GB2251990A - Sewing motor driving device - Google Patents
Sewing motor driving device Download PDFInfo
- Publication number
- GB2251990A GB2251990A GB9124074A GB9124074A GB2251990A GB 2251990 A GB2251990 A GB 2251990A GB 9124074 A GB9124074 A GB 9124074A GB 9124074 A GB9124074 A GB 9124074A GB 2251990 A GB2251990 A GB 2251990A
- Authority
- GB
- United Kingdom
- Prior art keywords
- sewing
- current
- rotating speed
- sewing motor
- detecting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P7/00—Arrangements for regulating or controlling the speed or torque of electric DC motors
- H02P7/06—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current
- H02P7/18—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power
- H02P7/24—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices
- H02P7/28—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices
- H02P7/285—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices controlling armature supply only
- H02P7/2855—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices controlling armature supply only whereby the speed is regulated by measuring the motor speed and comparing it with a given physical value
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- D—TEXTILES; PAPER
- D05—SEWING; EMBROIDERING; TUFTING
- D05B—SEWING
- D05B69/00—Driving-gear; Control devices
- D05B69/14—Devices for changing speed or for reversing direction of rotation
- D05B69/18—Devices for changing speed or for reversing direction of rotation electric, e.g. foot pedals
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/08—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors
- H02H7/093—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against increase beyond, or decrease below, a predetermined level of rotational speed
Description
1 2 -1 5 1 1 SEWING MOTOR DRIVING DEVICE The present invention relates to
a sewing motor drivinq device.
A known is sewing motor driving device controls the rotating speed of a sewing motor to an externally specified rotating speed (hereinafter referred to as "a speed command") by regulating power being supplied to the sewing motor based on a deviation between a current corresponding to the speed command and a current flowing through a winding of the sewing motor.
Such a sewing motor driving device for driving a sewing motor, for example, a dc motor, limits the allowable maximum winding current for the sewing motor below a fixed current because the deviation and the winding current increase during acceleration after the dc motor has been actuated, entailing the overheating of the winding, breakdown and the demagnetization of the permanent magnet.
In sewing a thick work of fabric, the dc motor is driven for operation at the lowest standard speed to drive the sewing machine. An industrial sewing machine, in particular, is often required to sew a very thick work having a plurality of superposed thick fabrics. In some cases, the dc motor is nearly locked in sewing such a very thick work due to the high resistance of the very thick work to the penetrating action of a needle. Therefore, the allowable maximum current is set to a comparatively high level, and the winding current is increased to the comparatively high allowable maximum current to enhance the penetrating force of the needle when the rotating speed of the dc motor decreases below the lowest standard speed.
As the allowable maximum winding current for the dc motor controlled by the conventional sewing motor driving device is comparatively high, the heat generating 2 rate of the winding increases during acceleration after the dc motor has been actuated and hence the dc motor overheats. Because the dc motor is started, accelerated, decelerated and stopped frequently during use of the sewing 5 machine, the dc motor is liable to overheat.
If the allowable maximum winding current is high, the output torque of the dc motor is excessively high and, consequently, an excessive load acts on the mechanical system of the sewing machine in starting and accelerating the sewing machine, so that the mechanical system wears rapidly.
If the sewing machine is provided with a beltpulley transmission mechanism for transmitting the driving force of the sewing motor to the mechanical system, the effective diameter of the driving pulley fixed on the output shaft of the sewing motor may be reduced to enhance the torque acting on the mechanical system. However, reduction in the effective diameter of the driving pulley reduces the maximum operating speed of the sewing machine, which adversely affects the high-speed operation of the sewing machine.
The invention provides a sewing motor driving device for a sewing machine having a sewing motor comprising:
power supply means for supplying power to said sewing motor; limiting means for limiting the power supplied by said power supply means below a predetermined limit power; detecting means for detecting that said sewing motor is nearly locked and/or that an overload is applied to said sewing motor, and generating a detecting signal; and changing means for increasing the predetermined limit power of-said limiting means when the detection signal is generated by said detecting means.
Preferably the detection means monitors the 3 rotating speed of the sewing motor and produces a signal when that rotating speed falls below a predetermined level.
In a preferred embodiment the invention provides a sewing motor driving device comprising: a power supply means for supplying power to the winding of a sewing motor; a current detecting means for detecting the current flowing through the winding of the sewing motor; a rotating speed detecting means for detecting the rotating speed of the sewing motor; a current control means for controlling the current being supplied by the power supply means, on the basis of the detected rotating speed and an externally specified speed; a current supply limiting means for limiting the current being supplied by the power supply means below a limit current; a decision means for determining if the rotating speed of the sewing motor detected by the rotating speed detecting means is lower than a lowest rotating speed determined previously for the lowest sewing speed of the sewing machine; and a limit current changing means for increasing the limit current below which the current supplied by the power supply means is controlled by the current limiting means when the response to a query made by the decision means is affirmative.
The current control means controls the current supplied by the power supply means on the basis of the rotating speed detected by the rotating speed detecting means and an external speed command, and the current supply limiting means limits the current below a predetermined limit current. For example, if the current is increased to the maximum limit current to adjust the rotating speed of the sewing motor to the specified speed, the maximum current is limited to the limit current. Accordingly, the output torque of the sewing motor is increased to a maximum when the current is increased to the limit current.
If the rotating speed of the sewing motor is reduced to a very low rotating speed due to the resistance, of a very thick work piece, to the action of the needle in sewing the very thick work piece and the decision means determines that the rotating speed of the sewing motor has decreased below the predetermined lowest rotating speed, the limit current changing means increases the limit current. Accordingly, while the sewing motor is operating at a rotating speed below the lowest rotating speed, the winding current is increased beyond the predetermined limit current to increase the output torque of the sewing motor beyond the maximum level.
As mentioned above, according to the invention thus structured, the current supplied to the sewing motor is increased beyond a predetermined limit current to enhance the output torque of the sewing motor only while the rotating speed of the sewing motor is lower than a predetermined lowest rotating speed and, consequently, the sewing motor does not overheat and the mechanical system of the sewing machine is not loaded excessively. Accordingly, the life of the sewing machine and the sewing motor will be prolonged.
Moreover, the effective diameter of the motor pulley need not be reduced and hence the output torque of the sewing motor during operation at a very low rotating speed below the lowest rotating speed is enhanced without reducing the maximum sewinq speed of the sewinq machine.
The invention will be more clearly understood from the following description given by way of example only with respect to the accompanying drawings in which:-
Fig. 1 is an electric circuit diagram of a dc power source and a power supply unit of a sewing machine driving device in a preferred embodiment according to the invention; Fig. 2 is an electric circuit diagram of a speed control unit of the sewing machine driving device; Fig. 3 is an electric circuit diagram of a driving unit of the sewing machine driving device; and Fig. 4 is a timing chart of assistance in explaining the operation of the sewing motor driving device.
Figs. 1 to 3 are electric circuit diagrams of components of the sewing motor driving device embodying the present invention. The sewing motor M is a permanent magnet commutator dc motor. The driving f orce of the sewing motor M is transmitted to a main shaft of a sewing machine so that a mechanical system such as a needle bar driving mechanism (not shown) is driven. An electromagnetic brake B is combined with the sewing motor M to brake the sewing motor M. A foot controller FC is disposed under a sewing table (not shown). The foot controller FC comprises a pedal P, a Hall device HD which provides a pedal comnand signal SSP specifying a rotating speed for the sewing motor M according to the movement of the pedal P, and a switch SW which is opened when the pedal P is depressed. The pedal P has a play to open the switch SW without providing any pedal command signal SSP when the pedal P is moved within the play. When the pedal P is depressed beyond the play, the pedal command signal SSP is provided.
As shown in Figs. 1 to 3, the sewing machine driving device for driving the sewing motor M comprises, as principal components, a dc power source 3 which receives ac power and provides dc power, a power supply unit 5 connected to the dc power source 3 to supply power to the sewing motor M, a driving unit 7 which provides a drive signal SDR for timing the power supply operation of the power supply unit 5, and a speed control unit 9 which controls the rotating speed of the sewing motor M by controlling the pulse duty factor of the driving signal SDR to regulate the power supplied by the power supply unit 5.
As shown in Fig. 1, the de power source 3 is a generally known rectifying and smoothing circuit comprising a diode bridge circuit DB and a smoothing capacitor C.
The power supply unit 5 comprises, as principal components, a power transistor Trl which is driven by the driving signal SDR provided by the driving unit 7 to supply power to the sewing motor M, a commutation diode D1 forming a path for back electromotive force generated in the armature winding (hereinafter referred to simply as "winding") L of the sewing motor M while the power transistor Trl is OFF, and a current detecting resistor Ri for detecting the current i flowing through the winding L. The power transistor Trl is driven by the driving signal SDR of a predetermined frequency provided by the driving unit 7. The period of the on-state of the power transistor Trl is controlled by the pulse width of the driving signal SDR. The winding current i varies according to the period of the on-state of the power transistor Tri, which will be later described.
As shown in Fig. 3, the. driving unit 7 is a generally known switching circuit having a transistor Tr2 as a principal component. The transistor Tr2 is driven by a pulse signal SPW, which will be described subsequently, applied thereto through a photocoupler PH by the speed control unit 9. Power is supplied by the power source VDD of the driving unit to the transistor Tr2, the emitter potential of the power transistor Trl is held at a negative potential, and the driving signal SDR of a pulse width equal to that of the input pulse signal SPW is applied to the base of the power transistor Trl. The period of the on-state of the power transistor Trl, namely, the winding current i, is controlled according to the pulse width of the pulse signal SM As shown in Fig. 2, the speed control unit 9 comprises, as principal components, a speed command circuit 9a which provides a -speed command signal VS specifying a rotating speed for the sewing motor M and a stop signal (VS = 0), a speed detecting circuit 9b which -11 detects the rotating speed N of the sewing motor M and provides a speed detection signal VN, a deviation detecting circuit 9c which detects the deviation between a specified rotating speed S and the detected rotating speed N (AN = S - N) and provides a deviation detection signal V-AN, a current control circuit 9d which regulates the winding current i flowing through the winding L according to the deviation detection signal V-AN and sets an allowable maximum current, a PWM (pulse width modulating) circuit 9e which controls the duty factor of the output pulse signal SPW according to the level of a threshold level signal STH provided by the current control circuit 9d, a maximum current change command circuit 9f which commands the current control circuit 9d to change the level of the threshold level signal STH between a high level and a low level, and a brake control circuit 9g which drives the electromagnetic brake B. The deviation detecting circuit 9c and the current control circuit 9d correspond to a current supply limiting means and the maximum current change command circuit 9f corresponds to a decision means.
The speed command circuit 9a comprises a lowest speed setting circuit ULS consisting of a voltage setting device VR1 and a diode D2 and a pass circuit UPS having a diode D3 which passes the pedal command signal SSP provided by the foot controller FC. The lowest speed setting circuit ULS is connected in.parallel to the switch SW of the foot controller FC and provides a command signal VLS specifying a lowest speed NLS for the normal operation of the sewing motor M when the switch SW is opened.
The speed command circuit 9a gives the lowest speed command signal VLS as the speed command signal VS to the deviation detecting circuit 9c when the pedal P of the foot controller FC is depressed slightly, or up to the end of the play, and gives the pedal command signal SSP provided by the foot controller as the speed command signal VS to the deviation detecting circuit 9c when the pedal P is depressed beyond the play. When the pedal P is released free to close the switch SW, the value of the speed command signal VS is zero.
The speed detecting circuit 9b is a differential amplifier having an operational amplifier OPI as a principal component. The speed detecting circuit 9b receives a voltage Vf across the terminals of the sewing motor M and a current detection signal If provided by a current detecting resistor Ri (the voltage across the terminals of the current detecting resistor Ri corresponds to the current i flowing through the winding L), and gives the speed detection signal VN, i.e., the potential difference between the voltage Vf and the current detection signal If, representing the rotating speed N of the sewing motor M, to the maximum current change command circuit 9f.
The reason for using the potential difference between the voltage Vf and the current detection signal If as the speed detection signal VN is as follows.
A dc commutator motor meets a known expression:
N = K.e = K(Vf - i.r) = K(Vf - If) where r is internal resistance, e (V) is a back electromotive force. N (rpm) is rotating speed, K is a motor constant and i (A) is winding current. The values of Vf and If are expressed in volts (V).
Accordingly, the speed detecting circuit 9b i able to provide the speed detection signal VN corresponding to the rotating speed N of the sewing motor M, if the external resistance of the operational amplifier OP1 is determined according to the motor constant K.
The deviation detecting circuit 9c comprises a differential amplifier DF having an operational amplifier OP2 as a principal component, and a current buffer BF having an operational amplifier OP3 as a principal component. The differential amplifier DF receives the speed command signal VS and the speed detection signal VN respectively from the speed command circuit 9a and the speed detecting circuit 9b, and provides the potential difference between the two signals. The current buffer BF amplifies the current of the signal received from the differential amplifier DF and limits its own output level below a predetermined value by a clamper consisting of a diode D4 and a Zener diode ZD. The clamper limits the output level to a value smaller than the breakdown voltage VZD of the Zener diode ZD in the negative region and to a value smaller than a circuit voltage VCC in the positive region.
Thus, the deviation detecting circuit 9c produces the deviation detection signal V-AN corresponding to the deviation AN between the specified rotating speed S and the actual rotating speed N from the difference between the speed command signal VS and the speed detection signal VN. The deviation detection signal V-AN is a negative value when the speed command signal VS is greater than the speed detection signal VN and is a positive value when the reverse is the case. The deviation detecting circuit 9c provides a reference value VRE, a small negative value, when the values of the two signals VS and VN are equal to each other to suppress the variation of the rotation of the sewing motor M by slightly accelerating the sewing motor M while the sewing motor M is driven for operation at a constant rotating speed.
The current control circuit 9d is an inversion amplifier having an operational amplifier OP4 as a principal component. The gain of the current control circuit 9d is adjusted by an external variable resistor VR2. The current control circuit 9d produces a threshold level signal STH through the inversion amplification of the sum of the current detection signal If and the deviation detection signal V-AN and gives the same to the PWM circuit 9e. Although the maximum value of the threshold level signal STH is dependent basically on the maximum value VZD of the deviation detection signal V-AN, the same is adjusted within a predetermined range by the variable resistor VR2.
A circuit consisting of an analog switch ASW and a changeover resistance RCV is connected in parallel to the variable resistor VR2. When the analog switch ASW is closed, the changeover resistance RCV is connected in parallel to the variable resistor VR2 to increase the gain of the operational amplifier OP4. That is, the maximum level of the threshold level signal STH is increased by a predetermined value by closing the analog switch ASW.
Hereinafter, a maximum level- for the threshold level signal STH when the analog switch ASW is opened is referred to as a lower maximum level, and a maximum level f or the same when the analog switch ASW is closed is referred to as a higher maximum level. The lower maximum level for the threshold level signal STH is determined so that the winding current coincides with a predetermined lower maximum current IMAXL, and the higher maximum level for the same is determined so that the winding current i coincides with a higher maximum current IMAXH higher than the lower maximum current IMAXL. The lower maximum current IMAXL is determined experimentally so that the sewing motor M does not overheat and the higher maximum current IMAXH is determined experimentally so that the sewing motor M is able to produce a sufficient torque to make the needle penetrate a very thick work piece.
The circuit comprising the variable resistor VR2, the analog switch ASW and the changeover resistance RCV corresponds to a limit current changing means.
The PWM circuit 9e is a generally known pulse width modulating circuit having a comparator CP1 as a principal component. The PWM circuit 9e produces the pulse signal SPW through the pulse width modulation of a triangular pulse signal of a predetermined frequency generated by a triangular pulse oscillator OC in accordance with the threshold level signal STH provided by the current control circuit 9d. The pulse width of the pulse signal SPW is dependent on the level of the threshold level signal STH. The pulse signal SPW is transmitted after inversion to the driving unit 7 which is electrically isolated from the speed control unit by the photocoupler PH.
1 is a comparator CP2. detection signal circuit 9b and a Thus, the period of the on-state of the power transistor Trl of the power supply unit 5, namely, the level of the winding current i, is controlled by changing the level of the threshold level signal STH.
The maximum current change command circuit 9f has The comparator CP2 compares the speed VN provided by the speed detecting voltage signal VBS set by a voltage setting device VR3, and provides a drive signal SSW to close the analog switch ASW when the speed detection signal VN is lower than the voltage signal VBS. Thus, the analog switch ASW is closed when the speed detection signal VN is lower the maximum output than the voltage signal VBS to raise level of the current control circuit 9d by a predetermined value.
The voltage signal VBS represents a very low speed NBS below the lowest standard speed NLS (VLS) for the sewing motor M. The very low speed NBS is determined with reference to the lowest possible rotating speed of the sewing notor M dependent on the electrical specifications of the sewing motor M and the construction of the inechanical system of the sewing machine and data obtained by sewing a very thick work piece.
The brake control circuit 9g comprises a comparator CP3 and a transistor TR3 through which a current is supplied to the solenoid BL of the electromagnetic brake B to apply the electromagnetic brake B. if the deviation detection signal V-AN"provided by the deviation detecting circuit 9c is on a positive level, the output of the comparator CP3 goes HIGH to turn on the transistor Tr3 and, consequently, the electromagnetic brake B is actuated.
The operation of the sewing motor driving device and the sewing motor M will be described with reference to a timing chart shown in Fig. 4.
As shown in Fig. 4, when the pedal P is depressed slightly to command the lowest standard speed NLS, the negative deviation detection signal V-AN between the speed command signal VS (VLS) and the speed detection signal VN exceeds the negative reference value VRE and the pulse width of the pulse signal SPW increases. The transistor Tr2 of the driving unit 7 provides the drive signal SDR according to the pulse signal SPW to drive the power transistor Tri of the power supply unit 5. Then, the' winding current i increases to accelerate the sewing motor M until the rotating speed of the sewing motor M reaches the lowest standard speed NLS. As the rotating speed of the sewing motor M increases, the negative deviation detection signal V-AN decreases to the negative reference value VRE and, consequently, the winding current i is held constant.
When the pedal P is depressed further, the negative deviation detection signal V-AN increases and reaches the negative maximum value VZD, and hence the pulse width of the pulse signal SPW increases to a maximum. Consequently, the winding current i increases to and is held at the lower maximum current IMAXL, the rotating speed N of the sewing motor M increases to the specified rotating speed S, and the negative deviation detection signal V-AN decreases to the negative reference value VRE. Upon the coincidence of the rotating speed N with the specified rotating speed S, the deviation detection signal VAN reaches the reference value VRE and, consequently, the winding current i is held constant and the sewing motor M operates at the specified rotating speed S.
As shown in Fig. 4, the speed command signal VS decreases to the value VLS corresponding to the lowest speed NLS and the deviation detection signal V-AN becomes positive. Then, the electromagnetic brake B is actuated to reduce the rotating speed N of the sewing motor M to the lowest speed NLS, the pulse width of the pulse signal SPW approaches zero and, consequently, the winding current i decreases sharply. Upon the coincidence of the rotating speed N with the lowest speed NLS, the deviation detection signal V-AN becomes negative, the electromagnetic brake B c is released and, consequently, the rotating speed N is fixed at the lowest speed NLS.
Suppose that the sewing machine starts sewing a very thick superposed portion in a thick work piece with the sewing motor M operating at the lowest. speed NLS. Then, the needle is subjected to the high resistance of the thick work piece, so that the rotating speed N of the sewing motor M decreases below the lowest speed NLS, the negative deviation detection signal V-AN increases and eventually reaches the negative maximum value WD. Consequently, the pulse width of the pulse signal SPW increases to the maximum width and the winding current i increases to the lower maximum current IMAXL.
In some cases, the rotating speed N of the sewing motor M decreases to a value below the very low speed NBS and the sewing motor M is nearly locked if the needle is unable to penetrate the very thick superposed portion of the work piece even though the winding current i is increased to the lower maximum current IMAXL to increase the output torque of the sewing motor M. In such a case, as shown in Fig. 4, speed detection signal VN drops below the voltage signal VBS corresponding to the very low speed NBS and the analog switch ASW is closed. Consequently, the level of the threshold level signal STH is raised and the pulse width of the pulse signal SPW is increased to increase the winding current i to the higher maximum current IMAXH.
Consequently, the output torque of the sewing motor M is enhanced to enable the needle to penetrate the very thick superposed portion of the thick work piece. After the needle has completed sewing the very thick superposed portion of the work, the rotating speed of the sewing motor M rises above the very low speed NBS, the analog switch ASW is opened, the threshold level signal STH returns to the low level and the winding current i decreases to the lower standard maximum current IMAXL. After the rotating speed N returns to the lowest speed NLS, the deviation detection signal V-AN is stabilized at the reference value VRE and the winding current i is stabilized at the current corresponding to the lowest speed NLS.
When the pedal P is released, the switch SW is closed. Then, the speed command signal VS drops to zero and, at the same time, the deviation detection signal V-AN becomes positive. Consequently, the electromagnetic brake B is actuated to brake the sewing motor M and power supply is stopped to stop the sewing motor M.
Thus, the sewing machine driving device in this embodiment limits the winding current i (power) to a value below the lower standard maximum current IMAXL in starting the sewing motor M and in accelerating the same from the lowest speed NLS, and increases the winding current i from the lower standard maximum current IMAXL to the higher standard maximum current IMAXH to enhance the output torque of the sewing motor M when the rotating speed N decreases below the very low speed NBS, for example, when the sewing motor M is nearly locked while the sewing machine is sewing a very thick work piece. Accordingly, the overheating of the sewing motor M is prevented and the sewing machine is able to sew a very thick work piece smoothly.
Furthermore, although the sewing motor may overheat due to the repetition of a cycle of acceleration from the lowest speed and deceleration similar to the sewing motor driven by the conventional sewing motor driving device for sewing a very thick work piece, the mechanical system of the sewing machine is not loaded excessively, and hence the respective service lives of the sewing motor M and the sewing machine are extended.
since the effective diameter of the motor pulley reduced, the output torque of the sewing motor M operation at a low rotating speed can be enhanced reducing the maximum sewing speed.
In this embodiment, the maximum current for the current i is changed from the lower standard current to the higher standard maximum current is not during without winding maximum when the rotating speed of the sewing motor M decreases below the lowest rotating speed. However, it is also possible to raise the maximum limit current for the winding current i when the rotating speed of the sewing motor M drops below the lowest rotating speed NBS and the deviation detection signal V-AN increases beyond a predetermined level.
16
Claims (5)
1. A sewing motor driving device for a sewing machine having a sewing motor comprising:
power supply means for supplying power to said 5 sewing motor; limiting means for normally limiting the power supplied by said power supply means below a predetermined limit power; detecting means for detecting that said sewing motor is nearly locked and/or that an overload is applied to said sewing motor, and generating a detecting signal; and changing means for increasing the predetermined limit power of said limiting means when the detection signal is generated by said detecting means.
2. The sewing motor driving device according to claim 1, further comprising:
rotating speed detecting means for detecting a rotating speed of said sewing motor; and judging means for judging whether the rotating speed of said sewing motor detected by said rotating speed detecting means is lower than a predetermined speed, wherein said detecting means generates the detecting signal when a judgement of said judging means is affirmative.
3. A sewing motor driving device for a sewing machine in accordance with claim 2 in which:
said power supply means supplies a current to a winding of said sewing machine; and said limiting means, detecting means and changing means comprise:- a current detecting means for detecting the current flowing through the winding of said sewing motor; rotating speed detecting means for detecting the rotating speed of said sewing motor; current control means for controlling the current 35 supplied by said power supply means based on the detected 1 1 17 rotating speed and an externally specified speed; current supply limiting means for limiting the current supplied by said power supply means below a predetermined limit current; decision means for determining if the rotating speed of said sewing motor detected by said rotating speed detecting means is lower than a lowest rotating speed determined previously for a lowest sewing speed of said sewing machine; and limit current changing means for increasing the predetermined limit current below which the current supplied by said power supply means is controlled by said current limiting means when a decision of said decision means is affirmative.
4. A sewing motor driving device substantially as hereinbefore described by reference to the accompanying drawings.
5. A sewing machine with a sewing motor driving device according to any of claims 1-6.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2320069A JPH04189392A (en) | 1990-11-22 | 1990-11-22 | Driving device for sewing machine motor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9124074D0 GB9124074D0 (en) | 1992-01-02 |
| GB2251990A true GB2251990A (en) | 1992-07-22 |
Family
ID=18117376
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9124074A Withdrawn GB2251990A (en) | 1990-11-22 | 1991-11-13 | Sewing motor driving device |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPH04189392A (en) |
| DE (1) | DE4134527A1 (en) |
| GB (1) | GB2251990A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1772994B (en) * | 2004-11-12 | 2011-07-20 | 爱信精机株式会社 | Sewing machine |
| CN107241038A (en) * | 2016-03-28 | 2017-10-10 | 陈宣泰 | Closed loop control device and method for mechanical sewing machine |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001038087A (en) * | 1999-07-29 | 2001-02-13 | Juki Corp | Controller for sewing machine motor |
| DE10259732A1 (en) * | 2002-12-19 | 2004-07-01 | Delphi Technologies, Inc., Troy | Control circuit for a motor vehicle windscreen wiper direct current motor, has a switching element to which a pulse modulated control signal is applied to for continuous control of motor speed |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1153929A (en) * | 1966-09-23 | 1969-06-04 | Mefina Sa | Improvements in or relating to A Sewing Machine Speed Control Device |
| GB2081033A (en) * | 1980-07-31 | 1982-02-10 | Lien Chich Li | Sewing Machine |
| US4384241A (en) * | 1979-10-19 | 1983-05-17 | Fritz Gegauf Aktiengesellschaft Bernina-Nachmaschinenfabrik | Sewing machine drive |
| GB2183412A (en) * | 1985-09-27 | 1987-06-03 | Porsche Ag | Overload protection circuit |
| GB2238677A (en) * | 1989-10-11 | 1991-06-05 | Patrick John Elderkin | Power economiser motor control system |
-
1990
- 1990-11-22 JP JP2320069A patent/JPH04189392A/en active Pending
-
1991
- 1991-10-18 DE DE4134527A patent/DE4134527A1/en not_active Withdrawn
- 1991-11-13 GB GB9124074A patent/GB2251990A/en not_active Withdrawn
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1153929A (en) * | 1966-09-23 | 1969-06-04 | Mefina Sa | Improvements in or relating to A Sewing Machine Speed Control Device |
| US4384241A (en) * | 1979-10-19 | 1983-05-17 | Fritz Gegauf Aktiengesellschaft Bernina-Nachmaschinenfabrik | Sewing machine drive |
| GB2081033A (en) * | 1980-07-31 | 1982-02-10 | Lien Chich Li | Sewing Machine |
| GB2183412A (en) * | 1985-09-27 | 1987-06-03 | Porsche Ag | Overload protection circuit |
| GB2238677A (en) * | 1989-10-11 | 1991-06-05 | Patrick John Elderkin | Power economiser motor control system |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1772994B (en) * | 2004-11-12 | 2011-07-20 | 爱信精机株式会社 | Sewing machine |
| CN107241038A (en) * | 2016-03-28 | 2017-10-10 | 陈宣泰 | Closed loop control device and method for mechanical sewing machine |
| CN107241038B (en) * | 2016-03-28 | 2019-07-05 | 陈宣泰 | Closed loop control device of mechanical sewing machine |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04189392A (en) | 1992-07-07 |
| DE4134527A1 (en) | 1992-05-27 |
| GB9124074D0 (en) | 1992-01-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |