JP2022011424A - Sewing machine and thread tension detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sewing machine and a thread tension detecting device capable of preventing plastic deformation of a tension plate and accurately detecting the tension of a needle thread. A yarn tension detecting device 30 includes a first protective plate 61. The extended portion 65 of the first protective plate 61 is located between the tension plate 70 and the mounting base 40 in the bending direction of the tension plate 70, and can come into contact with the surface of the tension plate 70 on the mounting base 40 side. Is. During sewing, the tension plate 70 bends according to the tension applied to the needle thread. The yarn tension detecting device 30 detects the bending of the tension plate 70 by the Hall element 55, and outputs a signal according to the detection result. When an allowable tension is applied to the needle thread, the tension plate 70 comes into contact with the extending portion 65 of the first protective plate 61 before being excessively bent. Therefore, since the sewing machine can prevent the tension plate 70 from bending excessively, it can prevent the tension plate 70 from being plastically deformed and the needle thread tension cannot be accurately detected. [Selection diagram] FIG. 7

Description

The present invention relates to a sewing machine and a thread tension detecting device.

The sewing machine described in Patent Document 1 includes a thread tension detecting device. The thread tension detecting device can detect the tension applied to the needle thread. The thread tension detection device is arranged between the main thread tensioner and the balance in the needle thread path. The needle thread comes into contact with the contact surface of the thread contact portion of the tension plate. The thread contact part bends due to the needle thread tension. The magnet moves in the front-rear direction according to the bending of the thread contact portion. The magnetic flux density of the magnet passing through the Hall element changes according to the movement of the magnet. The Hall element detects the change in magnetic flux density, converts it into a voltage signal, and outputs it as a sensor value. The sewing machine calculates the needle thread tension based on the sensor value output from the Hall element.

Japanese Unexamined Patent Publication No. 2019-150548

In the thread tension detecting device described in Patent Document 1, an allowable tension may be applied during sewing, and the tension plate may be plastically deformed. In that case, the distance between the Hall element and the magnet changes, and the sensor value output from the Hall element changes. Therefore, the range of the needle thread tension that can be detected changes, and the sewing machine cannot accurately calculate the needle thread tension. When the tension plate is plastically deformed, the magnet may hit the Hall element depending on the degree of deformation, and the Hall element may be damaged.

An object of the present invention is to provide a sewing machine and a thread tension detecting device capable of preventing plastic deformation of a tension plate and accurately detecting the tension of a needle thread.

The sewing machine according to claim 1 is provided in the needle thread path from the thread supply source to the sewing needle that holds the needle thread, and moves up and down with the vertical movement of the sewing needle to pull up the needle thread, and the needle thread path. Inside, a thread tensioner arranged between the yarn supply source and the balance and capable of controlling the tension applied to the needle yarn and provided in the needle yarn path so that the tension applied to the needle yarn can be detected. A thread tension detecting device is provided, and the thread tension detecting device is connected to a mounting portion to be attached to the sewing machine, a first fixing portion to be fixed to the mounting portion, and the first fixing portion, and is connected to the needle thread path. A tension plate having a thread contact portion extending in the intersecting direction and causing bending by contact with the needle thread and the bending generated in the thread contact portion are detected, and a signal is output according to the detection result. It has a sensor and a second fixing portion to be fixed to the mounting portion, and is provided at a position where the needle thread enters on the upstream side in the supply direction of the needle thread with respect to a predetermined position of the thread contact portion. It is provided with a first hole portion through which the needle thread passes, and a second hole portion provided at a position where the needle thread comes out on the downstream side in the supply direction of the needle thread with respect to the predetermined position, and the predetermined hole portion through which the needle thread passes. In a sewing machine provided with a guide member for guiding the needle thread so that the needle thread contacts and passes through the position, the tension plate is located between the tension plate and the mounting portion in a predetermined direction in which the tension plate bends. The tension plate is provided with a protective portion that can come into contact with the surface of the tension plate on the mounting portion side. During sewing with a sewing machine, the tension plate bends according to the tension of the needle thread. The yarn tension detection device detects the bending of the tension plate with a sensor and outputs a signal according to the detection result. When the needle thread is tensioned more than allowed, the tension plate comes into contact with the protection before it bends excessively. Therefore, since the sewing machine can prevent the tension plate from bending excessively, it can prevent the tension plate from being plastically deformed and the tension applied to the needle thread cannot be detected accurately.

The sewing machine according to claim 2 includes a magnet provided on one of the tension plate and the mounting portion, and a magnetic sensor provided on the other of the tension plate and the mounting portion, and the protective portion is provided in the predetermined direction. The end portion on the tension plate side is located between the tension plate and the magnet or the magnetic sensor provided in the mounting portion with a predetermined gap from the tension plate, and the end portion is located. The tension plate may be able to come into contact with a portion other than the portion provided with the magnet or the magnetic sensor. The magnetic flux density of the magnet detected by the magnetic sensor changes according to the bending of the thread contact portion of the tension plate. The magnetic sensor outputs a signal according to the change in magnetic flux density. Therefore, the sewing machine can detect the tension applied to the needle thread based on the signal output by the magnetic sensor. The end of the protection portion on the tension plate side is located between the tension plate and the magnet or magnetic sensor provided in the mounting portion with a predetermined gap from the tension plate. Therefore, the tension plate can be bent within a predetermined gap in a predetermined direction. The end of the protection portion on the tension plate side comes into contact with a portion other than the magnet or the magnetic sensor provided on the tension plate. Therefore, the sewing machine can prevent the end portion of the protective portion from coming into contact with the magnet or the magnetic sensor and being damaged.

The predetermined gap of the sewing machine according to claim 3 may be smaller than the separation distance between the magnet and the magnetic sensor in the predetermined direction. Therefore, the sewing machine can prevent the magnet and the magnetic sensor from colliding with each other even if the tension plate bends in a predetermined direction.

The magnet of the sewing machine according to claim 4 is provided on the tension plate, the substrate of the magnetic sensor is arranged along the mounting portion, and the protective portion sandwiches the substrate between the mounting portion and the mounting portion. Then, it may be fixed to the mounting portion together with the substrate. Therefore, the thread tension detecting device can fix the magnetic sensor and the substrate to the mounting portion together with the protective portion.

The protective portion of the sewing machine according to claim 5 may extend parallel to the tension plate and close to the magnet and the magnetic sensor. Therefore, when the tension plate is bent in a predetermined direction, the protective portion can quickly come into contact with the tension plate. Therefore, the sewing machine can surely prevent the tension plate from bending excessively.

In the sewing machine of claim 6, a first adjusting portion having a first thickness in the predetermined direction may be arranged between the first fixing portion and the protective portion of the tension plate. Therefore, the sewing machine can form a predetermined gap between the protective portion and the tension plate. By arranging the first adjusting portions having different first thicknesses in the sewing machine, a predetermined gap can be appropriately adjusted.

The size of the protective portion of the sewing machine according to claim 7 in the predetermined direction may be larger than the first thickness of the first adjusting portion. Therefore, the sewing machine can sufficiently leave a space between the tension plate and the mounting portion, so that the magnet and the magnetic sensor can be separated from each other.

According to the sewing machine of claim 8, the first fixing portion of the tension member is located between the second fixing portion of the guide member and the protection portion, and the first fixing portion and the second fixing portion are located. A second adjusting portion having a second thickness in the predetermined direction may be arranged between the portions. Since the sewing machine has a second adjusting part placed between the first fixing part and the second fixing part, by replacing it with the second adjusting part having a different second thickness, the guide member can be used with respect to the thread contact part of the tension plate. The position of the needle thread passing between the first hole and the second hole can be adjusted.

The thread tension detecting device of the sewing machine according to claim 9 may be provided between the thread tensioner and the balance in the needle thread supply path. In the sewing machine of this embodiment, when the balance pulls up the needle thread, there is no resistance between the balance and the sewing needle. Therefore, the thread tension detector does not interfere with sewing, and the sewing machine can form high-quality stitches on the cloth. Since the balance does not pull the needle thread portion where the thread tension detecting device detects the tension, the thread tension detecting device can detect the original tension applied to the needle thread.

The sewing machine according to claim 10 is provided between the balance and the thread tensioner in the needle thread path, and includes a thread take-up spring that controls the supply amount of the needle thread to the sewing needle in conjunction with the operation of the balance. The thread tension detecting device may be provided between the thread tensioner and the thread taking spring in the needle thread path. In the sewing machine of this embodiment, when the balance pulls up the needle thread, there is no resistance between the balance and the sewing needle. Therefore, the thread tension detector does not interfere with sewing, and the sewing machine can form high-quality stitches on the cloth. Since the balance does not pull the needle thread portion where the thread tension detecting device detects the tension, the thread tension detecting device can detect the original tension applied to the needle thread.

There are a plurality of the thread tensioners of the sewing machine according to claim 11 according to the number of the plurality of sewing needles, and the thread tension detecting device may be provided corresponding to each of the plurality of the thread tensioners. Therefore, the sewing machine of this embodiment can individually detect the tensions of the plurality of needle threads supplied to the plurality of sewing needles.

The sewing machine according to claim 12 includes a needle bar that supports the sewing needle, and the thread tension detecting device may be provided between the balance and the needle bar in the needle thread path. Since the thread tension detection device is located on the downstream side of the balance, the tension of the needle thread during sewing can be accurately detected at a position close to the sewing needle.

The sewing machine according to claim 13 is provided between the balance and the sewing needle, and includes a thread retainer that imparts resistance to the movement of the needle thread supplied to the sewing needle along the needle thread path, and the thread tension detecting device is provided. , May be provided between the balance and the thread retainer in the needle thread path. Since the thread tension detecting device is located on the downstream side of the balance, the tension of the needle thread being sewn can be accurately detected at a position close to the sewing needle.

There are a plurality of the thread tensioners of the sewing machine according to claim 14 according to the number of the plurality of sewing needles, and the thread tension detecting device collectively collects the tensions of all the needle threads supplied to each of the plurality of the sewing needles. It may be detected. Therefore, the sewing machine of this embodiment is a single thread tension detecting device, and can collectively detect the tensions of a plurality of needle threads supplied to a plurality of sewing needles.

The thread tension detecting device according to claim 15 is a thread tension detecting device provided in the needle thread path from the thread supply source of the sewing machine to the sewing needle holding the needle thread and capable of detecting the tension applied to the needle thread. The mounting portion to be attached to the sewing machine, the first fixing portion to be fixed to the mounting portion, and the first fixing portion are connected to each other and extend in a direction intersecting the needle thread path, and the contact with the needle thread causes itself. A tension plate provided with a thread contacting portion that causes bending, a sensor that detects the bending generated in the thread contacting portion and outputs a signal according to the detection result, and a second fixing portion that is fixed to the mounting portion. It is provided at a position where the needle thread enters on the upstream side in the supply direction of the needle thread with respect to the predetermined position of the thread contact portion, with respect to the first hole portion through which the needle thread passes and the predetermined position. It is provided at a position where the needle thread comes out on the downstream side in the supply direction of the needle thread, is provided with a second hole through which the needle thread passes, and is provided so that the needle thread passes in contact with the needle thread at the predetermined position. A guide member for guiding the needle thread is provided, and the tension plate is located between the tension plate and the mounting portion in a predetermined direction in which the tension plate bends, and can come into contact with the surface of the tension plate on the mounting portion side. It is characterized by having a protective part. The yarn tension detection device detects the bending of the tension plate with a sensor and outputs a signal according to the detection result. When the needle thread is tensioned more than allowed, the tension plate comes into contact with the protection before it bends excessively. Therefore, since the thread tension detecting device can prevent the tension plate from bending excessively, it is possible to prevent the tension plate from being plastically deformed and unable to accurately detect the tension applied to the needle thread.

Front view of sewing machine 1. The perspective view of the thread tension detection device 30. The plan view of the thread tension detection device 30. The front view of the thread tension detection device 30. The right side view of the thread tension detection device 30. An exploded perspective view of the thread tension detecting device 30. FIG. 3 is an enlarged cross-sectional view taken along the line I-I in the direction of arrow viewing. FIG. 3 is an enlarged cross-sectional view taken along the line II-II in the direction of arrow viewing. The figure which shows the resultant force V3 which a needle thread 6 pushes a tension plate 70. A front view (deformed example) of a two-needle sewing machine 1 in which two thread tension detecting devices 30 and 30 are fixed to an arm portion 4. A front view (deformed example) of a sewing machine 1 in which a thread tension detecting device 30 is fixed between a balance 28 and a thread retainer 29.

An embodiment of the present invention will be described with reference to the drawings. The following explanation uses left and right, front and back, and up and down indicated by arrows in the figure.

The configuration of the sewing machine 1 will be described with reference to FIG. The sewing machine 1 is a one-needle sewing machine including one sewing needle 10. The sewing machine 1 can be changed to a two-needle sewing machine (see FIG. 10) by attaching two sewing needles to the needle bar 9 described later.

The sewing machine 1 includes a bed portion 2, a pedestal portion 3, an arm portion 4, and a head portion 5. The bed portion 2 has a needle plate 7 on the left side of the upper surface thereof, and internally includes a hook mechanism, a lower shaft, a feed mechanism, a thread trimming mechanism (not shown), and the like. The sewn object is arranged on the upper surface of the bed portion 2. The hook mechanism has a rotary hook below the needle plate 7, and accommodates a bobbin (not shown) in which a bobbin thread is wound around the rotary hook. The lower axis extends in the left-right direction. The lower shaft rotates in synchronization with the main motor (not shown) described later. The hook mechanism is driven by the rotation of the lower shaft, captures the needle thread 6 held by the sewing needle 10, and entangles it with the bobbin thread. The feed mechanism includes feed dogs (not shown) that can appear and disappear on the needle plate 7. The feed mechanism drives the feed dog in synchronization with the rotation of the lower shaft, and moves the workpiece in the transport direction by a predetermined feed amount. The thread trimming mechanism includes a fixed blade, a movable blade, and a thread trimming solenoid (not shown). The movable blade is connected to the thread trimming solenoid. When the thread trimming solenoid is driven, the movable blade moves with respect to the fixed blade, and the thread trimming mechanism cuts the needle thread 6 and the bobbin thread in cooperation with the movable blade and the fixed blade. The pedestal portion 3 extends upward from the right end of the bed portion 2.

The arm portion 4 extends to the left from the upper end portion of the pedestal portion 3. The arm portion 4 is provided with an operation portion 12, a thread tension portion 15, a thread tension detecting device 30, and the like on the front surface thereof. The operation unit 12 includes a liquid crystal touch panel 13 and a switch unit 14. The liquid crystal touch panel 13 can display an image and input various instructions to the control unit (not shown) of the sewing machine 1. The switch unit 14 is provided on the right side of the liquid crystal touch panel 13. The switch unit 14 includes a plurality of switches and can input various instructions to the control unit.

The thread tension portion 15 is provided on the left side of the operation portion 12. The thread tensioning unit 15 has one auxiliary thread tensioner 21 and two main thread tensioners 22 in order from the upstream side of the path of the needle thread 6 (hereinafter referred to as the needle thread path) unwound from the thread piece (not shown). , 23 are provided. The main thread tensioner 22 is arranged diagonally downward to the left of the auxiliary thread tensioner 21, and the main thread tensioner 23 is arranged diagonally downward to the right of the main thread tensioner 22. The auxiliary thread tensioner 21 applies the tension required for cutting the needle thread 6 and the bobbin thread by the thread trimming mechanism to the needle thread 6. The main thread tensioners 22 and 23 optimize the tension acting on the needle thread 6 as the sewing machine 1 is sewn. The thread tension detection device 30 is provided between the main thread tensioner 23 and the thread take-up spring device 17 in the needle thread path. The thread tension detecting device 30 detects the tension of the needle thread 6 (hereinafter referred to as the needle thread tension). The specific structure of the thread tension detecting device 30 will be described later.

The arm portion 4 includes an upper shaft (not shown) and a main motor inside. The upper shaft extends in the left-right direction and is connected to the main motor via an upper shaft pulley (not shown). The upper shaft pulley is fixed to the right end of the upper shaft. The lower shaft pulley (not shown) is fixed to the right end of the lower shaft. The endless belt (not shown) is hung between the upper shaft pulley and the lower shaft pulley. When the upper shaft is rotated by the drive of the main motor, the lower shaft rotates synchronously via the endless belt.

The head 5 is provided at the left end of the arm portion 4. The head portion 5 projects downward from the left end portion of the arm portion 4 and faces the needle plate 7 from above. The head 5 supports the needle rod 9 extending downward so as to be able to move up and down. The lower end of the needle bar 9 projects downward from the head 5. The needle bar 9 is connected to the upper shaft via a vertical movement mechanism, and moves up and down above the needle plate 7 as the upper shaft rotates. A sewing needle 10 can be attached to the lower end of the needle bar 9. The sewing needle 10 holds the needle thread 6 inserted through the eye hole (not shown). The sewing needle 10 moves up and down together with the needle bar 9.

The head portion 5 is provided with a thread taking spring device 17, a balance 28, a thread retainer 29, and the like on the front surface thereof. The thread take-up spring device 17 is provided on the downstream side of the main thread tensioner 23 in the needle thread path, and is located diagonally downward to the left of the main thread tensioner 23. The thread take-up spring device 17 includes a thread take-up spring 27A. The thread take-up spring 27A controls the supply amount of the needle thread 6 to the sewing needle 10 in conjunction with the operation of the balance 28. The balance 28 is located diagonally upward to the left of the thread take-up spring device 17. The balance 28 moves up and down as the main motor is driven. The thread retainer 29 is provided between the balance 28 and the needle bar 9 in the needle thread path, and imparts resistance to movement along the needle thread path of the needle thread 6 supplied to the sewing needle 10.

The structure of the yarn tension detecting device 30 will be described with reference to FIGS. 2 to 6. In this embodiment, for convenience of explanation, the structure will be described in the orientation when the yarn tension detecting device 30 is placed on a horizontal plane. As shown in FIGS. 2 to 4, the yarn tension detecting device 30 extends in the left-right direction in a plan view and is a unit configured by assembling a plurality of members to each other. The thread tension detecting device 30 is arranged in the left-right direction so as to be orthogonal to the needle thread path extending in the front-rear direction.

As shown in FIG. 6, the thread tension detecting device 30 is, in order from the bottom, a mounting base 40, a sensor board 50, a first protective plate 61, a second protective plate 62, a first adjustment plate 91, 92, a tension plate 70, and a second adjustment. It includes plates 93, 94, guide member 80, fastening screws 102, 103, and the like.

The structure of the mounting base 40 will be described. The mounting base 40 is a pedestal for fixing the thread tension detecting device 30 to the wall surface of the sewing machine 1. Various materials such as metal and resin can be used as the material of the mounting base 40, and for example, it may be formed of a rolled steel plate. The mounting base 40 includes a pedestal portion 41 and a mounting portion 42.

The pedestal portion 41 is formed in a substantially rectangular shape that is long in the left-right direction in a plan view, and a fixed surface 45 is provided on the upper surface thereof. The fixed surface 45 includes a central portion 46 and support portions 47 and 48. The central portion 46 is provided at the center of the fixed surface 45 in the left-right direction, and is formed in an elongated substantially rectangular shape extending in the left-right direction in a plan view. The support portion 47 is provided on the right side of the fixed surface 45, and the support portion 48 is provided on the left side of the fixed surface 45, and each is formed in a substantially rectangular shape in a plan view. The support portion 47 is provided with a fixing hole 471 in the center. The support portion 48 is provided with a fixing hole 481 in the center.

The mounting portion 42 is formed in a substantially rectangular ring shape that is long in the left-right direction in a plan view. The mounting portion 42 is provided with an insertion hole 421 in the center. The insertion hole 421 is an oval hole that is long in the left-right direction in a plan view and penetrates in the vertical direction. The shaft portion of the adjusting screw 101 can be inserted into the insertion hole 421 from above, and can move inside the insertion hole 421 along the length direction. The head of the adjusting screw 101 has a diameter larger than the minor diameter of the insertion hole 421, and is locked to the edge of the insertion hole 421 from above.

The shape of the sensor board 50 will be described. The sensor board 50 is arranged on the fixed surface 45 of the pedestal portion 41 of the mounting base 40. The sensor board 50 is a circuit board on which an electric circuit of the Hall element 55 described later is formed. The sensor substrate 50 is made of resin and extends in the left-right direction in a plan view. The sensor board 50 includes a central portion 51 and fixed portions 52 and 53. The central portion 51 is provided in a region on the right side of the sensor substrate 50 excluding the right end portion from the center in the left-right direction, and is formed in an elongated substantially rectangular shape extending in the left-right direction in a plan view. The Hall element 55 is provided on the left end side of the upper surface of the central portion 51 and at the center position in the left-right direction of the sensor substrate 50. The Hall element 55 is a well-known semiconductor that detects the magnetic flux density of the magnet 78, which will be described later, and outputs an analog signal (voltage signal) proportional to the magnetic flux density as a sensor value. The Hall element 55 is a vertical detection type Hall element, and can detect the magnetic flux density of the magnet 78 described later that passes perpendicularly to the Hall element 55.

The fixing portion 52 is provided at the right end portion of the sensor substrate 50 and is formed in a substantially rectangular shape in a plan view. The fixing portion 52 is provided with a fixing hole 521 in the center. The fixing portion 53 is provided on the left side from the central portion in the left-right direction of the sensor substrate 50, and is formed in a substantially rectangular shape long in the left-right direction in a plan view. The fixing portion 53 is provided with a fixing hole 531 on the left end side.

Each shape of the first protective plate 61 and the second protective plate 62 will be described. The first protective plate 61 and the second protective plate 62 are resin parts. The first protective plate 61 is arranged on the upper surfaces of the central portion 51 and the fixing portion 52 of the sensor substrate 50. The first protective plate 61 has a predetermined thickness (height in the vertical direction), and includes a rectangular portion 64 and an extension portion 65. The rectangular portion 64 is formed in a substantially rectangular shape in a plan view, and has a fixing hole 611 in the center thereof. The fixing hole 611 penetrates the rectangular portion 64 in the vertical direction. The extending portion 65 extends to the left from the central portion in the front-rear direction of the left end portion of the rectangular portion 64, and is formed in a substantially rectangular shape long in the left-right direction in a plan view. The second protective plate 62 is arranged on the upper surface of the fixing portion 53 of the sensor substrate 50. The second protective plate 62 has the same predetermined thickness as the first protective plate 61, and has the same shape as the rectangular portion 64 of the first protective plate 61. The second protective plate 62 is provided with a fixing hole 621 in the center thereof. The fixing hole 621 penetrates the second protective plate 62 in the vertical direction.

The shape of the tension plate 70 will be described. The tension plate 70 is fixed to the fixing surface 45 of the mounting base 40 in the left-right direction via the first protective plate 61, the second protective plate 62, and the first adjusting plates 91 and 92 described later. The tension plate 70 is a metal member that bends by being pushed in contact with the needle thread 6. The tension plate 70 extends in the left-right direction in a plan view. The material of the tension plate 70 is not limited, but metal is preferable. In consideration of flexibility and durability, for example, a steel material for springs such as carbon tool steel material and stainless steel material may be used. The tension plate 70 includes a thread contact portion 71, fixing portions 72, 73, and a magnet 78.

The thread contact portion 71 is provided in an intermediate portion excluding both sides in the length direction of the tension plate 70, and is formed in a thin plate shape extending in the left-right direction in a plan view. The left-right length of the thread contact portion 71 is substantially the same as the left-right length of the central portion 46 of the fixed surface 45 of the mounting base 40. The thickness of the thread contact portion 71 is not limited, but may be set to 0.5 mm, for example, in consideration of durability. The upper surface of the thread contact portion 71 is a contact surface with which the needle thread 6 contacts. The intermediate position in the length direction of the contact surface is a predetermined position where the needle thread 6 comes into contact. The thread contact portion 71 includes guide portions 76 and 77. The guide portion 76 is provided at the front end portion of the thread contact portion 71 at an intermediate position in the length direction. The guide portion 77 is provided at the rear end portion of the thread contact portion 71 at an intermediate position in the length direction. The guide portions 76 and 77 face each other with the thread contact portions 71 in between. The guide portions 76 and 77 are inclined downward (toward the mounting base 40) and project in a direction orthogonal to the length direction of the thread contact portion 71. The guide portion 76 is formed in a substantially trapezoidal shape in a plan view that tapers toward the front. The guide portion 77 is formed in a substantially trapezoidal shape in a plan view that tapers toward the rear.

The fixing portion 72 is provided at the right end portion of the thread contact portion 71. The fixing portion 73 is provided at the left end portion of the thread contact portion 71. The fixed portion 72 and the fixed portion 73 are formed in a substantially rectangular shape in a plan view. The shapes of the fixed portion 72 and the fixed portion 73 are substantially the same as the shapes of the support portion 47 and the support portion 48 of the fixed surface 45 of the mounting base 40. The fixing portion 72 and the fixing portion 73 are each provided with circular fixing holes 721 and 731 in substantially central portions. The fixing hole 721 is an elongated hole having a major axis in the left-right direction.

The magnet 78 is fixed to the intermediate portion in the left-right direction on the back surface (lower surface) opposite to the contact surface (upper surface) of the thread contact portion 71 with an adhesive. Since the intermediate portion of the thread contact portion 71 includes the guide portions 76 and 77, the magnet 78 is hidden inside the guide portions 76 and 77. Therefore, it is possible to prevent the needle thread 6 from being caught by the magnet 78. Since the middle portion on the back surface of the thread contact portion 71 is bent in an arc shape in cross section by the guide portions 76 and 77 (see FIG. 8), the rigidity is high and it is difficult to bend. Therefore, the magnet 78 is difficult to peel off from the middle portion on the back surface of the thread contact portion 71.

The shape of the magnet 78 is not limited, and any shape such as a cylindrical shape, a square shape, or a cylindrical shape is possible, but a cylindrical shape is preferable. The cylindrical magnet 78 has one end surface as a fixing surface, and is fixed to the back surface of the thread contact portion 71 with an adhesive. The magnetizing direction of the magnet 78 is the height direction through which the cylindrical magnet 78 passes along the axial direction.

The structure of the guide member 80 will be described. The guide member 80 is made of metal, and has a sensor board 50, a first protective plate 61 and a second protective plate 62, a first adjustment plate 91, 92, a tension plate 70, and a second adjustment with respect to the fixed surface 45 of the mounting base 40. The plates 93 and 94 are sandwiched between them and fixed. The guide member 80 guides the needle thread 6 so that the needle thread 6 comes into contact with and passes through a predetermined position on the contact surface of the thread contact portion 71 of the tension plate 70. The guide member 80 is formed in a substantially rectangular shape that is long in the left-right direction in a plan view and in a substantially inverted U shape that opens downward in a side view. The guide member 80 includes a first wall portion 81, a second wall portion 82, connecting wall portions 83, 84 and the like. The first wall portion 81 and the second wall portion 82 are arranged apart from each other in the front-rear direction and in parallel. The separation distance between the first wall portion 81 and the second wall portion 82 is slightly longer than the length in the front-rear direction of the pedestal portion 41 of the mounting base 40.

The first wall portion 81 is provided with a thread guide portion 86 at the upper end portion at the center in the left-right direction. The thread guide portion 86 has a substantially inverted U shape when viewed from the front. The thread guide portion 86 is provided with a hole portion 861 inside the center. The hole 861 penetrates in the front-rear direction. The tip portion that bends downward of the thread guide portion 86 is separated upward from the upper end portion of the first wall portion 81, and a thread guide groove 862 is formed in the gap. The thread guide groove 862 has a width through which the needle thread 6 can pass, and communicates with the hole 861.

The left-right length of the second wall portion 82 is shorter than the left-right length of the first wall portion 81. The position of the left end portion of the second wall portion 82 corresponds to the position of the left end portion of the thread guide portion 86 of the first wall portion 81. The second wall portion 82 includes a thread guide portion 87 at the upper end portion on the left end side. The thread guide portion 87 has a substantially inverted U shape in the rear view like the thread guide portion 86. The thread guide portion 87 is provided with a hole portion 871 inside the center. The hole 871 also penetrates in the front-rear direction. The tip portion bent downward of the thread guide portion 87 is separated upward from the upper end portion of the second wall portion 82, and a thread guide groove 872 is formed in the gap thereof. The thread guide groove 872 has a width through which the needle thread 6 can pass, and communicates with the hole 871.

The connecting wall portion 83 is formed in a substantially inverted U shape in the right side view that opens downward, and is connected between the right side of the upper end portion of the first wall portion 81 and the right side of the upper end portion of the second wall portion 82. The connecting wall portion 83 includes a fixing portion 831 in the center. The fixing portion 831 is arranged with the surface direction facing up and down. The fixing portion 831 is provided with a circular fixing hole 832 in the central portion. The connecting wall portion 84 is formed in a substantially inverted L shape when viewed from the left side, protrudes upward from the left side of the upper end portion of the first wall portion 81, and the tip end side thereof extends rearward. The connecting wall portion 84 includes a fixing portion 841 in a portion extending rearward. The fixing portion 841 is arranged with the surface direction facing up and down. The fixing portion 841 is provided with a circular fixing hole 842 in the central portion.

The shapes of the first adjusting plates 91 and 92 will be described. The first adjusting plates 91 and 92 are iron plates having a substantially rectangular shape in a plan view. The first adjusting plate 91 is sandwiched between the rectangular portion 64 of the first protective plate 61 and the fixing portion 72 of the tension plate 70. The first adjusting plate 91 is provided with a fixing hole 911 in the center thereof. The first adjusting plate 92 is sandwiched between the second protective plate 62 and the fixing portion 73 of the tension plate 70. The first adjusting plate 92 is provided with a fixing hole 921 in the center thereof. As will be described later, the first adjusting plates 91 and 92 are spacers for forming a gap A1 (see FIG. 7) between the upper surface of the first protective plate 61 and the lower surface of the tension plate 70.

The shapes of the second adjusting plates 93 and 94 will be described. The second adjusting plates 93 and 94 are also iron plates having a substantially rectangular shape in a plan view like the first adjusting plates 91 and 92. The second adjusting plate 93 is sandwiched between the fixing portion 72 of the tension plate 70 and the fixing portion 831 of the connecting wall portion 83 of the guide member 80. The second adjusting plate 93 is provided with a fixing hole 931 in the center thereof. The second adjusting plate 94 is sandwiched between the fixing portion 73 of the tension plate 70 and the fixing portion 841 of the connecting wall portion 84 of the guide member 80. The second adjusting plate 94 is provided with a fixing hole 941 in the center thereof. As will be described later, the second adjusting plates 93 and 94 adjust the position of the needle thread 6 passing between the hole 861 and the hole 871 of the guide member 80 with respect to the thread contact portion 71 of the tension plate 70. Spacer.

The assembly process of the thread tension detection device 30 will be described. As shown in FIG. 6, the operator mounts the mounting base 40 on a horizontal base (not shown). The operator arranges the sensor board 50 on the fixed surface 45 of the mounting base 40. The fixing portion 52 of the sensor board 50 is arranged on the supporting portion 47 of the mounting base 40. The fixing portion 53 of the sensor board 50 is arranged on the supporting portion 48 of the mounting base 40. The operator arranges the rectangular portion 64 of the first protective plate 61 on the upper surface of the fixed portion 52 of the sensor board 50. The extended portion 65 of the first protective plate 61 is arranged on the upper surface of the central portion 51 of the sensor substrate 50. The operator arranges the second protective plate 62 on the left side of the upper surface of the fixing portion 53 of the sensor board 50. The operator arranges the first adjusting plate 91 on the upper surface of the rectangular portion 64 of the first protective plate 61. The operator arranges the first adjusting plate 92 on the upper surface of the second protective plate 62.

The operator arranges the fixing portion 72 of the tension plate 70 on the upper surface of the first adjusting plate 91. The operator arranges the fixing portion 73 of the tension plate 70 on the upper surface of the first adjusting plate 92. The tension plate 70 is in a state of being bridged between the first protective plate 61 and the second protective plate 62. The upper surface of the sensor substrate 50 faces the lower surface of the thread contact portion 71 of the tension plate 70 with a gap (see FIG. 7). The magnet 78 faces the Hall element 55 via the gap G (see FIGS. 7 and 8). The operator arranges the second adjusting plate 93 on the upper surface of the fixing portion 72 of the tension plate 70. The operator arranges the second adjusting plate 94 on the upper surface of the fixing portion 73 of the tension plate 70.

The operator guides the sensor board 50, the first protective plate 61 and the second protective plate 62, the first adjusting plates 91 and 92, the tension plate 70, and the mounting base 40 in which the second adjusting plates 93 and 94 are arranged. The member 80 is arranged so as to cover it from above (see FIGS. 4 and 5). The pedestal portion 41 of the mounting base 40 is inserted and arranged from below between the first wall portion 81 and the second wall portion 82 of the guide member 80. The operator arranges the fixing portion 831 of the connecting wall portion 83 of the guide member 80 with the second adjusting plate 93 interposed therebetween with respect to the upper surface of the fixing portion 72 of the tension plate 70. The operator arranges the fixing portion 841 of the connecting wall portion 84 of the guide member 80 with the second adjusting plate 93 interposed therebetween with respect to the upper surface of the fixing portion 73 of the tension plate 70.

The operator can use the fixing hole 832 of the connecting wall portion 83, the fixing hole 931 of the second adjusting plate 93, the fixing hole 721 of the tension plate 70, the fixing hole 911 of the first adjusting plate 91, and the fixing hole 611 of the first protective plate 61. , The fastening screw 102 is inserted from above into the fixing hole 521 of the sensor board 50 and fastened to the fixing hole 471 of the mounting base 40. The operator can fix the fixing hole 842 of the connecting wall portion 84, the fixing hole 941 of the second adjusting plate 94, the fixing hole 731 of the tension plate 70, the fixing hole 921 of the first adjusting plate 92, and the fixing hole 621 of the second protective plate 62. , The fastening screw 103 is inserted into the fixing hole 531 of the sensor board 50 from above, and fastened to the fixing hole 481 of the mounting base 40. In this way, the assembly of the thread tension detecting device 30 is completed (see FIGS. 2 to 5).

Since the tension plate 70 is detachably fixed to the mounting base 40 with the fastening screws 102 and 103, for example, the thread contact portion 71 may be attached according to the model of the sewing machine 1, the material, thickness, tension, etc. of the needle thread 6. It can be easily replaced with other tension plates of different thickness.

As shown in FIGS. 7 and 8, in the thread tension detecting device 30, the thickness of each of the first protective plate 61 and the second protective plate 62 is larger than the thickness of the first adjusting plates 91 and 92. Therefore, the sewing machine 1 can sufficiently leave a space between the tension plate 70 and the mounting base 40, so that the magnet 78 and the Hall element 55 can be separated from each other.

A method of fixing the thread tension detecting device 30 to the sewing machine 1 will be described. The operator arranges the mounting base 40 of the thread tension detecting device 30 shown in FIG. 3 at a predetermined position on the front surface of the arm portion 4 of the sewing machine 1. The predetermined position is, for example, a position in the needle thread path between the main thread tensioner 23 of the thread tension portion 15 and the thread take-up spring device 17 (see FIG. 1). The operator positions the mounting portion 42 so that the predetermined position of the thread contact portion 71 of the tension plate 70 is located on the needle thread path. The operator fastens the adjusting screw 101 (see FIG. 6) to the fixing hole (not shown) provided at a predetermined position on the front surface of the arm portion 4 via the insertion hole 421 of the mounting portion 42. Therefore, the thread tension detecting device 30 is fixed at a predetermined position on the front surface of the arm portion 4.

By loosening the adjusting screw 101, the thread tension detecting device 30 can move the mounting portion 42 along the length direction of the mounting base 40 within the range of the insertion hole 421. Therefore, the thread tension detecting device 30 can change the mounting position within the range of the insertion hole 421 in the direction parallel to the length direction of the tension plate 70. By changing the mounting position of the thread tension detecting device 30, the degree of bending of the needle thread 6 on the needle thread path changes. Therefore, the sewing machine 1 can easily make an adjustment to reduce the bending of the needle thread 6 on the needle thread path only by changing the mounting position of the thread tension detecting device 30 within the range of the insertion hole 421.

A method of passing the needle thread 6 through the thread tension detecting device 30 will be described. With the thread tension detecting device 30 fixed at a predetermined position on the front surface of the arm portion 4, the operator has a needle thread with respect to the hole 861 of the thread guide portion 86 of the guide member 80 and the hole 871 of the thread guide portion 87. Pass through 6 (see FIG. 2). The operator can easily pass the needle thread 6 from the thread guide groove 862 through the hole 861 and from the thread guide groove 872 through the hole 871. The operator brings the needle thread 6 into contact with a predetermined position on the contact surface of the thread contact portion 71 of the tension plate 70.

As shown in FIG. 8, the guide portions 76 and 77 of the tension plate 70 are curved and project toward the mounting base 40. For example, when the needle thread 6 moves from the hole portion 861 toward the hole portion 871, the guide portion 76 guides the needle thread 6 passing through the hole portion 861 to a predetermined position P on the contact surface. The guide portion 77 guides the needle thread 6 from the predetermined position P on the contact surface toward the hole portion 871. Although the needle thread 6 bends at the thread contact portion 71, it can be comfortably contacted with the contact surface by the two guide portions 76 and 77. Since a large load is not applied to the needle thread 6, the thread tension detecting device 30 can prevent the needle thread 6 from being cut at the thread contact portion 71. The needle thread 6 can be brought into contact with the thread contact portion 71 by sliding smoothly at a predetermined position.

The guide portions 76 and 77 position the needle thread 6 at a predetermined position P of the thread contact portion 71. As described above, since the predetermined position P is an intermediate position of the thread contact portion 71, it is possible to form a deflection in the entire thread contact portion 71. Therefore, since the thread contact portion 71 can be bent according to the needle thread tension, the thread tension detecting device 30 can detect the needle thread tension in a wide range.

The force with which the needle thread 6 pushes the tension plate 70 will be described with reference to FIGS. 8 and 9. As shown in FIG. 8, when the needle thread 6 passes through the guide member 80 and the tension plate 70, the inner edge portion of the hole portion 861, the predetermined position P of the contact surface of the thread contact portion 71 of the tension plate 70, and the inner edge portion of the hole portion 871. Contact each other. The predetermined position P of the contact surface of the thread contact portion 71 is located on the side opposite to the mounting base 40 with respect to the virtual straight line L (see FIG. 9) connecting the hole portion 861 and the hole portion 871. The thread contact portion 71 comes into contact with the needle thread 6 passing between the hole portion 861 and the hole portion 871 from the mounting base 40 side. Therefore, the needle thread 6 bends with respect to the virtual straight line L between the hole 861 and the hole 871. Therefore, the thread tension detecting device 30 can generate a force to push the thread contact portion 71 of the tension plate 70 toward the mounting base 40 at a predetermined position P by the needle thread tension, and the tension plate 70 can be easily bent.

As shown in FIG. 9, the needle thread 6 has a first tension V1 which is a vector of a force from the front end position of the predetermined position P toward the hole 861 side, and the needle thread 6 from the rear end position of the predetermined position P to the hole 871 side. A second tension V2, which is a vector of the toward force, is generated. The intersection of the line extending the first tension V1 and the line extending the second tension V2 is defined as the Q point. The vector of the force from the point Q toward the contact surface of the thread contact portion 71 in the direction orthogonal to the contact surface is the resultant force V3 of the first tension V1 and the second tension V2. The resultant force V3 is a force that pushes the thread contact portion 71 toward the mounting base 40 side. In this embodiment, the positional relationship between the thread contact portion 71 and the hole portions 861,871 can be adjusted so that the first tension V1 and the second tension V2 have the same magnitude. Since the first tension V1 and the second tension V2 have the same magnitude, the direction of the resultant force V3 in which the needle thread 6 pushes the thread contact portion 71 is perpendicular to the contact surface of the thread contact portion 71. Therefore, since the thread tension detecting device 30 can regulate the bending direction of the tension plate 70, it is possible to make it difficult for the tension of the needle thread 6 to be detected to vary.

The operation of the yarn tension detecting device 30 will be described with reference to FIG. 7. The needle thread 6 comes into contact with the contact surface (upper surface) of the thread contact portion 71 of the tension plate 70. The thread contact portion 71 bends downward due to the needle thread tension. The magnet 78 moves in the vertical direction according to the bending of the thread contact portion 71. The magnetic flux density of the magnet 78 passing through the Hall element 55 changes according to the movement of the magnet 78. The Hall element 55 detects a change in magnetic flux density and converts it into a voltage signal. The sewing machine 1 calculates the needle thread tension based on the sensor value output from the Hall element 55. In the present embodiment, the magnetic flux density detected by the Hall element 55 when the tension plate 70 is loaded with the needle thread tension is linear with respect to the magnetic flux density detected by the Hall element 55 when the tension plate 70 is in the state where the needle thread tension is not loaded. It is preferable that the change is large.

With reference to FIG. 7, the prevention of excessive bending of the tension plate 70 by the first protective plate 61 will be described. In this embodiment, the direction in which the thread contact portion 71 of the tension plate 70 bends is the D1 direction, and the direction orthogonal to the D1 direction and parallel to the extension direction of the tension plate 70 is the D2 direction. In FIG. 7, the D1 direction is the vertical direction, and the D2 direction is the horizontal direction.

In the D1 direction, the extending portion 65 of the first protective plate 61 is located between the lower surface of the thread contact portion 71 of the tension plate 70 and the upper surface of the sensor substrate 50. Between the lower surface of the thread contact portion 71 of the tension plate 70 and the upper end of the Hall element 55 provided on the sensor substrate 50, the upper surface of the extended portion 65 of the first protective plate 61 is the thread of the tension plate 70 via the gap A1. It is arranged so as to face the lower surface of the contact portion 71. Further, in the D2 direction, the extending portion 65 of the first protective plate 61 extends parallel to the tension plate 70 and to the left to the vicinity of the magnet 78 and the Hall element 55. There is a gap B1 between the left end portion of the extending portion 65 and the magnet 78 and the Hall element 55. The positions of the magnet 78 and the Hall element 55 at this time are the rightmost positions of the magnet 78 and the Hall element 55.

When the needle thread tension is applied to the upper surface of the thread contact portion 71 of the tension plate 70, a downward force is applied to the thread contact portion 71, so that the thread contact portion 71 bends downward. The thread contact portion 71 can bend downward within the range of the gap A1. For example, during the sewing operation of the sewing machine 1, a tension higher than the allowable tension may be applied to the needle thread 6. In this case, the thread contact portion 71 flexes greatly downward according to the needle thread tension, but the portion of the lower surface of the thread contact portion 71 other than the portion provided with the magnet 78 before excessively flexing is the first protective plate 61. It abuts on the upper surface of the extension portion 65. Therefore, since the thread tension detecting device 30 can prevent the tension plate 70 from being excessively bent, it is possible to prevent the tension plate 70 from being plastically deformed and unable to accurately detect the tension applied to the needle thread 6.

The gap A1 is smaller than the gap G between the magnet 78 and the Hall element 55 in the D1 direction. Therefore, the sewing machine 1 can prevent the magnet 78 and the Hall element 55 from colliding with each other even if the thread contact portion 71 bends downward.

Since the extended portion 65 of the first protective plate 61 extends to the vicinity of the magnet 78 and the Hall element 55, when the thread contact portion 71 bends downward, the upper surface of the extended portion 65 quickly becomes the lower surface of the thread contact portion 71. Can be in contact. Therefore, the sewing machine 1 can surely prevent the tension plate 70 from being excessively bent. The smaller the gap B1, the more the extension portion 65 limits the amount of downward bending of the thread contact portion 71. Therefore, the gap B1 presets an allowable range of the needle thread tension detected during sewing, and corresponds to the amount of downward bending of the thread contact portion 71 when the needle thread tension within the allowable range is applied to the thread contact portion 71. It is better to decide. For example, when the thread contact portion 71 bends downward, a gap is provided so that the lower surface of the thread contact portion 71 comes into contact with the upper surface of the extended portion 65 of the first protective plate 61 before the magnet 78 contacts the Hall element 55. B1 should be adjusted.

With reference to FIG. 7, a method of adjusting the gap A1 by the first adjusting plates 91 and 92 will be described. The first adjusting plates 91 and 92 form a gap A1 between the upper surface of the extended portion 65 of the first protective plate 61 and the lower surface of the thread contact portion 71 of the tension plate 70. In the sewing machine 1, the gap A1 can be easily adjusted by arranging the first adjusting plates 91 and 92 in place of the first adjusting plates having different thicknesses. Therefore, the sewing machine 1 can easily adjust the amount of bending of the thread contact portion 71 of the tension plate 70 by adjusting the gap A1. In addition, for example, the gap A1 may be adjusted by arranging a plurality of first adjusting plates 91 and 92 in the D1 direction in an overlapping manner.

A method of adjusting the position of the needle thread path by the second adjusting plates 93 and 94 will be described with reference to FIGS. 7 and 9. By adjusting the thickness of each of the second adjusting plates 93 and 94, the positions of the holes 861 and 871 of the guide member 80 can be adjusted with reference to the position of the thread contact portion 71 in the D1 direction. For example, the second adjusting plates 93 and 94 are arranged in place of the thick second adjusting plate. The holes 861,871 of the guide member 80 move in the direction (upward) away from the mounting base 40 side. As shown in FIG. 9, since the separation distance between the Q point and the virtual straight line L becomes short, the angle θ between the first tension V1 and the second tension V2 generated in the needle thread 6 becomes wider, and the resultant force V3 becomes smaller. On the contrary, the second adjusting plates 93 and 94 are arranged in place of the thin second adjusting plates. The holes 861,871 of the guide member 80 move in the direction (downward) toward the mounting base 40 side. Since the separation distance between the Q point and the virtual straight line L becomes long, the angle θ between the first tension V1 and the second tension V2 generated in the needle thread 6 becomes narrow, and the resultant force V3 becomes large. Therefore, the thread tension detecting device 30 can adjust the needle thread tension applied to the thread contact portion 71 by adjusting the thicknesses of the second adjusting plates 93 and 94, respectively, and can easily adjust the amount of bending of the thread contact portion 71. ..

As described above, the sewing machine 1 of the present embodiment includes a sewing needle 10, a balance 28, a thread tension portion 15, and a thread tension detecting device 30. The sewing needle 10 holds the needle thread 6 and can move up and down. The balance 28 is provided in the needle thread path from the thread supply source to the sewing needle 10, and moves up and down with the vertical movement of the sewing needle 10 to pull up the needle thread 6. The thread tension portion 15 is arranged between the thread supply source and the balance 28 in the needle thread path, and the tension applied to the needle thread 6 can be controlled. The thread tension detecting device 30 is provided in the needle thread path and can detect the tension applied to the needle thread 6.

The thread tension detecting device 30 includes a mounting base 40, a tension plate 70, a magnet 78, a Hall element 55, and a guide member 80. The mounting base 40 is attached to the sewing machine 1. The tension plate 70 includes fixing portions 72, 73 and a thread contact portion 71. The fixing portion 72 and the fixing portion 73 are fixed to the mounting base 40. The thread contact portion 71 is connected to the fixing portion 72 and the fixing portion 73, extends in a direction orthogonal to the needle thread path, and causes bending by contact with the needle thread 6. The magnet 78 is fixed to the thread contact portion 71 of the tension plate 70. The Hall element 55 is provided on the mounting base 40. The Hall element 55 detects the magnetic flux density of the magnet 78, which changes according to the bending generated in the thread contact portion 71, and outputs a signal according to the detection result. The guide member 80 includes fixing portions 831 and 841 and thread guide portions 86 and 87. The fixing portions 831, 841 are fixed to the mounting base 40. The thread guide portions 86 and 87 include holes 861 and 871. The hole 861 is provided at a position where the needle thread 6 enters on the upstream side in the supply direction of the needle thread 6 with respect to the predetermined position P of the thread contact portion 71, and the needle thread 6 passes through the hole portion 861. The hole 871 is provided at a position where the needle thread 6 comes out on the downstream side in the supply direction of the needle thread 6 with respect to the predetermined position P of the thread contact portion 71, and the needle thread 6 passes through the hole portion 871. The guide member 80 guides the needle thread 6 so that the needle thread 6 comes into contact with and passes through the predetermined position P of the thread contact portion 71.

In the sewing machine 1 having the above configuration, the thread tension detecting device 30 includes a first protective plate 61. The extended portion 65 of the first protective plate 61 is located between the tension plate 70 and the mounting base 40 in the bending D1 direction of the tension plate 70, and abuts on the surface of the tension plate 70 on the mounting base 40 side. It is possible. During sewing, the tension plate 70 bends according to the tension applied to the needle thread 6. The yarn tension detection device 30 detects the bending of the tension plate 70 with the Hall element 55, and outputs a signal according to the detection result. When an allowable tension is applied to the needle thread 6, the tension plate 70 comes into contact with the extending portion 65 of the first protective plate 61 before being excessively bent. Therefore, since the sewing machine 1 can prevent the tension plate 70 from being excessively bent, it is possible to prevent the tension plate 70 from being plastically deformed and the needle thread tension cannot be accurately detected.

Since the thread tension detection device 30 is provided between the main thread tensioner 23 of the thread tension portion 15 and the thread take-up spring 27A in the needle thread path, when the balance 28 pulls up the needle thread 6, the balance 28 and the sewing needle 10 There is nothing to resist in between. Therefore, since the thread tension detecting device 30 does not interfere with sewing, the sewing machine 1 can form a high-quality stitch on the object to be sewn. Since the balance 28 does not pull the needle thread portion for detecting the needle thread tension, the thread tension detecting device 30 can detect the original tension applied to the needle thread 6.

In the thread tension detecting device 30, the magnet 58 is provided on the thread contact portion 71 of the tension plate 70, and the sensor substrate 50 provided with the Hall element 55 is arranged along the fixed surface 45 of the mounting base 40, and the first protective plate 61 is provided. The second protective plate 62 is fixed to the mounting base 40 with the sensor board 50 sandwiched between the mounting base 40 and the mounting base 40. Therefore, the thread tension detecting device 30 can fix the Hall element 55 and the sensor substrate 50 to the mounting base 40 together with the first protective plate 61 and the second protective plate 62.

In the above description, the main thread tensioner 23 of the thread tension portion 15 is an example of the "thread tensioner" of the present invention. The mounting base 40 of the thread tension detecting device 30 is an example of the "mounting portion" of the present invention. The fixing portions 72 and 73 of the tension plate 70 are an example of the "first fixing portion" of the present invention. The Hall element 55 is an example of the "sensor" of the present invention. The fixing portions 831, 841 of the guide member 80 are an example of the "second fixing portion" of the present invention. The hole 861 is an example of the "first hole" of the present invention, and the hole 871 is an example of the "second hole" of the present invention. The first protective plate 61 is an example of the "protection unit" of the present invention. The gap A1 is an example of the "predetermined gap" of the present invention. The first adjusting plates 91 and 92 are examples of the "first adjusting unit" of the present invention. The second adjusting plates 93 and 94 are examples of the "second adjusting unit" of the present invention.

In addition to the above embodiments, the present invention can be modified in various ways. The sewing machine 1 of the above embodiment is a one-needle sewing machine in which one sewing needle 10 is attached to a needle rod 9, but a two-needle sewing machine in which two sewing needles are attached to a needle rod 9 is also used in the present embodiment. The thread tension detection device 30 can be used. In the case of a two-needle sewing machine, as shown in FIG. 10, the two needle threads 6A and 6B supplied from the two thread pieces (not shown) are the thread tension portion 15 and the thread corresponding to each of the thread tension portions 15 provided on the front surface of the arm portion 4. Hang each on the tone part 16. The thread tension portion 16 is arranged on the right side of the thread tension portion 15, and like the thread tension portion 15, one auxiliary thread tensioner 24 and two main thread tensioners 25 and 26 are arranged in this order from the upstream side of the needle thread path. To prepare for. The functions of the auxiliary thread tensioner 24 and the main thread tensioners 25 and 26 are the same as the above-mentioned functions of the auxiliary thread tensioner 21 and the main thread tensioners 22 and 23 of the thread tensioning unit 15. The two needle threads 6A and 6B that have passed through the thread tension portion 15 and the thread tension portion 16 are hooked on the thread take-up springs 27A and 27B of the thread take-up spring device 17, respectively, pass through the balance 28 and the thread retainer 29, and have two sewing needles. (Not shown). Like the thread take spring 27A, the thread take spring 27B controls the supply amount of the needle thread 6B to the sewing needle 10 in conjunction with the operation of the balance 28. The sewing machine 1 fixes the thread tension detection device 30 on the downstream side of the main thread tensioner 23 of the thread tension portion 15 in the supply direction of the needle thread 6, and the thread is on the downstream side of the main thread tensioner 26 of the thread tension portion 16. The tension detection device 130 is fixed. Therefore, the two-needle sewing machine 1 can individually detect the tensions of the two needle threads 6A and 6B supplied to the two sewing needles by the two thread tension detecting devices 30 and 130.

Although the example of FIG. 10 is an example of two sewing needles, the present invention can be applied to a sewing machine having three or more sewing needles. In this case, the thread tension detecting device 30 may be provided corresponding to each of a plurality of thread tensioners provided according to the number of sewing needles. Further, the sewing machine may collectively detect the tensions of all the needle threads supplied to each of the plurality of sewing needles with one thread tension detecting device. In this case, the sewing machine can collectively detect the tensions of a plurality of needle threads supplied to a plurality of sewing needles with a single thread tension detecting device 30.

In the sewing machine 1 of the above embodiment, the thread tension detection device 30 is provided between the main thread tensioner 23 of the thread tension portion 15 and the thread take-up spring 27A, and the main thread tensioner 23 and the balance 28 are provided in the needle thread path. If it is between, it may be provided on the downstream side of the thread take-up spring 27A. As shown in FIG. 11, the sewing machine 1 may arrange the thread tension detecting device 230 between the thread retainer 29 and the balance 28 in the needle thread path. Since the thread tension detecting device 230 is located on the downstream side of the balance 28, the tension of the needle thread 6 being sewn can be accurately detected at a position close to the sewing needle 10. When the thread tension detection device 30 is provided on the downstream side of the thread take-up spring 27A, the thread tension detection device 30 moves the mounting portion 42 within the range of the insertion hole 421 along the length direction of the mounting base 40, whereby the sewing machine 1 Can adjust the amount of pulling up when the balance 28 pulls up the needle thread 6.

The first adjusting plates 91, 92 and the second adjusting plates 93, 94 of the thread tension detecting device 30 may be omitted. When the first adjusting plates 91 and 92 are omitted, the thickness of the rectangular portion 64 of the first protective plate 61 is made larger than the thickness of the extending portion 65, and a gap is formed between the extending portion 65 and the tension plate 70. It is desirable to do.

In the thread tension detecting device 30 of the above embodiment, the left and right ends of the tension plate 70 are fixed to the pedestal portion 41 of the mounting base 40, respectively, but for example, only one end of both ends may be fixed. ..

The sensor board 50 may include only the central portion 51, or may include only the central portion 51 and the fixed portion 53. In this case, in the assembly of the thread tension detecting device 30, the rectangular portion 64 of the first protective plate 61 may be arranged on the support portion 47 of the mounting base 40.

The thread contact portion 71 of the tension plate 70 is arranged so as to extend in a direction orthogonal to the needle thread path, but may be arranged so as to intersect the needle thread path.

In the above embodiment, the bending generated in the tension plate 70 is indirectly detected by using the magnet 78 and the Hall element 55, but the bending of the tension plate 70 may be detected by another method, for example, using a strain gauge. The bending of the tension plate 70 may be directly detected. In addition, for example, a sensor such as an infrared sensor or a laser displacement meter may be used for detection.

In the tension plate 70, the predetermined position P in contact with the needle thread 6 is an intermediate position in the length direction of the thread contact portion 71, but if it is in contact with at least the contact surface of the thread contact portion 71, it is not an intermediate position. You may.

The guide member 80 includes thread guide portions 86 and 87. The tip portion of the thread guide portion 86 may be connected to the upper end portion of the first wall portion 81. The tip portion of the thread guide portion 87 may be connected to the upper end portion of the second wall portion 82. The thread guide groove 862,872 may be omitted. The holes 861,871 may be circular holes.

The magnetizing direction of the magnet 78 is the height direction through which the cylindrical magnet 78 passes along the axial direction, but for example, a cylindrical magnet through which the magnetic flux passes in the radial direction may be adopted.

The thread tension detecting device 30 detects the change in the magnetic flux density of the magnet 78 by the Hall element 55, but it may be detected by using another sensor, for example, a magnetic impedance element, a magnetoresistive effect element, or the like. Can be used.

1 Sewing machine 6 Needle 9 Needle bar 10 Sewing needle 23,26 Main thread tensioner 26 Main thread tensioner 27A, 27B Thread taker spring 28 Balance 29 Thread retainer 30 Thread tension detector 40 Mounting base 50 Sensor board 55 Hall element 61 First protection Plate 62 Second protective plate 65 Extension part 70 Tension plate 71 Thread contact part 72, 73 Fixed part 78 Magnet 80 Guide member 81 First wall part 82 Second wall part 83, 84 Connecting wall part 86, 87 Thread guide part 91 , 92 1st adjustment plate 93,94 2nd adjustment plate 831,841 Fixed part 861,971 Hole part A1 Gap

Claims (15)

A balance that is provided in the needle thread path from the thread supply source to the sewing needle that holds the needle thread, moves up and down with the vertical movement of the sewing needle, and pulls up the needle thread.
A thread tensioner arranged between the thread supply source and the balance in the needle thread path and capable of controlling the tension applied to the needle thread, and
A thread tension detecting device provided in the needle thread path and capable of detecting the tension applied to the needle thread is provided.
The thread tension detecting device is
The mounting part to be attached to the sewing machine and
A first fixing portion fixed to the mounting portion and a thread contact portion connected to the first fixing portion, extending in a direction intersecting the needle thread path, and causing bending by contact with the needle thread. With a tension plate and
A sensor that detects the deflection that occurs in the thread contact portion and outputs a signal according to the detection result.
It has a second fixing portion to be fixed to the mounting portion, is provided at a position where the needle thread enters on the upstream side in the supply direction of the needle thread with respect to a predetermined position of the thread contact portion, and the needle thread passes through. It is provided with a first hole portion and a second hole portion provided at a position where the needle thread comes out on the downstream side in the supply direction of the needle thread with respect to the predetermined position and through which the needle thread passes. In a sewing machine provided with a guide member for guiding the needle thread so that the needle thread passes through the sewing machine in contact with the needle thread.
The sewing machine is located between the tension plate and the mounting portion in a predetermined direction in which the tension plate bends, and is provided with a protective portion capable of contacting the surface of the tension plate on the mounting portion side. .. A magnet provided on one of the tension plate and the mounting portion,
A magnetic sensor provided on the other of the tension plate and the mounting portion is provided.
The end of the protection portion on the tension plate side in the predetermined direction has a predetermined gap with the tension plate between the tension plate and the magnet or the magnetic sensor provided in the mounting portion. Position to,
The sewing machine according to claim 1, wherein the end portion can be brought into contact with a portion of the tension plate other than the portion provided with the magnet or the magnetic sensor. The sewing machine according to claim 2, wherein the predetermined gap is smaller than the separation distance between the magnet and the magnetic sensor in the predetermined direction. The magnet is provided on the tension plate.
The substrate of the magnetic sensor is arranged along the mounting portion, and the substrate is arranged along the mounting portion.
The sewing machine according to claim 2 or 3, wherein the protective portion is fixed to the mounting portion together with the substrate in a state where the substrate is sandwiched between the protective portion and the mounting portion. The sewing machine according to claim 4, wherein the protective portion extends in parallel with the tension plate and extends to the vicinity of the magnet and the magnetic sensor. The invention according to any one of claims 1 to 5, wherein a first adjusting portion having a first thickness is arranged between the first fixing portion and the protective portion of the tension plate in a predetermined direction. Sewing machine. The sewing machine according to claim 6, wherein the size of the protective portion in the predetermined direction is larger than the size of the first thickness of the first adjusting portion. The first fixing portion of the tension member is located between the second fixing portion of the guide member and the protection portion.
The sewing machine according to any one of claims 1 to 7, wherein a second adjusting portion having a second thickness is arranged between the first fixing portion and the second fixing portion. .. The sewing machine according to any one of claims 1 to 8, wherein the thread tension detecting device is provided between the thread tensioner and the balance in the needle thread supply path. It is provided between the balance and the thread tensioner in the needle thread path, and is provided with a thread take-up spring that controls the supply amount of the needle thread to the sewing needle in conjunction with the operation of the balance.
The sewing machine according to any one of claims 1 to 9, wherein the thread tension detecting device is provided between the thread tensioner and the thread taking spring in the needle thread path. There are a plurality of the thread tensioners according to the number of the plurality of sewing needles.
The sewing machine according to claim 10, wherein the thread tension detecting device is provided corresponding to each of the plurality of thread tensioners. A needle bar for supporting the sewing needle is provided.
The sewing machine according to any one of claims 1 to 8, wherein the thread tension detecting device is provided between the balance and the needle bar in the needle thread path. A thread retainer provided between the balance and the sewing needle to provide resistance to the movement of the needle thread supplied to the sewing needle along the needle thread path is provided.
The sewing machine according to any one of claims 1 to 8, wherein the thread tension detecting device is provided between the balance and the thread retainer in the needle thread path. There are a plurality of the thread tensioners according to the number of the plurality of sewing needles.
The invention according to any one of claims 1 to 10, 12, or 13, wherein the thread tension detecting device collectively detects the tensions of all the needle threads supplied to each of the plurality of sewing needles. Sewing machine. A thread tension detecting device provided in the needle thread path from the thread supply source of the sewing machine to the sewing needle holding the needle thread and capable of detecting the tension applied to the needle thread.
The mounting part to be attached to the sewing machine and
A first fixing portion fixed to the mounting portion and a thread contact portion connected to the first fixing portion, extending in a direction intersecting the needle thread path, and causing bending by contact with the needle thread. With a tension plate and
A sensor that detects the deflection that occurs in the thread contact portion and outputs a signal according to the detection result.
It has a second fixing portion to be fixed to the mounting portion, is provided at a position where the needle thread enters on the upstream side in the supply direction of the needle thread with respect to a predetermined position of the thread contact portion, and the needle thread passes through. It is provided with a first hole portion and a second hole portion provided at a position where the needle thread comes out on the downstream side in the supply direction of the needle thread with respect to the predetermined position, and a second hole portion through which the needle thread passes. It is provided with a guide member for guiding the needle thread so that the needle thread contacts and passes through.
A thread located between the tension plate and the mounting portion in a predetermined direction in which the tension plate bends, and provided with a protective portion capable of contacting the surface of the tension plate on the mounting portion side. Tension detector.

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