JP2019180802A - sewing machine - Google Patents

Abstract

To provide a sewing machine in which the residual amount of a bobbin thread wound around a bobbin can be easily checked.SOLUTION: In a sewing machine 1, a bobbin 9 around which a bobbin thread 300 is wound is accommodated in an inner shuttle 7. An outer shuttle 5 which rotates with respect to the inner shuttle 7 has a rotational center different from the rotational center of the bobbin 9 accommodated in the inner shuttle 7, and a light-receiving part 11b is arranged on a bottom 5c of the outer shuttle at a position apart from the rotational center of the outer shuttle 5 in a radial direction. Consequently, due to the rotational movement of the outer shuttle 5 according to the sewing operation of the sewing machine, the light-receiving part 11b performs relative movement having a trajectory L with respect to the bobbin 9. As a result, the light-receiving part 11b can continuously detect the presence or absence of the bobbin thread while performing relative movement with respect to the bobbin 9, so that the residual amount of the bobbin thread can be calculated on the basis of the detection results.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a sewing machine capable of confirming the remaining amount of lower thread.

  The sewing machine interlaces the upper thread and the lower thread by the movement of the needle and the shuttle, and forms a seam on the cloth. Since the upper thread is installed on the upper part of the sewing machine, the operator can visually check the remaining thread amount at any time. On the other hand, the bobbin around which the lower thread is wound is disposed inside the hook. The hook is located under the needle plate. There is a sewing machine in which a part of the needle plate and the bobbin are transparent materials so that they can be easily seen, but they are covered with the cloth being sewn during sewing. In order to visually check the remaining amount of the bobbin thread, it is necessary to confirm the operation such as once interrupting the work, shifting the cloth being sewn, opening the needle plate, and taking out the bobbin.

  In order to perform sewing after confirming the remaining amount of the lower thread, it is necessary to reset the bobbin and to perform sewing resuming work such as taking out the lower thread onto the needle plate, which is troublesome. However, if sewing is performed without checking the remaining amount of the lower thread, the lower thread disappears at an unexpected timing of the operator. If the lower thread runs out during sewing, the needle only penetrates the object to be sewn, and no seam is formed. Therefore, when the lower thread runs out, it is necessary to interrupt the sewing once and cut the upper thread. Even if the bobbin is wound around the bobbin and the sewing is performed again, the previous sewing is interrupted, so the stitches that are sewn halfway will be adversely affected. There is a possibility that it will be necessary to solve.

  As a typical method for checking the remaining amount of lower thread without opening the needle plate and taking out the bobbin, a non-contact type lower thread detection mechanism using a light emitter and a light receiving sensor is known.

  The non-contact type lower thread detection mechanism is roughly divided into a transmission type and a reflection type. In the transmission type, the light emitter-bobbin-sensor is arranged on a straight line (for example, Patent Document 2). When a thread is wound around the bobbin, the light emitted from the light emitter passes through the bobbin but is blocked by the lower thread. On the other hand, when the thread is reduced, the light passes through the bobbin and reaches the sensor. By adjusting the positions of the light emitter and the sensor, it is possible to detect the presence or absence of the lower thread at a certain point. For example, when the total amount of lower thread wound around the bobbin becomes 30% or less, the positions of the light emitter and the sensor are adjusted so that the light emitted from the light emitter reaches the sensor. Thereby, the timing when the lower thread becomes 30% or less of the total amount of the lower thread wound around the bobbin is detected.

  On the other hand, in the reflection type, the illuminator irradiates the lower thread with light, and the sensor receives the reflected light, so that the presence or absence of the lower thread at a certain point can be detected as in the transmission type (for example, patents) Reference 3).

  However, in these methods, only binarization information, that is, information indicating whether the lower thread is, for example, 30% or more can be obtained, and it cannot be said that the remaining amount is accurately detected. A mechanism that can provide a plurality of points for detecting the presence / absence of a lower thread by using a plurality of light emitters and sensors has been proposed (for example, Patent Document 4), but the mechanism may be increased in size and essential. It's not a solution to a problem. In view of this, a mechanism has been proposed in which the lower thread detecting unit is movable in the radial direction of the bobbin so that the presence or absence of the lower thread can be detected at an arbitrary point.

JP-A-61-213091 JP-A-2-255177 JP-A-4-166189 Japanese Utility Model Publication No.59-90773

  However, a drive source is naturally required to drive the lower thread detection unit in the bobbin radial direction. In Patent Document 1, a lever for driving the operator is provided. However, the fact that the operator has to drive the lower thread detection unit means that the sewing operation must be interrupted each time, This burdens the user with complicated work. Of course, it is also conceivable to drive the motor using a motor or the like. However, driving by a motor not only increases the size of the apparatus, but also, as described above, the bobbin is supported by rotating parts such as an inner hook and an outer hook on the lower side and there is a work space on the upper side. A mechanical space for installing a drive source such as a motor is extremely limited, and is practically extremely difficult.

  The present invention has been proposed in order to solve the above-described problems of the prior art, and provides a sewing machine that can accurately and easily check the remaining amount of the lower thread wound around the bobbin. To do.

  Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

  In order to achieve the above object, a sewing machine according to the present invention is a sewing machine that forms a seam by interlacing an upper thread and a lower thread wound around a bobbin by passing a needle through a cloth, and scanning through which light passes. An inner hook having a light passage portion at the bottom, an outer hook having a rotation center at a position different from the rotation center of the bobbin housed in the inner hook, a light emitting portion for irradiating the bobbin with light, and the light emission And a light receiving portion that receives light that has passed through (transmitted) the scanning light passage portion and the flange of the bobbin, and the light receiving portion is spaced apart from the rotation center of the outer hook in the radial direction. The sewing machine is arranged at the bottom of the outer hook.

  The distance R from the rotation center of the outer hook to the light receiving portion is expressed as “the flange radius of the bobbin−the distance D ≦ the distance,” where D is the distance between the rotation center of the bobbin and the rotation center of the outer hook. R ≦ the distance D + the bobbin bobbin winding radius ”may be satisfied.

  The light emitting unit may be disposed on the needle plate.

  The light emitting unit and the light receiving unit may be disposed at the same position, and a reflection unit that reflects light from the light emitting unit may be further provided at a position facing the light emitting unit and the light receiving unit.

  A timing determination unit that determines the timing of detecting the light received by the light receiving unit according to the rotational speed of the outer hook, and a lower thread calculation that calculates the remaining amount of the lower thread based on the detection result of the light receiving unit May be further provided.

  And a notifying unit for notifying the lower thread remaining amount calculated by the lower thread calculating unit.

  According to the present invention, it is possible to check the remaining amount of the lower thread without taking out the bobbin, and it is possible to prevent a failure in sewing due to a shortage of the lower thread during sewing.

FIG. 1A is a perspective view showing the overall configuration of the sewing machine according to the first embodiment, and FIG. 1B is a schematic view showing the first embodiment in a skeleton form. It is a perspective view which shows the structure of the outer hook, inner hook, and bobbin of 1st Embodiment. It is a perspective view which shows the structure of the outer hook of 1st Embodiment. FIG. 4A is a perspective view showing the configuration of the inner hook of the first embodiment, and FIG. 4B is a plan view showing the configuration of the inner hook of the first embodiment. FIG. 5A is a perspective view showing the configuration of the bobbin, and FIG. 5B is a perspective view of the bobbin in a state where the maximum amount of lower thread is wound. It is a perspective view which shows the structure of the throat plate of 1st Embodiment. It is a block diagram which shows the structure of the control part of the sewing machine of 1st Embodiment. It is sectional drawing which shows the structure in 1st Embodiment, and the outline | summary of an optical path. It is a schematic diagram which shows the positional relationship of the scanning path | route by the light-receiving part of 1st Embodiment, and a bobbin. It is a schematic diagram which shows the influence which the light emission part in 1st Embodiment, a light-receiving part, a bobbin, and a bobbin thread remaining amount have on an optical path, and the detection result of a light-receiving part, (a) b) shows the case where the remaining amount of the lower thread is the maximum amount, and (c) shows the case where the remaining amount of the lower thread is about half of the maximum amount. FIG. 11A is a schematic diagram showing the positional relationship between the scanning path and the bobbin by the light receiving unit of Modification Example 1. FIG. 11B shows the positional relationship between the scanning path of the light receiving unit of Modification Example 2 and the bobbin. FIG. It is sectional drawing which shows the structure of the lower thread detection mechanism of 2nd Embodiment. It is a perspective view which shows the structure of the needle plate of 2nd Embodiment. It is the schematic which shows the influence which the light emission part in 2nd Embodiment, a light-receiving part, a bobbin, and a bobbin thread remaining amount have on an optical path, and the detection result of a light-receiving part. It is a schematic diagram of the modification which has a light emission part which irradiates diffused light with respect to 1st Embodiment.

[1. First Embodiment]
[1-1. Constitution]
(Whole structure of the sewing machine)
As shown in FIG. 1A, the sewing machine 1 forms a seam by allowing the needle 3 to pass through the cloth 100 placed on the needle plate 2 and entangle the upper thread 200 and the lower thread 300. Thus, it is a household, professional or industrial device for sewing the fabric 100.

  As shown in FIG. 1B, the sewing machine 1 has a needle bar 4 and an outer hook 5. The needle bar 4 extends perpendicularly to the needle plate 2 and is attached so as to be vertically movable in the vertical direction. The needle bar 4 supports the needle 3 that holds the upper thread 200 at the tip of the needle plate 2 side. The outer hook 5 has an inner hollow drum shape that is open on one plane, is attached to the needle plate 2 horizontally or vertically, and is rotatable in the circumferential direction. The outer hook 5 accommodates an inner hook 7 (not shown in FIG. 1B) inside, and the inner hook 7 accommodates a bobbin 9 around which a lower thread 300 is wound.

  In the sewing machine 1, when the needle bar 4 moves up and down, the needle 3 penetrates the fabric 100 with the upper thread 200, and when the needle 3 is raised, an upper thread loop is formed due to friction between the fabric 100 and the upper thread 200. Is done. Then, the upper thread loop is captured by the rotating outer hook 5, and the bobbin 9 passes through the upper thread loop as the outer hook 5 rotates, whereby the upper thread 200 and the lower thread 300 are entangled to form a seam. The

  The needle bar 4 and the outer hook 5 are driven via respective transmission mechanisms using a common sewing machine motor 6 as a power source. An upper shaft 61 extending horizontally is connected to the needle bar 4 via a crank mechanism 62. The rotation of the upper shaft 61 is converted into a linear motion by the crank mechanism 62 and transmitted to the needle bar 4 so that the needle bar 4 moves up and down. A horizontally extending lower shaft 63 is connected to the outer hook 5 via a gear mechanism 64. When the outer hook 5 is installed horizontally, the gear mechanism 64 is a screw gear whose shaft angle is 90 degrees, for example. When the gear mechanism 64 converts the rotation of the lower shaft 63 by 90 degrees and transmits it to the outer hook 5, the outer hook 5 rotates horizontally. An inner hook 7 having a space for accommodating the bobbin 9 is provided inside the outer hook 5.

  Each of the upper shaft 61 and the lower shaft 63 is provided with a pulley 65 having a predetermined number of teeth. The pulley 65 is connected by a toothed belt 67. When the upper shaft 61 rotates with the rotation of the sewing machine motor 6, the lower shaft 63 rotates through the pulley 65 and the toothed belt 67. Thereby, the needle bar 4 and the outer hook 5 operate in synchronization.

  Further, the sewing machine 1 has an upper shaft encoder 8. The upper shaft encoder 8 includes a shielding plate 8a attached to the upper shaft 61 and a photo interrupter 8b attached to the sewing machine casing. The shielding plate 8a is a member on a thin disk having a slit hole, and the photo interrupter 8b is a so-called optical sensor having a light receiving surface and a light emitting surface on opposite surfaces of the groove. The upper shaft encoder 8 including the shielding plate 8a and the photo interrupter 8b shields light from the photo interrupter 8b by the shielding plate 8a that rotates as the upper shaft 61 rotates. The rotation angle and rotation speed of the upper shaft 61 can be detected by counting the length of light reception time and the number of times of light reception by the photo interrupter 8b. That is, it is possible to detect the position and speed of the needle 3 synchronously connected to the upper shaft 61 and the rotation angle and speed of the outer hook 5.

(Detailed configuration diagram of outer pot and inner pot)
As shown in FIG. 2, an inner hook 7 is accommodated inside the outer hook 5, and a bobbin 9 is accommodated inside the inner hook 7. The inner hook 7 is rotatably accommodated with respect to the rotating outer hook 5, and the rotation of the sewing machine casing is restricted. That is, the outer hook 5 rotates by receiving power from the lower shaft 63, but the inner hook 7 does not rotate. A bobbin 9 is accommodated in the inner hook 7. The bobbin 9 is rotatably arranged with respect to the inner hook 7. The bobbin 9 accommodated in the inner hook 7 is drawn and rotated by the lower thread 300 that is fed out during sewing.

  As shown in FIG. 3, the outer hook 5 includes a drum 5a and a rotating shaft 5b. The drum 5a and the rotating shaft 5b are connected via a connecting portion. The rotating shaft 5b has a cylindrical shape, and one end thereof is supported so as to be rotatable with respect to the sewing machine casing, and the outer hook 5 is rotatable around the rotating shaft 5b. A part of the rotating shaft 5 b is a screw gear and constitutes a gear mechanism 64. Therefore, the outer hook 5 rotates around the rotation shaft 5 b by the rotation of the lower shaft 63 via the gear mechanism 64.

  The drum 5a has a bottomed cylindrical shape. Let the bottom of the drum 5a be the bottom 5c of the outer hook. The bottom 5c of the outer hook extends in a direction perpendicular to the rotation shaft 5b of the outer hook 5 and faces the bottom surface of the bobbin accommodating portion 7a of the inner hook 7 disposed in the outer hook 5. A hook tip 5e for supplementing the upper thread loop is provided on the side surface of the drum 5a. An inner hook groove 5f into which the inner hook 7 is fitted is provided at the upper end of the side surface of the drum 5a. On the bottom 5c of the outer hook, which is the bottom of the drum 5a of the outer hook 5, a light receiving portion 11b is provided at a position away from the rotation center of the outer hook 5 by a distance R. The light receiving surface of the light receiving unit 11b is directed to a light emitting unit 11a, which will be described later, and receives light irradiated by the light emitting unit 11a and transmitted through the bobbin. The light receiving unit 11b includes a light receiving sensor that detects the amount of light, and detects the lower thread 300 wound around the bobbin 9 based on the detected amount of light.

  As shown in FIG. 4, the inner hook 7 is a substantially disk-shaped member having a bobbin housing portion 7 a for housing the bobbin 9. The outer diameter of the disk portion of the inner hook 7 is smaller than the inner diameter of the inner hook groove 5f by a predetermined clearance. The inner hook 7 is provided with a locking portion 7 b for fixing the position of the inner hook 7 accommodated in the outer hook 5. The locking portion 7 b is locked with the locking portion 10 disposed on the frame that does not rotate in conjunction with the rotation of the outer hook 5. Thereby, even if the outer hook 5 rotates, the inner hook 7 does not rotate.

  The bobbin accommodating portion 7 a is a bottomed hole for accommodating the bobbin 9. The bottom of the bobbin accommodating portion 7a is defined as an inner pot bottom 7c. When the inner hook 7 is accommodated in the outer hook 5, the inner hook bottom 7 c extends in a direction perpendicular to the rotation shaft 5 b of the outer hook 5. As shown in FIG. 4B, the inner hook bottom 7c is provided with a scanning hole (scanning light passage portion) 7f penetrating the inner hook bottom 7c. A part of the light emitted toward the inner hook passes through the scanning hole 7f, so that it passes from the front surface of the inner hook bottom 7c to the back surface. That is, the scanning hole 7f serves as a scanning light passage portion that allows light to pass therethrough. The scanning hole 7f opens in accordance with the scanning path L of the light receiving portion 11b when the outer hook 5 rotates. When the inner hook is set on the outer hook, the bottom 5c of the outer hook is positioned so as to face the back surface of the inner hook bottom 7c. When sewing the sewing machine, the inner hook bottom 7c is fixed to the casing of the sewing machine, but the outer hook bottom 5c rotates around the rotation center of the outer hook 5. At that time, the light receiving portion 11b also rotates in conjunction with the bottom 5c of the outer hook. The locus of the light receiving unit 11b at this time is defined as a scanning path L. The scanning hole 7f is long along the circumferential direction of the scanning path L, and the width of the hole that coincides with the radial direction of the scanning path L is wider than the light receiving sensor of the light receiving unit 11b.

  As shown in FIG. 5 (a), the bobbin 9 includes a cylindrical bobbin 9a and flanges 9b provided at the upper and lower ends of the bobbin 9a. In the bobbin 9, the height dimension of the cylindrical portion of the bobbin 9a is the height dimension of the bobbin 9. The dimension in the height direction of the bobbin 9 is lower than the depth of the bobbin housing portion 7a by a predetermined clearance. The outer diameter of the bobbin 9 is the diameter of the flange 9b. The outer diameter of the bobbin 9 is smaller than the inner diameter of the bobbin housing portion 7a by a predetermined clearance. For this reason, even if the bobbin 9 rotates as the lower thread 300 is discharged, the force due to the rotation is not transmitted to the inner hook 7.

  FIG. 5B shows the bobbin 9 around which the lower thread 300 is wound. The bobbin winding portion 9a is a cylinder with no bottoms, and the outer periphery of the bobbin winding portion 9a is a portion around which the lower thread 300 is wound. The center axis of the bobbin 9a is the rotation center O2 of the bobbin 9. The flange 9b serves as a screen for preventing the lower thread 300 wound around the bobbin winding portion 9a from shifting in the central axis direction of the bobbin winding portion 9a. FIG. 5B shows the bobbin 9 in which the lower thread 300 is wound by the maximum amount. As shown in FIG. 5B, the lower bobbin winding diameter is set so as not to exceed the flange 9b diameter even at the maximum lower bobbin winding amount. The bobbin 9 is made of a transparent resin. Therefore, as will be described later, the light emitted from the light emitting unit 11a can pass through the bobbin.

  FIG. 6 is a perspective view showing the configuration of the needle plate 2. The needle plate 2 is fixed to the sewing machine housing so as to be positioned above the outer hook 5, and has a needle hole 2a through which the needle 3 penetrates and a feed dog hole 2b through which a feed dog (not shown) can protrude and retract. Further, the needle plate 2 is provided with a rectangular hole, and the square plate 2c is detachably attached to the hole.

  The square plate 2c is held by a slidable claw member (not shown), and the claw member can be slid and removed by sliding the square plate removal lever 2d. Since the size of the rectangular hole is such that the bobbin 9 can be taken in and out, the bobbin can be replaced by removing the square plate 2 c without removing the entire needle plate 2. Furthermore, since the square plate 2c is made of a transparent resin material, the operator can visually check the state of the bobbin 9 and the remaining amount of the lower thread 300 without removing the square plate 2c.

  Further, a light emitting portion 11a is provided on a part of the square plate 2c. The light emitting unit 11 a is a surface light emitting unit that irradiates parallel light or diffused light toward the bobbin 9. When the lower thread 300 is not wound around the bobbin 9, the light emitted from the light emitting unit 11a passes through the bobbin 9, and further passes through the scanning hole 7f and reaches the bottom 5c of the outer hook. A light receiving portion 11b is provided on the bottom 5c of the outer hook. As will be described later, the light from the light emitting unit 11a needs to pass through the bobbin, pass through the scanning hole 7f, and irradiate the outer periphery from the bobbin 9a of the bobbin 9 in the scanning locus L of the light receiving unit 11b. Therefore, it is desirable that the position, shape, and size correspond to at least the scanning hole 7f. For example, the shape of the light emitting portion 11a may be a rectangle larger than the scanning hole 7f so that the scanning hole 7f does not protrude from the light emitting portion 11a when the scanning hole 7f is projected onto the light emitting portion 11a. it can.

(Installation position of light emitting unit and light receiving unit)
The sewing machine 1 includes a light emitting unit 11a and a light receiving unit 11b in order to detect the lower thread wound around the bobbin 9. The light receiving unit 11b moves relative to the bobbin 9 in conjunction with the outer hook 5, and receives light from the light emitting unit 11a at a plurality of points. Thereby, the presence or absence of the lower thread 300 wound around the bobbin 9 is detected, and the remaining amount of the lower thread 300 is calculated from the result.

  FIG. 7 is a block diagram illustrating a functional configuration of a computer included in the sewing machine 1. The computer 12 is built in the sewing machine 1 and includes a CPU, a memory, and an interface connected to a motor driver of a sewing machine motor 6 that is a power source of the other configuration of the sewing machine 1.

  The control unit 12 a outputs a pulse signal to the sewing machine motor 6 to drive each component of the sewing machine 1. At the same time, the control unit 12a determines the measurement period of the lower thread continuous detection according to the period of the pulse signal. On the other hand, the timing determination unit 11c determines the measurement timing of the continuous detection of the lower thread based on the pulse signal information from the control unit 12a and the detection information from the upper shaft encoder 8. Specifically, the lower thread detection range α of the outer hook 5 for detecting the lower thread is determined from the angle information of the outer hook 5 calculated from the detection result by the upper shaft encoder 8, and the sewing machine driving calculated from the pulse signal is performed. The lower thread detection cycle is determined from the speed, that is, the rotational speed of the outer hook 5. The lower thread detection timing is determined by the lower thread detection range α and the detection cycle. While the outer hook 5 passes the determined lower thread detection range α, the timing determination unit 11c outputs a light emission command to the light emitting unit 11a. Thereby, in the light emission part 11a, irradiation of light is started at the determined timing. The lower thread calculating unit 11d detects the amount of received light q received by the light receiving unit 11b at the determined timing. The received light amounts detected at a plurality of points are stored in the lower thread calculation unit 11d, and the lower thread remaining amount is calculated from the results. The calculated lower thread remaining amount is displayed on the display unit 13 and compared with the set lower thread threshold value stored in the lower thread comparison unit 11e. Control to perform a predetermined operation such as displaying a message or stopping the operation of the sewing machine. In the present embodiment, the display unit 13 that can display characters and figures as a notification unit is described as an example of the notification unit, but a message can be transmitted to the user by other means. . As a notification unit other than the display unit, for example, a speaker that outputs sound, a signal transfer unit that transfers a signal to a mobile terminal possessed by a user via a network, and the like can be used.

  FIG. 8 is a cross-sectional view showing an outline of the configuration and the optical path in the first embodiment. As shown in FIG. 8, a light emitting portion 11 a is provided on a part of the needle plate 2. A light receiving portion 11b is provided on the bottom 5c of the outer hook which is the bottom of the drum 5a of the outer hook 5. The light receiving part 11b receives light emitted from the light emitting part 11a, transmitted through the flange 9b of the bobbin 9, and passed through the scanning hole (scanning light passage part) 7f. Then, a received light amount q corresponding to the amount of received light is output to the lower thread calculating unit 11d. The lower thread calculating unit 11d detects the amount of received light q detected by the light receiving unit 11b in two stages, hi and low. Then, the lower thread calculation unit 11d detects the presence or absence of the lower thread 300 wound around the bobbin 9 based on the amount of received light q received at a plurality of points, and calculates the remaining amount of the lower thread 300.

  That is, if the light receiving unit 11b receives a received light amount equivalent to the irradiation amount of the light emitting unit 11a, then the lower thread 300 is between the light emitting unit 11a and the light receiving unit 11b. When it is determined that the lower thread 300 is not present at the measurement point, and the amount of received light is remarkably small or zero compared to the amount of light emitted from the light emitting portion 11a, light emission It is determined that the lower thread 300 is interposed between the portion 11a and the light receiving portion 11b, that is, the lower thread 300 is “present” at the measurement point.

  The light receiving portion 11b is disposed at a position away from the center of the outer hook 5 by a distance R in the circumferential direction. Therefore, the light receiving portion 11 b rotates in synchronization with the rotation of the outer hook 5. Therefore, the scanning path L by the light receiving unit 11b is a circle centered on the rotation center O1 of the outer hook 5. A signal line 11f for transmitting and receiving signals is connected to the light receiving unit 11b. The rotary shaft 5b is hollow inside, and the signal line 11f transmits and receives signals via the hollow rotary shaft 5b.

  In the sewing machine 1 according to the present embodiment, by using the relative movement of the outer hook 5 and the bobbin 9 in the sewing operation, the light receiving unit 11b can be used for the bobbin 9 with the bobbin winding 9a and the bobbin 9 without an actuator for driving the light receiving unit 11b. It is possible to detect the presence or absence of a lower thread at a plurality of measurement points continuously while scanning, that is, moving across the flange 9b. Therefore, it is possible to obtain information as to which measurement point the lower thread has run out, and from this, the winding amount of the lower thread 300 can be detected accurately and without interrupting the sewing.

(Installation position and movement of the light detector of the thread detector)
FIG. 9 is a schematic diagram showing the positional relationship between the scanning path L of the light receiving unit 11b and the bobbin 9. In FIG. The rotation center O1 indicates the rotation center of the outer hook 5, and the rotation center O2 indicates the center axis of the bobbin 9a, that is, the rotation center of the bobbin 9. A circle centering on the rotation center O1 and the scanning path L indicate the movement locus of the light receiving unit 11b as the outer hook 5 rotates, and the circle on the scanning path L indicates the detection position (timing) of the presence or absence of the lower thread.

  As shown in FIG. 9, the rotation center O1 of the outer hook 5 and the rotation center O2 of the bobbin 9 are different. And the light-receiving part 11b is arrange | positioned at the distance R from the rotation center O1 of the outer hook 5 in the radial direction. The distance between the rotation center O1 of the outer hook 5 and the rotation center O2 of the bobbin 9 is D, and the distance D is not less than the radius of the bobbin 9 winding portion 9a and not more than the radius of the flange 9b of the bobbin 9. That is, in FIG. 9, the rotation center O1 of the outer hook 5 is located between the bobbin 9a and the flange 9b.

The scanning path L of the light receiving unit 11b needs to cross the lower thread 300. For this purpose, a condition is required for the scanning path L of the light receiving portion 11b to intersect the bobbin 9a of the bobbin 9 at at least one point and to intersect the outer periphery of the flange 9b at at least one point. Therefore, as shown in FIG. 9, in order to satisfy the condition, the distance R is preferably within the range of the following equation (1).
[Formula 1]
Rmax ≦ distance R ≦ Rmin (1)
Then, the distance between the rotation center of the bobbin and the rotation center of the outer hook is D, and the range of the distance R can be expressed by the following equation (2) using the distance D.
[Formula 2]
(Radius of flange 9b−distance D) ≦ distance R ≦ (distance D + radius of bobbin 9a) (2)
If the distance R is in the range of more than Rmin and less than Rmax as in the first embodiment shown in FIG. 9, the scanning path L intersects the outer periphery of the flange 9b and the pincushion part 9a at two points, respectively. It can cross from 9a to the outer periphery of the flange 9b. On the other hand, as will be described later, even when the distance R is the same as Rmax or the distance R is the same as Rmin, the scanning path L crosses the bobbin 9a from the outer periphery of the flange 9b. As shown in b), the intersection between the scanning path L and the bobbin 9a or the flange 9b is one point.

  In order to detect the lower thread remaining amount, it is necessary to continuously measure the presence or absence of the lower thread 300 at least in the range from the bobbin 9a to the flange 9b. This range is a range of an angle α ° that coincides with the scanning hole 7f as shown in FIG. In the explanatory view shown in FIG. 9, the light receiving unit 11 b performs the measurement at a period in which the lower thread can be detected 30 times like the points illustrated on L at equal intervals while making a round of the scanning path L. At this time, when the rotational speed of the outer hook 5 is the speed of the sewing machine motor 6 that rotates once per second, the measurement period of the lower thread detection is 1/30 second. The measurement points at α °, which is the lower thread detection range, are a total of 6 points from X1 to X6 as shown by white circles.

(Lower thread continuous detection and lower thread remaining amount detection)
At this time, an outline of a method in which the light receiving unit 11b continuously detects the lower thread while moving along the scanning path L and calculates the lower thread remaining amount from the detection result will be described with reference to FIG. FIG. 10 is a diagram schematically showing the relative movement of the light receiving unit 11b with respect to the bobbin 9 and the lower thread 300 and the detection result thereof. The light reception amount q indicates the lower thread detection result, that is, the light reception amount in the light receiving unit 11b, and the detection results from X1 to X6 shown in the graph correspond to the measurement positions from X1 to X6 shown in FIG. 10A shows a case where the lower thread is not wound at all, that is, when the lower thread remaining amount of the bobbin 9 where the lower thread remaining amount is zero is detected, FIG. When FIG. 10 is wound, FIG. 10C shows a case where the remaining amount of the lower thread is about half of the maximum amount.

  Since the light receiving unit 11b rotates in synchronization with the outer hook 5 having the rotation center O1, in FIG. 10 viewed from the side with respect to the rotation plane, the light receiving unit 11b reciprocates left and right on the scanning path L illustrated by the dotted line. . As described above, in the lower thread detection range α in the scanning path L, the light receiving unit 11b continuously performs lower thread detection while moving. In FIG. 10A, the light Ac irradiated from the light emitting unit 11a is received by the light receiving unit 11b regardless of the position of the light receiving unit 11b. Accordingly, in the lower thread detection range α, at any point where six points are continuously detected, a light amount equivalent to the irradiated light amount is received, although there is a slight difference due to the influence of irregular reflection during diffusion and transmission. That is, the received light quantity q is detected as hi for all six points. On the other hand, in FIG. 10B, for example, when the light receiving unit 11b is located at the illustrated position, the light Ac irradiated from the light emitting unit 11a is absorbed or diffusely reflected by the lower thread 300, so that the light receiving unit 11b receives the light. It will never be done. Therefore, as illustrated in FIG. 10B, the light receiving amount of the light receiving unit 11b at the five points where the light irradiation is shielded by the lower thread among the six measurement points is the light amount irradiated from the light emitting unit 11a. On the other hand, it is zero or extremely low. That is, the received light quantity q is detected as low at 5 points and as hi at 1 point.

  Since the range in which the irradiation light of the light emitting unit 11a is shielded differs depending on the remaining amount of the lower thread, this continuously detected lower thread detection result group varies depending on the remaining amount of the lower thread, and is illustrated in FIG. Thus, if the lower thread remaining amount is, for example, about half of the maximum, the received light quantity q is detected as 3 points low and detected as 3 points hi. Therefore, the lower thread remaining amount can be calculated by counting the number (ratio) of low in the lower thread continuous result group in the lower thread detection range α. In FIGS. 9 and 10, for the purpose of explanation, the number of times of continuous detection of the lower thread in the lower thread detection range α is 6 points. Can be high.

  By the way, in order not to change the lower thread remaining amount detection accuracy with respect to the change in the rotational speed of the outer hook 5, control is performed so that the number of lower thread detections in the lower thread detection range α is not changed by the rotational speed of the outer hook 5. It ’s fine. In the description of FIG. 9 and FIG. 10, the measurement cycle of the lower thread detection is 1/30 seconds. Here, for example, the control speed of the sewing machine motor 6 is changed, and the rotational speed of the outer hook 5 is 2 per second. Suppose that it is a rotation. Then, since the time for the light receiving unit 11b to pass through the lower thread detection range α is relatively reduced, the measurement points that can be measured when the lower thread detection measurement period remains 1/30 seconds are shown in FIG. Of the measurement points, X1, X3, and X5 decrease to a total of three times. Decreasing the number of times of measurement means that the resolution with respect to the lower thread remaining amount calculated from the measurement result is reduced, and the measurement accuracy is lowered. Therefore, for example, when the speed of the sewing machine motor is doubled by the control of the control unit 12a and the timing determining unit 11c, the timing determining unit 11c adjusts the measurement period of the lower thread detection to 1/30 at the same time. By performing control to change from 1 second to 1/60 seconds, the number of times of lower thread detection in the lower thread detection range α is constant regardless of the operating speed of the sewing machine.

[1-2. Effect]
As described above, the sewing machine 1 accommodates the bobbin 9 wound with the lower thread 300 in the inner hook 7. The rotation center of the rotating outer hook 5 is different from the rotation center of the bobbin 9 accommodated in the inner hook 7, and the light receiving portion 11b is separated from the rotation center of the outer hook 5 on the bottom 5c of the outer hook by a distance R. In the position. Therefore, the light receiving portion 11b performs a relative motion having an L locus with respect to the bobbin 9 by the rotational motion of the outer hook 5 according to the sewing operation of the sewing machine 1. As a result, the light receiving unit 11b can continuously detect the presence or absence of the lower thread 300 while performing a relative motion having an L locus with respect to the bobbin 9, and calculate the lower thread remaining amount from these detection result groups. Is possible.

  In other words, by utilizing the relative movement between the outer hook 5 and the bobbin 9 in the sewing operation, the light receiving unit 11b can be moved from the bobbin 9 to the outer periphery of the bobbin 9 without an actuator for scanning the light receiving unit 11b. The presence or absence of the lower thread 300 can be continuously detected while scanning. Accordingly, it is possible to accurately detect the remaining amount of the lower thread 300 without interrupting the sewing, and it is possible to prevent a failure in sewing due to a shortage of the lower thread during sewing. In the present embodiment, the light receiving portion 11b is provided on the bottom 5c of the outer hook extending in the direction perpendicular to the rotation shaft 5b of the outer hook 5. Thereby, it is possible to scan from the bobbin 9a of the bobbin 9 accommodated in the inner hook 7 to the outer periphery of the bobbin 9 with a simple configuration.

  The scanning path L of the light receiving unit 11b intersects with the bobbin 9a of the bobbin 9 at at least one point, and the range where the lower thread 300 is wound when the outer periphery of the bobbin 9, strictly speaking, intersects with the maximum lower bobbin winding outer periphery at at least one point. Can be reliably scanned.

  Further, the light emitting portion 11 a is provided on the back surface of the needle plate 2. In the case of a horizontal hook, the needle plate 2 is removed, and the bobbin 9 is arranged in the vertical direction with respect to the inner hook 7. That is, by providing the needle plate 2 with the light emitting portion 11a, the bobbin 9 and the scanning hole 7f can be irradiated with light from the vertical direction. For this reason, the amount of light passing through the scanning hole 7f increases immediately below the scanning hole 7f, and the light receiving unit 11b scans that portion, so that the lower thread can be detected efficiently. Further, there is no shield between the needle plate above the bobbin 9 disposed in the inner hook 7 and the bobbin 9. Therefore, the light emitted from the light emitting unit 11a provided on the needle plate 2 can reach the bobbin 9 without being blocked by other members. Therefore, compared with a case where a member for fixing the light emitting unit 11a is prepared as a separate member, the light emitted from the light emitting unit 11a is emitted from the light emitting unit 11a to the bobbin 9 or the light receiving unit 11b with a simple configuration. Can be irradiated.

  The inner hook 7 has an inner hook bottom 7c that supports the bobbin 9, and the inner hook bottom 7c is provided with a scanning hole 7f that matches the scanning path L of the light receiving portion 11b. Thereby, the scanning path L can be secured with a simple work. In this embodiment, the scanning hole 7f is provided. However, instead of providing the hole, a transmissive member may be fitted along the scanning path L. Further, the inner pot bottom 7c itself may be formed of a permeable member.

  The first embodiment is an aspect of the invention. Therefore, if the relational expression is satisfied, the positional relationship of each member can be changed due to design constraints, required accuracy, and the like. Therefore, the following modifications can be considered.

[Modification 1]
FIG. 11 is a schematic diagram showing the positional relationship between the bobbin 9 and the scanning path L of the light receiving unit 11b as in FIG. 9. The rotation center O1 indicates the rotation center of the outer hook 5 and the rotation center O2 indicates the bobbin 9. Indicates the center of rotation. FIG. 11A shows a modification 1 in which the distance R2 from the rotation center O1 of the outer hook 5 to the light receiving portion 11b is longer than R in the first embodiment, that is, the distance R = Rmax is satisfied. In the first modification, the scanning path L2 of the light receiving portion 11b is in contact with the bobbin 9a of the bobbin 9 at one point and intersects the flange 9b at two points.

  By setting it as such a positional relationship, the ratio of the angle between the bobbin part 9a and the flange 9b in the scanning path | route L can be expanded. That is, it is possible to provide a wider lower thread detection range for detecting lower thread when α2> α. For example, even in the same lower thread detection cycle as in the first embodiment, the lower thread detection range is lower than that in the first embodiment. Yarn detection can be performed. In addition, as shown in FIG. 11 (a), it is possible to detect a large amount of bobbin thread, particularly in the vicinity of the bobbin 9a, and therefore more accurate when the remaining amount of the bobbin thread 300 decreases. The remaining amount of the lower thread 300 can be detected.

[Modification 2]
On the other hand, FIG. 11B is a second modification in which the distance R3 from the rotation center O1 of the outer hook 5 to the light receiving portion 11b is shorter than R in the first embodiment, that is, the distance R = Rmin is satisfied. In the second modification, the scanning path L3 of the light receiving unit 11b intersects the bobbin 9 with the bobbin 9a and the flange 9b at one point.

  With this positional relationship, as shown in FIG. 11 (b), it is possible to perform scanning between the bobbin 9's bobbin 9a and the flange 9b regardless of the position of the light receiving portion 11b. It becomes. Accordingly, since the lower thread detection range α3 is 360 °, that is, the entire range, more lower thread detection can be performed, and the lower thread detection range α is set based on the angle of the upper shaft 61. There is no need, and the remaining amount of the lower thread 300 can be detected with high accuracy by simple control.

[2. Second Embodiment]
[2-1. Constitution]
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. The sewing machine 1 in the second embodiment is obtained by changing the configuration of the lower thread detection device in the first embodiment. That is, in the first embodiment, the light emitting portion 11a is arranged on the needle plate 2. In this embodiment, the light emitting portion 11a is arranged on the bottom 5c of the outer hook together with the light receiving portion 11b, and the light emitting portion 11a is arranged on the needle plate 2. Is provided with a reflecting portion 2e for reflecting the light transmitted through the flange 9b of the bobbin 9.

  FIG. 12 is a cross-sectional view illustrating a configuration of the sewing machine 1 according to the second embodiment. As shown in FIG. 12, a light receiving portion 11b and a light emitting portion 11a are provided on the bottom 5c of the outer hook which is the bottom of the drum 5a of the outer hook 5, and a reflecting portion 2e is provided on the needle plate. The light emission direction of the light emitting portion 11a installed on the bottom 5c of the outer pot is such that parallel light or diffused light parallel to the rotation center of the bobbin is applied to the scanning hole 7f (scanning light passage portion) and the bobbin 9. Irradiate. The light that has passed through the scanning hole 7f (scanning light passage part) and the bobbin is reflected by the reflection part 2e, passes through the bobbin 9 again, and reaches the light receiving part 11b. The light receiving unit 11b is located on the reflection path of the light emitted from the light emitting unit 11a from the reflection unit 2e.

  The needle plate 2 is provided with a reflecting portion 2 e perpendicular to the rotation center of the bobbin 9. As shown in FIG. 13, the reflecting portion 2e has at least a position, shape, and size corresponding to the scanning hole 7f shown in FIG. That is, the reflecting portion 2e has a shape in which the scanning hole 7f of the inner hook 7 located below the needle plate 2 is projected upward, and has the same arc shape as the scanning hole 7f as shown in FIG. . However, since the irradiated light is slightly diffused in practice, the reflection part 2e is not exactly the same size as the scanning hole 7f in consideration of the influence and error at the time of attachment, for example, about once. You may enlarge it.

  An optical path of light emitted from the light emitting unit 11a is defined as an optical path Ag. As shown in FIG. 14, the light emitting unit 11 a irradiates the bobbin 9 accommodated in the inner hook 7 with light. Since the distance between the light emitting portion 11a and the scanning hole 7f is short, the light emitted from the light emitting portion 11a passes through the flange 9b with almost no diffusion. Even if diffused, the scanning hole 7f becomes a slit, and the light passing through the scanning hole 7f and passing through the bobbin 9 has a property close to parallel light. The light that has passed through the bobbin reaches the reflecting portion 2e, is reflected by the reflecting portion 2e, passes through the flange 9b again, passes through the scanning hole 7f, and reaches the light receiving portion 11b.

(Lower thread continuous detection and lower thread remaining amount detection)
An outline of a method for continuously detecting the lower thread while the light emitting unit 11a and the light receiving unit 11b move along the scanning path L and calculating the remaining lower thread from the detection result will be described with reference to FIG.

  In FIG. 14A, the light emitted from the light emitting portion 11a passes through the flange 9b of the bobbin 9 and reaches the reflecting portion 2e as light Ag regardless of the position of the light receiving portion 11b. And it reflects with the reflection part 2e, and is received by the light-receiving part 11b as reflected light Ac. Therefore, the received light quantity q is detected as all six points hi. On the other hand, in FIG. 14B, for example, when the light receiving portion 11b is located at the illustrated position, the light Ag is absorbed or diffusely reflected by the lower thread 300, and the light emitted from the light emitting portion 11a is reflected by the reflecting portion 2e. Not reach. At this position, the amount of light received by the light receiving unit 11b is zero or significantly lower than the amount of light emitted from the light emitting unit 11a. As shown in FIG. 14C, if the lower thread remaining amount is, for example, about half of the maximum, the received light quantity q is detected as 3 points low and 3 points hi. As described above, also in this embodiment, the lower thread remaining amount can be detected by counting the number (ratio) of low in the lower thread continuous result group in the lower thread detection range α.

[2-2. Effect]
As described above, the light emitting portion 11a of the present embodiment is attached to the bottom 5c of the outer hook and rotates around the rotation center. Further, there is provided a reflecting portion 2e that reflects light emitted from the light emitting portion 11a and transmitted through the flange 9b of the bobbin 9. The reflection part 2 e is provided perpendicular to the rotation center of the bobbin 9. The light receiving unit 11b is provided on the reflection path from the reflection unit 2e of the light emitted from the light emitting unit 11a.

  According to the present embodiment, the light emitting unit 11a and the light receiving unit 11b can be installed very close to each other, and wiring associated with the installation can be facilitated. Further, since the needle plate 2 can be realized by simply providing the reflecting portion 2e, as shown in FIG. 13, only a part of the square plate 2c, which is a transparent resin, may be mirror-finished. In that case, not only the implementation is easy, but other than the mirror-finished portion remains transparent, the conventional confirmation method of the lower thread remaining amount, the operator confirms visually from the transparent square plate 2c, The sewing machine that can coexist with the above method can be provided.

  On the other hand, the reflecting portion 2 e may be provided on the flange 9 b of the bobbin 9 without being provided on the needle plate 2. In this case, one of the two flanges 9b facing each other is a reflecting surface. If the bobbin 9 is installed so that the reflecting surface is located on the upper side, the light emitted from the light emitting part 11a below the bobbin 9 is transmitted through the lower flange 9b and reflected by the upper flange 9b to the light receiving part 11b. . In this case, since the bobbin 9 rotates unlike the reflecting portion 2e of the needle plate 2, the upper surface of the flange 9b needs to be a reflecting surface.

[Other Embodiments]
Although the embodiments of the present invention have been described above, various omissions, replacements, and changes can be made without departing from the scope of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  For example, in the description of the first embodiment, the lower thread detection range is from the bobbin 9 winding portion 9a to the flange 9b outer periphery, but strictly speaking, it may be to the flange 9b outer periphery. As described above, the bobbin winding mechanism is generally set so that the bobbin diameter does not exceed the flange 9b when the lower thread 300 is wound around the bobbin 9 to the maximum. Therefore, the effect of the present invention can be obtained if the lower thread detection range is the maximum bobbin diameter from the bobbin 9a of the bobbin 9. Further, the lower thread detection range may be only in the vicinity of the bobbin 9 winding portion 9a. This is because the user wants to determine the lower thread replacement time in accordance with the sewing work, so that the lower thread remaining amount detection function in the sewing machine can be accurately informed of when the lower thread will disappear. First is seeking. Therefore, if the lower thread remaining amount is detected and notified when the remaining amount becomes less than half, the distance R is “the radius of the flange 9b of the bobbin 9−distance D ≦ distance R ≦ distance D + the bobbin 9 winding portion. For example, the distance R may be such that the scanning path L passes from the bobbin winding portion 9a of the bobbin 9 to the circumference of ½ of the size of the outer periphery of the flange 9b. . Therefore, the distance R being within the range of “the radius of the flange 9b of the bobbin 9−the distance D ≦ the distance R ≦ the distance D + the radius of the bobbin 9's bobbin 9a” is effective in order to maximize the effects of the invention. However, this does not necessarily mean that the invention cannot be implemented unless the distance R is within the range.

In the description of the embodiments, the general sewing machine size and positional relationship have been followed. For this reason, the distance D is equal to or less than the radius of the flange 9b, but the distance D may exceed the radius of the flange 9b. However, in that case, the range of the distance R for obtaining the effect of the present invention is the range of the following formula (3).
[Formula 3]
(Distance D−Radius of bobbin 9a) ≦ Distance R ≦ (Distance D + Radius of bobbin 9a) (3)
Even in this case, the scanning path L can scan between the bobbin winding portion 9a and the flange 9b, and the same effect as in the first embodiment can be obtained.

  In the description of the first and second embodiments, the light receiving unit 11b is the light receiving element itself, but may be a light receiving unit including a light guide member and a light receiving element, for example. Specifically, a light guide member such as a mirror, a prism, or an optical fiber is provided at a position (light receiving position) that is a distance R away from the rotation center O1 of the outer hook 5 in the outer hook 5 shown in the embodiment. It may be configured to be provided inside the outer hook other than the bottom 5c of the outer hook, and to guide the light received at the light receiving position by the light guide member to the light receiving element. In this case, since the light receiving elements can be provided inside the outer hook 5 other than the bottom 5c of the outer hook, it is possible to arrange the light receiving elements more appropriately in terms of design.

  In the description of the first embodiment, the light emitting unit 11a is the light emitting element itself, but may be a light emitting element including a light guide unit, for example. Specifically, a configuration may be employed in which a light guide member such as a mirror, a prism, or an optical fiber is provided, the light of the light emitting unit emitted at another place is guided to the light emitting unit 11a, and the light is irradiated.

  In the first embodiment, the lower thread is continuously detected during the passage of the lower thread detection range α of the light receiving unit 11b in the sewing operation for one stitch, and the lower thread remaining amount is calculated from the results. However, the lower thread detection in the sewing operation for one stitch may be performed once, for example. This is particularly conceivable during high-speed sewing. For example, when the sewing machine is driven at a sewing speed at which 1200 stitches are sewn per minute, the upper shaft 61 rotates 20 times per second. The outer hook 5 is rotated 40 times per second by the action of the gear mechanism 64. At this time, when the lower thread detection range α is 60 °, the time for the light receiving unit 11b to pass through the lower thread detection range α is only 1/240 seconds. In such a case, even if the measurement period of the lower thread continuous detection is set to be short, there is a possibility that the lower thread detection cannot be correctly performed the number of times set during one rotation of the outer hook 5. In this case, for example, when the Nth stitch is sewn, only the lower thread is detected at the X1 point, and when the N + 1st stitch is sewn, only the lower thread is detected at the X2 point. The lower thread remaining amount may be calculated by performing lower thread detection for a plurality of stitches and combining the lower thread detection results for several stitches. In the description of the present embodiment, for the sake of explanation, the description using a specific reflection angle and the description using a specific positional relationship such as parallel or perpendicular to each axis have been given. However, it is not limited to them.

  In the present embodiment, the light emitted from the light emitting unit 11a has been described using light emitted in parallel. However, the light is not limited thereto, and may be diffused light, for example. FIG. 15 shows a modified example having the light emitting part 11a for irradiating diffused light with respect to the first embodiment, and is a schematic diagram corresponding to FIG. The light emitting unit 11a in the present embodiment is a point light emitting unit, and irradiates diffused light radially around the light emitting point. Therefore, the light received by the light receiving unit 11b in the vicinity of X3 and X4 near the light emitting unit 11a is nearly vertical, but the light received by the light receiving unit 11b as X1 or X6 and the position away from directly below 11a. The angle becomes larger. And the influence becomes large in proportion to the distance of the light emission part 11a and the light-receiving part 11b. However, in the actual positional relationship between the light emitting unit 11a and the light receiving unit 11b in the sewing machine, the distance is short, and it is considered that the substantial influence can be almost ignored. Accordingly, FIG. 15 shows the output of the received light quantity q when the remaining amount of the lower thread 300 is about half as in FIG. 10C, but X1, X2, and X3 are low, X4, X5, and X6. Is hi, which is the same as the detection result of FIG.

DESCRIPTION OF SYMBOLS 1 ... Sewing machine 2 ... Needle plate 2a ... Needle hole 2b ... Feed dog hole 2c ... Square plate 2d ... Square plate removal lever 2e ... Reflecting part 3 ... Needle 4 ... Needle bar 5 ... Outer hook 5a ... Drum 5b ... Rotating shaft 5c ... Outer hook bottom 5e ... Hook tip 5f ... Inner hook groove 6 ... Machine motor 61 ... Upper shaft 62 ... Crank mechanism 63 ... Lower shaft 64 ... Gear mechanism 65 ... Pulley 67 ... Toothed belt 7 ... Inner hook 7a ... Bobbin accommodation Part 7b ... Locking part 7c ... Inner hook bottom 7f ... Scanning hole 8 ... Upper shaft encoder 8a ... Shielding plate 8b ... Photo interrupter 9 ... Bobbin 9a ... Bobbin 9b ... Flange 10 ... Locking part 11a ... Light emitting part 11b ... Light receiving unit 11c ... Timing determining unit 11d ... Lower thread calculating unit 11e ... Lower thread comparing unit 11f ... Signal line 12 ... Computer 12a ... Control unit 13 ... Display unit 100 ... Fabric 200 ... Upper thread 300 ... Lower thread

Claims (6)

A sewing machine that forms a seam by penetrating a needle and interlacing an upper thread and a lower thread wound around a bobbin,
An inner hook having a scanning light passage portion through which light passes;
An outer hook having a rotation center at a position different from the rotation center of the bobbin housed in the inner hook;
A light emitting unit that emits light to the bobbin;
A light receiving unit that receives the light irradiated from the light emitting unit and passed through the scanning light passing unit and the flange of the bobbin;
With
The light receiving portion is arranged at the bottom of the outer hook, spaced radially from the rotation center of the outer hook;
A sewing machine characterized by The distance R from the rotation center of the outer hook to the light receiving portion is:
When the distance between the rotation center of the bobbin and the rotation center of the outer hook is D,
Flange radius of the bobbin−the distance D ≦ the distance R ≦ the distance D + the bobbin bobbin radius,
The sewing machine according to claim 1, wherein:   The sewing machine according to claim 1, wherein the light emitting unit is disposed on a needle plate. The light emitting unit and the light receiving unit are arranged at the same position,
The sewing machine according to claim 1, further comprising a reflection unit that reflects light from the light emitting unit at a position facing the light emitting unit and the light receiving unit. A timing determining unit that determines the timing of detecting the light received by the light receiving unit according to the rotational speed of the outer hook;
A lower thread calculating unit that calculates a remaining amount of the lower thread based on a detection result in the light receiving unit;
The sewing machine according to any one of claims 1 to 4, further comprising: A notifying unit for notifying the lower thread remaining amount calculated by the lower thread calculating unit;
The sewing machine according to claim 5, further comprising:

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