JP5419423B2 - Sewing thread tension device - Google Patents

Description

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

In a conventional thread tension device of a sewing machine, a pair of thread tension plates is a sewing thread using a drive unit (for example, a voice coil motor or the like) composed of a pair of thread tension plates that sandwich the sewing thread, and permanent magnets and coils. 2. Description of the Related Art A thread tension device that adjusts tension applied to a thread is known. This thread tension device controls the tension on the sewing thread by increasing or decreasing the energization current value for the coil.
In such a thread tension device, the thrust applied to the thread tension tray by the permanent magnet and the coil is generated according to Fleming's left-hand rule by energizing the coil. The magnitude of the thrust is proportional to the energization current value. It is also possible to change the direction of thrust generated by changing the direction of current flow.

By the way, in general, a permanent magnet has a property of causing a change in magnetic flux density generated when there is a temperature change. That is, when the temperature of the permanent magnet changes due to a temperature change in the use environment of the sewing machine, the thrust of the drive unit changes. For this reason, there has been a disadvantage that the yarn tension by the yarn tensioning device may change, resulting in a yarn tension that is not intended by the operator. Therefore, there is a thread tension device for a sewing machine that reduces a change in thread tension by energizing a coil with a predetermined heating current, preheating the drive unit, and maintaining the temperature of the permanent magnet above a certain level (for example, Patent Documents). 1).
JP 2005-334238 A

  However, in the conventional sewing thread tension device, the heating current applied to the coil is constant regardless of the temperature of the permanent magnet. For this reason, it took a long time to heat the permanent magnet to a temperature above a certain level. Therefore, the conventional thread tension device of the sewing machine has a problem that the temperature control of the permanent magnet cannot be performed quickly, and it may take a long time to obtain the intended thread tension. Although it is conceivable to shorten the heating time by controlling the heating current according to the temperature of the permanent magnet, in that case, the maximum heating current that can flow through the coil depends on the drive circuit of the coil, the power source capacity, etc. Due to the limitations, there was a limit to the heating time that could be shortened.

  In view of the above-described problems, an object of the present invention is to provide a thread tension device for a sewing machine that is controlled so as to obtain an intended thread tension more quickly.

A thread tension device for a sewing machine according to a first aspect of the present invention includes a thread tension member that applies tension to a sewing thread, a permanent magnet, and a coil, and the tension by the thread tension member according to a current flowing through the coil. a variable capable of driving means, disposed between the coil and the power supply, a controllable switching circuit current amount from the power supply to the coil by the PWM control, a temperature detecting means for detecting a temperature of the permanent magnet, the first storage means for the tension of the thread tension member stores the first temperature is a temperature defined in the appropriate temperature range required for the permanent magnet to produce the intended tension of the operator, the a first temperature determination means for determining the temperature level of the permanent magnet relative to the first temperature, by energizing a predetermined heating current to the coil by the PWM control by controlling the switching circuit in a non-sewing Above Comprising a heating control means for raising the temperature of the permanent magnet, and said heating control means, when the temperature of the permanent magnet is determined to less than the first temperature, the energization OFF period of the PWM control the induced current generated in the coil refluxed to the power supply side, the case where the temperature of the permanent magnet is determined to the be the first temperature or more, the switching circuit so as to circulate the induction current in the coil And the heating current is supplied to the coil.

According to a second aspect of the invention, the thread tension device of a sewing machine according to claim 1, What the first high temperature der than temperature, the permanent magnet to produce the intended tension of the operator second storage means for storing a second temperature which is the upper limit temperature of the suitable temperature range needed, a second temperature determining means for determining the level of temperature of the permanent magnet relative to said second temperature , wherein the heating control means, when the temperature of the permanent magnet by the second temperature determining means is determined to satisfy the second temperature, wherein the predetermined to by the coil and the heating control means The heating current is not supplied.

According to a third aspect of the invention, the thread tension device of a sewing machine according to claim 2, the wire temperature detection means for detecting a wire temperature of the coil, a temperature higher than the second temperature, the coil third temperature determination means but to determine a third storage means for storing a third temperature for coil breakage prevention is the temperature at which the overheating, the height of the conductor temperature for the third temperature when, wherein the heating control means, when the wire temperature is determined to satisfy the third temperature by said third temperature determination means, wherein the predetermined heating to said coil by said heating control means It is characterized in that no current is supplied.

  According to a fourth aspect of the present invention, in the thread tension device of the sewing machine according to the third aspect, the conductor temperature detecting means is detected by a resistance value detecting means for detecting a resistance value of the coil and the resistance value detecting means. Conductor temperature calculating means for calculating the conductor temperature based on the resistance value.

According to the first aspect of the invention, the heating control means, when the temperature of the permanent magnet by the first temperature determination means it is determined to less than the first temperature, the coil energization OFF period of the PWM control The switching circuit is controlled so that the generated induced current flows to the power source. At this time, the induced electromotive force generated in the coil is increased by causing the induced current to flow through the power source having a high potential, and the heat generation of the coil is increased. On the other hand, if the temperature of the permanent magnet is determined to be the first temperature or higher, the induced current by controlling so as to circulate in the coil, prevents the induced electromotive force becomes larger than necessary, the coil Increase the temperature slowly. Therefore, if the temperature of the permanent magnets is less than the first temperature, heating of the permanent magnets due to heat generation of the coil as compared with the case where the temperature of the permanent magnet satisfies a first temperature is more rapidly performed. At this time, the first temperature is the temperature at which the tension of the thread tension member is defined in a suitable temperature range required for the permanent magnet to produce the intended tension operator. That is, the permanent magnet is rapidly warmed to a temperature within the temperature range, and the yarn tension by the driving means is controlled so as to quickly reach the intended yarn tension. Therefore, in the conventional thread tension device of the sewing machine, the problem that the temperature control of the permanent magnet could not be performed quickly and much time was required to obtain the intended thread tension was solved, and the intended thread was more quickly It is possible to provide a thread tension device for a sewing machine that is controlled so as to obtain tension. In particular, immediately after turning on the sewing machine, the permanent magnet can be warmed rapidly, such as when the permanent magnet is at a temperature significantly lower than that temperature because the coil of the drive means has not been energized for a long time. It is possible to provide a thread tension device for a sewing machine that can quickly obtain an intended thread tension after the sewing machine is turned on.
Further, since the switching circuit has a configuration for PWM control of the driving means, the heating control of the permanent magnet can be performed using the configuration for operating the driving means. Therefore, without particularly providing a structure for controlling heat generation i.e. the permanent magnet heating control of the coil, it allows control heating temperature of the permanent magnet according to whether they meet the first temperature.
The heating control means may control, when the temperature of the permanent magnet is determined to be the first temperature or higher, since the induced current circulates in the coil, after the temperature of the permanent magnet satisfies a first temperature also, the temperature of the permanent magnets of the permanent magnet heating is continued while reducing the heat generation of the coil than in the case where less than the first temperature. For example, when the first temperature and a temperature lower of the within a reasonable temperature range required for the permanent magnet to produce the intended tension operator,
Since the permanent magnet is heated gently continuation of the permanent magnet even after filling the first temperature, energized according to the level of the temperature of the permanent magnet relative to the first temperature, to completely cut off the energization of the coil The temperature of the permanent magnet is easily maintained within the temperature range as compared with the case where the coil temperature is maintained by selecting one of the OFF state and the above-described reflux of the induced current to the power supply side.

According to the second aspect of the invention, the heating control means, when the temperature of the permanent magnet by the second temperature determining means is determined to satisfy the second temperature, a predetermined heating of the coil by the heating control means Do not energize current. Therefore, when the permanent magnet is sufficiently heated and no further heating is required, it is possible to prevent a power loss due to further heating current being applied to the coil, and to provide an efficient thread tension device for a sewing machine.
Further, for example, the second temperature, that the upper limit of the suitable temperature range required for permanent magnets to produce the intended tension of the operator, the heat generation of the coil, the permanent magnet the intended tension of the operator Therefore, it is possible to prevent overheating exceeding an appropriate temperature range required for the permanent magnet. Therefore, it is possible to provide a thread tension device for a sewing machine that can more reliably obtain the thread tension intended by the operator.

According to the third aspect of the present invention, the heating control means, if the conductor temperature by the third temperature determination means is determined to satisfy the third temperature, the predetermined heating current to the coil by the heating control means Do not energize. At this time, the third temperature is a temperature at which abnormality or damage to the coil does not occur. That is, when it is determined by the third temperature determining means that the coil is in an overheated state that may cause an abnormality or damage, the heating control means controls the coil not to be energized with a predetermined heating current. Suppresses further heat generation and prevents the coil from becoming abnormal or damaged. Therefore, it is possible to provide a highly reliable sewing thread tension device that does not cause any abnormality or damage to the coil due to the heat generated by the coil.

  According to the invention of claim 4, the conductor temperature detecting means detects the resistance value of the coil, and the conductor temperature calculation for calculating the conductor temperature based on the resistance value detected by the resistance value detecting means. Means. The resistance value and temperature of a coil are determined by constant values from various factors such as the temperature coefficient of resistance, the cross-sectional area of the conductor, and the conductor length specified by the material of the coil conductor, so the resistance of the coil based on these factors. Based on the correspondence between the value and the coil temperature, the conducting wire temperature calculating means can calculate the coil temperature from the coil resistance value detected by the resistance value detecting means. Such coil temperature calculation is not affected by external factors (such as the temperature of the surrounding area of the thermometer) compared to the calculation using a thermometer that directly measures the coil temperature. Since it can be calculated, a more accurate coil temperature can be obtained. Therefore, it is possible to control whether or not a predetermined heating current is applied to the coil based on a more accurate coil temperature, and to prevent the coil from being abnormal or damaged due to overheating of the coil. Therefore, a more reliable sewing thread tension device Can provide.

(Overall structure of the invention)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The thread tension device of the sewing machine according to the present invention is a thread tension device that is provided in the sewing machine and adjusts the thread tension of the sewing thread.
FIG. 1 is a perspective view of a sewing machine equipped with a thread tension device 10 according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view of the thread tension device 10.
As shown in the drawing, the thread tension device 10 is provided in the middle of a thread path from the sewing thread supply source (not shown) to the sewing needle 1, the main structure of which is a sewing machine surface.
The thread tension device 10 mainly supports a pair of thread tension trays 21 and 22 as a pair of thread tension members 21 that sandwich and hold a sewing thread fed by sewing and a pair of thread tension trays 21 and 22. A support shaft 23, a voice coil motor 30 as a drive means for adjusting tension acting on the sewing thread between the thread tension plates 21 and 22 via the support shaft 23, and an output shaft 31 of the voice coil motor 30 are provided. And a press contact spring 24 that presses the respective thread tension plates 21 and 22 and a control system for the voice coil motor 30.

(Machine configuration of thread tension device)
The thread tension plates 21 and 22 are discs having the same outer diameter, and are supported adjacent to each other in a state where the support shaft 23 is inserted through a central through hole provided in each of the thread tension plates 21 and 22. Then, a sewing thread is passed between these thread tension plates 21 and 22, and tension is applied in a clamped state.
A nut 26 is attached to the support shaft 23 through a washer in a state where one end of the support shaft 23 is inserted into the central through hole of each thread tension plate 21, 22, and supports the thread tension plates 21, 22 so as not to drop off. Yes. However, the thread tension plates 21 and 22 are supported so as to be movable in the direction along the support shaft 23. The other end of the support shaft 23 is connected to one end of the output shaft 31 of the voice coil motor 30 while being inserted into the ring body 25. That is, when the support shaft 23 is driven (retracted) by the voice coil motor 30 to the other end side, one thread tension tray 21 is pressed to the other thread tension tray 22 side via the nut 26, and each thread tension Tension is applied by sandwiching the sewing thread between the plates 21 and 22.
Note that at the other end of the output shaft 31 of the voice coil motor 30, the pressure contact spring 24 presses the output shaft 31 in the backward drive direction, so that, as with the voice coil motor 30, one thread tension is provided via the nut 26. The tray 21 is pressed against the other thread tension tray 22 side. However, even if the pressure spring 24 is output free when the voice coil motor 30 is not energized, the pressure spring 24 acts on the thread tension plates 21 and 22 to provide the minimum pressing force necessary to hold the sewing thread. It is provided to grant.

FIG. 3 is a sectional view taken along the output shaft 31 of the voice coil motor 30.
As shown in FIG. 3, the voice coil motor 30 has an output shaft 31 that moves forward and backward along its longitudinal direction, a permanent magnet 32 that is fixedly mounted on the output shaft, and the output shaft 31 and the permanent magnet 32 inside. The coil 33 is inserted, and a yoke 34 that constitutes a housing for storing the coil 33 and the permanent magnet 32 is provided.
The permanent magnet 32, the coil 33, and the yoke 34 constitute a magnetic circuit. That is, the output shaft 31 is inserted along the center line direction of the cylindrical coil 33, and the permanent magnet 32 is disposed inside the coil 33. Further, the output shaft 31 is supported by the yoke 34 in a state in which both end portions thereof protrude, and can be moved to any end side.
The coil 33 is energized and controlled by a configuration of a control system, which will be described later, via a lead wire 33a (see FIG. 4) wired outside the yoke 34, and is applied to the permanent magnet 32 and the output shaft 31 according to the energization direction of the current. A forward or backward moving force is applied along the axial direction. Further, the forward / backward driving force of the output shaft 31 is controlled in accordance with the current value to the coil 33.

  As described above, the output shaft 31 of the voice coil motor 30 is always pressed by the pressing spring 24 in the backward driving direction with the minimum pressing force. The coil 33 is normally energized in the direction in which the amount of movement is generated in the backward drive direction as in the case of the pressing spring 24, and as the current value increases, the backward movement force increases and is applied to the output shaft 31, The tension on the sewing thread generated between the thread tension plates 21 and 22 increases, and as the current value decreases, the backward movement force decreases and is applied to the output shaft 31, and finally the pressing force of only the pressing spring 24. As a result, the thread tension plates 21 and 22 are in a state where tension is applied to the sewing thread.

  FIG. 4 is an explanatory view showing an arrangement state of the temperature detecting means 43 with respect to the voice coil motor 30. The temperature detection means 43 is a temperature sensor that outputs a signal according to the ambient temperature, such as a thermistor or a thermocouple, and is attached to the surface of the casing formed of the yoke 34 of the voice coil motor 30, and the casing surface temperature (outer skin temperature). ) Is detected. Thereby, the temperature detection means 43 detects the temperature of the permanent magnet 32 indirectly. The detected temperature signal of the temperature detecting means 43 is output to the control device 50 described later. The temperature detector 43 also functions as a conductor temperature detector that detects the conductor temperature of the coil 33 together with the permanent magnet 32, and indirectly detects the conductor temperature of the coil 33.

(Control system of thread tension device)
FIG. 5 is a block diagram showing a control system of the thread tension device 10. As shown in FIG. 5, the thread tension device 10 detects a current flowing through the coil 33 and a switching circuit 41 that enables connection / disconnection between the voice coil motor 30 and the power source 71 (see FIG. 6). Current detection means 42, temperature detection means 43 for detecting the jacket temperature of the coil 33, lead wire temperature detection means for detecting the lead wire temperature of the coil 33, and the switching circuit 41 based on the detected skin temperature and lead wire temperature. And a control device 50 that controls energization of the coil 33.

The switching circuit 41 switches between connection / disconnection of the coil 33 and the power supply 71 between the power supply 71 (see FIG. 6) for energizing the coil 33 and the coil 33 according to the control of the control device 50. And energization is performed at a current value according to the control of the control device 50.
The current detection means 42 includes a current detection resistor R provided between the switching circuit 41 and the ground circuit, and the current detection resistor R generates a potential difference generated by an energization current of the coil 33 that flows from the switching circuit 41 to the ground circuit. To the control device 50. The control device 50 controls the switching circuit 41 to energize the coil 33 with a predetermined heating current described later. As will be described later, the control device 50 functions as a conducting wire temperature detecting means, and calculates the conducting wire temperature of the coil 33 from the resistance value obtained from the detection voltage of the resistance value detecting means constituted by the arithmetic device 52.

  The control device 50 controls the operation of the switching circuit 41 to control energization to the coil 33. Specifically, based on the input of the detected current of the coil 33 detected by the current detecting means 42 and the skin temperature detected by the temperature detecting means 43, the calculation unit 52 stores various control programs and data stored in the ROM 51. The switching circuit 41 is controlled through the control logic 53 c for controlling the switching circuit 41 included in the microcomputer 53.

  As shown in FIG. 5, the control device 50 includes a ROM 51 that stores various control programs and data to be described later, and an arithmetic unit 52 that executes various programs and performs various processes and controls. The microcomputer 53 includes a circuit and an interface, and a RAM 54 that temporarily stores various programs and data and serves as a work area.

ROM51 is, TcaseMiddle as a first temperature, stores TcoilMAX as TcaseMAX and third temperature as a second temperature. Accordingly, the ROM 51 functions as a first storage unit, a second storage unit, and a third storage unit.
TcaseMiddle and TcaseMAX are temperatures determined within an appropriate temperature range required for the permanent magnet 32 when the backward driving force by the voice coil motor 30 generates the yarn tension intended by the operator. It is desirable that TcaseMiddle and TcaseMAX be within an average temperature at the time of sewing of the thread tension device 10, or a temperature at which a good operation or a tension obtained in advance by an operation test or the like is stably stabilized. . For example, as shown in FIG. 8 to be described later, it is conceivable that TcaseMiddle and TcaseMAX are set between 45 [° C.] and 50 [° C.].
TcoilMAX is generally higher than the above-mentioned TcaseMiddle and TcaseMAX, and it is desirable that TcoilMAX be a temperature at which no abnormality or damage occurs in the coil. In particular, the coil 33 is provided with an insulating film for ensuring insulation between the conductive wires wound adjacent to the surface thereof. It is more desirable that the temperature does not occur.

The ROM 51 stores a heating current value indicating the current value of the heating current. The heating current value may be a constant current value or a current value set in advance based on the detected permanent magnet temperature, as long as the current value can rapidly increase the temperature of the permanent magnet 32. The current value may be controlled and increased according to the pattern.
In addition, the ROM 51 records a temperature table indicating the relative relationship between the resistance value of the coil 33 detected by the resistance value detection means and the temperature of the coil 33. Since the correspondence relationship between the resistance value and the temperature of the coil 33 is determined to be a constant value from various factors such as the resistance temperature coefficient, the conductor cross-sectional area, and the conductor length specified by the material of the conducting wire of the coil 33, The correspondence between the resistance value based on the characteristics and the temperature of the coil 33 is stored in the ROM 51 as a temperature table. In addition, although not shown, the ROM 51 stores various control programs and data that are read and executed by the calculation unit 52.

The calculation unit 52 performs current control of the coil 33 by the switching circuit 41. In addition, the calculation unit 52 performs a process of determining whether or not the sewing work by the sewing machine provided with the thread tension device 10 has been started. In addition, the calculation unit 52 may perform various kinds of operation control of the sewing machine including the thread tension device 10.
Various controls and processes by the arithmetic unit 52 are performed by so-called software processing that reads various control programs and data from the ROM 51 and executes them. Various programs and data read by the calculation unit 52, parameters temporarily generated by the processing of the calculation unit 52, and the like are stored in the RAM 54.

  The microcomputer 53 is a collection of circuits that perform processing based on predetermined processing contents among the processing performed by the control device 50. As a configuration included in the microcomputer 53, for example, a comparison circuit 53b that determines whether the skin temperature satisfies TcaseMiddle or TcaseMAX, a control logic 53c that controls energization of the coil 33 by the switching circuit 41 in accordance with the control of the calculation unit 52, and the like. is there.

Next, current control for supplying a predetermined heating current to the coil 33 and processing related to the current control will be described.
When the skin temperature detected by the temperature detection means 43 is output to the control device 50, the comparison circuit 53b compares the skin temperature of the coil 33 with TcaseMiddle or TcaseMAX, and the skin temperature is high or low with respect to TcaseMiddle or TcaseMAX. Is determined. That is, the comparison circuit 53b functions as a first temperature determination unit and a second temperature determination unit.
When the skin temperature is less than TcaseMiddle or TcaseMAX, the calculation unit 52 controls the switching circuit 41 so that a predetermined heating current is supplied to the coil 33 and the coil 33 generates heat. The permanent magnet 32 is warmed by the heat generated by the coil 33. That is, the calculation unit 52 functions as a heating control unit.

  The calculation unit 52 performs so-called PWM control for controlling the current flowing through the coil 33 by changing the ratio (duty ratio) between the ON section and the OFF section of the energization with respect to the coil 33 in a predetermined period T, and performs predetermined control on the coil 33. Apply heating current. When the skin temperature is less than TcaseMiddle, the calculation unit 52 performs current control in the Fast Deacy mode in which the induced current caused by the induced electromotive force generated in the coil 33 is circulated to the power source side during the PWM control energization OFF period. On the other hand, when the skin temperature satisfies TcaseMiddle and does not satisfy TcaseMAX, the arithmetic unit 52 performs current control in the Slow Deacy mode in which the induced current caused by the induced electromotive force generated in the coil 33 is returned to the coil 33 during the energization OFF period of PWM control. I do.

Hereinafter, current control of a predetermined heating current flowing through the coil 33 will be described with reference to the circuit diagrams of FIGS. 6 and 7 and the graph of FIG. FIG. 6 is a circuit diagram of the drive circuit 41 connected to the coil 33.
The switching circuit 41 is a so-called full bridge type circuit. The switching circuit 41 includes a total of four transistors 61, 62, 63, 64 connected to two poles of the coil 33, and four diodes 65, connected to two poles of the coil 33, respectively. , 66, 67, 68, and a current detection resistor R as current detection means 42 that detects a current flowing through the coil 33 and outputs the current to the calculation unit 52.

  Of the four transistors, the one connected to one electrode of the coil 33 is referred to as transistors 61 and 62, and the one connected to the other electrode is referred to as transistors 63 and 64. The transistors 61 and 63 are constituted by, for example, PNP transistors, and the collectors of the transistors 61 and 63 are connected to one electrode and the other electrode of the coil 33, respectively, and the emitters of both transistors are connected to the power source 71. It is connected. The transistors 62 and 64 are composed of, for example, NPN transistors, and the collectors of the transistors 62 and 64 are connected to one electrode and the other electrode of the coil 33, respectively. The detection resistor R is grounded. The four transistors 61, 62, 63, and 64 are switching elements that connect (ON) / disconnect (OFF) a current path between the coil 33 and the power source 71 or between the coil 33 and the ground. Is controlled by a control signal of a control logic 53c connected to the base of each transistor.

  Of the four diodes, one electrode of the coil 33 is connected to the anode of the diode 65 and the cathode of the diode 66, the cathode of the diode 65 is connected to the power supply 71, and the anode of the diode 66 is connected. Further, the anode of the diode 67 and the cathode of the diode 68 are connected to the other electrode of the coil 33, the cathode of the diode 67 is connected to the power source 71, and the anode of the diode 68 is grounded.

The current detection resistor R is a resistor for the calculation unit 52 to detect the value of the current flowing through the coil 33. The calculation unit 52 is connected to the current via a D / A converter (not shown) provided in the calculation unit 52. Based on the voltage generated in the detection resistor R, the current flowing in the coil 33 is detected.
The power supply 71 is a power supply device that functions as a DC power supply capable of constant voltage output.

  With the above configuration, a full bridge circuit is configured, and the control logic 53c controls the ON / OFF of each transistor via the switching circuit 41 under the control of the arithmetic unit 52 based on the current of the coil 33 detected by the current detection resistor R. By so-called PWM control by switching, switching of ON / OFF of voltage application to the coil 33 is repeated, and the amount of current supplied to the coil 33 is substantially adjusted by changing the ON ratio (duty ratio) of voltage application. When a predetermined heating current is passed through the coil 33, when a voltage is applied (ON) to the coil 33 by PWM control, the transistors 61 and 64 are turned on and the transistors 62 and 63 are turned off. The As a result, as indicated by an arrow A in FIG. 6, current flows from the power source 71 through the transistor 61 to the coil 33 and then through the transistor 64 to the ground side. At this time, a magnetic flux due to a heating current is generated in the coil 33. Note that the connection state of the switching circuit 41 when a voltage is applied (ON) to the coil 33 by PWM control is common in the Fast Decay mode and the Slow Decay mode.

FIG. 7 is a circuit diagram showing the flow of the induced electromotive force of the heating current. FIG. 7A shows the case of Fast Decay mode, and FIG. 7B shows the case of Slow Decay mode. The Fast Decay mode and the Slow Decay mode differ in the connection state in the energization OFF section from when the applied voltage by PWM control is turned off to when the applied voltage is turned on next time.
When the switching circuit 41 is controlled so that the applied voltage is turned off as shown in FIGS. 7A and 7B after the heating current is applied, the coil 33 generated by the heating current The magnetic flux disappears, but at this time, the coil 33 generates an induced electromotive force so as to cancel the change in the magnetic flux, so that the coil 33 continues to pass an induced current that is a current in the same direction as the heating current.

In the fast decay mode, all four transistors 61, 62, 63, and 64 are controlled to be turned off. At this time, the induced current caused by the induced electromotive force generated in the coil 33 flows from the ground side through the diode 66 through the diode 66 and then through the diode 67 to the power source 71 side as indicated by an arrow B in FIG. It will flow. In other words, when the skin temperature is less than TcaseMiddle, the calculation unit 52 generates an induced current so as to release the induced electromotive force generated in the coil 33 to the power supply 71 when the heating current is passed during the PWM control energization OFF period. The coil 33 is controlled to flow (circulate) from the power source 71.
On the other hand, in the slow decay mode, the transistor 61 is continuously turned on, and the transistors 62, 63, and 64 are controlled to be turned off. At this time, as indicated by an arrow C in FIG. 7B, the induced current caused by the induced electromotive force generated in the coil 33 returns to the coil 33 through the diode 67 and the transistor 61. That is, when the skin temperature satisfies TcaseMiddle, the calculation unit 52 short-circuits both ends of the coil 33 via the diode 67 and the transistor 61, and circulates (circulates) the coil 33 in the coil 33 without flowing the induced current to the power source 71. Control as follows.

  FIG. 8 is a graph showing a current waveform and a voltage waveform of the coil 33 that is PWM-controlled at a predetermined period T. FIG. 8A shows a current waveform and a voltage waveform in the Fast Decay mode, and FIG. 8B shows a current waveform and a voltage waveform in the Slow Decay mode. Note that, in both the fast decay mode and the slow decay mode, the ratio of the energization ON period in which both the transistor 61 and the transistor 64 are both ON to the period T is the coil 33 detected by the current detection resistor R by the arithmetic unit 52. Is determined by turning off at least one of the transistor 61 and the transistor 64 via the control logic 53c when it is determined that the current value has reached the predetermined current value Imax. In the graphs shown in FIGS. 8A and 8B, in the section where the current value is rising (energization ON section), the timing when the heating current is supplied from the power source 71 to the coil 33 and the current value are falling. The section (energization OFF section) corresponds to the timing when the induction current of the coil 33 flows.

  In the Fast Decay mode, the induced current of the induced electromotive force is caused to flow to the power supply 71 side, so that the voltage of the induced electromotive force increases by attempting to flow the current with respect to the potential of the power supply 71, and the current is attenuated. It occurs rapidly. On the other hand, in the slow decay mode, the induced current due to the induced electromotive force does not flow to the power source 71 but circulates in the circuit including the coil 33, the diode 67, and the transistor 61. The increase in voltage is smaller than that in the case, and the current value is attenuated more slowly than in the fast decay mode. Therefore, as shown in FIGS. 8A and 8B, in the Fast Decay mode, the energization ON section is set to Slow in the section of the next period T in order to make the rapidly attenuated current value reach Imax again. This is longer than in Decay mode. However, in any mode, the average current value flowing through the coil 33 is hardly changed. In this case, strictly speaking, since the duty ratio in the PWM control is determined only by the same current value Imax, as shown in FIG. 8A and FIG. The average current value Iav flowing is slightly smaller in the Fast Decay mode than in the Slow Decay mode, but in reality, the difference is very small because the period T is sufficiently short, and is substantially the same in all modes. It can be said that the average current Iav is flowing.

  Further, as described above, in the Fast Decay mode, the counter electromotive force generated by the coil 33 during the PWM control energization OFF period tends to flow a current with respect to the potential of the power supply 71. Is a voltage higher than the voltage Vd of the power supply 71 (strictly speaking, the sum of the forward voltage drops Vf (about 0.7 V) of the two diodes 66 and 67 (2Vf = about 1.4 V) to the voltage Vd. The applied voltage Vd + 2Vf) is generated. On the other hand, in the slow decay mode, the back electromotive force generated in the coil 33 during the PWM control energization OFF period is a potential obtained by adding the forward voltage drop Vf of the diode 67 and the voltage drop Vce between the collector and emitter of the transistor 61. Therefore, a small voltage (Vce + Vf = 0.2V + 0.7V... About 0.9V is applied to both ends of the coil 33 as compared with the case of the fast decay mode. Only). In both Fast Decay mode and Slow Decay, the voltage drop (Vce) of each of the two transistors 61 and 64 from the voltage Vd of the power supply 71 is applied to both ends of the coil 33 during the energization ON period of PWM control. A voltage obtained by subtracting the applied voltage is applied.

The power consumed by the coil 33 can be obtained by the product of the average current Iav flowing through the coil 33 and the voltage Vm at both ends. As described above, the average current flowing through the coil 33 is the slow decay mode even in the case of the fast decay. In this case, since the current Iav is almost the same, the power consumed by the coil 33 differs between the Fast Decay and Slow Decay modes by the voltage generated at both ends of the coil 33.
Since the voltage Vm across the coil 33 contributes to the power consumption of the coil 33 is the absolute value of the voltage Vm across the coil 33, the voltage Vm across the coil 33 is related to the power consumption of the coil 33 as shown in FIG. ) And the area of the shaded portion of the voltage waveform shown in FIG. 8B, and it can be seen that in both modes, the power consumption of the coil 33 is overwhelmingly in the case of Fast Decay. And since most of the power consumption of the coil 33 in this case is consumed in order to heat the coil 33, the heat generation of the coil 33 also becomes larger in the case of Fast Decay.
Depending on the inductance of the coil 33 and the value of the voltage Vd of the power supply 71, for example, when the power supply voltage Vd = 10V, the power consumption of the coil 33 in the fast decay mode is compared with that in the slow decay mode. And about 5 to 8 times.

  Therefore, the heating of the permanent magnet 32 by the heat generation of the coil 33 in the fast decay mode is performed more rapidly than in the slow decay mode.

FIG. 9 is a graph showing an example of the temperature change of the skin temperature. The temperature change of the skin temperature is indicated by a curve L.
When the skin temperature is less than TcaseMiddle, the coil 33 is energized in the fast decay mode, and the permanent magnet 32 is rapidly heated. On the other hand, when the skin temperature satisfies TcaseMiddle and does not reach TcaseMAX, the coil 33 is energized in the slow decay mode, and the permanent magnet 32 is heated more slowly than in the fast decay mode.
In addition, when the skin temperature satisfies TcaseMAX, the calculation unit 52 performs control so that the energization current of the coil 33 is set to 0 [A] and no heating current is passed. Thereby, the heat generation of the coil 33 is stopped, and the permanent magnet 32 is prevented from being overheated.

  In addition, the calculation unit 52 calculates the coil from the current value detected by the current detection means 42 energized to the coil 33 and the detection voltage value detected by the resistance value detection means in non-sewing according to a predetermined control program. A process of calculating a resistance value at 33 is performed. The calculation unit 52 calculates the temperature of the coil 33 by a so-called resistance method that specifies the temperature of the coil 33 with reference to the temperature table in the ROM 51 from the calculated resistance value of the coil 33. That is, the calculation part 52 functions as a conducting wire temperature calculation means. Specifically, as shown in FIG. 6, the resistance value detecting means has both end portions v <b> 1 and v <b> 2 of the coil 33 connected to the calculation unit 52 via a D / A converter (not shown), and the calculation unit 52 is connected to the coil 33. Is calculated to calculate the resistance of the coil 33 based on the potential difference between the both end portions v1 and v2 and the current value detected by the current detection means 42, and the calculation unit 52 also functions as a resistance value detection means.

The calculation unit 52 compares the conducting wire temperature of the coil 33 with TcoilMAX, and determines whether the conducting wire temperature of the coil 33 with respect to TcoilMAX is high or low. When the conducting wire temperature of the coil 33 satisfies TcoilMAX, the calculation unit 52 performs control so that no heating current is supplied to the coil 33. At this time, skin temperature does not reach the first temperature or the second temperature, also already in a state of conduction in the heating current to the coil 33 has been performed, calculating unit 52, the heating current to the coil 33 Is switched to 0 [A], and the switching circuit 41 is controlled so that no heating current flows. In this control, for example, when an overcurrent flows through the coil 33 due to some factor and overheating occurs, the temperature rise is detected from the resistance value of the coil 33 before the increase in the outer skin temperature is detected by the temperature detecting means 43. To be done.

(Explanation of operation of thread tension device)
FIG. 10 is a flowchart showing the heating current control of the coil 33 by the control device 50. The heating current control will be described based on FIG.
When the main power supply of the sewing machine is turned on, power is supplied to the control system of the thread tension device 10 such as the temperature detecting means 43 and the control device 50, and these function. The calculation unit 52 detects the jacket temperature and the conductor temperature of the coil 33 from the detected temperatures of the temperature detector 43 and the conductor temperature detector, and the comparison circuit 53b determines whether or not the conductor temperature of the coil 33 is less than TcoilMAX. (Step S1). When the conducting wire temperature of the coil 33 does not satisfy TcoilMAX (step S1: YES), the comparison circuit 53b determines whether or not the skin temperature detected by the temperature detecting means 43 is lower than TcaseMiddle (step S2). When the skin temperature is less than TcaseMiddle (step S2: YES), the calculation unit 52 performs current control of the heating current in the fast decay mode and energizes the coil 33 with the heating current (step S3).

If the skin temperature satisfies TcaseMiddle in step S2 (step S2: NO), the comparison circuit 53b determines whether the skin temperature is lower than TcaseMAX (step S5). When the skin temperature is less than TcaseMAX (step S5: YES), the calculation unit 52 controls the heating current in the slow decay mode and energizes the coil 33 with the heating current (step S6).
When the skin temperature satisfies TcaseMAX in step S5 (step S5: NO) and when the temperature of the coil 33 satisfies TcoilMax in step S1 (step S1: NO), the calculation unit 52 sets the energization current of the coil 33 to 0 [A]. (Step S8).

  After step S6 or step S8, the control device 50 determines whether or not sewing work by the sewing machine has been started (step S9). When the sewing work is started (step S9: YES), the process is terminated. If the sewing work has not been started (step S9: NO), the process returns to step S1.

  Note that the above-described processing based on the flowchart of FIG. 10 may be performed again after the sewing work is completed. Further, the above-described processing based on the flowchart of FIG. 10 may be performed only after the sewing machine is turned on until the first sewing start.

(Operational effect of the thread tension device according to the present embodiment)
According to the present embodiment, when the comparison circuit 53b determines that the outer skin temperature does not satisfy TcaseMiddle, the arithmetic unit 52 performs predetermined processing so that the heat generation of the coil 33 is greater than when the outer skin temperature satisfies TcaseMiddle. The flow of the induced electromotive force generated in the coil 33 by the heating current is controlled. That is, when the outer skin temperature is less than TcaseMiddle, the permanent magnet 32 is heated more rapidly by the heat generated by the coil 33 than when the outer skin temperature satisfies TcaseMiddle. At this time, TcaseMiddle is a temperature determined within an appropriate temperature range required for the permanent magnet 32 so that the tension of the thread tension member causes the tension intended by the operator. Therefore, the permanent magnet 32 is rapidly warmed to a temperature within the temperature range, and the yarn tension by the voice coil motor 30 is controlled so as to reach the intended yarn tension more quickly. Therefore, in the conventional thread tension device of the sewing machine, it was possible to solve the problem that the outer skin temperature control could not be performed quickly and took a long time to obtain the intended thread tension, and the intended thread tension was more quickly It is possible to provide a thread tension device for a sewing machine that is controlled so as to be obtained. In particular, when the permanent magnet 32 is at a temperature significantly lower than the temperature because the coil 33 of the voice coil motor 30 is not energized for a long time, such as immediately after the sewing machine is turned on, the permanent magnet 32 is rapidly turned on. Therefore, it is possible to provide a thread tension device for a sewing machine that can quickly obtain an intended thread tension after the sewing machine is turned on.
In addition, even after the skin temperature reaches TcaseMiddle, the heating of the permanent magnet 32 is continued in a state where the heat generation of the coil 33 is smaller than when the skin temperature is less than TcaseMiddle. For example, when TcaseMiddle is set to a low temperature within an appropriate temperature range required for the permanent magnet 32 to generate the tension intended by the operator, the heating of the permanent magnet 32 is slow even after the permanent magnet 32 satisfies TcaseMiddle. Therefore, it becomes easy to maintain the skin temperature within the temperature range.

Further, when it is determined that the skin temperature is less than TcaseMiddle, the calculation unit 52 controls the switching circuit 41 so that the induced current caused by the induced electromotive force flows to the power source 71 and energizes the coil 33. At this time, the induced electromotive force generates a high voltage in the coil 33, so that the heat generated in the coil 33 increases. On the other hand, when it is determined that the skin temperature satisfies TcaseMiddle, control is performed so that the current due to the induced electromotive force is circulated in the coil 33 without flowing to the power source 71. When the induced electromotive force is recirculated into the coil 33, the induced electromotive force is gradually attenuated without generating a high voltage.
Since the switching circuit 41 is configured to switch connection / disconnection between the coil 33 of the voice coil motor 30 and the power source, the switching circuit 41 can also be used as a configuration for driving the voice coil motor 30. Therefore, heating control according to whether or not the outer skin temperature satisfies TcaseMiddle can be performed without particularly providing a configuration for heat generation control of the coil 33, that is, heating control of the permanent magnet 32.

Furthermore, when the comparison circuit 53b determines that the skin temperature satisfies TcaseMAX, the calculation unit 52 does not energize the coil 33 with a predetermined heating current. Therefore, when the permanent magnet 32 is sufficiently heated and no further heating is required, it is possible to prevent a power loss due to the heating current being supplied to the coil 33 and to provide an efficient thread tension device for a sewing machine. .
Further, for example, by setting TcaseMAX as the upper limit of an appropriate temperature range required for the permanent magnet 32 in order to generate the tension intended by the operator, the permanent magnet 32 generates the tension intended by the operator due to the heat generation of the coil 33. Therefore, it is possible to prevent an overheating state exceeding an appropriate temperature range required for the permanent magnet 32. Therefore, it is possible to provide a thread tension device for a sewing machine that can more reliably obtain the thread tension intended by the operator.

  Further, when it is determined that the conducting wire temperature of the coil 33 detected by the conducting wire temperature detecting means satisfies TcoilMAX, the calculation unit 52 does not energize the coil 33 with a predetermined heating current. At this time, TcoilMAX is a temperature for preventing the coil 33 from being abnormal or damaged. That is, when it is determined that the coil 33 is in an overheated state that may cause an abnormality or damage, the calculation unit 52 controls the coil 33 so that a predetermined heating current is not applied, thereby suppressing further heat generation of the coil 33. The coil 33 is prevented from being abnormal or damaged. Therefore, it is possible to provide a highly reliable sewing thread tension device that does not cause any abnormality or damage to the coil 33 due to the heat generated by the coil 33.

  Further, the temperature detection of the coil 33 is performed by calculating a wire temperature for calculating the wire temperature of the coil 33 based on the resistance value detecting means for detecting the resistance value of the coil 33 and the resistance value detected by the resistance value detecting means and the temperature table. The calculation part 52 as a conducting wire temperature detection means performs. The temperature calculation of the coil 33 is not affected by external factors (for example, the temperature around the thermometer) as compared with the calculation by a thermometer or the like that directly measures the temperature of the coil 33. Therefore, the temperature of the coil 33 can be obtained more accurately. Therefore, since the presence or absence of a predetermined heating current to the coil 33 is controlled based on the more accurate temperature of the coil 33 and the coil 33 is prevented from being abnormal or damaged due to overheating, a more reliable sewing machine Can be provided.

(Other)
The thread tension device for a sewing machine according to the present invention may take an embodiment different from the above-described embodiment without departing from the characteristics of the present invention.
For example, in the above-described embodiment, the temperature detecting means 43 is indirectly attached by attaching a temperature sensor that outputs a signal corresponding to the ambient temperature, such as a thermistor or a thermocouple, to the surface of the casing formed of the yoke 34 of the voice coil motor 30. Although the temperature of the permanent magnet 32 is detected, the temperature of the permanent magnet 32 may be detected based on the temperature of the coil 33 by using the conductor temperature detecting means by the calculation unit 52 as the temperature detecting means 43. good.

Further, the calculation unit 52 may perform the processing content of the comparison circuit 53b.
Further, instead of various controls and processing contents performed by software processing, a dedicated device corresponding to the various controls and processing contents may be provided. An analog circuit may be used.

  Moreover, the temperature corresponding to TcaseMiddle and TcaseMAX shown in FIG. 8 is an example, and may be appropriately changed according to various conditions such as the performance of the voice coil motor.

1 is a perspective view of a sewing machine equipped with a thread tension device according to an embodiment of the present invention. It is a disassembled perspective view of a thread tension device. It is sectional drawing along the output shaft of a voice coil motor. It is explanatory drawing which shows the arrangement | positioning state of the temperature detection means with respect to a voice coil motor. It is a block diagram which shows the control system of a thread tension device. It is a circuit diagram of the drive circuit connected to the coil. It is a circuit diagram which shows the flow of the induced electromotive force of the heating current in the case of Fast Decay mode. It is a circuit diagram which shows the flow of the induced electromotive force of the heating current in the case of Slow Decay mode. It is a graph which shows the current waveform and voltage waveform of a coil in ON / OFF control of the heating current in the case of Fast Decay mode. It is a graph which shows the current waveform and voltage waveform of a coil in ON / OFF control of the heating current in the case of Slow Decay mode. It is a graph which shows an example of the temperature change of skin temperature. It is a flowchart which shows the heating current control of the coil by a control apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Thread tension device 21, 22 Thread tension plate 30 Voice coil motor 33 Coil 41 Switching circuit 42 Current value detection means 43 Temperature detection means 50 Control apparatus 51 ROM
52 arithmetic unit 53b comparison circuit 53c control logic 61-64 transistor 65-68 diode 71 power supply

Claims (4)

A thread tension member for applying tension to the sewing thread;
A drive means having a permanent magnet and a coil, and capable of varying the tension of the thread tension member in accordance with a current flowing through the coil;
A switching circuit which is provided between the coil and the power source and can control a current amount from the power source to the coil by PWM control;
Temperature detecting means for detecting the temperature of the permanent magnet;
First storage means for the tension of the thread tension member stores the first temperature is a temperature defined in the appropriate temperature range required for the permanent magnet to produce the intended tension operator,
A first temperature determination means for determining the temperature level of the permanent magnet relative to the first temperature,
Heating control means for controlling the switching circuit during non- sewing and energizing a predetermined heating current to the coil by the PWM control to increase the temperature of the permanent magnet,
Said heating control means, when said temperature of the permanent magnet is determined to less than the first temperature, refluxed an induced current generated in the coil energization OFF period of the PWM control on the power supply side, the If the temperature of the permanent magnet is determined to the be the first temperature or more, the energizing of the heating current to the coil of the induction current and controls the switching circuit so as to circulate in the coil Characteristic sewing thread tension device. Second storing What the first high temperature der than temperature, the second temperature is the upper limit temperature of the suitable temperature range required for the permanent magnet to produce the intended tension of the operator Storage means,
And a second temperature determination means for determining the level of temperature of the permanent magnet relative to said second temperature,
Said heating control means is energized when said temperature of said permanent magnet by the second temperature determining means is determined to satisfy the second temperature, wherein the predetermined heating current to the coil by the heating control means The thread tension device for a sewing machine according to claim 1, wherein the thread tension device is not performed. A conductor temperature detecting means for detecting a conductor temperature of the coil;
A third storage means for storing a third temperature a higher temperature than the second temperature is the temperature at which the coil is overheated,
And a third temperature determination means for determining the level of the conductor temperature for the third temperature,
It said heating control means, when the wire temperature is determined to satisfy the third temperature by said third temperature determination means, perform energization of said predetermined heating current to the coil by the heating control means The thread tension device for a sewing machine according to claim 2, wherein there is no thread tension device. The conductor temperature detecting means is
Resistance value detecting means for detecting a resistance value of the coil;
The thread tension device for a sewing machine according to claim 3, further comprising: a conductor temperature calculating means for calculating the conductor temperature based on the resistance value detected by the resistance value detecting means.

Images