JPS6070991A - Drive device for sewing machine - Google Patents

Abstract

PURPOSE:To endure against the operation at a middle speed for a long period by composing a motor coupled with a low inertial frictional electromagnetic type brake and a control mechanism for the brake in a brushless motor. CONSTITUTION:When a pedal 51 is depressed, e1 becomes a positive voltage, a motor 61 starts rotating to drive a sewing machine through a belt, compares with a sewing machine speed e2, a PWM 56 applies a pulse waveform of a duty along this feedback loop to the following drive circuit 59, thereby rotating the sewing machine at the speed in response to the depressing amount of the pedal 51. When the pedal 51 is returned to the neutral, a discriminator 54 outputs a low speed set signal e1', a comparator 53 compares it with a speed signal e2', and the motor is shifted to a low speed. Then, when a needle position signal 66 is inputted, a low speed set signal e1' is set, a brake 63 is driven by a drive circuit 60, and a motor 61 is stopped at the needle stopping position of the sewing machine.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 2'' The present invention relates to a sewing machine drive device, and particularly to a sewing machine drive device that performs variable speed operation including stopping the sewing machine and stopping the sewing machine needle at a fixed position.

Conventional Structure and Problems An industrial sewing machine and its driving device generally have the structure shown in FIG. In Fig. 1, 1 is a sewing machine head, 2 is a detector for detecting the speed and needle position of the sewing machine, and 3 is a sewing machine head.
Reference numeral 4 indicates a drive motor, 4 a control unit that receives signals from the detector 2 and the pedal and controls the drive motor 3 and the solenoid of the sewing machine, 5 a sewing machine table, and 6 a sewing machine pedal.

The conventional structure of this drive motor 3 is as shown in FIG. This electric motor has a structure in which an induction motor and a clutch/brake mechanism are integrated. The drive shaft 7 of the induction motor, the flywheel 8 and the clutch friction disk 9 coupled thereto rotate continuously, and the flywheel 8 stores rotational energy. The movable clutch disc 1o and the movable brake disc 11 can slide in the axial direction on the spur line 13 of the spur 31 press-fitted into the output shaft 12, and each has a lining 14, 15 bonded thereto. Now, when the clutch electromagnet 16 is excited, a magnetic flux 17 is generated, the clutch movable disk 1o moves to the left, the lining 14 is pressed against the continuously rotating friction disk 9, and the rotational force of the flywheel 8 is It is transmitted to the output shaft 12 via the spline 13. Next, when the brake electromagnet 18 is excited, the movable brake disc 11 moves to the right, the lining 15 comes into pressure contact with the brake friction disc 2o fixed to the placket, and the output shaft 12 quickly stops. The rotational force of the output shaft 12 is normally transmitted to the sewing machine head 1 via a belt. The speed of the sewing machine is controlled by feeding back the speed signal detected by the detector 2 and adjusting the excitation current of the clutch electromagnet 16 to produce a half-clutch state.

In recent years, with the increasing functionality of industrial sewing machines and the development of automatic sewing machines, there has been a strong tendency for this drive motor to be used for long periods of time at an intermediate speed instead of being stopped as in the past.

In the electric motor with the conventional structure shown in Fig. 2, the intermediate speed is
As mentioned above, since the lining 14 is allowed to slip and is used in a half-clutched state, wear of the lining is accelerated and the service life is not sufficient. This lining is generally composed of cork as its main component, but methods such as impregnating it with special oil or applying grease containing molybdenum disulfide as its main component have been put into practical use. Although considerable longevity has been achieved through attempts to improve heat dissipation to the maximum extent possible, there are still limitations such as periodic application of grease and the need to change the lining.

In order to improve this problem of lifespan, a method has been proposed in which the friction type electromagnetic clutch is replaced with an eddy current clutch, and has been put into practical use in some cases. Since this method transmits the rotational force of the flywheel to the output shaft without contact, it has clearly improved the life of the various clutches mentioned above, but on the other hand, it has the fatal drawback of not being able to obtain sufficient transmission torque. has. Engineering 6, - - - The performance required for the drive motor of a commercial sewing machine is the first
The second reason is that the acceleration/deceleration is fast (acceleration/deceleration time to 4ooorpm is about 1oOnIS), and secondly, it requires instantaneous large torque (about 1.0kg・m) when sewing thick materials such as jeans. In the current clutch method, an eddy current generating disk (
! There was a limit to the performance of these products due to thermal deformation of the parts (or cups).

Furthermore, both the friction electromagnetic clutch method and the eddy current clutch method have the disadvantage that they consume unnecessary power because the drive motor is constantly kept rotating regardless of whether the sewing machine is running or stopped. Normally, the operating time of a sewing machine is 20 to 30%, and the remaining 70 to 80% of the time the electric motor is idle, and the time is 1φ40.
A ciW motor wastes about 1ooW, and a 3φ400W motor wastes about eioW.

OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned conventional drawbacks, endures long-term operation at intermediate speeds, achieves energy savings, and
The aim is to obtain good stopping characteristics.

Composition of the Invention The sewing machine drive device of the present invention has a permanent magnet in the rotor,
It consists of a so-called brushless motor that switches the energization phase of the stator winding according to the rotor position, a low-inertia friction-type electromagnetic brake combined with an electric motor, and its control mechanism, eliminating all of the drawbacks of conventional motors. The purpose of the present invention is to provide a new sewing machine driving device.

Description of examples Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a structural sectional view of the drive motor. In Fig. 3, 21 is a base attached to the sewing machine table;
2 is a frame, and 23 is a stator core, which has, for example, 24 slots. A stator winding 24 is embedded in the slot and connected to the stator winding. A permanent magnet 25 is bonded to the yoke 26 and magnetized into four poles in the circumferential direction.

In addition, the outer circumference of the permanent magnet 25 is taped with a taper 7/ for reinforcement.
−・ Processed. 27 is the shaft, 28 is the placket, 29
is a pole sensor magnet for detecting the position of the rotor, and like the magnet 25, it is magnetized into four poles. 3o is a printed circuit board, and three magnetic sensors are arranged in the circumferential direction at positions facing the magnet 29. 31 is a brake friction disk made of a magnetic material, 32 is a brake boss made of a non-magnetic material H such as aluminum, a lining 33 is adhered to the end face, and at the same time it is fixed to the shaft with a key 34. 35 is a brake electromagnet, 36 is a screw dovetail, and a pin 38 is fixed to the bracket 28.

Reference numeral 37 denotes a sleeve support, which is fixed to the brake friction disk 31 by a press-fit method. 39 is a coil spring which lightly presses the friction disk 31 against the lining. 4o
is a cover, 41 is a pulley, 42 is a pulley cover, and 43 is a cooling fan.

The stator winding 29 is controlled by switching the energization phase and performing PWM (pulse width variation) control using the method described below.
Torque of any magnitude in any direction can be generated on the rotor magnet 26.

The brake friction disk 31 is movable in the axial direction by sliding between the pin 38 and the cylindrical bearing 37 and is supported in a fixed manner in the rotational direction, so when the brake electromagnet 35 is energized, it is pressed against the lining 33 and the brake boss 32 via which the shaft 27 comes to a rapid stop.

FIG. 4 shows the drive circuit of the drive motor. The stator windings 24 in FIG. 3 are connected as indicated by R, S, and T. Power transistor T1
．． T2. T3. T4. T5. T6 are connected in a three-phase bridge configuration, and T1. Connection point of T4.

T3. Connection point of T6, T5. The connection point of T2 is connected to the aforementioned R, S, and T phase windings, respectively, and each transistor is connected to a flywheel diode D1. D2. D3. D4
D5. D6 is connected. magnetic sensor P for detecting the position of the rotor magnet 25], + P2 + P3
The signal is input to a distribution circuit 58 and is configured to drive the power transistor via an amplification circuit 67.

FIG. 6 shows details of the distribution circuit 68 in the form of a time chart. Sections 1 to 6 indicate the case where the forward rotation torque 9 is generated at the knee, and sections 1' to 6' indicate the case where the reverse rotation torque is generated. T1 to T6 are power transistors, and the shaded portions indicate the on state. e
R+ eB + eT are the R phases of the stator windings, respectively.

It shows the voltages applied to the S phase and the T phase, and the shaded area shows the application state of positive or negative voltage.

eHB + eB T l elR indicates the line-to-line applied voltage, and the shaded area indicates the application state of positive or negative voltage.

First, looking at the first section, power transistors T1 and T
When 6 is on, the R phase is connected to the +E power supply.

A current flows through the S phase and returns to the -E power supply, and the voltages of each phase become as shown in FIG. 5, and a rotational torque in the positive direction is generated due to the relationship with the rotor magnet 25. When entering the next second period, transistor TI continues to be on, T6 is turned off, and T2
By turning on, current flows from the R phase to the T phase, and rotational torque in the positive direction continues.

When the distribution circuit 58 is switched by a signal from a determination circuit to be described later, it is switched to sections 1' to 6', and the 6th
In the state shown in the figure, a voltage of 1 ol.- is applied to the stator winding, and rotational torque in the opposite direction is generated.

FIG. 6 shows a block diagram of the entire embodiment. 51 is a sewing machine pedal, which corresponds to 6 in FIG.

A pedal position detector 52 converts the amount of displacement of the pedal into an electrical signal and outputs a speed setting signal e1.

The comparison circuit 63 receives the front Mf1 and the sewing machine speed signal e, which will be described later.
2 and outputs a signal eo""e1e2.

The determination circuit 54 is a circuit that outputs a low speed setting signal e1' when the pedal is changed from the depressed state to the neutral state, and also outputs an AND output of the condition that the pedal position is neutral and the condition that the needle position signal is present. The amplification circuit 65 receives the output e of the comparison circuit.

The signal is amplified and outputted as Keo. The PWM circuit (pulse width modulation circuit) 56 is a switching regulator, and the PWM circuit (pulse width modulation circuit) 56 is a switching regulator.

It receives an input and outputs an output whose data changes at a constant frequency (around 2KHz). The determination circuit 57 is a circuit that determines whether the output Keo of the amplification circuit 55 is positive or negative. The distribution circuit 58 receives the ball sensor output described later and the determination circuit 5 described above.
This is a logic circuit which receives the output of No. 7 and gives an output as shown in FIG. 511/-- to the drive circuit 59. The drive circuit 59 is as shown in FIG. The drive circuit 60 uses the output of the determination circuit 64 to
This is a circuit that drives a brake 63, which will be described later. electric motor 61
．． The ball sensor 62 and the brake 63 are all as described in detail in FIG. The speed detector 64 generates a pulse with a frequency proportional to the speed of the sewing machine, which is converted into an analog signal e2 by a subsequent F//v converter 66. The needle position detector 66 obtains a needle position signal using a photogravitational or magnetic method, and inputs the signal to the determination circuit 54 described above.

Next, the operation shown in FIG. 6 will be explained.

When the pedal is in the neutral state, e1=o, and since the sewing machine is not running, e2=O, so eo-K
eo=O. Therefore, the electric motor 61 does not operate. When the pedal 61 is depressed, el becomes a positive voltage, the electric motor 61 starts rotating, the sewing machine is driven via the belt, and the speed is compared with the sewing machine speed e2. 4) By applying the pulse waveform of the data to the subsequent drive circuit 59, the electric motor 61 generates the necessary torque, and the sewing machine rotates at a speed corresponding to the amount of depression of the pedal 51. When the amount of pedal depression is returned, the width increaser circuit 56
The output of Akira. becomes negative, the determination circuit 57 switches the distribution circuit 58 to the section 1' to 6' in FIG. Then, the sewing machine decelerates, and when the speed reaches a speed corresponding to the amount of pedal depression, the electric motor 61 is again switched to positive rotational torque and shifts to stable operation.

When the pedal 61 is returned to the neutral position, the determination circuit 64 outputs the low speed setting signal e1', which is compared with the speed signal e2 in the comparison circuit 53, and the motor shifts to low speed as described above.

Thereafter, by inputting the needle position signal 66, the low speed setting signal ef is reset and a signal is output to the drive circuit 60, the drive circuit 60 drives the brake 63, and the electric motor 61 stops at the needle position of the sewing machine. do.

1st', -3' FIG. 7 shows the above-mentioned operation in a time chart. P, indicates the pedal depression state, M (FW) indicates the forward energization state to the motor stator winding, V (BY) indicates the reverse energization state to the motor stator winding, and BR indicates the brake state. ND indicates the energization state, ND indicates the output signal of the needle down state of the sewing machine, and sp indicates the sewing machine speed. Regarding the sewing machine speed SP, 81 indicates a high speed state, and S2 indicates a low speed state.

When the pedal is depressed at time tl, a pulse voltage in the forward rotation direction is applied to the electric motor, accelerating the sewing machine speed sp, and when the sewing machine speed approaches the set speed S1, the above-mentioned PWM circuit reduces the duty of the output pulse and adjusts the time. It reaches S2 and shifts to a stable speed. Although not shown, by adjusting the amount of depression of the pedal PD, the duty of the pulse voltage applied to the motor changes, and the sewing machine speed sp can be freely adjusted accordingly. At time t3, when the pedal is returned to neutral, a pulse voltage in the reverse rotation direction is applied to the motor.
It is operated at 2. Then, at time t5, the needle signal is 5JN.
When D is input, brake BR is driven and the sewing machine stops at the needle down position. After a certain period of time, at time t6, the brake excitation is released and the brake is released.

Effects of the Invention As is clear from the above description, the present invention transmits the rotational force of an electric motor directly to the sewing machine without using a clutch, and connects the electric motor to a rotor having a permanent magnet and a stator winding connected in three phases. The electric current to the stator winding is PW
M control enables variable speed operation, and by configuring the permanent magnet with a material with high magnetic flux density and small external dimensions, low inertia can be achieved, and the starting torque of the direct motor can be reduced. Coupled with the basic characteristic of being large, it is possible to realize extremely fast variable speed and deceleration performance, as well as instantaneous large torque generation suitable for sewing thick materials.

At the same time, since there are no contact parts or sliding parts on the drive side, it is possible to achieve an extremely long life that can sufficiently withstand continuous intermediate speed operation. Since the sewing machine drive motor is driven only when the sewing machine is operating, it is possible to realize a sewing machine driving device with extremely low power consumption.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing a configuration example of a general sewing machine and a sewing machine drive device, Fig. 2 is a sectional view showing the structure of a conventional drive motor, and Fig. 3 is a sectional view showing the structure of the drive motor section of the present invention. 4 is a circuit diagram showing the drive section of the present invention, and FIG. 6 is a time chart showing the operation of the distribution circuit of the present invention.
The figure is a block diagram showing the overall operation of the present invention, and FIG.
It is a time chart for supplementary explanation of the operation|movement of a figure. 24...Stator winding, 25...Permanent magnet, 29...Pole sensor magnet, 51...
...Pedanope52...Pedal position detector, 56.
... PWM circuit, 69 ... Drive circuit, 6
2... Ball sensor, 64... Speed detector, 66... Needle position detector. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A sewing machine drive mechanism having an electric motor and a braking device, a sewing machine speed detector and a sewing machine needle position detector connected to the output side of the electric motor, and a speed control mechanism that controls the speed of the electric motor according to the pedal position of the sewing machine. The electric motor includes a stator winding connected in three phases, a rotor having a permanent magnet, and a position detection element for detecting the position of the rotor,
The speed control mechanism includes an error amplification circuit that generates a PWM waveform based on the difference between the pedal position signal and the speed detector signal, and a stator winding phase of the motor according to the output signal of the position detection element. What is claimed is: 1. A sewing machine driving device comprising: a switching drive circuit; and the drive circuit is configured to invert a phase of energization to the stator winding based on an output of the error amplification circuit.