to improve stitch quality by the sewing machine 100.

[0196] In addition, the control device 90 calculates the variation in the feed amount of the stitch needle 11 along the sinusoidal curve and controls the first motor 25 and the second motor 26 to feed the workpiece accordingly.

[0197] This allows the first motor 25 and the second motor 26 to be controlled based on design values such as the dimensions of the respective members of the sewing machine 100, thereby eliminating the need for prior measurements or sensor detection, while reducing the difference between the needle feed amount and the belt feed amount and enabling smooth feed of the workpiece.

[0198] Additionally, the control device 90 can also control the first motor 25 and the second motor 26 to feed the workpiece in accordance with the feed amount of the stitch needle 11 at the height of the upper surface of the needle plate 101, instead of the variation in the feed amount along the sinusoidal curve.

[0199] Accordingly, the difference between the needle feed amount and the belt feed amount is further reduced, making it possible to feed the workpiece more smoothly. Additionally, it becomes possible to further improve stitch quality.[Example in which a detection device for detecting a position of the stitch needle on the throat plate is provided]

[0200] FIG. 15 is a plan view of an example in which a detection device 103 for detecting a position of the stitch needle 11 on the throat plate 101 is provided on the eye 13 of the throat plate 101.

[0201] The detection device 103 includes a light source that is provided at the right inner edge portion of the eye 13, at the height of the upper surface of the needle plate 101, and emits light leftward from at least the entire movement range of the stitch needle 11. Additionally, the detection device 103 includes a plurality of light-receiving elements that are arranged in parallel in the front-and-rear direction over at least the entire movement range of the stitch needle 11, at the left inner edge portion of the eye 13. Note that the arrangement of the light source and the plurality of light-receiving elements may be reversed left and right.

[0202] During sewing, when the stitch needle 11 descends and is inserted into the eye 13, the detection device 103 can detect the position in the front-and-rear direction of the stitch needle 11 at the height of the upper surface of the needle plate 101, based on the position at which the amount of light received from the light source decreases due to the stitch needle 11 blocking the light.

[0203] Then, the CPU 91 of the control device 90 detects, in real time, the position in the front-and-rear direction of the stitch needle 11 at the height of the upper surface of the needle plate 101 during each needle feed in sewing, and controls the first motor 25 and the second motor 26 to follow the position, thereby making it possible to reduce the difference between the needle feed amount and the belt feed amount.[Others]

[0204] Each embodiment of the present disclosure has been described. However, the present disclosure is not limited to the above embodiments. For example, in the above embodiments, a component integrally formed by a single member may be replaced with a component divided into a plurality of members and connected or fixed to each other. Additionally, a component formed by connecting a plurality of members may be replaced with a component formed integrally by a single member. In addition, the details described in the embodiments may be appropriately changed without departing from the spirit of the invention.

[0205] For example, the lower feed mechanism 20 need not be configured to enable front-and-rear or left-and-right differential feed in which the feed speeds of a plurality of lower belts are made different by a plurality of motors.

[0206] In this case, only one motor may be used as the drive source of the lower feed mechanism 20. Additionally, the number of lower belts may be reduced. For example, one belt may be arranged on each of the front and rear sides or the left and right sides of the eye, and the belts may be driven by a single motor. Additionally, a single belt may be arranged near the front or rear side of the eye and conveyed by a single motor.

[0207] The present application is based on Japanese Patent Application No. 2023-057774 filed on March 31, 2023, the contents of which are incorporated herein by reference.

Claims

1. A sewing machine comprising: a lower feed mechanism configured to feed a workpiece from below a throat plate by a conveyor belt driven by a lower feed motor, a needle up-and-down movement mechanism configured to move up and down, by a sewing machine motor, a needle bar configured to hold a stitch needle, a needle feed mechanism configured to swing, by the sewing machine motor, the needle bar configured to hold the stitch needle along a feed direction of the workpiece, and a control device configured to control the lower feed motor to feed the conveyor belt in accordance with a feed amount of the stitch needle along the feed direction of the workpiece, the feed amount being caused by swinging of the needle bar.

2. The sewing machine according to claim 1, wherein the control device controls the lower feed motor to feed the workpiece in accordance with a variation in the feed amount along a sinusoidal curve of the stitch needle.

3. The sewing machine according to claim 1, wherein the feed amount of the stitch needle along the feed direction of the workpiece, the feed amount being caused by swinging of the needle bar, is a feed amount at a height of an upper surface of the throat plate.

4. The sewing machine according to claim 3, comprising a detection device configured to detect a position, at the height of the upper surface of the throat plate, of the stitch needle along the feed direction of the workpiece, the position being caused by swinging of the needle bar, wherein the control device controls the lower feed motor to convey the workpiece in accordance with the position of the stitch needle detected by the detection device.

Images