JP3740188B2 - Lower thread remaining amount detection device for sewing machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a lower thread remaining amount detection device of the sewing machine, in particular, the detection rod detects that the lower thread has decreased before the lower thread of the bobbin housed in the hook is lost, The present invention relates to a bobbin thread remaining amount detecting device that is effective for preventing the occurrence of defective products.
[0002]
[Prior art]
In the sewing machine, the bobbin around which the bobbin thread is wound is housed in the bobbin case, and this bobbin case is attached to the hook at the bottom of the needle bar of the sewing machine. I can't. In view of this, an apparatus has been developed and used to detect that the lower thread has decreased before the lower thread of the sewing machine has run out, and one of them is disclosed in, for example, Japanese Utility Model Publication No. 63-136591. There is something that has been.
[0003]
In the lower thread remaining amount detecting device disclosed in this publication, when the sewing machine that has been sewn is stopped at a fixed position, a driving means such as a rotary solenoid is actuated to move the detection rod so that its tip is moved into the hook. The lower thread is detected by bringing it into contact with the outer periphery of the lower thread wound around the bobbin and then reciprocating back to the original position. In other words, if the travel distance when the detection rod is moved forward is small, the remaining amount of the lower thread is large, and the travel distance gradually increases, and when it reaches the limit, the lower thread consumption detection signal is generated, Notify the operator of the need for yarn replenishment.
[0004]
[Problems to be solved by the invention]
However, since the conventional lower thread remaining amount detection device can only detect that the lower thread has fallen below the specified amount, until then, the operator knows the specific lower thread remaining amount during the sewing operation. Therefore, even if a buzzer indicating that there is no lower thread remaining suddenly or the lamp lights, there is a problem that preparation of a new bobbin fully wound with lower thread is not in time and work efficiency tends to decrease. It was.
[0005]
The present invention has been made to solve the above-mentioned conventional problems, and can accurately detect the specific lower thread remaining amount at an arbitrary point in time during the sewing operation, thereby improving the efficiency of the sewing operation. It is an object of the present invention to provide a lower thread remaining amount detection device that can be realized.
[0006]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a lower thread remaining amount detection device for a sewing machine in which a detection bar is inserted into a hook in which a bobbin is accommodated and the remaining amount of lower thread wound around the bobbin is detected. The contact means detects the vibration wave that occurs when the tip of the detection rod that is driven forward and the tip of the detection rod that is driven forward contacts the lower thread outer circumference. And a movement time measuring means for measuring a movement time required for the detection rod to move between the standby position and the lower thread outer circumferential contact position based on the detection of the contact detection means, and the movement time measurement means The above-mentioned problem has been solved by providing a conversion means for converting the movement time of the detection rod measured by the method into a remaining amount of yarn.
[0007]
That is, as a result of various studies, the present inventors have used the fact that the movement time of the detection rod and the movement distance are in a proportional relationship, and specifically calculated the lower thread remaining amount from the measured movement time of the detection rod. I found out that it can be detected.
[0008]
The present invention has been made on the basis of the above knowledge, and measures the time required for the detection rod to move between the standby position and the position where it comes into contact with the outer periphery of the lower thread, and the time required for the movement is wound around the bobbin. Since it can be converted into the remaining amount of the lower thread, a specific lower thread remaining amount at an arbitrary time during the sewing operation can be accurately detected each time.
[0009]
In the present invention, the contact detection means, in order so as the tip of the forward driven detection rod detects vibration wave generated when in contact with the lower thread outer periphery, only detection rod it is sufficient to move forward and backward Therefore, it is not necessary to attach extra members such as magnets to the detection rod compared to the technology that detects changes in the magnetic field due to the permanent magnet fixed to the detection rod, which is generally used, so the hardware configuration is simple. In addition, since the detection rod can be moved at high speed, the lower thread remaining amount detection operation can be performed at high speed.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The embodiment of the present invention described in detail below corresponds to the case where the moving time of the detection rod is a required time from the start of forward movement to the lower thread outer peripheral contact in the present invention. In this case, since the moving speed of the detection rod is easier to control in the forward direction than in the reverse direction, the detection rod can be moved forward at a stable speed, so the movement time that is proportional to the movement distance is measured. be able to. Therefore, a specific lower thread remaining amount can be detected with high accuracy as a change in the thickness of the winding diameter in the radial direction of the lower thread wound around the bobbin from a change in the measured moving time.
[0011]
Further, this embodiment corresponds to the case where the driving means is a linear actuator in which the detection rod is fixed to the movable portion in the present invention. In this case, the entire movable part including the detection rod can be made very lightweight, so that the detection rod can be advanced and retracted at a very high speed, and the lower thread remaining amount can be detected at high speed. Become. As a result, for example, when the main spindle of the sewing machine is not rotating at a high speed, the detection operation can be executed even during the sewing operation.
[0012]
Hereinafter, specific embodiments will be described in detail with reference to the drawings.
[0013]
In describing a bobbin thread amount detecting device according to an embodiment of the present invention, first, a linear actuator (driving means) constituting the basic hardware and its function will be described in detail. Incidentally, a lower thread remaining amount detection device using this linear actuator as a hardware body has already been proposed by the present applicant in Japanese Patent Application No. 6-167068.
[0014]
1A, 1B, and 1C are a plan view, a BB cross-sectional view, and a front view, respectively, of the lower thread remaining amount detection device (linear actuator). FIG. 2 is a perspective view showing the detection device with a part broken away. In the figure, reference numeral 1 is a detection rod bearing, 2A and 2B are permanent magnets that give a substantially uniform magnetic field within a span in which a coil 5B to be described later can move, and 3A and 3B are inner sides of the permanent magnets 2A and 2B, respectively. , 4 is an iron core parallel to the permanent magnets 2A and 2B, and the permanent magnets 2A and 2B both have the same magnetic pole face directed to the iron core 4.
[0015]
Reference numeral 5 denotes a coil assembly that can freely slide on the iron core 4. The coil assembly 5 includes a coil bobbin 5A and a coil 5B for obtaining a linear thrust based on the operating principle of the linear DC motor when energized. It is made up of. Reference numerals 6A and 6B denote return springs (shown by alternate long and short dash lines) that urge the coil assembly 5 to the right end of FIG. 1A, and 7 a rear end is fixed to the coil assembly 5 and a tip thereof is This is a detection rod that moves so as to come into contact with the outer periphery of the bobbin thread wound around the bobbin inside the hook assembly when the coil assembly 5 moves.
[0016]
Reference numeral 8 is a pressure sensor that detects pressure using a change in resistance, a change in piezoelectric element or capacitance, and the like 9 is fixed to a yoke 10A that defines a retracted end and guides the movement of the coil assembly 5. It is the lower guide rod that fulfills.
[0017]
The yoke 10A is in contact with the side surface in the length direction of the iron core 4, and the yoke 10B is in contact with the second magnetic pole surface side of the permanent magnet and the side end surface of the yoke 10A. In addition, the frame of the lower thread remaining amount detection device is configured.
[0018]
In the lower thread detecting device, the permanent magnets 2A and 2B, the gaps 3A and 3B, the iron core 4, the coil assembly 5, and the yokes 10A and 10B constitute a linear motor. As shown by the symbol A in FIG. 3, this detection device is attached inside the sewing machine at a position close to the shuttle 14 in which the bobbin 12 around which the lower thread 11 is wound is accommodated. When the lower thread is detected when the assembly 5 is moved, when the assembly 5 is moved forward by applying a current in a predetermined direction to the coil of the coil assembly 5 from the state before the start of the detection operation shown in FIG. The detecting rod 7 is inserted into the hook 14 as shown in FIG. 5B or FIG. At that time, when the lower thread 11 remains sufficiently as shown in FIG. 3B, the tip of the detection rod 7 collides with the outer peripheral portion of the lower thread 11 to generate a small vibration wave. When the length is less than the specified length as shown above, the winding diameter of the lower thread is reduced, so that the tip of the detection rod 7 does not reach. As a result, the coil assembly 5 itself collides with the front yoke (frame body front end) 10A, A strong mechanical shock noise (vibration wave) is generated. Thus, the presence or absence of the lower thread can be detected by the strength of the vibration wave when the detection rod 7 is moved forward.
[0019]
Therefore, in the lower thread detection device, as shown in FIG. 4, the vibration wave detection element (ultrasonic sensor made of a piezoelectric element or the like) 15 is provided outside the yoke 10 </ b> B, as shown in a state of being attached to the attachment member 13 of the sewing machine body. The vibration wave detected by the vibration wave detection element 15 is identified using two types of comparators having different reference voltages shown in the circuit diagram of FIG. 5 to detect the lower thread.
[0020]
That is, the detection signal from the ultrasonic sensor 15 is input to one input terminal of the comparator set to the reference voltage of 100 mV shown in the upper part of FIG. 5 and the comparator set to the reference voltage of 600 mV shown in the lower part. It has become. The outputs of these comparators are connected to the inputs of separate monostable multivibrator (one-shot) LM555, and the one-shot output is identified by a determination circuit (not shown).
[0021]
FIG. 6 shows two comparators with different reference voltages and two one-shot output waveforms obtained when the movable part (coil assembly) 5 is input from the ultrasonic sensor 15 to the vibration wave identification circuit. From this figure, when the detection rod advances and hits the lower thread 11 and when the coil assembly 5 returns and hits the rear wall (the rear end of the frame), the reference voltage is set to 100 mmV. Only the one-shot on the side outputs a pulse.
[0022]
On the other hand, when the bobbin thread is less than the specified value, when the strongly biased coil assembly 5 moves forward and hits the front wall, the vibration wave reaches a maximum value of 700 mmV. Both the one-shot on the side set to V and the one-shot on the side set to the reference voltage of 600 milliV send an output pulse. Accordingly, the bobbin thread remaining amount detection device already proposed by the applicant described in detail above combines the presence / absence of the outputs of the two one-shot circuits and the forward / return operation control of the coil assembly. Thus, it is possible to reliably identify the presence or absence of the lower thread and whether or not the moving part has been correctly moved forward and backward with the single ultrasonic sensor 15.
[0023]
The main hardware configuration and the basic operation principle of the lower thread remaining amount detection device of the present embodiment have been described above. The features of the lower thread remaining amount detection device of the present embodiment will be described in detail below.
[0024]
The bobbin thread remaining amount detecting device according to the present embodiment, in addition to the basic structure already proposed, has the same position as the standby position shown in FIG. The moving time measuring means for measuring the moving time required to move between the lower thread outer peripheral contact positions shown in FIG. (B) and the measured moving time of the detection rod 7 are converted into the lower thread remaining amount. Conversion means.
[0025]
FIG. 7 is a front view showing an outline of a head portion of a sewing machine in which the lower thread remaining amount detecting device of the present embodiment is adopted, and the display panel 20 provided in the sewing machine has the lower thread remaining amount. There are provided a% display unit 22 for displaying the remaining amount of the lower thread detected by the detection device as a% with a maximum winding diameter of 100%, and an m display unit 24 for displaying the remaining length. The display panel 20 is provided with a thread count / hook type changeover switch 26, and the parameter used for calculating the remaining amount of lower thread is changed according to the thread count and hook type used by the switch 26. Can be done.
[0026]
The moving time measuring means and the lower thread remaining amount converting means provided in the lower thread remaining amount detecting device of the present embodiment are configured by software in a main control device that controls the operation of the entire sewing machine. That is, as shown in FIG. 8, the CPU (central processing unit) of the main control device causes the detection rod 7 to advance to detect the lower thread remaining amount and the detection rod 7 to move forward. Thereafter, when a vibration sensor signal detected by the ultrasonic sensor 15 when the tip collides with the lower thread outer periphery is input, the CPU calculates the movement time of the detection rod 7. As shown in FIG. 9, the time t until the one-shot output is first detected at the time tb after the detection rod driving current is applied at the time ta is calculated based on the clock signal. It corresponds to being.
[0027]
When the movement time t is measured in this way, the CPU converts the time t into a specific value of the lower thread remaining amount using a conversion parameter prepared in advance, and displays it on the display panel 20.
[0028]
There are two types of conversion parameters. One is as shown schematically in FIG. 10 for the lower thread wound around the bobbin. The difference ΔR between the maximum winding diameter Rmax and the minimum winding diameter Rmin is 100%. It is used to display the ratio of the difference ΔRt between the diameters Rt and Rmin when measured with respect to ΔR in%. Since the moving distance of the detection rod becomes longer as the winding diameter becomes smaller, there is a linear relationship as shown in FIG. 11 between the moving time proportional to the moving distance and the lower thread remaining amount. It is requested from.
[0029]
Specific examples of the ΔR can include 12 to 13 mm, and the moving time of the detection rod that moves the distance corresponding to the ΔR can include 16 msec. It can be calculated as a correct value. The moving time t can be adjusted to a desired value by changing the moving speed of the detection rod. However, it is necessary to set the speed so as to generate a vibration that can be detected by the ultrasonic sensor 15 when the tip of the detection rod comes into contact with the outer periphery of the lower thread.
[0030]
Another conversion parameter is used to display the lower thread remaining amount as a specific length, for example, “7 m remaining”, and is a curve as shown in FIG. 12 with respect to the movement time t. It can be given as a function representing.
[0031]
11 and 12, for example, if the size of the hook to be used is different, the size of the bobbin is also limited by the size, so that the maximum winding diameter also changes. Accordingly, each parameter can be set for each type of hook, and when changing the hook, the operator uses the switch 26 to set the hook type to the CPU and instruct to change the parameter. .
[0032]
Also, when the lower thread remaining amount is displayed in m, although not shown in the figure, since the parameters differ depending on the thickness of the thread being used, the thread count is similarly set by the changeover switch 26. Yes.
[0033]
Next, according to the present embodiment, a processing procedure when detecting a specific lower thread remaining amount will be described with reference to the flowchart of FIG.
[0034]
First, after the sewing operation is started, a request for lower thread remaining amount detection is waited (step S1). This request may be automatically made while the sewing machine spindle is stopped every time the sewing operation for one piece of work is finished, or may be made manually by the operator.
[0035]
When the lower thread remaining amount detection is requested in step S1, the CPU outputs a control signal for driving the detection rod forward to the detection rod driving means (linear actuator) as shown in FIG. 8 (step S2). At the same time, the CPU starts measuring the travel time. When the ultrasonic sensor 15 detects a vibration wave generated when the tip of the detection rod starts moving forward and comes into contact (collision) with the outer periphery of the lower thread (step S4), the measurement of the movement time is finished. (Step S5), a time t required until the detection rod comes into contact with the outer periphery of the lower thread from the standby position is measured.
[0036]
Next, the measured required time t is converted into a lower thread remaining amount and displayed on the display panel 20 (step S7). At this time, even if both the% value and the m value obtained by converting the required time t using the function representing the relationship shown in FIGS. 11 and 12 as parameters are displayed on the display units 22 and 24 of the display panel 20, Only one of them may be selectively displayed.
[0037]
When the operator determines that it is not necessary to replenish the lower thread by looking at the result displayed in the step S7 and continues the sewing operation, the process returns to the step S1 to repeat the same process. Is determined to be necessary, it is replaced with a new bobbin (step S8).
[0038]
As described above in detail, according to the present embodiment, the discrimination circuit shown in FIG. 5 can detect the presence or absence of a specified amount of lower thread remaining, and the lower thread remaining at an arbitrary time during the sewing operation. The specific value of the quantity can be displayed each time.
[0039]
Therefore, the operator can accurately grasp the specific lower thread remaining amount while observing the lower thread remaining amount display, so that the lower thread is sufficiently wound before the lower limit specified remaining amount of the lower thread is detected. Bobbins can be prepared.
[0040]
Further, as described above, the parameter coefficient used when converting the time required from when the current for driving the detection rod is applied until the ultrasonic sensor 15 outputs the detection signal to the remaining amount of the lower thread is changed. Therefore, it is possible to cope with various types of yarns and bobbins.
[0041]
Furthermore, the lower thread remaining amount detection device of this embodiment can be reduced in size as compared with a conventional device using a plunger magnet and a rotary solenoid, so that it can be easily retrofitted to the sewing machine. There is also an advantage that can be applied to.
[0042]
Although the present invention has been specifically described above, the present invention is not limited to that shown in the above embodiment, and various modifications can be made without departing from the scope of the invention.
[0043]
For example, the detection rod driving means is not necessarily limited to a linear actuator.
[0044]
In the above-described embodiment, the case where the lower thread remaining amount detection operation is performed while the sewing machine is stopped is shown. However, for example, the timing at which the detection rod can be inserted into the hook during the low-speed rotation of the sewing machine main shaft about 200 rotations is captured. Then, the detection operation may be performed. For such a detection operation during the sewing machine operation, the linear actuator shown in the above-described embodiment capable of executing the forward and backward movement of the detection rod at a high speed is extremely suitable as a drive unit.
[0045]
Further, in the above embodiment, as the moving time for calculating the lower thread remaining amount, the time from the start of advancement of the detection bar until the tip abuts the lower thread outer periphery is used. The time required to return from the lower thread outer peripheral contact position to the original standby position may be used.
[0046]
【The invention's effect】
As described above, according to the invention of claim 1, a specific lower thread remaining amount at an arbitrary time during the sewing operation can be accurately detected each time.
[0047]
According to the invention of claim 2, since there is no need to attach an extra member to the movable part such as the detection rod as in the case of using the Hall element, the detection rod can be advanced and retracted at high speed.
[Brief description of the drawings]
FIG. 1 is a plan view, a cross-sectional view, and a front view showing a schematic configuration of a linear actuator that constitutes a lower thread remaining amount detection device according to an embodiment of the present invention. FIG. FIG. 3 is a schematic sectional view showing the relationship between the linear actuator and a bobbin case housed in the hook. FIG. 4 is a front view showing a state where an ultrasonic sensor is attached to the linear actuator. FIG. 5 is a circuit diagram showing a vibration wave identification circuit incorporated in the lower thread remaining amount detection device. FIG. 6 is a diagram showing a vibration waveform detected by the vibration wave identification circuit. FIG. 8 is a conceptual view of a main control unit that constitutes a moving time measuring unit of a detection rod and a lower thread remaining amount converting unit. [Figure 9] Lower thread FIG. 10 is an explanatory diagram schematically showing a state in which the lower thread is wound around the bobbin case. FIG. 11 is a lower thread remaining in the bobbin case radial direction. FIG. 12 is a diagram showing the relationship between the length of the lower thread remaining amount and the movement time. FIG. 13 is a flowchart showing the flow of the lower thread remaining amount detecting operation according to the embodiment. Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Detection rod bearing 2A, 2B ... Permanent magnet 3A, 3B ... Gap 4 ... Iron core 5 ... Coil assembly 5A ... Coil bobbin 5B ... Coil 6A, 6B ... Return spring 7 ... Detection rod 8 ... Pressure sensor 9 ... Lower guide rod 10A DESCRIPTION OF SYMBOLS 10B ... Yoke 11 ... Lower thread 12 ... Bobbin 13 ... Mounting member 14 ... Hook 15 ... Vibration wave detection element (ultrasonic sensor)
20 ... Display panel 22 ...% display section 24 ... m display section 26 ... Thread count / hook type selector switch

Claims (1)

In the bobbin thread remaining amount detecting device for detecting the remaining amount of the bobbin thread wound around the bobbin by inserting a detection rod into the hook in which the bobbin is housed,
Driving means for moving the detection rod forward from the standby position toward the hook, and then returning to the original position;
The tip of the forward driven detection rod is, a contact detection means for detecting vibration waves generated when in contact with the lower thread outer periphery,
A movement time measuring means for measuring a movement time required for the detection rod to move between the standby position and the lower thread outer circumferential contact position based on the detection of the contact detection means ;
A bobbin thread remaining amount detecting device for a sewing machine, comprising: a converting unit that converts the moving time of the detection rod measured by the moving time measuring unit into a bobbin thread remaining amount.

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