JPH0446590A - Sewing machine motor drive device - Google Patents

Abstract

PURPOSE:To protect a discharge circuit against overvoltage without depending on a fuse by stopping discharge until output voltage of a DC power supply drops below a predetermined level and sustaining power supply to conducting phase windings. CONSTITUTION:When the voltage of an AC power supply 3 exceeds a rated voltage and thereby a source voltage VDC exceeds a voltage limit Vref, a remarkably larger amount of charge is stored in a capacitor 5b as compared with regenerative charges and several mS to several seconds may be required for the source voltage VDC to drop below the limit voltage Vref through discharge of capacitor. When the discharge time exceeds a time limit, logic signal S3 of a flipflop FF goes Low thus pulling the stop signal Sstop of an AND circuit Low. Consequently, a transistor Trd is turned OFF to stop discharge. At the same time, output signals S3 from the flipflop FF are fed to a conduction control circuit 20 and a latch circuit 30 and a phase winding current 1 having maximum current level is fed to phase windings Lu-Lw thus protecting a discharge circuit 9 without blowing a fuse F.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a driving device for a sewing machine motor.

[Prior Art] Traditionally, as a driving device for a sewing machine motor, a sewing machine motor rectifies an alternating current power source to create a direct current. Sewing machine motors that drive or brake (so-called inverter operation) are known. In this type of drive device, when braking, magnetic energy is accumulated in the phase windings due to the power generation action of the sewing machine motor. As the power is regenerated in the capacitor attached to the power supply, a discharge circuit is installed to discharge the charge in the capacitor in a timely manner to prevent the voltage of the DC power supply from rising too much.For example, if the voltage is discharged for a few milliseconds, The voltage of the DC power supply is made to drop below the limit voltage.

By the way, in sewing factories, etc., the voltage of the AC power supply that feeds the sewing machine motor rises above the rated voltage due to the influence of power receiving/distribution equipment and other cage-type induction motors, and as a result, the voltage of the DC power supply exceeds the limit voltage. It may rise above. In such a case, the charge accumulated in the capacitor is much larger than the regenerative charge mentioned above, and even if it is not discharged for several hundred milliseconds to several seconds, the power supply voltage will not fall below the limit voltage. .

If the discharge time becomes longer in this way, there is a risk that the discharge circuit will be damaged by heat, so it is considered that the discharge circuit can be protected by installing a fuse that melts due to the weekly current and forcibly stopping the discharge.

[Problem to be Solved by the Invention] However, the drive device with the above-mentioned protective fuse added is one step above.
Every time a fuse blows out, the sewing machine motor has to stop running and the fuse needs to be replaced, which is very time-consuming and can interfere with sewing work if the AC power supply voltage rises frequently. Ta.

Therefore, it is an object of the present invention to provide a sewing machine motor drive device that can protect a discharge circuit from overvoltage without relying on a good fuse.

[Means for Solving the Problems] The gist of the present invention is to provide a direct current power source that rectifies alternating current input from an alternating current power source, smooths it with a power storage means, and outputs direct current; An energizing means for energizing a wire, a control means for driving or braking the sewing machine motor by controlling the energization timing of the energizing means, and storing magnetic energy stored in each phase winding as an electric charge when the sewing machine motor is braked by the control means. In the sewing machine motor drive device, the sewing machine motor drive device includes a discharge means for discharging the electric charge accumulated in the power storage means when the output voltage of the DC power supply exceeds a predetermined voltage value, and a discharge means for discharging the electric charge accumulated in the power storage means; a determining means for determining whether or not exceeds a predetermined voltage value for a predetermined period; and when the determining means makes an affirmative determination, stopping discharging by the discharging means until the output voltage of the DC power source falls below the predetermined voltage value. and energization continuation means for controlling the energization means to continue energizing the phase windings that were energized at the time of the affirmative determination.

According to the sewing machine motor drive device of the present invention constructed as described above, when the sewing machine motor is braked by the song control means, the magnetic energy accumulated in the phase winding is transferred to electric charge by the power regeneration means. As the charge of the power storage means increases, the output voltage of the DC power supply exceeds a predetermined voltage value.Then, the discharge means discharges the charge of the power storage means, and as a result, the output voltage of the DC power supply increases. It goes down quickly.

However, for some reason, when the voltage of the AC power supply rises above the rated value, the charge stored in the storage means is much greater than the regenerated charge, and even if the discharge means discharges the charge, the output voltage of the DC power supply will be It does not go down easily, and the duration of discharge by the discharge means exceeds a predetermined period. Then, the determining means makes an affirmative determination.

As a result, the energization continuation means stops discharging by the discharging means until the output voltage of the DC power source falls below a predetermined voltage value, and controls the energization means to connect the phase windings that were energized at the time of the affirmative determination. Continue to energize. Since the period during which current is applied to the phase winding is extended, the current flowing through the phase winding increases, and the charge stored in the power storage means is rapidly reduced.

Therefore, the output voltage of the DC power supply (quickly drops below a predetermined voltage value).

U example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an electric circuit diagram showing a sewing machine motor drive device to which Yoshiki's invention is applied.

As shown in the figure, the drive device 11 includes a DC power supply 5 that rectifies the AC input from the AC power supply 3 to create DC, an energizing circuit 7 for energizing the AC motor M for driving the sewing machine, and the DC power supply 5. A DC power supply 5 provided between the
a discharge circuit 9 which discharges when the voltage of The main part includes an energization lock command circuit 13 that instructs to lock the energization state of the AC motor M.

A DC power supply 5 (composed of a diode bridge circuit 5a, which is well known as a rectifier circuit, a smoothing capacitor 5b, and its protective resistor 5C).

In this embodiment, the capacitor 5b corresponds to the above-mentioned power storage means.

The energizing circuit 7 (so-called inverter) includes six power transistors (hereinafter simply referred to as transistors) that turn on/off energization to each phase winding Lu, Lv, Lw of the AC motor M: Tru, Trv, Trw, Trx.
, T ry, T rz, and each phase winding u, Lv, L
6 commutating diodes D for regenerating charge from w]
The phase winding Lu is connected to the connection point Pu between the transistors Tru and Trx, and the phase winding Lu is connected to the connection point Pu between the transistors Tru and Trx.
The phase winding Lv is connected to the connection point Pv with the transistor Tr.
A phase winding Lw is connected to a connection point Pw between w and Trz, respectively.

In this embodiment, commutation diodes D to D6 correspond to power regeneration means.

Discharge circuit 9 (a series circuit consisting of a parallel circuit of a supply power consumption resistor R1 and a diode DIO, a fuse F for circuit protection, and a transistor Trd for switching), when the transistor Trd is turned on, the charge accumulated in the capacitor 5b is However, from the power consumption resistor R1 to the transistor Tr
d and is consumed by causing the power consuming resistor R1 to generate heat.

Energization control unit 11 (each phase winding Lu, L by friend energization circuit 7
The energization control circuit 20, which controls the rotation of the AC motor M by controlling the timing of energization to V and Lw, generates the energization control signal Spwm that determines the energization period and the energization period by the energization circuit 7, and the switching pulse UB. -Distributor 2 that outputs ZB to the bases of each transistor Tru to Trz
It is composed of 2 and 2 as the main parts.

The energization control circuit 20 (a well-known pulse width modulation control circuit, which detects the rotational speed and direction of rotation of the AC motor M with detection signals SENI and SEN2 from two encoders EN) and the sewing machine table ( A speed command signal SS from a speed command device SP that commands the operating speed of the sewing machine according to the amount of depression of a foot pedal P provided on a path (as shown in the figure)
Based on P, the energization control signal 5t) WITI 0N-
The OFF duty is determined and output to the distributor 22.

Further, when a signal S3 (described later) is input from the energization control circuit 20 [1 flip-flop FF, the energization control signal Sp
It is configured to maximize the ON pulse width of wm and output it to the distributor 22.

Note that the configuration of the energization control circuit 20 is well known for inverter control, so the details will be omitted.

The distributor 22 is made up of a well-known logic element circuit (path shown), and receives the energization control signal Spwm from the energization control circuit 20 and the magnetic sensor SEN that detects the magnetic pole position of the AC motor M via the latch circuit 30. Each phase winding Lu, Lv, L is connected in a predetermined sequence based on the magnetic pole detection signal Smg.
(2. Each transistor Tru-Trz
The base 1 switching pulse US-ZB is outputted to control the ON-FF of each transistor Tru-Trz.

For example, when driving the AC motor M, the transistors Tru-Trw are driven in the circulating order of the transistors Tru-Trv-Trw based on the magnetic pole detection signal Smg at the timing to generate forward rotation torque, and the magnetic pole detection signal Based on Smg and energization control signal Spwm,
When transistor Tru is ON, transistor Try
-Trz, when transistor Trvh<ON, transistor Trz-Trx, transistor Trwf)<ON
At this time, the transistors Trx-Trz are chopper-driven in the sequence Trx-Try.

On the other hand, during deceleration operation of the AC motor M, at the timing when reverse rotation torque is generated, the transistors Tru to Trw are driven in the same circulation order as during driving based on the magnetic pole detection signal Smg, and the magnetic pole detection signal Smg and the energization control signal S are driven.
The transistors Trx-Trz are chopper-driven in the same sequence as in driving based on pwm.

The AC motor M is operated in this way, and its rotational speed is determined by the duty ratio of the energization control signal Spwm, and as the ON period becomes longer, the amount of current flowing through the phase windings Lu-Lw increases, increasing the speed. Furthermore, during deceleration, the braking torque is increased by lengthening the ON period.

Furthermore, when S3 (described later) is input from the flip-flop FF, the distributor 22LL continues to hold the input data at that time. Transistors Tru~TrW-Trx so that Lu~Lw are continuously energized.
- Drive TrZ.

Further, the distributor 22 has a current 1 flowing through the phase windings, u-Lw.
(detected by the current detection resistor R2) exceeds a predetermined maximum allowable current value, the transistor Tru
~ Control the drive of Trw and phase windings LLl, LV, Lw
It is configured to limit the current 1 flowing through the current 1 to a maximum allowable current value or less.

Energization lock command circuit] 3 (comparator OP that compares the voltage VDC of the DC power supply 5 detected by the detection resistor R3 and the predetermined limit voltage V ref of the DC power supply 5)
and a determination signal S from a comparator ○P], a timer circuit T that starts counting a predetermined time limit;
It consists of a flip-flop FF to which the time-up signal S2 of the timer circuit T is input, and an AND circuit AND to which the judgment signal S1 from the comparator OP and the signal S3 from the flip-flop FF (inverted Q terminal) are input. . Flip-flop FF1i timer circuit T
When the time-up signal S2 (High level) is input, the Low active signal S3 is input to the AND circuit AND.
, is output to the energization control circuit 20 and the latch circuit 30. Note that the signal S3 returns to High level by the reset signal.

The AND circuit AND operates when the signals S] and S3 from the comparator OP and the flip-flop FF are both at High level, that is, when the power supply voltage VDC reaches the limit voltage V
When the value exceeds ref, a fi Hgh active output signal 5stop (hereinafter referred to as a stop signal) is output to the transistor Trd of the discharge circuit 9. After that, when the time limit elapses and the time-up signal S2 is input from the timer circuit T to the flip-flop FF, the output signal S3 of the flip-flop FF becomes Low, so the output level of the AND circuit AND also becomes Low. .

In this embodiment, the energization lock command circuit 3 corresponds to the above-mentioned determination means, and the energization lock command circuit 13 and the energization control section]
] and the latch circuit 30 correspond to the above-mentioned energization continuation means.

Next, the operation of the drive device will be explained.

When the AC motor M is braked by the energization control unit 11, the AC motor M enters the power generation mode and the phase winding Lu-
Magnetic energy is stored in Lw.

This magnetic energy becomes an electric charge and the commutating diodes D1 to D
6 regenerates to capacitor 5b Capacitor 5b
will accumulate more charge. As a result, the power supply voltage V
DC exceeds the limit voltage V ref.

Then, the output signal (hereinafter referred to as a stop signal) of the AND circuit AND (hereinafter referred to as a stop signal) Sstoρ becomes High level (the level of the logic signal s3 from the flip-flop FF, let,
High), transistor Trd is ON+, and discharge is performed. Due to discharge, the power supply voltage VDC decreases to the limit voltage V r
When the voltage falls below ef, the transistor Trd is turned off. This discharge time is on the order of several milliseconds.

However, due to the influence of the power receiving/distributing equipment and squirrel cage induction motor in the factory (2), the voltage of the AC power supply 3 rises above the rated value, and as a result, the power supply voltage VDC increases to the limit voltage V ref
(Table) The charge accumulated in capacitor 5b is much larger than the regenerated charge, and even if it is discharged, the power supply voltage V
It may take hundreds of milliseconds to several seconds for the DC to drop below the limiting voltage V ref.

When the discharge time becomes longer in this way (when the upper discharge time exceeds the limit time), the logic signal S of the flip-flop FF
3 becomes Low level, the stop signal 5stop of the AND circuit AND becomes Low level. Therefore, the transistor Trd is turned OFF and the discharge is stopped. At the same time, the output signal S3 of the flip-flop FF is transmitted to the energization control circuit 20.
and is input to the latch circuit 30. Based on this signal S3, the energization control circuit 20 turns on the energization control signal Spwm.
Maximize pulse width.

At the same time, based on the magnetic pole detection signal Smg signal that remains latched in the latch circuit 30 (the magnetic pole detection signal when S3 is input), the distributor 22 is turned on at that time.
The transistors Tru to Trw that are currently being driven are kept turned on, and the transistor Trx- that is being driven at that time is turned on.
Continue chopper driving Trz (ON pulse width becomes maximum). Then, the phase winding current 1 (Y2 phase winding L
Continues to flow only from u to Lw. That is, the phase windings L,, u-
L v, phase winding Lu-Lw, phase winding Lv-Lw, phase winding Lv-Lu, phase winding L w-L u, phase winding L w-L
The flow continues only in one of the courses of v and flows through one of the phase windings and does not flow to u-Lw. Therefore, although the phase winding current 1 reaches the maximum allowable current value, the distributor 22
is limited to the maximum allowable current value. Therefore, since the phase winding current 1 continues to flow at that level, the charges accumulated in the capacitor 5b are discharged all at once, and the DC voltage VDC is reduced to the limiting voltage V
It drops below ref.

DC voltage VDC drops below limit voltage V ref +1
The energization control unit 11 brakes the AC motor M again in the normal braking sequence, and the AC motor M stops.

Then, while the AC motor M is stopped, the power supply voltage VDC is changed again.
exceeds the limit voltage V ref and this state continues beyond the limit time (as in the case of braking, the latch circuit 3
Based on the magnetic pole detection signal Smg latched to 0,
The distributor 22 turns on the transistor Tru=Trw.
and the transistor Trx"Trz to the maximum O
The DC voltage VDC is lowered to the limit voltage V ref or less by performing chopper driving with an N pulse width and flowing the phase winding current 1 having the maximum allowable current value. At this time, in the AC motor M, suction torque acts so that the rotor (the path shown in the figure) is locked to the stopped phase magnetic pole, and the AC motor M is locked to the stopped phase.

As explained above, in this embodiment, when the discharge time exceeds the time limit, the discharge is stopped, and the phase windings that were energized at the time the time limit was exceeded are switched to the maximum current value level from U to W. Since the phase winding current 1 is configured to flow, the discharge circuit 9 is protected and the fuse F is not blown.

Therefore, after confirming the voltage drop of the AC power supply 3, 1. T.

The AC motor M can be immediately redriven, and the operation of the sewing machine can be resumed immediately.

Also, when the voltage of the AC power source 3 suddenly rises abnormally and the voltage of the DC power source 5 also far exceeds the limit voltage V ref, an overcurrent flows into the discharge circuit 9, but at this time, the timer lower is in the middle of timing. Since the transistor Trd is ONL, the fuse is blown due to overcurrent and protects the discharging circuit 9 and the current carrying circuit 7. Therefore, in this embodiment, the discharging is stopped depending on the rising state of the voltage of the AC power supply 3.・Since the protection function by locking the energized state and the protection function by blowing the fuse F are respectively performed, the discharge circuit 9 and the energization circuit 7
is protected, and the fuse F does not blow out frequently.

[Effects of the Invention] According to the present invention described in detail above, (i) discharging is stopped until the output voltage of the DC power source falls below a predetermined voltage value, and
Since the phase windings that were energized when a predetermined period of time has passed since the output voltage of the DC power supply exceeded a predetermined voltage value are continuously energized, the output voltage of the DC power supply can be quickly brought below the predetermined voltage value. It can be lowered to protect the energizing means and discharging means.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing a driving device for a sewing machine motor according to an embodiment. ]... Drive device 3... AC power supply 5... DC power supply 5b... Capacitor 7... Energization circuit 9...-Discharge circuit 11... Energization control unit ] 3... Energization lock command circuit 20... Energization control circuit 22... Distributor 30... Latch circuit M... AC motor D1-D
6... Commutating diode Lu, Lv, Lw... Phase winding OP... Comparator T... Timer FF... Flip-flop A
ND...Logic product circuit

Claims (1)

[Scope of Claims] A DC power source that rectifies alternating current input from an alternating current power source, smoothes it with a power storage means, and outputs direct current; an energizing means that energizes each phase winding of a sewing machine motor from the direct current power source; A control means for driving or braking the sewing machine motor by controlling the energization timing of the means, and regenerating the magnetic energy stored in the windings of each phase as a charge in the electricity storage means when the control means brakes the sewing machine motor. power regeneration means;
A sewing machine motor drive device comprising: a discharge means for discharging the charge accumulated in the electricity storage means when the output voltage of the DC power supply exceeds a predetermined voltage value; a determining means for determining whether or not a predetermined period of time has been exceeded; and when the determining means makes an affirmative determination, stopping the discharging by the discharging means until the output voltage of the DC power source falls below a predetermined voltage value; A driving device for a sewing machine motor, comprising: energization continuation means that controls the energization means to continue energizing the phase windings that were energized at the time of the affirmative determination.