JP2013180791A - Seal power control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact seal power control device, which is reduced in power loss and capable of accurately and stably controlling a heater under a feedback control.SOLUTION: A seal power control device is configured to control the power of a heater 5 provided in a sealer in a sealing section of a packaging machine. The seal power control device includes: a three-phase full-wave rectification circuit 11 with a smoothing capacitor to rectify a three-phase AC power source 10, which supplies power to the heater 5, to have a direct current; and a seal transformer 12 configured to supply the power rectified by the rectification circuit 11 to the heater 5. The state of the heater 5 on the secondary side of the seal transformer 12 is detected by a feedback circuit 14, and the DC power source rectified by the rectification circuit 11 is cut by a switching element Q1 in accordance with the value, and then, the pulse width of the DC power source to be supplied to the heater 5 is controlled.

Description

  The present invention relates to a seal power control device that controls a power source of a sealer disposed in a seal section of a rotary packaging machine or a vacuum packaging machine, for example.

FIG. 4 is a partially enlarged view of the sealing section of the rotary packaging machine, in which both sides of the packaging bag 1 are clamped by the clamps 3 of the clamp arm 2 and the upper edge of the packaging bag 1 is sealed by the sealer 4. . A rod-like heater 5 is mounted in the sealer 4, and power is supplied to the heater 5 to heat the sealer 4.

FIG. 5 is a schematic diagram of a power supply circuit that supplies power to the heater 5 from a single-phase AC power supply. A voltage is dropped from the single-phase AC power source 6 by a transformer for seal power transformation (seal transformer 7) to supply power to the heater 5. However, this conventional power circuit has the following problems.
1) If power is taken out in a single phase with respect to the three-phase AC power supply, the output will be unbalanced and the power will be weakened, so the capacity of the power supply facility must be increased to increase the power.
2) When the power supply fluctuates, the seal of the bag mouth of the packaging bag 1 by the sealer 4 is not stable.
3) Since the seal state is unstable, feedback control is difficult even if feedback control is attempted to stabilize the temperature of the heater 5.
4) In order to use a low commercial frequency (50 Hz or 60 Hz), it is necessary to use a large-capacity seal transformer 7 in order to increase the voltage. I can't.

On the other hand, Patent Document 1 discloses a method for controlling a packaging material seal condition that automatically sets a welding temperature, a welding time, and a cooling time after welding according to the material or thickness of various packaging materials. Has been.

The packaging device of Patent Document 1 records in advance a voltage, current value, or temporal data corresponding to the material or thickness of various types of packaging materials in a storage device, and identifies the packaging material with a barcode reader. Information (barcode) is read, the read information is input to the central processing unit, and recorded information corresponding to the input information is output from the storage device by collation. Based on this output information, the voltage is adjusted by a voltage converter provided in the power supply circuit, and the heating temperature of the heater is set to a value suitable for the packaging material.

JP-A-6-278719

  However, since the packaging material sealing condition control method disclosed in Patent Document 1 adjusts the heating temperature of the heater with a voltage converter for the circuit voltage, power loss occurs. In addition, voltage, current values, or temporal data corresponding to the materials or thicknesses of various types of packaging materials are recorded in advance in the storage device, and this data information is extracted from the storage device to be a voltage converter. Therefore, the feedback control is not performed to control the electric power in accordance with the state of the heater that occurs every moment. Therefore, there is a problem that the seal cannot be stably controlled.

An object of the present invention is to provide a compact seal power control device that reduces power loss and enables accurate and stable heater control by feedback control.

A sealing power control device according to the present invention is a sealing power control device for controlling the power of a heater provided in a sealer of a sealing section of a packaging machine, and a smoothing capacitor that rectifies a three-phase AC power source that supplies power to the heater into a direct current. A three-phase full-wave rectifier circuit or a three-phase half-wave rectifier circuit, and a seal transformer for supplying the power rectified by the rectifier circuit to the heater, and a feedback circuit for the state of the heater on the secondary side of the seal transformer According to the detected value, the DC power source rectified by the rectifier circuit is cut by the switching element, and the pulse width of the DC power source supplied to the heater is controlled.

With the above configuration, the seal power control apparatus of the present invention detects the state of the heater with a feedback circuit, and according to the value, the switching element is turned on and off to increase or decrease the power to the heater. However, even if the power supply fluctuates, a stable power supply can be obtained by controlling the switching element.

The seal power control device of the present invention includes a PWM circuit for controlling the switching element, detects the heater state with a feedback circuit, inputs an output signal of the feedback circuit to the PWM circuit, and turns on and off the switching element. To control.

  Further, in the seal power control device according to the present invention, when the feedback circuit detects that the heater voltage is low, the PWM circuit generates a PWM wave corresponding to the detected voltage and supplies power to the heater via the switching element. On the contrary, if the heater voltage is high, the power to the heater is reduced, and even if the power supply fluctuates, a stable power supply can be obtained by controlling the switching element.

  The heater state detected by the feedback circuit may be any of voltage, current, power, temperature information from the temperature sensor, or a combination thereof.

  According to the present invention, the power loss is small, and accurate and stable heater control is enabled by feedback control, and a compact seal power control device is enabled.

Circuit diagram of seal power control device of the present invention Partial circuit diagram of seal power control device of the present invention Waveform diagram of seal power control device of the present invention Partial enlarged view of the sealing section of a rotary packaging machine Schematic diagram of a power supply circuit that supplies power from a conventional single-phase AC power supply

Hereinafter, a seal power control device of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram of a seal power control apparatus of the present invention. The packaging machine used in the present invention includes all packaging machines such as a rotary packaging machine, a linear line packaging machine, a vacuum packaging machine, and a pillar packaging machine.

The present invention uses a three-phase AC power source 10. The reason why the three-phase AC power supply 10 is used is that the electric power is balanced as compared with the single-phase AC power supply 6 of FIG. . Three-phase alternating current consists of three phases, a-phase, b-phase, and c-phase. The phase voltage of each phase is represented by the symbols va, vb, vc, and there are 120 between the phase voltages va, vb, vc. There is a phase difference by degrees.

The three-phase AC power supply 10 has two diodes arranged in series in parallel and is full-wave rectified by a total of six diodes D1 to D6. The three-phase alternating current va phase is connected between the series diodes D1 and D2, the vb phase is connected between the series diodes D3 and D4, and the vc phase is connected between the series diodes D5 and D6. 1 shows the three-phase full-wave rectifier circuit 11, a three-phase half-wave rectifier circuit may be used.

As is clear from the circuit diagram of FIG. 1, the three-phase full-wave rectifier circuit 11 flows from the phase with the highest phase voltage, and flows from the phase with the lowest phase voltage. Therefore, the output voltage vout is equal to the maximum absolute value of the three line voltages. A smoothing capacitor C1 is joined in parallel to the full-wave rectifier circuit 11, and the ripple voltage of the output voltage vout is reduced by the effect of the smoothing capacitor C1.

The three-phase AC power supply 10 is converted into a smooth DC current by the full-wave rectifier circuit 11 with a smoothing capacitor and input to the primary side of the seal transformer 12. Since the switching element Q1 is connected in series to the primary side of the seal transformer 12, the current from the full-wave rectifier circuit 11 can be passed and cut off by turning the switching element Q1 on and off. In the present embodiment, a MOSFET is used as the switching element Q1.

The MOSFET as the switching element Q1 needs to allow switching at about 100 kHz, but this MOSFET preferably has a proper breakdown voltage and a low on-resistance.

The drain (D) of the MOSFET and one end of the primary side of the seal transformer 12 are connected, and the source (S) is connected to the negative side of the full-wave rectifier circuit 11 via a resistor R2. Further, the gate (G) of the MOSFET and the PWM circuit 13 are connected, and a PWM output (PWM wave) is input to the gate (G). The PWM circuit 13 will be described later.

A heater 5 of the sealer 4 is connected to the secondary side of the seal transformer 12, and power from the seal transformer 12 is supplied to the heater 5 to heat the sealer 4. A voltage value is sent from the heater 5 toward the feedback circuit 14. The value of the heater 5 voltage (feedback voltage) is input to the feedback circuit 14, converted into a command voltage, sent to the PWM circuit 13, and a PWM wave corresponding to the heater 5 voltage (feedback voltage) is generated. The switching element Q1 is ON / OFF controlled. 4 shows the heat seal type sealer 4, it may be an impulse seal type sealer 4. In the heat sealing method, it takes time to increase the temperature of the sealer 4 and there is a time lag. Therefore, the impulse sealing method is preferable.

PWM is referred to as (Pulse Width Modulation), and the PWM circuit 13 is a well-known pulse width modulation circuit in which a circuit for generating PWM output is incorporated in a microchip. Since the principle of the PWM circuit 13 is well known, only a PWM circuit using an operational amplifier and a PWM circuit using a clock circuit (both not shown) will be briefly described below.

The PWM circuit by the operational amplifier generates a triangular wave by two operational amplifiers, and a comparator (voltage comparator) compares the triangular wave with the command voltage from the feedback circuit 14 and outputs a square wave (PWM wave). The switching element Q1 (MOSFET) performs a switching operation with a PWM wave output from a comparator (not shown) to control electric power.

A PWM circuit using a clock circuit (not shown) is different from a PWM circuit using the operational amplifier in that a square wave generated by the clock circuit is converted into a triangular wave by an integrating circuit. Other than that, the comparator compares the triangular wave with the command voltage from the feedback circuit 14 and outputs a square wave (PWM wave).

FIG. 2 shows the feedback circuit 14. As described above, the feedback circuit 14 measures the heater voltage (feedback voltage) of the heater 5 and inputs it to the comparator of the PWM circuit 13 as a command voltage. In this feedback circuit 14, the square wave of the secondary heater voltage is converted into a DC command voltage suitable for the PWM circuit 13 with less ripple by using the rectifier circuit 15 and the ripple filter circuit using the transistor T 1. Convert. The AC component of the voltage is smoothed by R3 and C3.

In response to the command voltage from the feedback circuit 14, the PWM circuit 13 generates a PWM output (PWM wave) having a duty ratio (D) corresponding to the command voltage, and the three-phase full-wave rectifier circuit using the switching element Q1 according to the PWM wave. The DC voltage from 11 is cut.

FIG. 3 shows a waveform (PWM wave) generated by the PWM circuit 13. In FIG. 3, the lower layer is a triangular wave 17 generated in the PWM circuit 13, and the upper layer is a square wave (PWM wave 16) output by comparing the triangular wave 17 with the command voltage from the feedback circuit 14 by a comparator. ).

VL and VH indicated by broken lines overlapping the triangular wave 17 are command voltages output from the feedback circuit 14, VL indicates that the voltage of the heater 5 is low, and VH indicates that the voltage of the heater 5 is high. . In FIG. 3, VL and VH are shown as separate lines for easy understanding, but the actual command voltage is a single continuous line of an inclined line or a curve or a straight line.

When the triangular wave 17 and the command voltage VL or VH are input to the comparator, both are compared. Since the width of the intersection between the triangular wave 17 and the command voltage VH is narrow, a narrow PWM wave 16a with a small duty ratio (D) is generated. When this narrow PWM wave 16a is input to the switching element Q1, current flows through the heater 5 by the width ratio, so the power flowing through the heater 5 is reduced and the temperature of the sealer 4 can be lowered.

On the contrary, when the command voltage becomes low like VL, the width of the intersection of the command voltage VL and the triangular wave 17 becomes wide as shown on the right side. On the contrary, the width of the PWM wave 16b becomes wide so that the heater 5 The flowing power increases and the temperature of the sealer 4 rises.

As described above, when the feedback circuit 14 detects that the voltage of the heater 5 is low, the power to the heater 5 is increased via the PWM circuit 13 and the switching element Q1, and when the voltage of the heater 5 is high, the heater 5 Even when the power supply fluctuates, the three-phase AC power supply can be made a stable power supply by controlling the switching element Q1.

In the above embodiment, the voltage of the heater 5 is measured by the feedback circuit 14, and the width (duty ratio D) of the PWM wave 16 is controlled by the switching element Q <b> 1 via the PWM circuit 13. The flowing current or power may be used as a reference. Further, the temperature of the heater may be measured by a temperature sensor (not shown), and the width (duty ratio D) of the PWM wave 16 may be controlled by the current value. If a current-voltage conversion circuit (not shown) using an operational amplifier is used, it can be easily converted to a voltage when the current is used as a reference or the current from the temperature sensor is used as a reference. The duty ratio D can be modulated. Furthermore, the switching element Q1 may be controlled by a command voltage processed by a feedback circuit by combining these voltages, currents, and powers.

As described above, the size of the seal transformer 12 can be drastically reduced by using the commercial-frequency three-phase AC power supply 10 with the switching element Q1 of about 100 kHz. An apparatus can be provided.

In the above embodiment, the switching element Q1 is connected in series with the primary side of the seal transformer 12. However, the switching element Q1 may be provided in parallel as in the smoothing capacitor C1.

Further, the PWM circuit 13, the switching element Q1, and the feedback circuit 14 may be provided on the secondary side of the seal transformer 12.

The present invention is useful, for example, as a seal power control device that controls power to a heater used in a sealer of a seal section such as a rotary packaging machine or a vacuum packaging machine.

5 Heater 10 Three-phase AC power supply 11 Full wave rectifier circuit 12 Seal transformer 13 PWM circuit 14 Feedback circuit 16 PWM wave 17 Triangular wave C1 Smoothing capacitor Q1 Switching element

Claims (3)

In a seal power control device for controlling the power of a heater provided in a sealer of a seal section of a packaging machine,
A three-phase full-wave rectifier circuit or a three-phase half-wave rectifier circuit with a smoothing capacitor that rectifies a three-phase AC power source that supplies power to the heater into direct current; a seal transformer that supplies the heater with the power rectified by the rectifier circuit; With
The state of the heater on the secondary side of the seal transformer is detected by the feedback circuit, and the DC power source rectified by the rectifier circuit is cut by the switching element according to the value, and the pulse width of the DC power source supplied to the heater is controlled To
A seal power control device characterized by that. A PWM circuit for controlling the switching element is provided, the heater state is detected by a feedback circuit, an output signal of the feedback circuit is input to the PWM circuit, and the switching element is controlled by ON and OFF pulse widths. Item 2. The seal power control device according to Item 1. The state of the heater detected by the feedback circuit is either the voltage, current, power, or temperature information from the temperature sensor, or a combination thereof.
The seal power control apparatus according to claim 1 or 2, characterized by the above.

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